# APHIS Evaluation of the Rhipicephalus (B o ophilus) spp. Status of Sonora

, Mexico

Animal and Plant Health Inspection Service Veterinary Services, National Center for Import and Export Regionalization Evaluation Services Staff



### August, 20112 

## Table of Contents

Abbreviations

................................ ................................ ................................ ...................... 3

Executive Summary

................................ ................................ ................................ ............ 5

Introduction

................................ ................................ ................................ ......................... 8

Background

................................ ................................ ................................ ......................... 9

Hazard Id entification

................................ ................................ ................................ ........ 14

Release Assessment

................................ ................................ ................................ .......... 19

1. Authority, organization, and infrastructure of the veterinary services

..................... 19

2. Rhipicephalus tick status of the region

................................ ................................ ..... 26

3 . Rhipicephalus tick status of adjacent regions

................................ ........................... 28

4. Extent of active tick control program

................................ ................................ ....... 31

5. Vaccination status of the region

................................ ................................ ................ 36

6. Separation from adjac ent regions of higher risk

................................ ....................... 36

7. Movement controls and biosecurity from higher

- risk regions

................................ .. 38

8. Livestock demographics and mar keting practices in the region

............................... 52

9. Tick surveillance in the region

................................ ................................ .................. 56

10. Diagnostic laboratory capacity

................................ ................................ ............... 58

11. Emergency response capacity

................................ ................................ ................. 60

Conclusions

................................ ................................ ................................ ................... 61

Exposure Assessment

................................ ................................ ................................ ........ 63

Consequence Assessment

................................ ................................ ................................ . 65

Risk Estimation

................................ ................................ ................................ ................. 68

References

................................ ................................ ................................ ......................... 693 

## Abbreviations

AGL Asociaciones Ganaderas Locales (Local Cattlemen’s Associations)

APHIS Animal and Plant Health Inspection Service

CENAPA Centro Nacional de Servicios de Constatación en Salud Animal ( National

Animal Health Ver ification Services Center)

CENASA Centro Nacional de Servicios de Diagnóstico en Salud Animal (National Center for Diagnostic Services in Animal Health)

CFR Code of Federal Regulations

CFTEP Cattle Fever Tick Eradication Program

CIGAM C entros d e Inspección de Ganado en Lugares de Alta Movilización (Centers of Livestock Inspection for High Movement)

CN Consumo Nacional (National Consumption)

CPA Comision Mexico

- Estados Unidos para la prevención y control de la fiebre aftosa y otras enfermada des exoticas ( Mexico

- United States

Commission for the Prevention of Foot

- and

- Mouth Disease and Other

Exotic Animal Disease )

DGICA Dirección General de Inocuidad y Calidad Agroalimentaria (Agrofood Safety and Quality Control General Directorate)

DGIF Dirección General de Inspeccion Fitozoosanitaria (Animal and Plant Health Inspection Service General Directorate)

DGSA

DGSG Dirección General de Salud Animal (Director ate of Animal Health)

Dirección General de Servicios Ganaderi os (Director General of

Livestock Services )

DINESA Dispositivo Nacional de Emergencia de Sanidad Animal (National Animal Health Emergency Operation)

DIVE Dirección de Vigilancia Epidemiológica (Directorate of Epidemiological Surveillance)

GEESA Grupo Estatal de Emerg encia en Salud Animal (State Animal Health Emergency Group)4 N OM Norma Oficial Mexicana (Mexican Official Standards)

OIE Office International des Epizooties (World Organization for Animal Health)

PVI Puntos de Verificación e I nternal ( Internal Ve rification Post )

SAGARPA Secretaría de Agricultura, Ganadería, Desarollo Rural, Pesca Y Alimentación (Ministry of Agriculture, Livestock, Rural Development, Fishing, and Food)

SAGAR H PA Secretaría de Agricultura, Ganadería, Recursos Hidraulicos Pesca y Aquaculture (Ministry of Agriculture, Livestock, Water Resources, Fisheries and Aquaculture )

SENASICA Servicio Nacional de Sanidad, Inocuidad y Calidad Agroalimentaria (National Service of Health, Safety and Quality Agrofood)

SINIIGA Sistema Nacio nal de Identificacion Individual de Ganado (National Individual Cattle Identification System)

UGR S La Unión Ganadera Regional Sonora (Sonora Regional Livestock Association)

U SDA United States Department of Agriculture

VS Veterinary Services5 

## Ex ecutive Summary

In 2002, Mexico’s Ministry of Agriculture, Livestock, Rural Development, Fishing, and Food, Mexico ( Secretaría de Agricultura, Ganadería, Desarollo Rural, Pesca Y

Alimentación , or SAGARPA ), officially requested that the United States Depart ment of Agriculture ( USDA ) Animal and Plant Health Inspection Service ( APHIS ) review the Rhipicephalus (formerly Boophilus ) annulatus and R hipicephalus microplus tick status of

the State of Sonora , Mexico . These ticks, known as cattle fever ticks, are the North American vectors for bovine babesiosis, or cattle fever.

Upon receipt of this request, APHIS initiated an evaluation of the status of Sonora with regard to the Rhipicephalus spp. tick s named above . This report represents APHIS’

evaluation of Son ora with regard to the status, infrastructure, and control measures in place for Rhipicephalus spp. ticks and assesses the likelihood that these ticks could be imported into the United States via cattle and other susceptible livestock from Sonora

. Support ing documentation us ed in th is evaluation consists of information submitted by

SAGARPA

, site visit team observations during three site visit s , information from the World Organization for Animal Health (OIE), peer

- reviewed articles, and other technical

sour ces. This risk analysis was conducted according to OIE guidelines and therefore includes a hazard identification section, a release assessment, an exposure assessment, a consequence assessment, and a risk estimate.

Release Assessment

Sonora has demonst rated that it has the infrastructure, personnel, and legal framework to
prevent i ncursions of Rhipicephalus spp. ticks through its program of r outine tick inspection and dipping during movement from areas at risk for tick infestation combined with strategi c location of inspection stations along major transportation routes that enter

into and traverse the State. Sonora’s transit guide system , which requires identification of livestock during movement and links tick inspection and treatment requirements to t he origin and destination of livestock, ensur es that appropriate control measures are applied to all livestock engaged in transit. T his system, in combination with the annual livestock census, helps ensure that animals are not moved illegally thereby evad ing tick inspection and treatment procedures. An important component of Sonora’s successful control and eradication program is its Federal

- State

- private partnerships, which have been instrumental in accomplishing and maintaining Sonora’s Rhipicephalus

- fre e status.

The desert

- like climate in most of Sonora does not support the survival of Rhipicephalus tick spp. eggs. Consequently, this area , consisting of the northern and central portions of Sonora, has historically remained naturally free of Rhipicephal us spp. ticks. The southern tip of Sonora, near its border with Sinaloa, is more hospitable to these ticks, and occasionally experiences incursions. Delineations between the tick free area and the southern area (or buffer zone), are similar to those in p lace along the border between the U.S. per manent tick quarantine zone in South Texas and the rest of the United States.6 Four Rhipicephalus spp. infestations have been detected since eradication of this tick was declared in Sonora in 1972 ; however, all o ccurred exclusively within Sonora’s buffer zone, were detected before the infestation became widespread, and were contained and controlled within time frames established by SAGARPA. Movement controls and additional tick inspection and dipping requirements are in place for livestock that move from the buffer zone into the historically tick

- free region of Sonora. These controls have

been successful in restricting any incursions to the buffer zone.

If Rhipicephalus spp. ticks were to enter into Sonora, tick inspection requirements on premises and during movement could be expected to detect these ticks on Sonoran livestock. Surveillance efforts have proven effective at detecting tick incursions in the buffer zone in a timely manner. Surveillance for Rhipice phalus spp. ticks is multi

pronged and comprehensive, and includes routine surveillance through an integrated system of tick inspection tied to movement, an annual tick survey directed by SAGARPA, and active inspections in high risk areas within the buffer zone.

Although APHIS has concerns about the delay in the turnaround time for acaricide analysis results from cattle dipping vats, Sonoran officials and inspectors demonstrate the willingness and ability to maintain appropriate acaricidal concentrations in the dipping vats. This factor, when combined with Sonora’s low environmental suitability for cattle fever ticks, excellent detection and response capabilities, and overlapping movement control procedures, results in the finding of a very low likelihoo d that Sonora would

become infested with Rhipicephalus spp. ticks.

APHIS concludes that the likelihood that cattle imported from Sonora w ould introduce Rhipicephalus spp. ticks into the United States is very low.

Exposure Assessment

APHIS assessed the l ikelihood of exposure of U.S. livestock to Rhipicephalus spp. ticks from cattle exported from Sonora to be low. The most likely route of introduction is through the legal importation of cattle. Successful exposure via this route would require

that multip le steps take place in sequence following the importation of undetected Rhipicephalus

- infested cattle into the United States , including the failure of tick inspection s and any treatment s applied at the U .S. border ports , transport of infested

cattle to an environment suitable for tick survival and replication, and contact between

the resulting larval ticks and domestic livestock populations

. Beca use multiple, successive events would be required for the successful exposure of domestic livestock to Rhipiceph alus spp. ticks as a result of the importation of infested cattle from Sonora, the likelihood of an exposure event is low.

Consequence Assessment

The consequences of Rhipicephalus spp. ticks entering into the United States, resulting in

a domestic inf estation, would likely result in the implementation of a control campaign, which could be costly, especially if it becomes extensive. Costs of a single outbreak7 (defined as 3 infestations) in Texas were recently estimated at $123 million USD for the

first year. If the outbreak expanded to the U.S. historic Rhipicephalus spp. tick range, cost estimates increased substantially, to $1.2 billion USD

.

I f the tick infestation resulted in a resurgence of bovine babesiosis in the indigenous cattle population, the additional consequences could be expected to be significant , with morbidity rates of up to 50% and mortality rates in excess of 90% in affected cattle

. Additionally, movement restrictions within the United States, as well as export trade losses, could be expected to add to these consequences.

Risk Estimation

In summary, although the consequences of an outbreak of Rhipicephalus spp. ticks in the U.S. cattle population could be costly, especially if associated with bovine babesiosis,

APHIS considers th e likelihood of Rhipicephalus

- infested cattle entering the United States from Sonora resulting in exposure to U.S. cattle to be very low.8 

## Introduction

Rhipicephalus microplus and Rhipicephalus annulatus ticks 1 are important because they

are the North American vectors f or bovine babesiosis, or cattle fever

. Before this disease

was e radicated from the U nited States (with the exception of the quarantine zone along Texas’ southern border with Mexico) in the 1940s it resulted in significant economic

losse s due to decreased productivity of cattle and movement restrictions both within and

outside of the U nited S tates

.

The United States received a request for recognition of Sonora, Mexico as free of Rhipicephalus spp. ticks in 200 2 . Since then

, Mexico h as provided additional information from Sonora regarding its ability to prevent the entry of these ticks, detect them if they occur, and eradicate any infestations should they occur . In addition

, APHIS

has conducted t hree site reviews in Sonora, in 2002

, 2006, and 20 1 1

, to evaluat e procedures associated with their tick control program.

C urrent U.S. regulation s , contained in the Title 9 of the Code of Federal Regulations ( 9 CFR) in section 93.427 and expanded upon in Veterinary Services Memorandum No.

591 .69 , require that cattle from Mexico offered for entry into the United States receive a “scratch” inspection by an inspector employed by the APHIS. A scratch inspection is a

visual and hands

- on inspection of cattle, with emphasis on the preferred tick att achment sites such as the neck, dewlap, and axillary region for the presence of ticks. If cattle are found to be free from ticks, they will be given one acaricide 2 dipping treatment on the

Mexican side of the border port , in the form of an immersion bath 3 , and then allowed to

cross into the United States . If cattle are found to be infested with Rhipicephalus spp. ticks, the entire lot of cattle will be rejected, dipped, and held in quarantine on the Mexican side of the border under the supervision of the inspectors at the port . After 10 to 14 days the cattle will be inspected again, dipped, and then allowed to cross through the border port to the United States if no ticks are found.

1 Rhipicephalus microplus and Rhipicephalus annulatus ticks were formerly referred to as Boophilus microplus and Boophilus ann ulatus , respectively. Due to morphological similarities, the two Boophilus species became part of the Rhipicephalus genus of ticks. Subsequently, they will be referred to individually as Rhipicephalus microplus or Rhipicephalus annulatus or together as R hipicephalus spp. ticks or cattle fever ticks (because they are both vectors for bovine babesiosis or cattle fever) in this document. Other, non

- cattle fever tick species of Rhipicephalus ticks will be referred to by their full name. The term Boophilus w ill be retained when referring to official titles of programs, regulations, or documents.

2 Acaricides are pesticides that kill (or interrupt the life cycle of) ticks or mites. For the purposes of this
assessment, acaricide will refer to chemicals used i n the treatment of livestock for ticks and acaricidal solution will refer to those chemicals maintained in solution in cattle dip vats.

3 An immersion bath consists of a narrow tank filled with an acaricidal solution that is used to fully

immerse cattle i n order to treat or prevent infestation with ticks. Corrals and chutes are used to move cattle into and through the baths. The immersion bath is generally located below ground level, with cattle descending a ramp into the bath, swimming through the solut ion, and ascending another ramp at the end,

re

- emerging at ground level. Immersion baths may also be referred to as dip vats, dipping vats, or dip

baths.9 APHIS propose s to amend this section of the CFR to a llow eligible cattle from Sonora to
be excluded from the dipping process when presented at land border port s of entry into

the United States from Sonora . However, scratch inspections will be conducted on individual animals prior to entry into the United States

.

Cattle and o ther livestock will still be required to be accompanied with certification by an official veterinarian employed by SAGARPA that the animals have been inspected and found visibly free from fever ticks and any evidence of communicable disease, and that,

as f ar as it is possible to determine, they have not been exposed to splenetic, southern, or tick fever, during the 60 days immediately preceding their movement to the port of entry.

Recognizing Sonora as free of Rhipicephalus spp. ticks and exempting Sonor an cattle from acaricide dipping at the port will facilitate trade with Sonora by minimizing economic costs associated with dipping procedures at U.S. port s . Additionally, the potential hazards to people and animals associated with the exposure to acarici des will be
reduced, a s will the additional time required to complete the dipping process at the U.S.

port s of entry.



## Background

H istory and control of bovine b abesiosis and Rhipicephalus spp. ticks in the U nited

States

The presence of bovine babesi osis in the southern United States in the late 19 th and early

20 th century cost the U

. S

. cattle industry n ot only through production losses resulting

from clinical disease

, but also because of market exclusion from northern, disease

- free

U

. S

. States and ex port to other countries . These losses led to the creation of the Cattle Fever Tick Eradication Program (CFTEP) in 1906, which was tasked with the goal of eradicating the tick vectors responsible for transmitting bovine babesiosis. The program targeted af fected states , including Texas, Oklahoma, Arkansas, Louisiana, Mississippi, Alabama, Georgia, Florida, South Carolina, North Carolina, Virginia, Tennessee, Kentucky, Missouri, and southern California [1] (see Figure 1)

.

Figure 1. Distribution of Rhipicephalus spp. tick s in the U nited States (in blue) during the early 1900s

.10 Source: [2]

The eventual eradication of Rhipicephalus annulatus and R. microplus ticks and their

associated diseases from the continental U nited S tates was achieved through a centrally planned and coordinated program that combined quarantine, mandatory dipping o f cattle

, surveilla nce, and pasture rotation. The campaign began at the northern perimeter of the

infested zone and moved south

. Although planning occurred at the central level, the CFTEP was an example of one of the first cooperative State

- Federal eradication efforts

, bene fitting from and ultimately succeeding due to s trong producer buy

- in [3, 4]

.

By 1943, the eradication campaign had been almost entirely complete d ; however, a small

area remain ed along the Rio Grande in south Texas in which ticks were unable to be completely eradicated due to this region’s proximity to areas in Mexico co ntaining the

ticks . This area is referred to as the permanent quarantine zone or buffer zone . It currently consists of a strip of land approximately 500 miles long extending from Del Rio to Brownsville, Texas which ranges from 123 yards to 8 miles in wid th ( the area between

the red line and the Mexican border depicted in Figure 2 ) [5

- 7]

.

Figure 2. P ermanent tick quarantine zone
, 2006

.11 Source: [5]

Many of the activities th at were used in the U nited States to eradicate ticks under the CFTEP are currently employed as control measures in the permanent quarantine zone

. Current efforts focus on surveillance by State and Federal CFTEP personnel, including approximately 85 mounte d patrol inspectors known as “tick riders

. ” Tick riders patrol

livestock premises within the buffer zone, conduct inspections and tick treatments for cattle moving within and out of the quarantine zone, perform trace

- out and trace

- back investigations

, con duct surveillance for potentially tick

- infested wildlife, maintain all program dipping vats, conduct inspections at selected livestock sale barns, and apprehend stray or illegal livestock crossing the Rio Grande [3, 7]

.

In addition, CFTEP officials inspect all native l ivestock being moved within or outside of the quarantine zone

. Premises are placed under quarantine if even a single fever tick is found on a single animal within a herd. The duration of the quarantine ranges from 6

- 9 months, depending on the time of yea r. By Texas state law, cattle under quarantine must be dipped every 7

- 14 days with an acari cide or removed from the infe s ted pasture after two “clean” scratch and dip ping treatments

. In addition, cattle on all adj acent premises,

as well as the herds of o rigin of cattle that have recently entered the herd or destination

herds of those that have recently left, are inspected for the presence of ticks [3, 7

- 9]

.

Tick incursions or the threat of incursions in areas outs ide of the permanent quarantine zone in recent years have led to a temporary expansion of the quarantine zone. The

detection of cattle fever ticks outside the permanent quarantine zone in 2007

- 2009 led to the institution of temporary preventive quarantin e areas adjacent to the permanent quarantine zone. Discrete sections of t he temporary quarantine zone s w ere lifted as surveillance and treatment measures as described above were satisfactorily completed in

those areas [6, 10, 11]

.

The incursions were likely due

, in part

, to the maintenance of cattle fever ticks in w ild ungulates , especially white

- tailed deer , which coexist in and around domest ic cattle herds12 in South Texas and are known to be effective hosts for Rhipicephalus ticks

. Additional

factors were favorable weather conditions for tick harborage

, the continued movement of stray and illegal cattle from Mexico

, and U.S. resource shortage s [5, 7]

.

In response to increasing fever tick infestations, several tactics are currently in use to combat ticks in the permanent quarantine zone and surrounding areas. These include the use of p asture management tools

, feeders and neckbands d esigned to apply topical

acaricides to white

- tailed deer, and the use of treated feed for wild ungulates [5, 12, 13]

. Several new developments, including r esearch into new acaricid al drugs and treatment protocols

, and vaccination programs against fever ticks, are also under investigation [12

- 17]

. An other mitigation measure being considered includes the Tick Control Barrier, an

8

- foot high gam e fence, along portions of the pe rmanent tick quarantine line to prevent
further unobstructed movement of tick

- infested white

- tailed deer and exotic ungulates

into the free areas of South Texas [18, 19]

.

History and control of Rhipicephalus spp. ticks in Sonora

Sonora is located on Mexico’s northern border, south of Arizona and east of the Gulf of Mexico (Figure 3). Northern Sonora has historically remained free from Rhipicephalus spp. tick infestation because of its inhospitable climatologic conditions (high altitude and

desert

- like co nditions), although ticks have occasion ally been found in the southern portion of the State referred to as the buffer zone because of its proximity to a tick

infested region of Sinaloa and southwestern Chihuahua

.

Figure 3 . Map of Sonora, Me xico and surrounding area.

Source: http://www.map

- of

- mexico.org/mexico

- states.gif

The campaign to officially eradicate Rhipicephalus spp. ticks from the entire State of Sonora formally began in 1932. The campaign was initiated by cattlemen who wished to13 gain freedom from these ticks for the entire State and approached the State government in order to gain regulatory and technical support to be able to do so [20]

.

In the beginning of the eradication effo rt, a zoo sanitary (animal health) line was established, divid ing Sonora into a clean (northern) and an infested (southern) region. Using a process of strict movement controls, which includ ed a requirement to treat and inspect all livestock prior to moveme nt from infested areas to clean areas, the line demarcating infestation was slowly pushed southward until the entire State was

considered free of Rhipicephalus spp. tick s . As of November 1972, Sonora was officially declared free of these tick species by t he Mexican government via a decree published in the Federation Official Diary (the equivalent of a U

. S

. Federal Register Notice) [20]

.

Although there have been occasional incursions of ticks into Sonora since its declaration

of freedom from th ese ticks , all of the infestations were detected in Sonora’s buffer zone

and were quickly detected, thoroughly investigated

, and successfully resolved with in required time period s [20]

.

The Government of Mexico currently considers the entire States of Sonora, Baja

California

, Aguascalientes, and Tlaxcala

, alon g with the Federal District

, as areas entirely

f ree of Rhipicephalus spp. ticks. Presumably, the absence of vector ticks in these states

also gives rise to B abesia

- free cattle populations . States in Mexico that are partly free of

these ticks include Baja California Sur , Chihuahua, Coahuila, Nuevo Leon, Tamaulipas, Durango, Zacatecas, the plateau of San Luis Potosí, Guanajuato, Hidalgo, Federal District, and Puebla [21, 22] . However, APHIS has not yet evaluated any of these states and currently does not recognize them as tick

- free (Baja California is currently under evaluation) [23]

.

Figure 4 , below, displays a map of Mexico’s tick status according to the Nationa l Campaign against Rhipicephalus spp. ticks as of April 2011

. The green Free Zone ( Libre ) is a geographical area that has been determined to be free of Rhipicephalus spp

. ticks by Campaign eradication activities or natural climatic conditions. The yellow Eradication Zone ( Erradicación ) is a geographical area in which a system of tick treatments, movement controls and surveillance activities aimed at total elimination of Rhipicephalus spp . ticks is practiced , requiring treatments of 100% of susceptible anim als

for ticks . The red Control Zone ( Control ) is a geographical area with strategic and targeted tick treatments and surveillance aimed at reducing the number of Rhipicephalus

spp. ticks and the percentage of infected animals [22, 24]

.

Figure 4 . Status of the National Campaign against Rhipicephalus spp. ticks, Mexico, April 2011.14 Source: [22]



## Hazard Identification

Hazard i dentification involves identifying the pathogenic agent(s) in animals or animal products which could potentially produce adverse health effects associated with its importation into a region [25]

. In this assessment, the identified hazards (disease agent of concern) are the two protozoan organisms, Babesia bovis and Babesia bigemina

. However, th e assessment itself is focused on the eradication of the tick vectors for these two organisms, Rhipicephalus microplus and Rhipicephalus annulatus. These vectors are integral in the maintenance of Babesia infection in cattle, and elimination of the vector s is the mode of disease eradication used in the affected region under discussion.

Bovine Babesiosis

Bovine b abesiosis, known variously by such names as piroplasmosis, Texas fever, cattle fever, redwater, or tick fever, is a febrile disease of cattle ca used by tick

- borne intraerythrocytic protozoan parasites of the genus Babesia . The disease is widespread in the subtropics and tropics, where, historically, it has had serious economic impact on cattle production. Six different species of Babesia are kno wn to infect cattle; the most significant species for cattle in the Western hemisphere are Babesia bovis and Babesia bigemina

. Babesia spp. are transmitted primarily by ixodid (hard

- bodied) ticks [26, 27]

.

Etiology15 Babesia spp. are protozoan parasites that invade red blood cells. B abesia bigemina characteristically appears with in mature erythrocytes as two joined, pear

- shaped bodies.

B abesia bovis is smaller and pleomorphic; it is considered the more virulent of the two species.

Host range/Species affected Cattle are the primary hosts for both B. bigemina and B. bovis ; however, it is possible for other animals to maintain the infection. Buffalo have reportedly been infected with both organisms, but this is considered uncommon and unlikely to present a reservoir of

infection. White

- tailed deer ( Odocoileus virginianus ) can be in fected with B. bigemina

and B. bovis ; however, their overall role in the epidemiology of b abesiosis, particularly in deer populations that coexist among domestic cattle , is currently unknown [26, 28]

.

Transmissio n Bovine b abesiosis is transmitted primarily through the bite of infected R

. microplus and

R

. annulatus ticks. Ticks acquire their infections when they feed on infected cattle and can pass the parasites transovarially to their larvae. In the case of B. bovis

, infection is transmitted to the cattle host by the larval stage of the tick, whereas with B. bigemina

, transmission occurs from the nymph or adult tick. Mechanical transmission by biting flies and contaminated fomites can occur; however, this is in cidental and insufficient to maintain the disease in a population without competent tick vectors [26]

.

Incubat ion period The incubation period is approximately 2

- 3 weeks for B. bigemina and slightly longer for

B. bovis

. However, since B. bovis is passed to the host during an earlier phase of the tick’s development than B. bigemina , the prepatent period for the tw o agents is roughly equivalent [26]

.

Clinical signs

Clinical manifestations of bovine b abesiosis vary greatly, depending on host characteristics and the strain of the organism. Cattle of all breeds are susceptible to

b abesiosis, though it is apparent that Bos indicus breeds, such as Brahman, and their

crosses are more resistant to both the Babesia organism and it s tick vectors than European breeds of Bos taurus , such as Hereford or Angus

. Calves rarely show clinical signs of infection; however, in adult cattle, the disease may be severe and mortality in a herd of naïve adult cattle may exceed 50% [26, 29]

.

Initial signs include fever, anorexia, and lethargy; affected cattle may separate from the herd and exhibit arched backs, roughened coats, and dyspnea. A drop in milk production and increased abortion rates are frequen tly noted in affected herds. As the disease progresses, lysis of erythrocytes results in anemia, which is evidenced by pale mucous membranes, hemoglobinemia, and hemoglobinuria. A neurological syndrome known as

cerebral b abesiosis develops in some animal s, characterized by such clinical signs as incoordination, circling, or head pressing, and in terminal stages, convulsions or coma [26, 27]

.16 B abesia bovis is considered the most pathogenic cause of bovine b abesiosis, as it kills more than half the susceptible cattle it infects. In contrast, only a relatively small proportion of B. bigemina cases are fatal, and central nervous system signs are less frequently seen with B. bigemina infections [30]

.

In the absence of exacerbating stress, many animals survive with or without treatment, though recovery from the anemia

- induc ed weakness and loss o f condition is often protracted

. Cattle surviving initial infection with B. bovis or B. bigemina usually remain persistently infected but resistant to clinical disease following re

- exposure to the same

strain

. While parasite levels in the persistently infected animals are often undetectable, ticks may still be capable of acquiring infection from them. Thus, persistently infected, but apparently healthy cattle are potentially important reservoirs for the natural maintenance of the pa rasite [26, 31

- 34]

.

Treatment A number of drugs have been used to treat bovine b abesiosis, but only imidocarb and diminazene are still in common use. In certain countries, such as the United States, the

use of b ab esiacidal drugs is restricted or they may be commercially unavailable. B abesia

bovis , like other small Babesia spp., is more difficult to treat than B. bigemina and may require additional therapeutic rounds. Supportive treatment such as blood transfusion s or anti

- inflammatory medications can be life

- saving for severely affected animals [27, 35]

.

Vaccination Vaccination against Babesia using a live, attenuated strain of the parasi te has been used in several countries, but is not generally used in either the U nited States or Mexico; the

focus in these countries remains on eradication of the tick vector [27]

.

Rhipicephalus microplus and R

. annulatus ticks

Rhipicephalus microplus and R

. annulatus are hard bodied ticks that tend to infest a single animal over their lifetime. Although heavy infestation with either of these two ticks may lead to production losse s and damage to hides, their primary importance is based on their status as the two North American tick vectors responsible for transmitting

bovine b abesiosis and anaplasmosis [8, 9]

.

Life cycle

Both R

. microplus and R

. a nnulatus are one

- host ticks, meaning that all three stages

- larva, nymph, and adult

– reside

, feed , and mate on the same animal throughout their

lifetime. The life cycle is completed when an adult female tick drops off the host to lay

thousand s of eggs i n the environment and then dies. The eggs hatch in the environment and larvae crawl up grass or other vegetation to attach to a new host. The larvae are usually found on the soft skin along the brisket or inside the flanks, thighs, or forelegs.

An immat ure tick molts twice after feeding, developing from larva into nymph and finally into the mature, adult stage. Each stage feeds only once over a period of several days. The entire life cycle of the tick is completed within 3

- 4 weeks once attached to a17 ho st; however, the ticks can live for up to 6 months in the environment while waiting to

find a host [8, 9]

.

Naïve ticks acquire Babesia organisms during feeding on infected animals. The infection is then passed within the o varies of a mature female tick to her eggs. The percentage of infected larvae produced by an infected female varies from 0% to greater than 50% and is dependent primarily on the level of parasitemia of the host animal [33]

.

Both temperature and relative humidity are key factors gove rning tick survival and establishment of viable populations of ticks. It has been shown that climatologic factors, including soil temperatures above 25°C or below 17°C and arid conditions reduces the viability of eggs and can break the transmission cycle of the tick. Air temperature also has an effect on the passage and development of Babesia parasites in the egg and larval stages of the host tick; development of the parasites within R

. microplus and R

. annulatus appears to be inhibited at temperatures be low 20 o C [36

- 41]

.

Hosts Although R . annulatus prefers cattle hosts, the tick can occasionally be found on other hoofed animals, such as horses and deer, and rarely on goats and sheep. Rhipicephalus microplus is f ound on a wider range of hosts, infesting cattle, buffalo, and deer, and infrequently, horses, donkeys, sheep, goats, and camelids [8, 9]

.

Geographic range Rhipicephalus microplus , considered the most important parasite of livestock in the world, has been introduced from Asia to tropical and subtropical regions of Africa, Australia, Central and South America, Mexico, and the Caribbean. The range of R

. annulatus is also widespread throughout the warmer regions of the world; o riginally from the Middle East and Mediterranean regions, the tick was probably imported with livestock from Spain during t he early colonization of Mexico

. Following outbreaks of

Babesia bovis that resulted in devastating economic losses to the U.S. cattl e ind ustry, both tick species were eradicated from the continental United States between 1906 and

1943 . Today, a permanent quarantine zone remains along the border between Texas and Mexico, extending from Brownsville to Del Rio, to prevent reintroduction of the disease

vectors into the United States. Both tick vectors remain prevalent in parts of Mexico [42

- 45]

.

Extensive portions of Mexico as well as the southeastern U nited States have climates that

could support the life cycle of Rhipicephalus spp. ticks infected with Babesia spp organisms. In Mexico, areas with suitable habitat include Veracruz, Tabasco, Chiapas, Quintana Roo, and the Yucatan Peninsula. Areas that are not conducive to tick survival and propagat ion include Baja California, Sonora, and a large patch in the central region

of Mexico . Development of the tick and the parasite are inhibited by environmental temperatures less than 20 o C . In the U.S., mean annual temperatures below 20 o C appear north of latitude 36° N, which crosses the country near the northern border of Texa s; thus, regions of the U.S. located below latitude 36 o N are more likely to have favorable environments to support establishment of populations of Rhipicephalus ( = Boophilus) spp. tic ks carrying Babesia spp. parasites [37, 39, 40, 46, 47]

.18 Control Measures Treatment of cattle with pesticides by spray, dip ping vat , or pour

- on methods, lies at the center of most tick control and eradication campa igns, both for tick elimination as well as prevention of infestation. Control of Rhipicephalus spp. ticks in the continental United States, where these ticks have been eradicated from all states except the quarantine zone at the southern boundary of Texas , focuses on surveillance, movement controls, and tick treatments. Epidemiologic investigations are also conducted to trace sources of infection into an area and to evaluate for potential exposure to other herds. In areas where these

ticks are found to e xist, multiple control methods may be employed, including pesticide treatment, pasture rotation, environmental modification, and other integrated biologic and chemical control strategies [45, 48]

.

Resistance issu es All currently used pesticides for tick control, or acaricides, can be grouped in three main chemical classes: organophosphates, synthetic pyrethroids, and amidines. Over the last decade, Rhipicephalus spp. ticks in North America have been found to be re sistant to the all three classes of acaricides used for control and eradication purposes. In Mexico, resistance to organophosphate acaricides first developed in the 1980s, and resistance to pyrethroids was subsequently discovered in the 19 90s

. Amitraz, a n amidine acaricide, was introduced to control organophosphate

- resistant ticks in Mexico in 1996; however,

the first case of amitraz resistance from Mexico was confirmed in 2001 in R

. microplus in

the S tate of Ta basco . Acaricide resistance is now widespre ad throughout Mexico; cattle

fever ticks resistant to one or more classes of chemicals have been foun d in at least 15

Mexican states

. Results from a 2007 survey conducted in Mexico revealed that less than 10% of ticks surveyed were susceptible to all thre e acaricides while approximately 40%

were resistant to all three

. Chemical resistance in Rhipicephalus spp. ticks has not been reported in Sonora [49

- 52]

.19 

## Release Assessment

A release assessment describes the biological pathway(s) necessary for an importation activity to introduce pathogenic agents of animal health into a particular environment and estimates the probability of that introduction [25] . This release assessment addresses the 11 factors described under 9 CFR 92.2 for the evaluation of foreign animal disease status.

APHIS evaluated the curr ent status of Sonora , Mexico with regard to Rhipicephalus spp. ticks to decide whether it can recognize Sonora as free of Rhipicephalus spp. ticks.

Those factors are:

1. The authority, organization, and infrastructure of the veterinary services organization in the region.

2. Disease status.

3. The status of adjacent regions with respect to the agent.

4. The extent of an active disease control program, if any, if the agent is known to exist in the region.

5. The vaccination status of the region.

6. The degree to which the r egion is separated from adjacent regions of higher risk through physical or other barriers.

7. The extent to which movement of animals and animal products is controlled from regions of higher risk, and the level of biosecurity regarding such

movements.
8. Livest ock demographics and marketing practices in the region.

9. The type and extent of disease surveillance in the region.

10. Diagnostic laboratory capacity.

11. Policies and infrastructure for animal disease control in the region, i.e., emergency response capacity.

1

. Authority, organization, and infrastructure of the veterinary services

Sonora’s Rhipicephalus spp. tick monitoring and control program is based on a n integrated system o f organizations and laws that regulate the movement of livestock into,

out of and w ithin Sonora. It re quires tick inspection and treatment of livestock (including cattle, horses, sheep and goats) at strategically placed inspection stations located throughout Sonora

. Livestock enter ing Sonora from the neighboring Mexican S tates of

Chihu ahua and Sinaloa are required to be inspected for ticks and treated with an acaricidal solution by official inspectors , as are those that are moved within or out of

Sonora’s tick buffer zone. ( Livestock transiting Sonora from Baja California are exempted from dipping and will be discussed later.) The buffer zone is comprised of portions of Álamos, Navojoa, H uatabampo and Etchojoa municipalities, and is located along Sonora ’s south ern border (see figure 5 )

. This area is co nsidered to be a t relatively high risk for Rhipicephalus tick incursion s based on its proximity to areas that are currently infested with these ticks [53]

.20 Figure 5 . Tick buffer zone in southern Sonora (green shaded area)

Source: [54]

Legal Authority The legal framework for Sonora’s Rhipicephalus tick surveillance, monitoring, and

eradication activities are formed by different layers of overlapping legislation.

Mexico’s Federal Law on Animal Health ( Ley Federal de Salud Animal ) outlines the authorities of the Federal government in the implementation, enforcement and monitoring of animal health programs throughout Mexico, including the National Tick Eradication Campaign. It provides a regulatory fra mework for the use of measures to protect animal health, including animal health certificates, movement restrictions, and inspection procedures at international and domestic inspection points. It also provides the

authorization for the administration of t ick dipping and inspection stations [55]

.

Federal Laws provide the framework for regulations contained in the Normas Oficiales

Mexicanas (NOMs). NOMs are analogous to the regulations within the U.S. Code of Federal Regulations. All regulatory actions are publically available and published in the Federal Official Newspaper or Diario Oficial de la Federacion

.

NOMs created from the Federal Law on Animal Health stipulate the rules and procedures for federal animal health programs. The primary Federal regulation governing the

National Tick Eradicatio n Campaign is NOM

- 019

- ZOO

- 1994 (National Campaign against the Tick or Campaňa Nacional contra la Garrapata Boophilus spp .) . NOM

- 019

- ZOO

- 1994 outlines specific p rovisions related to the Rhipicephalus tick control and eradication program in Mexico . One of its general provisions is the institution of21 movement restrictions in order to protect the tick

- free status of States or regions. It also includes specific information on the measures to be employed at different stages of the tick eradication program, acc eptable diagnostic tests for ticks and tick

- borne diseases, the appropriate administration of acaricide treatments, general acaracide management principles for both dipping vats and spray equipment, appropriate quarantine measures in

the event of an incurs ion, cleaning and disinfection requirements for vehicles transporting infested livestock, and movement requirements for livestock moving between zones with

different tick status [24, 56, 57]

.

Several o ther NOMs are indirectly involved in t he control of ticks, providing guidance and regulations for the movement of livestock and their pro ducts, quarantine procedures, animal health inspection points, epidemiological surveillance, and acaricidal efficacy testing, among other things

.

State regulations governing tick

- related activities include Sonora ’s Livestock Law ( Ley de Ganaderia para el Estado de Sonora ) , which spells out requirements for the importation of livestock into Sonora as well as information on the assignment, organi zation, and duties of livestock inspectors

, movement requirements and penalties for

noncom pliance. It also provides specific guidance on the application of quarantine s an d

notification in the event of Rhipicephalus tick incursions and lays out the penalti es for

non

- compliance . In ad dition, Sonora also maintains an operati onal manual that provides detailed guidance on tick inspection and treatment procedures, recordkeeping requirements, documentation review, sample collection

, and acaricidal soluti on

manag ement [20, 58]

.

There are also phytosanitary (plant health) requirements and standards that regulate the importation of cro p products that may contain Rhipicephalus spp. ticks, including a lfalfa,

o ats, b arley, c orn, h ay, s orghum, w heat

, and g rass into tick

- free areas [56]

.

Federal Animal Hea lth Authorities

The Ministry of Agriculture, Livestock, Rural Development, Fishing, and Food ( Se cretaría de Agricultura, Ganadería, Desarrollo Rural, Pesca, y Alimentación , or SAGARPA ) is Mexico’s F ederal agency responsible for oversight and regulation of agricultur e , including animal health programs such as the National Tick Eradication Program

. SAGARPA is the counterpart to the United S tates Department of Agriculture

.

Within SAGARPA, the National Service of Food He a lth, Safety

, and Quality ( Servicio

Nac ional de Sanidad, Inocuidad y Calidad Agroalimentaria , or SENASICA ) is responsib le for the oversight of animal and food health and safety issues

. SENASICA is the equivalent of USDA’s Animal and Plant He alth Inspection Service (APHIS) and is responsible fo r coordinating the implementation and oversight of the Federal Law on

Animal Health and its NOMs at the Federal and State levels.

Within SENASICA, there are three agencies involved with animal health issues: the

Directorate of Animal Health ( Dirección Gen eral de Salud Animal , or DGSA), the Animal and Plant Health Inspection Service General Directorate ( Dirección General de22 Inspeccion Fitozoosanitaria

, or DGIF )

, and the Agrofood Safety and Quality Control General Directorate ( Dirección General de Inocuidad y Calidad Agroalimentaria

, or DGICA ) [59]

.

The DGSA oversees the animal health campaigns (c ampañas zoosanitarias ) including

control and eradication measures for Rhipicephalus spp. ticks. The Chief Veterinary

Officer of Mexico heads the DGSA and overseas several animal health di visions that provide support for the activities for the prevention and eradication of ticks in livestock, including the Directorate of Epidemiological Surveillance ( Dirección de Vigilancia Epidemiológica

, or DIVE ), the Directorate of Animal Health Campaign s ( Dirección de Campañans Zoosanitarias ), and the Directorate of Import, Export, and Livestock Services and Certification ( Dirección de Importación, Exportación, Servicios y Certificación Pecuaria ). Additionally, the animal health activities of DGSA are

su pported by the Mexico

- USA Commission for the Prevention of Foot

- and

- mouth Disease and other Foreign Animal Diseases ( Comision Mexico

- Estados Unidos para la prevención y control de la fiebre aftosa y otras enfermadades exoticas

, or CPA ) and two

national ref erence laboratories, the National Center for Diagnostic Services in Animal Health ( Centro Nacional de Servicios de Diagnóstico en Salud Animal

, or CENASA ) and the National Animal Health Verification Services Center ( Centro Nacional de Servicio de

Constatac ión en Salud Animal

, or CENAPA ). CENAPA serves as the official national reference laboratory for both tick identification and acaricide evaluation [59, 60]

.

State Animal Health Authorities Animal health programs in Sonora , including tick programs, are conducted under an

interwoven network of authorities and resources. Each State c ontains a Federal SAGARPA delegate and other Federal personnel under the delegate who are responsible for certain animal health programs. Examples of activities under the authority of both

SAGARPA and State officials includ e quarantine and movement restri ction

, accreditation of professionals to perform official program activities

, implementation and enforcement

of reporting requirements for specific diseases

, establishment of an emergency animal disease response network

, provision of diagnostic services

, i ncluding reference service s and confirmatory diagnosis

, and depopulation of affected and exposed animals [54]

.

The State of Sonora’s animal health authority rests with in its Ministry of Agriculture, Livestock, Water Resourc es, Fisheries and Aquaculture ( Secretaria de A gricultura

G anaderia R ecursos H idraulicos P esca y A quaculture , or SAGARHPA) . Within SAGARHPA, the Director General of Livestock Services ( Dirección General de

Servicios Ganaderios , or DGSG) oversees livestock programs, including inspection, registration, quarantine stations, and animal health issues [60, 61]

.

Local Animal Health Authorities

The livestock zone is the basic operati onal unit for control of livestock movement and

health in Sonora . Sonora is comprised of 72 municipalities which are in turn divided up

into 482 livestock zones in all (see Figure 6 for a map of Sonoran municipalities) [20]

.

Figure 6 . Map of Sonora’s municipalities

.23 Source: [62]

E ach livestock zone is under the authority of a livestock inspector, who has primary responsib ility for official livestock activities within his or her zone. There is also a

ba ckup livestock inspector for each zone. The activities and authority of the livestock inspectors are provided i n Sonora’s Livestock Law

. Livestock inspectors are private

individuals who reside in the l ivestock z one for which they are responsible

. They a re appointed by the DGSG based on a nominat ion from the Local Cattlemen’s Association

, and are paid from user fees collected by the A ssociation for movement, slaughter

, and export of cattle . The position of livestock inspector is one of honor in the commu nity,

and nominations are based on the inspector’s knowledge of livestock, knowledge of their

zone, and their moral character within the community . The inspector must have at least a secondary education and lived in the community for at least two years

. There are 486 livestock inspectors in Sonora, 64 of which are located in the buffer zone [20, 58]

.

Livestock inspectors are responsible for many animal health activities, including issuing

and cancelling transit guide s for all livestock producers within their zone

. Livestock inspectors also maintain and enforc e quarantines when necessary . If Rhipicephalus spp. ticks are dete cted in a herd

, a quarantine of the originating premises will be authorized by either State or Federal sanitary authorities and overseen by the livestock inspectors.24 Additionally, livestock inspectors are responsible for conducting the annual inventory of

all livestock , delivering identification tags, and counseling producers on livestock program issues for all premises in their zone. They are ultimately responsible for identifying and regulating the movement of all livestock within their assigned livesto ck

zone [20, 54, 63]

.

Oversight of livestock inspectors is provided by 10 regional supervisors , each of whom

oversees 40

- 45 livestock inspectors. As with the livestock inspectors, the supervisors are

also appointed by the SFG, but un like the livestock inspectors , the supervisors are paid by

the State of Sonora

. The regional supervisor is responsible for providing training, supervision, and guidance for livestock inspectors within their area, and also review ing and following up on mov ement documents , inventory reports, and quarantine documents issued by the inspectors to make sure that the documents are complete and that appropriate actions were taken . The supervisors communicate with officials in the

DGSG , providing a month ly report of all livestock activities with in their jurisdiction [20, 54, 60]

.

In addition to the livestock inspectors and the ir supervisors, Sonora also directly employs approximately 50 inspectors at 12 Centers of Livestock Inspection for High Movement ( C entros de I nspección de G anado en L ugares de A lta M ovilización or CIGAMs). These high movement centers are located around ar eas near border crossings and corrals for livestock assembly and/or export. The inspectors at these centers primarily issue and

cancel movement documents (i.e. transit guides) for livestock moving in and out of their

affiliated facilities . In doing so, t hey verify that all documentation is present and appropriate to the intended movement, that seals are intact, and identification numbers

and brands of the animals match th ose listed in the documentation. They also provide a brief health inspection (visual ), and check that animals intended for export have received the proper tests and are appropriately tagged . They also confirm that a nimals originating from the southern part of the state are accompanied by tick dipping certificates

. If
necessary, t hey may serve as backup inspectors for livestock inspectors in their livestock

zone [54]

.

Livestock Industry Partnerships Private cattlemen’s groups have been instrumental in eradication and continual exclusion

of Rhipicephalus spp . ticks from Sonora. The Regional C attlemen’s Union of Sonora ( La Unión Ganadera Regional de Sonora , or UGRS) is composed of 83 local cattlemen’s associations ( Asociaciones Gan a deras Locales , or AGLs) , and includes 35,000 active members representing appro ximately 95% of cattle producers in Sonora. This group spearhead ed the eradication campaign and organized the first request to recognize Sonora

as tick

- free to SAGARPA, with the ultimate goal of being recognized by the U.S.
government as tick

- free, and to potentially eliminat e the tick dipping requirement for

Sonoran cattle exported to the United States [20]

.

The AGLs provide oversight of tick dipping procedures at the line dipping vats, in the

buffer zone (the line dip ping vats consist of a string of strategically placed dip ping vats within the buffer zone) . The presidents of the AGLs from the three municipalities that25 make up the buffer zone are the leaders of the Dip ping V at Operative Subcommittee (the Committee). The Committee operates under a joint agreement between the UGRS, SAGARPA, the State of Sono ra, and the AGLs of the three municipalities that make up the majority of the buffer zone. The Committee provides operating guidelines and general oversight of the tick program, while the AGLs are responsible for ensuring that dipping and inspection proce dures conducted in the buffer zone are adequate. SAGARPA provides the technical standards, operating personnel for programs, monitoring and inspection, financial and physical resources. The State of Sonora provides training, personnel, and performs movem ent control activities, as well as contributing financial and physical resources. The UGRS provides the remaining funding as well as dissemination of information and promotion of activities to be employed by producers in order to comply with all measures. And the AGLs agree to make their cattle and land available for treatment and inspection, and also promote and disseminate information about the program [20, 54]

.

The State of Sinaloa also works with Sonoran officials and AGLs from both States in order to conduct control activities in premises near or on the borde r between Sinaloa and

Sonora [54]

.

Similarly

, members of AGLs from livestock zone s border ing the State of Chihuahua also cooperate with the Sonora officials in the maintenance and staffing of the zoosanitary cord, which hel ps to ensure the inspection of every animal that cross es the border into

Sonora from Chihuahua

. Th e zoosanitary cord consists of a number of inspection

stations along the border with Chihuah u a . E ach is owned and maintained by the AGLs of

the municipalit y in which the facility is located

. T echnical guidance and oversight of the facilities is provided by S tate officials while on

- site operations are managed by the livestock inspectors for each respective livestock zone [20]

.

The AGLs also wor k with State and Federal sanitary authorities on other disease eradication efforts, such as tuberculosis and brucellosis [20]

.

Discussion

The overlapping system of laws and agencies used by Sonora to maintain programs and

staff for identific ation , movement control, and tick surveillance, inspection, and

treatment, provides significant assurance that these activities are carried out effectively by personnel.

The movement control system, in combination with identification requirements, tick inspections, and check stations, appears to be very effective at tracking movement of livestock and assuring that appropriate treatments and inspections are provided.

Sonora has the legal authority to enforce both Federal and State Rhipicephalus tick

er adication regulations, and the personnel and in frastructure necessary to carry out
livestock movement control activities. S ite v isit t eam s were impressed with the overall knowledge and professionalism of the staff and field personnel , in particular those at the dipping and quarantine stations

. In addition, compliance with identification, inventory,26 inspection, treatment, and movement requirements by livestock producers in Sonora appears very high. T he active participation of the Local and State Cattlemen ’s Associations with government animal health p rograms appears to work well in maintaining Sonora’s tick

- free status.

2. Rhipicephalus t ick status of the region

The State of Sonora was declared free from Rhipicephalus spp

. ticks by the Mexican

governme nt on November 27, 1972, via a decree published in the Federation Official Diary [20]

.

Historically, the nor thern region of Sonora has not been subject to infestation with Rhipicephalus spp. ticks due to its warm , dry climate and high altitude

. However, th e se ticks were present in the southern portion of Sonora, which has a climate that is more amenable to Rhipicephalus and other tick species. In an effort to eradicat e these ticks

from the entire State of Sonora , hopefully leading to fewer ex port restrictions

, cattlemen

from the southern region of the State combined their efforts for the first time , forming the

Local Cattlemen ’s Association , or AGL , in 1932. A private c ommittee was formed specifically to coordinate all activities necessary to officially eradicate Rhipicephalus

t icks, which i nclud ed requesting regulatory and technical support from State and Federal

authorities in addition to providing personnel, money and motivation [20]

.

In itially , a sanitary line was established, divid ing the State in to two regions : clean (northern) and infested (southern). S trict movement controls between the two regions

were imposed by the DGSA of SAGARPA, specifically a requirement that all livestock moving north from infected to clean region s receive a tick inspection and treatment. Tick dipping stations were placed at strategic locations along the sanitary line so that

cattlemen with small operations could reach them on a regular basis in order to treat their

cattle before moving them across the line (big ranches often ha d their own dip ping bath

facilities at that time ) . B athing schedules and protocol s for the use of acari cidal products

were established

, quarantine stations (which included tick dipping facilities) were created

on the access highways leading into the State, and additional tick inspection and dipping stations were put in place along s maller roads leading into and across the State [20]

.

The campaign gradually advanced from north to south, increasing the area include d in the

tick

- free zone under the direction of the DGSA until 1972, at which point the entire State

of Sonora was formally declared free of Rhipicephalus spp. t icks (with the recognition of the existence of a buffer zone adjacent to non

- tick

- free regions i n northern Sinaloa and

southwestern Chihuahua, which is equivalent to the U.S. permanent quarantine zone for ticks in South Texas)

. By 1972, n o ticks had been found in Sonora for 10 years prior

. At this point the authority and responsibility for maintena nce of the tick

- free status was passed from SAGARPA to Sonora [20]

.

In order to verify freedom from Rhipicephalus spp. ticks , the Mexican government require d surveillance over a period of a year and a half

, starting at the beginning of summer and extending through the end of the following summer. Surveillan ce activities27 consisted of on

- farm inspections by official personnel every 14

- 21 days on every

livestock premises in the proposed free

- zone

. The detection of any ticks during th e surveillance period would mean treatment of all livestock in the proposed ar ea , and restarting the surveillance clock. N o ticks were found during the surveillance period for Sonora; therefore, at the conclusion of the surveilla nce , a notice w as published for

comment in the Federation Official Diary , and the area was declared free of Rhipicephalus spp. t icks [24]

.

Tick incursions into the buffer zone since 1972

S ince eradication was declared in 1972

, there have been instances of Rhipicephalus spp.

re

- infestations in Sonora , all entirely contained wi th in the buffer zone
, and specifically along the border with Sinaloa

. Since the incursion s were located entirely within the

buffer zone

, Sonora was not required to restart the treatment and surveillance cycle for

the entire State

. T he affected premises p lus neighboring premises we re placed under quarantine for a year and a half (two summers with a winter season in between) during which time they under went surveillance as described above. Additionally, any farms containing livestock that had moved into or out of infested farms (i.e. epidemiologically linked farms) were evaluated for the presence of ticks. If the epidemiologically linked

farms we re not found to be infested they were released from quarantine without having to

und ergo prolonged surveillance measures [20, 63]

.

Two of the tick incursions into Sonora occurred in the 1990s ( 1993 and 1998). These incursions were brought under control and eradicated in accordance with procedures

established in the NOM

- 019

- ZOO

- 1994 , incl uding treatment of all livestock on the

affected properties and inspection of livestock on neighboring and epidemiologically linked properties, followed by an extended period of surveillance as described above

. Following the successful completion of the s urveillance period, which was conducted

under the su pervision of the DGSA , the State of Sonora regained its tick

- free status [20]

.

O n January 13, 2006

, the local livestock inspector detected an infestation of Rhipicephalus microplus on fou r out of 48 cattle while inspect ing a herd located in the Huatabampo municipality , within the buffer zone

. Subsequent investigation identified the spread of the ticks to five additional farms , all within the buffer zone

. This incident precipitated an eme rgency response involving quaranti ne and investigation of epidemiologically linked farms

. S urveillance activities were co nducted on all premises for the required time period with no additional ticks found , and all quarantines were subsequently lifted

. Th is infestation uncovered a deficiency in Sonora’s livestock

movement system . It was determined that the infestation was allowed to spread to epidemiologically linked premises because there had been no requirement for livestock moving exclusively within th e buffer zone to be inspected and dipped for ticks prior to

movement

. Subsequent actions, including a new r equirement for tick inspection and the

use of transit guide s (movement control documents) for livestock movement within the buffer zone, even if the animals w ere not enter ing the tick

- free portion of Sonora, were implemented as a result of the finding a nd remain in place today. Additional training in emergency response and investigation, and enhancement of surveillance activities in the

buffer zone w ere also enacted in response to the outbreak [63, 64]

.28 Rhipicephalus mic r oplus ticks were again detected in the buffer zone in October 2008 in

80 head of cattle on a farm in the Alamos municipality. The incursion was d etermined to

be the result of movement of cattle onto the farm from a neighboring premises in the El Fuerte municipality of Sinaloa

. The affected premises and adjacent premises we re place d under quarantine and all animals dipped with coumaphos 4 and injected with ivermectin 5

. Movement controls were established and regular inspections during the mandated quarantine period of one and one half years . No additional ticks were detected during this time, and the quarantine was subsequently lifted [54, 65]

.

Routine surveillance activities conducted throughout Sonora during 2009 identified four

new farms with Rhipicephalus microplus infestation. Of 347 premises inspected in the

buffer zone during the 2009 systematic state

- wide surveillance activities

, Rhipicephalus microplus ticks were collected at four different premises , all located in the Alamos municipality, and all at or near the border with Sinaloa. Rhipicephalus microplu s ticks

were found on one animal out of 600 inspected on one farm on June 26, 2009; on three animals out of 475 on Dec. 2, 2009; on two animals out of 1,200 on Oct. 1, 2009; and on six animals out of 260 on Dec. 18, 2009.

Livestock located on affected p remises receive d an injection of ivermectin that is labelled as effective against Rhipicephalus ticks every 60 days. The first summer and winter inspections were conducted as part of the official surveillance activities by the Animal

Health Campaign and E pidemiologic Surveillance Office of the DGSA , the DGSG of

SAGARHPA , and the TB and Brucellosis Campaign Committee . N o Rhipicephalus spp. ticks were found on any anima ls on the affected or adjacent farms ( adjacent farms consist

of 14 premises with 5,358 ca ttle total)

.

Discussion The operational measures used to maintain the Rhipicephalus free status of Sonora have

been largely successful, as can be seen by the maintenance of this status over most of the

State since 1972. When incursions have occurred wit hin the buffer zone, they appear to

have been identified prior to significant spread (with the exception of the 2006 outbreak,

which led to identification and correction of deficiencies in Sonora’s tick control operations) . In addition, control efforts, i ncluding movement controls (both general controls and enhanced controls aimed at quarantined premises) and repeated inspection

and treatment for ticks on affected and associated premises, have been successful in preventing infestations from occurring outsi de of the buffer zone despite repeated incursions, which is similar to the situation in the U.S. permanent tick quarantine zone

.

3

. Rhipicephalus tick status of adjacent regions

4 Coumaphos is an organophosphate pesticide that is used in the control of ticks. Commercial formula tions of coumaphos include Asuntol®, a product of Bayer Animal Health.

5 Ivermectin is a broad spectrum antiparasitic agent that is available in many different formulations and is used in the control of ticks and other parasites.29 The western border of Sonora consists of the Gulf of California, while the northern edge

is bordered by two U.S. States ( Arizona and New Mexic o )

, and the small northwestern tip adjoins Baja California

. To the east is the State of Chihuahua and along the narrow

southern border lies the State of Sinaloa (see figure 7 ).

Figure 7

. Map of Sonora and surrounding areas

.

Source: http://www.map

- of

- mexico.co.uk/images/sonoraenglish.gif

The U

. S

. State s of Arizona and New Mexico are considered free of Rhipicephalu s spp. ticks.

Two of the three Mexican States surrounding Sonora are considered completely or partially free of Rhipicephalus spp. ticks by SAGARPA , although none have been officially declared free by APHIS to date

. Baja California was declared free of Rhipicephalus spp. ticks by the Mexican government in October 2007 [66]

. SAGARPA

considers t he majority of Chihuahua to be free of these ticks , with two municipalities currently undergoing eradication and f our still considered infested . The fou r non

- tick

free areas are located in south western Chihuahua, along its border with Sinaloa [21, 67]

. Although n either Baja California nor Chihuahua is currently considered free of Rhipicephalus spp. ticks by APHIS , Baja California is currently under evaluation by

APHIS regarding its tick status , and SAGARPA has requested a tick review of Chihuahua by APHIS [10, 23]

.30 The m ajority of Sinaloa is currently considered by SAGARPA to be infested with Rhipicephalus ticks . Sinaloa n officials are currently working with S AGARPA as well as

Sonoran officials and local AGLs (in both Sonora and Sinaloa) in a campaign to establish

a tick

- free zone in Sinaloa’s northern region, consisting of the municipalities of Ahome, Choix, and E l Fuerte and extending from the border between Sinaloa and Sonora to the El Fuerte River ( see Figure 8 ). This area is currently considered to be in the Eradica tion phase of Mexico’s National Campaign against Boophilus spp. ticks. S urveillance and inspection activities are underway with movement restrictions similar to those in place in

Sonora’s buffer zone

. The intent is for surveillance activities to be succe ssfully completed and the zone declared Free in 2012 [68, 69]

.

Figure 8 . Proposed Rhipicephalus tick

- free zone in northern Sinaloa (northern border of

Sinaloa to the blue line , which represents the El Fuerte River)

.

Source: [68]

Discussion

The desert habitat throughout most of Sonora and northern Mexican States is inhospitable

to the survival and maintenance of Rhipicephalus spp. ticks, limiting their potential for

infe station and subsequent distribution in these areas

.

The area of Sonora at greatest risk for tick incursions is along its southern boundary,

which adjoin s the State of Sinaloa , much of which is infested with Rhipicephalus spp. ticks. A dditional protecti ve measures implemented along the southern region of Sonora (i.e., within the buffer zone), such as tick inspection and dipping requirements prior to

movement

, supplemen tal tick surveillance of livestock, and routine administration of tick

treatments on hi gh risk premises adjoining the border with Sinaloa, appear to have

limit ed the spread of Rhipicephalus spp. ticks within this region and prevented expansion

of outbreaks out of the buffer zone . However, recent detections of infested cattle close to

the Si naloan border indicate that the risk of infestation persists along this border. The31 a chievement of tick

- free status of the northern portion of Sinaloa, if it occurs, could mitigate this risk.

4. Extent of active tick control program

The State of Sono ra, in combination with SAGARPA and the Cattlemen’s Union, conducts many different activities which, even if not specifically developed for the purpose of detecting, controlling, and preventing the introduction of ticks, serve the tick control program in s ome capacity

.

Livestock inspection and dipping stations The cornerstone of Sonora’s tick program is the network of official tick inspection and dipping stations located throughout the State. Sonora employs the use of a number of different types of stat ions at targeted locations, each of which meets different needs with respect to movement controls and tick inspection and dipping (see Section 7 for additional information)

.

The type and location of the various inspection and dipping stations are repres ented in

F igure 8 , below. They include the seven Estaciones Cuarentenarias , or quarantine stations, which contain livestock corrals and facilities for scratch inspection and tick treatment (including dipping vats) for livestock. Three of the quarantine s tations are located at Sonora’s borders and are used to inspect and treat incoming livestock while four are located internally and are used to inspect and treat livestock moving within

Sonora. The baňos de linea, or line dipping vats , which consist of seven additional inspection and dipping stations located in Sonora’s buffer zone, provide additional inspection and treatment facilities for livestock that are transiting or moving out of the

buffer z one. The cordon zoosanitario , or zoosanitary cord, is made up of smaller livestock inspection stations located along the mountainous border with Chihuahua; the Centros de inspection are large livestock inspection stations located throughout the State;

th e casetas are large agricultural inspection stations that handle both plant and animal inspections; the localidads are smaller agricultural inspection stations that may or may not provide livestock inspection but will inspect their documentation; and the p untos are truck inspection points that inspect paperwork [20, 60]

.

Figure 9. Agricultural Inspection Stations, Sonora, Mexico

.32 Source: [63]

The primary barriers to the entry of tick

- infested livestock into Sonora are the quarantine stations, particularly those located along Sonora’s border. The three major quarantine stations located along the main routes of entry from surrounding Mexican States are: Puerto San Luis, at the northern entry road from Chihuah ua into Sonora; Maycoba, along the central access road from Chihuahua; and Estaci ó n Don, at the point of entry from Sinaloa to Sonora. One additional point of entry, San Luis Rio Colorado, is located along the narrow juncture between Baja California and S onora; however, this station only includes a documentation check and only allows entry of livestock that are transiting

Sonora.

These stations provide assurance that all livestock entering the State are evaluated for

ticks and other animal health condit ions. The first step is a review of the accompanying documentation for completeness and accuracy with respect to the number, type, and identification of animals in the shipment and verification that the numbers on any official

vehicle seals match those on the documentation. Inspectors also verify that required health documents are present according to the animal health status of the region of origin33 of the livestock. Livestock also receive a scratch inspection for ticks, and treatment for ticks, usually in the form of dipping in an acaricidal solution. If any ticks are found on any of the incoming animals, the entire lot is either returned to its place of origin or quarantined at the inspection facility and re

- inspected and re

- treated for ticks until the lot

has been found free of ticks [20, 54]

.

There are four additional quarantine stations located within Sonora along major roads within the State. All livestock entering Sonora (with the exception of Baja California) or moving from higher tick risk areas within Sonora are required to stop at one of the quarantin e stations for documentation verification, scratch inspection

, and treatment as

described above [20, 70]

.

The line dipping vats provide additional opportunities for tick inspection and dipping for

l ivestock transiting or moving out of the buffer zone (in line with movement requirements for livestock originating from or transiting this area) [20, 60]

.

The other types of inspection stations are overseen by State, Federal, or local authorities

and perform documentation checks on shipments of livestock moving within Sonora. These stations are located througho ut Sonora. The inspectors at all of the stations listed, even those that are not intended to provide livestock inspection, evaluate the documentation of all livestock shipments in order to verify that they are accompanied by the appropriate paperwork, inc luding documents verifying current tick inspections and treatment when required by Federal and State regulations [20, 60]

.

Operations and facilities at the quarantine stations and line dipping vats will be discussed in greater detail below in section 7.

Tick surveillance Sonora also has a robust surveillance network that has been shown to provide rapid

identifi cation of ticks found on livestock within the State ( which has only occurred within

the buffer zone to date ). The inspection and dipping stations located throughout Sonora are part of this network, in that official inspections are provided routinely to an imals engaged in movement throughout Sonora. The system of movement checks and penalties makes it very difficult for livestock producers to evade these inspection points

.

In addition, enhanced surveillance activities are conducted by State officials in S onora’s buffer zone, due to the increased risk of ticks or infested livestock moving from the tick

eradication area in Sinaloa and southwestern Chihuahua into Sonora. Measures employed here include campaigns conducted in the high risk area of the buffer z one (i.e., premises located along the border with Sinaloa), which involve inspection and treatment

of livestock in these areas every 4

- 6 months . Portable chutes are brought onto the properties if necessary in order to conduct scratch inspection s and treat ment s of all livestock on the properties (either spray treatment with acaricide or ivermectin inject ion

for cattle that will be going to pasture for several months and won’t be accessible ) . The brigades operate in addition to the regular livestock inspect ors located in the buffer zone,34 consisting of 3 teams of 2 individuals each. They also work with personnel from the government of Sinaloa when working areas on the border between the tw o States [54]

.

Sonoran officials als o collect ticks as part of a National tick survey orchestrated by SAGARPA. The survey is designed to detect ticks if present in 1% of the cattle herds in

Sonora with a confidence of 9 9 % (within herd confidence is 9 5 % confidence of detection at 10% prevale nce). This study is conducted across Mexico to determine the national prevalence data for tick infestations. This sampling was instrumental in identif ying the four infested premises in the buffer zone during the 2009 cycle. The 2010 tick survey

, which t ested over 14,000 head of cattle on 481 premises throughout Sonora, and the 2011 survey, which has tested 151 premises as of September 2011, have not detected any Rhipicephalus spp. ticks in any area of Sonora [62, 71]

. Addi tional information is provided in section 9

, below.

Tick control measures When ticks are identified on Sonoran livestock

, measures are immediately taken to identify the ticks, determine their resistance profile, provide treatment and inspection of

the ani mals until the ti cks have been eliminated, destroy any contact materials, such as food and bedding, and restrict movement of the animals until the infestation has been

cleared. When ticks are identified in animals that originate from Sonora, whether at an inspection station or on the farm during surveillance activities, the entire farm of origin of the animal(s) is immediately placed under quarantine by the local livestock inspector (the quarantine is based on both Federal and State authority) and Sonora a nd SAGARPA

officials are notified . All of the animals on the farm are inspected for ticks . A ny ticks

found are submitted to CENAPA for identification and determination of resistance, and

all livestock on the farm are treated for ticks. Animals are re

- in spected and re

- treated every 60 days until the conclusion of the quarantine period [10, 54]

.

An epidemiologic investigation is also conducted by Sonoran livestock officials at this time. Any farms that have received or sent livestock to any affecte d premises are placed under quarantine until an investigation into their herd or flock can be conducted. If no ticks are found on any of the animals the quarantine is lifted and animals are free to move [54]

.

All animals on premises where ticks have been detected (or livestock with ticks have originated) are maintained under quarantine by the local livestock inspector for an extended surveillance period which must encompass at least one inspection during

successive summers and one inspection during the intervening winter season, for a duration of approximately one a nd one half years (once the infestation has been completely cleared and assuming no additional ticks are found on any of the animals). All premises within 10 km of the affected herd are considered within the perifocal zone and are also placed under movement restrictions. During the quarantine period

, livestock on affected premises are only allowed to leave after first getting a permit from State authorities, and then are subject to an on

- farm inspection; if not ticks are found they are then allowed to go to a designated dipping vat facility for treatment. Livestock on perifocal premises (within 10km of the affected premises) must go immediately to a35 dipping facil ity and receive a dipping certificate before being allowed to move further [54, 65]

.

In addition, all premises within a 10 km radius of the infested farm are investigated and all livestock on these farms are inspected for ticks by the livestock in spector (and backup or supervisory inspector if necessary) . If any ticks are found they are treated as above

and the 10 km radius is expanded to address any additional premises located near the new premises. Animals located within the 10 km radius of inf ested premises are also under limited movement restrictions for the duration of the quarantine of the affected/infested premises. These animals must receive a tick inspection (and treatment) prior to leaving their premises of origin, but once they have re ceived these and no ticks were found, they are free to move without further restriction (other than those they would normally be subjected to) [54, 62]

.

If ticks are found on livestock presented to inspection stations an inve stigation is immediately conducted on the premises of origin as described above if the animals originate from Sonora. If the animals are from another State, that State will be notified as well as SAGARPA and will conduct its own on

- farm investigation [20, 54]

.

In the meantime, the animals present at the inspection station will be treated for ticks, placed under quarantine for 72 hours on

- site (in the in

- take or “dirty” corrals) , re

inspected and, if no ticks are found, treated again and then released to their original

destination. If ticks are found upon re

- inspec tion , then the cycle is repeated until the

animals have been found to be clean of ticks. Different acaricides are used depending on

the number of treatments required and the resistance profile of the ticks once those results

have been received (for exampl e, coumaphos will be used at 400ppm after the second failed inspection and ivermectin may also be used)

. Additionally, any bedding or feed that arrived on the transport vehicle with the load is disinfected and incinerated on

- site

and the vehicle is cleane d and disinfected . Any bedding or feed left over from the quarantine corral where infested livestock were maintained is disinfected and incinerated

in the same manner. The corrals used to house the animals are thoroughly cleaned and

disinfected after the animals’ d eparture [20, 54]

.

All ticks collected by inspecto rs or other livestock officials , regardless of the site of the collection, are submitted to the CENAPA laboratory for identification and resistance

characterization via courier through the regional supervisor (for livestock inspectors) or supervisor (for q uarantine and inspection stations) at the State level. These officials also notify SAGARPA of the submission

. CENAPA reports test results electronically. Samples and information on the date of collection, owner of the animals, location of the premises o r origin, etc. are submitted on controlled forms [20, 54]

.

It is important that a sufficient number of ticks are collected, since approximately 20 engorged females are needed for resistance determination to multiple acaricides . This has been a problem with regard to some tick collection s on livestock presenting at the quarantine stations as few ticks have been found, hampering the ability of CENAPA to

test for resistance . Taxonomic results take approximately 4

- 5 days to return, including36 transport time; however, officials, particularly those at quarantine stations and the ir supervisors, are usually able to provide unofficial identification on

- site . The determination of resistance takes considerably longer, due to the need for ticks to complete certain stages of their life cycle [54]

.

Discussion Sonora’s tick exclusion, detection and control measures have been demonstrably effective. Officials are knowledgeable and effectively track movement of livestock, tying it together with all necessary tick inspection and treatment documentat ion according to the location of the point of origin of the livestock. Detection of incursions appears to be done in a timely manner and control measures, including quarantine, further inspections, investigations, and treatment have been effective

.

The i nterrelated measure described above and throughout this document indicate the active role that Sonora, SAGARPA, and the livestock industry play in preventing, detecting, and controlling tick incursions in Sonora.

5. Vaccination status of the region

Son ora does not currently vaccinate against Babesia organisms nor the ir associated tick

vectors

.

6. Separation from adjacent regions of higher risk

Sonora’s borders include two U.S. States, three Mexican States

, and the Gulf of

California , comprising desert and mountain terrain as well as water

. See Figure 10 for a map of Sonora and surrounding areas.

Figure 10 . Map of Mexican States surrounding Sonora, Me xico

.37 Sour ce: http://www.map

- of

- mexico.org/mexico

- states.gif

Much of the land area surrounding Sonora is considered free of Rhipicephalus spp. ticks, by either Mexico or the U nited States

. Sonora’s northern border, which adjoins the U.S.

States of Arizona and New Mexico, is relatively flat and free of geographic barriers. It consists mostly of desert terrain and is not conducive to the survival and propagation of Rhipicephalus spp. ticks. Additionally, both U.S. States are free of these ticks

.

Baja California shares a small land border with Sonora’s north western tip . The only
entry point between Sonora and Baja California is located in San Luis Rio Colorado . The Colorado River and the Altar Desert form most of the border between the two States, creating an a rea that is inhospitable to Rhipicephalus spp. ticks . It is considered free of Rhipicephalus spp. ticks by Mexico and is currently under evaluation by APHIS. The

remainder of Sonora’s western border consists of the Gulf of California.

Along the eastern border of Sonora lies the Western Sierra Madre mountain range, which provides a physical barrier between Sonora and Chihuahua, particularly along the northern portion of this border. Because of the difficult nature of the t errain in this region , there are only two major access roads with entry points between the States of

Chihuahua and Sonora. Although Chihuahua has been declared tick

- free by the Mexican government, it has not yet been evaluated by APHIS and therefore is not currently recognized as free by the U nited S tates

.

Sonora borders Sinaloa to the south, along a relatively narrow strip of land. An inspection point is located along the main route of entry, at Estación Don, and although there are other points of entry from Sinaloa, these roads ar e generally impassable to shipments of livestock . H owever
, individual livestock may be able to pass back and forth between premises adjacent to or straddling the border between the two States

. The State

of Sinaloa is not considered free of Rhipicephalus spp. tick at this time.

There is a potential for infested wildlife to enter Sonora from the surrounding Mexican States. Unlike Sinaloa, Baja California and the majority of Chihuahua, including the part which adjoins Sonora, have been declared free of Rh ipicephalus spp. ticks by the Mexican government and are not a likely route for entry of infested wildlife

. T he border

with Sinaloa , which is the only adjoining area to Sonora likely to harbor Rhipicephalus spp. ticks

, is relatively short , providing minim al opportunity for entry of infested wild life. Additionally, supplemental surveillance and routine treatment measures against ticks are in place for livestock located in the buffer zone in southern Sonora , providing enhanced protection of livestock along this border, in order to combat a possible incursion of Rhipicephalus spp. ticks from infested wildlife into the livestock population.

D iscussion Sonora appears to have sufficient physical barriers to effectively isolate the state from areas of high risk for Rhipicephalus spp. ticks . It is surrounded along most of its borders by natural physical barriers which allow it to funnel traffic coming into Sonora from these areas through a small number of paved roads, each of which is equipped with inspection and dipping facilities . Areas without physical barriers tend to adjoin tick

- free38 regions. The southern border of Sonora poses a risk for occasional introduction of ticks into Sonora’s buffer zone due to its proximity to a tick

- infested region and its relati ve lack of natural borders; however, a number of factors, including enhanced measures for the detection and prevention of tick infestations in the region and fencing along the State line with Sinaloa, have been successful in mitigat ing the risk of spread t o the northern part of Sonora. Additional measures to reduce the risk of future incursions are described

below.

7. Movement controls and biosecurity from higher

- risk regions

Sonora ’s primary barrier to movement of Rhipicephalus spp. ticks from highe r

- risk regions (including from s urrounding States as well as Sonora’s buffer zone) is its network of tick dipping and inspection stations . These include quarantine stations both at points of entry into Sonora as well as internal quarantine stations

, their associated inspection points, the line dipping vats in Sonora’s buffer zone, and other inspection and document check stations, including the sanitary cord inspection stations, agricultural inspection stations and local inspection points. Integral to the successful operation of these facilities

i s the State of Sonora’s transit guide, which provides a system for movement tracking and verification of livestock combined with mandatory origin identification that allows inspection officials to determine complia nce with tick treatment and other animal health requirements

.

Transit guide system The cornerstone of Sonora’s livestock movement program is its transit guide ( Guías de Tránsito) system. No livestock may be moved anywhere in Sonora without a transit

gu ide. The transit guide is a controlled form issued by the State of Sonora that tracks the origin and movement of livestock. It also captures information on the number and type of animals being moved, dates of movement, premises of origin and destination, and herd

identification number and brands [54, 56, 63]

.

Transit guides are issued by live stock inspectors or quarantine station officials. Before issuing a transit guide to animals leaving their premises, a livestock inspector checks the health of the animals being moved through a thorough inspection, verifies their ownership, and makes sure that the animals have been properly identified, using either the Sonora herd identification system or the National voluntary tagging system, both of which include a code that lists the animals’ herd and municipality of origin. Transit guides include an ex piration date that is based on the expected amount of time necessary to complete the movement. Most transit guides expire after 24 hours, although some may be issued for 48 hours. Once animals have reached the official station, a new transit guide may be issued for any destination within Sonora once the animals and/or their documents have passed inspection and received any necessary treatment. Under Sonora’s Livestock Law, individuals who violate the terms of the transit guide or attempt to travel

withou t one are subject to legal sanctions, including fines or even forfeiture of the livestock involved in the illegal movement [54, 56, 63]

.39 Once livestock reach the destination stated on the transit guide th e transit guide is cancelled by livestock officials (either quarantine inspectors or local livestock inspectors) . In the case of animals that are en route to their final destination a new transit guide will be issued. Some of the officials at inspection stations are able to access the electronic database for transit guides and can enter and cancel transit guides in this system directly, but mos t local livestock officials only handle paper forms. Copies of transit guides are sent to the State offices where the information is entered into the electronic movement database (if it has not already been entered) and officials there verify that livesto ck reached their destinations within the allotted amount of time [54]

.

During the 2011 site visit, quarantine officials stated that this activity was currently conducted by hand, but that they were nearing completion of an automated system. Also, in many cases the livestock official will call an inspection station to alert them to an incoming load or when the inspection stations have access to the electronic movement database, they will know immediately if a livestock load fails to show up. If this happens the regional supervisors at the origin of the livestock will be contacted and will perform an investigation. If necessary, the police will be notified to assist with locating the

livestock . This has been a very rare oc currence in Sonora [54]

.

Movement of ruminant livestock and horses into Sonora The importation of livestock into the S tate of Sonora is regulated by the Federal Law of

Animal Health

, the Livestock Law of the State Governm ent of Sonora

, and the NOM

019

- ZOO

- 1994 (National Campaign against the tick Boophilus spp.). All livestock entering Sonora, either as a final destination or for transit purposes, must first acquire a permit from the State of Sonora DGSG . The requirements for receipt of a permit depend on the disease and ectoparasite status of the State or country of origin of the livestock [54, 56]

.

Livestock entering Sonora from neighboring M exican States must pass through one of the

official quarantine station s located along the main routes of entry into Sonora. These quarantine stations are situated on paved highways entering Sonora and their facilities

include livestock holding pens, a scr atching chute for tick inspections, a tick dipp ing vat

, and spray equipment for horses and small ruminants

. They include Estaci ó n Don, on the southern entry route into Sonora from Sinaloa, Puerto San Luis, on Sonora’s western edge along the northern road from Chihuahua, and Maycoba, also on Sonora’s western edge, but located midway along Chihuahua’s border. The San Luis Rio Colorado station

, on the border between Sonora and Baja California, does not provide scratch inspection and dipping functions since l ivestock from Baja California are currently only allowed to

transit Sonora and thus are only required to undergo a documentation check since they

will not be unloaded within Sonora [20, 63, 72]

.

All livestock entering Sonora are required to be accompanied by a n entry permit, a transit guide

, a z oosanitary certificate , a herd of origin certificate, and a tick dipping certificate

. The zoosanitary certificate is a general livestock health certificate required by

SAGARPA for movement between Mexican States and issued by an official or accredited

veterinarian. It includes information on the number, type, origin and desti nation of40 animals in a shipment. A ll vehicles transporting livestock into Sonora must b e sealed at

the point of origin , with the quarantine station at the entry point of Sonora responsible for verifying that seals are intact and that the seal number match es that provided on the zoosanitary certificate and transit guide

. Livestock that are entering Sonora from other countries must also be accompanied by a z oosanitary requirements sheet , which spells out the requirements for entry of livestock into Mexico a nd is verified by SAGARPA

officials at the internal verification points (or PVIs) [3, 20, 54, 56, 60]

.

Each entry quarantine station is associated with a PVI. Whereas the quarantine stations are run by the State of Sonora, the PVIs are operated by SAGARPA; therefore the focus of their inspection is primarily on Federal entry requirements. The PVI addresses both animal and plant health concerns whereas the quarantine station addresses animal health. The PVI may be located before the quarantine station, as is the case with Estaci ó n Don, or after the quarantine station , as with Puerto San Luis and Maycoba

. P ersonnel at the PVI focus their evaluation on the documentation accompanying the livestock load. They

check to make sure the appropriate documents have been acquired, that the information on the documents matches the animals in the load (number and type of animals, identification tags and brands), and that the seals an d vehicle licenses also match [54]

.

In addition to the documentation check at the PVI, livestock entering Sonora must also pass through the quarantine station. The quarantine station is under the control of the

State authorities and staffed by personnel employed b y the State of Sonora. Its personnel provide inspection and dipping for ticks, as well as a second review of the accompanying documentation, with a focus on State requirements. Livestock that have passed documentation checks are unloaded into the “dirty” corrals, which are used to hold animals that have not yet been inspected and dipped for ticks, then moved to chutes for individual inspection. Most of the chutes used at Sonora’s entry quarantine stations are narrow enough to maintain cattle in single

- fi le formation, use grat es for flooring to allow

fec es and other organic material to pass through (reducing contamination of the dip ping vat), and include slats that open up to allow for scratch inspection of the ventral area of

livestock for ticks. An exc e ption to this was noted at Estaci ó n Don during the 2011 site

visit. Sl ats were observed to be used as flooring for the chutes, rather than grates, which are generally less effective at maintaining sanitation , and the chutes were not as narrow, allowing ca ttle to bunch up and making inspection more difficult [54]

.

Once the tick inspection has been completed, livestock proceed through the dip ping vat
where quarantine station personnel provide assistance in ensuring that all cattle are adequately covered, including their heads. Cattle then enter a drying pen where they stay

for 5

- 10 minutes to allow excess acaricide to run off and be recycled back into the tank

, then proceed to the “clean” corrals where they can be re

- loaded onto vehicles and continue their journey . (Horses and small ruminants are treated using spray equipment.)

Provid ed no ticks were found during the physical inspection

, and all paperwork was found to be accurate and complete

, quarantine station personnel w ill issue a dipping

certificate and transit guide for the animals’ destination (or port of exit in Sonora if transiting the State) . If the animals have been traveling for long periods , then they may be allowed to rest for a few hours in the clean pens bef ore being re

- loaded; however, if41 the livestock are from another state they will not be allowed to use their own feed and must purchase local feed from the station [20, 54]

.

The number of cattle imported into Sonora from other Mexican States ranged from 162,000 to 2 77 ,000 head per year from 2008 to 2010. The vast ma jority (between 92 and 96%) of these animals were transiting the State, destined for the Mexicali Valley feedlots in Baja California. Cattle at these feedlots all receive the “CN” brand and are intended for domestic consumption (within Mexico) only. The intended uses for the relatively small number of cattle destined to remain in Sonora include feeding, b reeding, and sport, for the most part [54, 61]

.

Imports of livestock from outside of Mexico require a permit from SAGARPA prior to entering the country and issuance of a zoosanitary requirements sheet. The specific requirements are based on the animal disease and ectoparasite sta tus of the exporting
country [20, 54]

.

The vast majority o f livestock imported into Mexico from other countries originate from

within the U nited States

. Cattle imports from the U nited States averaged 20,000 head per year during 2009 and 2010, and imports from Canada made up the remainder of imports, averaging ap proximately 1,500 head per year. Sheep and goat imports all originated in

the U nited States for 2009 and 2010. Equine imports ranged from 80,000 to over 100,000 head during this time period, with approximat e ly 99% originating from the

U nited S tates [73]

.

To date, no ticks have ever been found at inspection stations on animals originating from Sonora, however, there have been tick identifications on animals entering Sonora from

other State s, most notably at Estaci ó n Don, at the southern end of the State in the buffer

zone [54]

.

L ivestock transiting Sonora from Baja California Livestock transiting Sonora f rom B aja California to other Mexican States (either for residence or eventual export to the U nited States ) via the entry point at San Luis Rio

Colorado are not off

- loaded for tick inspection and treatment . A document check is completed

, seals and license plates are checked

, and the animals are issued a transi t guide to the port of export. The r ationale for this process is to reduce the ris k of introducing

acaricide resistant ticks into Sonora . Off

- loading the animals could result in dropping ticks in the area of the quarantine station if ticks are present, w ith the possible infestation of subsequent animals passing through or held at the quarantine station . However, the risk of introducing infested livestock via this route is significantly mitigated by Baja

California’s Rhipicephalus spp. tick

- free status as declared by Mexico [74]

.

Movement of livestock from the buffer zone to the northern part of Sonora

The area of southern Sonora that adjoins Sinaloa and the southwestern corner of

Chihuahua is referred to as the bu ffer z one for Rhipicephalus spp. ticks

. It is comprised

of portions of the municipalities of Á lamos , Huatabampo, Nav o joa , and Etchojoa

. Due to

its proximity to areas considered infested with Rhipicephalus spp. ticks and the lack of42 significant geographical barrier s between infested and free zo nes , th e buffer zone is

considered at risk for re

- infestation with Rhipicephalus spp. ticks (and incursions have been detected in recent years) . Therefore, enhanced detection , prevention

, and control measures are employed in the buffer zone [20, 53, 72]

.

Livestock originating from premises in the buffer zone that are planning to move into the

northern tick

- free area of Sonora are required to stop at the Bahuises quarantine facility

which is located at the northe rn border of the buffer zone, where their documents are checked, and the animals are inspect ed and dipp ed before be i ng moved out of the buffer

zone. No ticks have been found in livestock presented at the Bahuises facility [53]

.

T here are seven line dipping vats , or dipping vat facilities, located a long Sonora’s

southern border . These provide an additional layer of surveillance and tick treatment for

livestock within or moving through the buffer zone

. T he line dipping vats , located along the major access roads, have facilities for inspecting and dipping cattle (or spray treating other livestock)

. Transit guide s may be issued from line dip bath personnel and local livestock inspectors in the buffer zone for movement to the nearest quarantine station (Bahuises) only

. See F igure 1 1 for a diagram of the line dipping vats and quarantine stations used by livestock departing the buffer zone . The seven line dip bath facilities are represented by yellow text, a nd include: San Bernardo, Las Chinacas, El Sabino, Masiaca, Palos Chinos, Maquipo, and Tapizuelas. The green text represents the quarantine stations: internal stations Guasimas and Bahuises on the road leading out of the buffer zone; and import station Es taci ó n Don with its associated PVI (in red) at the road leading into Sonora from Sinaloa [20, 54, 72]

.

Figure 1 1 . Tick inspection and dipping facilities in Sonora’s buffer zone.

Source: [62]43 Livestock residing in the area of the buffer zone adjoining Sinaloa and Chihuahua must go to a line dip bath (which are concentrated in these areas) before leaving the buffer zone. There they will be inspected and treated for ticks and a transit guide will be issued by the dip ping vat inspector with the Bahuises quarantine station as the destination. At the Bahuises quarantine station the livestock will be inspected and dipped again before being al lowed to proceed to the northern part of Sonora (or Guasimas if traveling at night)

. Livestock from other areas within the b uffer zone will be issued a transit guide directly to the Bahuises quarantine station by the livestock inspector for their area. T he se livestock will receive a tick inspection and treatment at the quarantine station and the inspector can then issue a transit guide to their final destination. Any livestock shipments that try to avoid the Bahuises station (which only operates during o ne 8 hour shift each day) will be intercepted at the Guasimas inspection point, which is farther north along the highway and operates 24 hours a day [54]

.

Therefore all livestock moving into northern Sonora from the b uffer z one will receive at

least one inspection and tick treatment at a state

- run quarantine station facility

, and livestock originating from the higher risk area of the b uffer z one (i.e. areas near tick

infested borders) will receive an additional inspection and treatment at a locally

- run line dip bath. Approximately 30% of cattle in the buffer zone reside in the higher risk area and are subject to two tick inspections and two treatments before moving out of the

buffer zone (cattle on these ranches also receive ivermectin injections two to three times per year) [54]

.

When ticks are found on livestock presented at any of the dipping stations , the tick (s) and

information about the circumstances of the collection and origin of the l ivestock are provided to the supervisor (there is one supervisor for the quarantine entry stations, one for the internal quarantine stations, and another for the line dipping vats ; all are employed by the State of Sonora) . The supervisor sends the ticks a nd submission form to the CENAPA laboratory for identification and resistance analysis via courier and results are sent back to the supervisor electronically and the supervisor notifies his chain of command in Sonora, as well as SAGARPA and the dipping sta tion inspector . In the meantime the infested shipment is quarantined, treated

, and re

- inspected as described in

S ection 4 [20, 54]

.

Movement of livestock entirely within t he buffer zone Movement of animals entirely within the buffer zone requires a transit guide prior to movement. Tick dipping is not required if no ticks are identified during the inspection process and if the animal is not moving outside of the buffer zone [71, 74, 75]

.

However, cattle from high risk areas within the buffer zone, particularly premises located along the border with Sinaloa or Chihuahua, are required to receive a tick inspection and dipping certificate before the livestock inspector will issue a transit gui de for movement. Livestock owners may acquire advanced approval by telephone from the livestock inspector to move their livestock to the nearest line dip bath in order to be dipped [71]

.44 Movement of livestock exclusively within the northern tick

- free area of Sonora

Movement of ruminant livestock and horses within the tick

- free region of Sonora requires

that a transit guide be issued by a livestock inspector prior to the animals leaving the farm of origin. Although a thor ough scratch inspection for ticks is not required for this type of movement, a thorough inspection of general health is required, which would potentially detect a tick infestation, if present. A dipping certificate is not needed as long as the

animals do not transit the buffer zone [20]

.

Dip ping vat managemen t An integral component of Sonora’s tick control program , with respect to prevention of entry as well as enhanced detection and control of spread, is its system of dipping stations located throughout the State. Tick dipping is generally accomplished by im mersing cattle in a vat or bath filled with acaricide solution. The vat itself is often located below ground level, and cattle walk down a ramp until their entire body is submerged in the solution.

Handlers make sure that each animal’s head also becomes immersed. Horses and small ruminants are treated using spray equipment. Although there are different types of stations, each of which meets different needs, the dipping facilities themselves are all managed in a similar manner

. Specific guidance on proc edures at quarantine stations and line dipping vats , including acaricidal solution maintenance and sample collection, tick collection, record keeping, and document review, are contained in Sonora’s operational manual for quarantine stations and line dippin g vats

.

Dip ping vat f acilities and operations There are different types of stations used in the inspect ion and treat ment of livestock for ticks as they move into and throughout Sonora. This section will focus only on those facilities that contain dip ping vats , including the quarantine stations of entry into Sonora, the internal quarantine stations, and the line dipping vats

.

The official q uarantine stations , both for entry and internal movement, operate under the oversight of the S tate of Sonora (althoug h the PVIs associated with entry quarantine stations are under Federal control). The inspectors who work at these stations are employed by the State of Sonora. All livestock entering Sonora , or moving north into the

tick

- free area of Sonora must pass thr ough one of these quarantine stations [20, 70]

.

The line dipping vats , located in Sonora’s buffer zone, are managed and operated by the

local AGLs (Local Cattlemen’s Association) , with official oversi ght of day to day procedures provided by the Committee, but ultimate supervision and inspection provided by the State of Sonora. The local livestock inspector for the livestock zone in which a line dip bath is located runs the day to day operations of the line dip bath [20, 54]

.

Physical equipment and infrastruct ure at dip ping vat facilities of the quarantine station

include an office with internet, fax, and phone . Also evident are m aps of Mexic an States

delineated accor ding to tick status, procedural posters and instruction manuals. The

offices also contain a ca ricide sample collection jars for submission to the laboratory for analysis , tick collection tubes ( with 70% alcohol for dead ticks for taxonomy and clean tubes for lives ticks for resistance characterization)

, and pH test strips. Storage facilities45 were also viewed, containing pump aerators, acaricide concentrate for recharging and/or replacing the dip ping vat solution, and sodium hydroxide for pH adjustment. Line dip bath inspectors d o not maintain an on

- site office or storage facility, but ke ep these i tems in a locked storage facility at home instead and transport them to the dip ping vat when

necessary [54]

.

All dip ping vat stations include the necessary facilities for inspection, dipping, and

maintenance of the dip ping v at solution, although some are better maintained than others. All quarantine stations and line dipping vats contained “dirty” corrals for unloading uninspected livestock and “clean” corrals for holding the inspected and treated livestock prior to re

- loadi ng. All of the stations also include chutes for tick inspection of cattle (other livestock are inspected individually) , most of which squeezed the cattle into single file and included boards that could stop the cattle for individual inspection, and also

c ontained ventral panels that opened for scratch inspection of the flank and brisket area and grates on the floor to allow for removal of waste prior to entry of cattle into the dip ping vat [54]

.

The exception was the quara ntine station located at Estaci ó n Don as observed during the

2011 site visit , which allowed for bunching of cattle and did not have grates on the floor. It was commented that individual inspection could be conducted in a separate area when necessary, and on

- site inspection of the facilities by the 2011 site visit team was able to determine that scratch inspection was conducted adequately. Other aspects incorporated into the design of both the quarantine stations and line dipping vats included covers over the dip ping vat area to prevent rain and sunlight from reducing the effectiveness of the dip ping vat solution, cement

- floored drip pans for cattle that were just dipped, with drain lines equipped with filters to recycle the acaricide solution back into the dip ping vat

, and evaporation pools for discarded acaricide solution resulting from changing out the dip ping vat [54]

.

Each dipping station also maintains a log book in which information on each shipment of livestock passing through is recorded. The information includes the number and type of animals inspected and dipped in each shipment, their identification information (ear tag or brand), premises number, the name of the owner, the origin and destination of the shipment, a nd the results of the tick inspection and quarantine information if appropriate

. This information is kept in the log book at the dipping station and also compiled into a bimonthly report, copies of which are sent to State and Livestock Committee offices [54]

.

In addition to the log book, all dipping facilities also maintain a registry that captures information about the dip ping vat solution and its maintenance, including the number of

animals dipped

, the acaricide concentr ation, pH, pollution level

, and dates of recharging and replacement of the acaricide solution . All records are maintained for five years [20, 54, 56]

.

Operations at facilities that include dipping vats are overseen by a supervisor with the

DGS G who visits the stat ion once a month (in the case of the quarantine stations) or twice a month ( for line dipping vats ). The supervisor reviews the entries in the dip ping46 vat solution registry book to evaluate whether or not tests are conducted at the appropriate frequency, d ip ping vat solution s have been maintained at adequate concentrations, determines whether current procedures are adequate or need to be adjusted, and also review s on

- site procedures. Visits can take up to three days for quarantine stations. The supervisor consults with the inspector in charge of the station and compiles a report with the results of his inspection and any recommendations that need to be made. Copies of the report are shared with State and Federal officials and the

Livestock Association

. T he supervisor checks on the next visit to make sure that any recommended actions were taken in a timely manner and verifies the effectiveness and timeliness of the actions based on follow up laboratory results [54]

.

In addit ion

, an annual audit of dipping station facilities is conducted by State , Federal and Committee officials. This review is more intensive than the monthly visit and includes evaluation of the facilities, as well as procedures and personnel. It includes in specting the dipping vat roof to verify that the dipping solution is not exposed to direct sun or rain

water, which can reduce its effectiveness ; checking the drying area and the solids decanting tank to make sure waste and other organic material s aren’t e ntering the dip ping

vat ; checking to make sure the acaricide concentrate is maintained properly ; the aerator and other equipment is functioning properly ; and evaluating day to day procedures [54, 56]

.

Dip ping vat personnel Inspectors at all quarantine stations are employe es of the State of Sonora. These

pe rsonnel generally consist of employees with different backgrounds

, some primarily plant health and others animal health, bu t all inspectors receive training in both. Inspectors include agricultural techs, agronomists, and vet erinarians. All inspectors receive training in livestock inspection and handling, tick identification, and the administration and management of acaricid al products by technical personnel from the

DGSG and the laboratories that produce the acaricides . The supervisor o r veterinarian at the station may always be contacted for assistance if necessary. Pe rsonnel at the larger quarantine stations with 24 hour a day operations g enerally work in 8

- hour shifts, while the smaller stations only operate during daylight hours (although these are associated with 24 hour document inspection stations that can hold shi pments if inspection is required [20, 54]

.

The livestock inspectors also act as the head inspector for the line di p bath located in their livestock zone. They are responsible for coordinating movement of animals within their zone through their line dip bath, maintaining records, and keeping the log books. The inspector is also responsible for making sure that the di p ping vat solution is adequately monitored and maintained, which include s providing daily aeration even if no animals are

scheduled to be dipped [54]

.

During site visits, i nspectors and their supervisors were found to poss ess overall knowledge of the eradication program and its requirements, as well as a high degree of professionalism. In addition, t he number of personnel providing inspection services and staffing of the dipping and quarantine stations w as found to be suff icient during all three47 site visits . While some documentation reflecting monthly reports was found to be less frequent than stated, the reports that were viewed were complete, and appropriate measures were taken as indicated in the reports [54, 63, 72]

.

Acaricide management

The t hree dip ping vats at the quarantine stations of entry into Sonora use amitraz 6 at a
concentration of 400 ppm, which is twice the strength recommended on the product label. The CENAPA laboratory determined this concentration to be effective against amidine

resistant ticks in other parts of Mexico. T he four internal quarantine stations and line dipping vats use organophosphates in their dip ping vats . Organophosphate acaricide

solution at a concentration of 200 ppm is also used in spray equipment used to tr eat
horses and small ruminants [54, 60]

.

All acaricides used in Mexico are registered by SAGARPA and have passed biological testing performed at CENAPA de monstrat ing a minimum efficacy of 98% prevention of successful feeding, egg laying, and larval emergence according to the Mex ican Official

Standard NOM

- 006

- ZOO

- 1994 [60]

.

Although the type and purpose of many of Sonora’s tick dipping stations vary, handling

and control procedures for the dipping solution s are the same, with a number of different

methods used to monitor their effectiveness. Thes e procedures are reviewed on a monthly or bi

- monthly basis by the dip ping vat supervisors. The State Supervisor of the SFG is ultimately responsible for ensuring that these activities are carried out in an appropriate and timely manner [60]

Acaricide solution can lose i ts effectiveness if exposed to excessive organic matter or other sediment. Sonora uses pump filtration systems in its dip ping vats to provide continual removal of mud, ha ir , and other organic material that can end up in the solution. The pump is set up t o filter the entire content of the dip ping vat every 1000 animals . In addition, the c ontamination level of the tick bath solution is checked every 2 50 animals or every month , whichever is more frequent

. This is done by measuring the sediment

level in a o ne

- liter test tube filled with the used acaricide solution. When the level of

sediment reaches 15% the entire tank must be changed . Records reviewed at the 2011 site visit showed that pollution levels rarely exceeded 10% before the dip ping vat
solution w as replaced completely [54, 56, 60]

.

The lack of consistent and effective mixing, or agitation of the dip ping vat solution during previous site visits was found to result in inadequate suspension of the acaricidal

chemical in the dip ping vat solution and lowered concentration levels . As a result, APHIS recommended that all dip vats acquire pump aerators and aerate the dip ping vat
solution for 40

- 50 minutes at the beginning of every day, whether or not animals were

scheduled to be dipped that day. The 2011 APHIS site review team was able to verify that all dipping stations had pump aerators equipped with T

- bar attachments to the hoses

6 Amitraz is an amid ine antiparasitic agent that is available in different formulations and is effective against

cattle fever ticks.48 for better distribution and the inspectors demonstrated that the solution was aerated every day

, b eginning at the start of the day [54, 63]

.

Maintenance of proper pH levels is important to the maintenance of the acaricide

concentration l evel and, in the case of organophosphate acaricides, to prevent the buildup of toxic byproducts of decomposition of the acaricide. Label recommendations advise that the pH of the acaricide solution be evaluated daily for the amidines

, and it appeared

that this was done regularly by dip ping vat employees

. For a mitraz, the pH should be 12 or higher ( this is corrected by adding c alcium h ydroxide or lime to the bath if the pH is

too low ) , and for organophosphates the pH should be as close 7 as possible . The pH levels are adjusted when indicated by adding calcium hydroxide (to increase the pH when amidines acaricide is being used) or acidifiers as necessary. The pH levels of acaricidal solution are evaluated by CENAPA along with pollution levels when the sol ution is submitted for concentration analysis, but the staff at the dipping stations keep pH strips

on hand and can monitor and rec ord results in real time [54, 76]

.

The APHIS team recommended that Sonora begin evaluating the pH of their organophosphate dip ping vat solution on a daily bas i s and maintaining the levels closer to 5.5 using triple phosphate to decrease the pH when necessary. Recent research at APHIS’ Agricultural Research Station revealed that maintaining the coumaphos at this level helped maintain the concentration of the acaricidal solution and eliminated or

reduced the amount of toxic byproducts. Sonoran officials requested that APHIS share the protocol they had developed based on this information so they could impl ement it as soon as possible (they were currently following the label recommend ations for coumaphos, which advised a neutral pH) [54, 56, 60]

.

Each dipping station has instructions on how to recharge the dip ping vat contents with

f resh acaricidal concentrate and when this is necessary in order to maintain an appropriate concentration. Each dip ping vat contains a n adjacent r echarging container

that contains measurement s to assist with adding new acaricidal solution to the dip ping

va t. The specific amounts of concentrate, water, and calcium hydroxide are provided in Sonora’s quarantine station operating procedures manual in a formula for a standard recharging . Additionally, C ENAPA will provide specific recommendations and amounts

fo r recharging in the event that the concentration of acaricidal solution is low and

additional concentrate needs to be added. Re

- loading of the acaricide in the dipping

solution is scheduled to occur after 250 animals have been dipped (for a mitraz) or when the solution level in the dip ping vat tank has declined by 500 liters (for both a mitraz and

c oumaphos). In addition, a sample of dip ping vat solution is collected in a clean brown glass collection vial and sent to CENAPA for a concentration analysis ever y 1000 head (or every 3 months, whichever is sooner) [54, 56, 76]

.

The dip ping vat solution must be completely replaced ever y 5,500 head or when the pollution level reaches 15% (whiche ver comes first) or once per year in the event that fewer than 5,500 cattle are dipped in a year’s time (as is the case at all of the line dipping

vats ). The discarded solution is emptied into an evaporation tank which allows the

unused acaricidal solutio n to volatize safely [54, 76]

.49 The on

- site registries for dip ping vat solution management viewed during the 2011 site

visit demonstrated that inspectors were conducting the above activities as prescribed, and

were able to maintain ac aricide concentrations withi n the effective zone. Amitraz

concentrations at the external quarantine stations were usually above 4 00 ppm and rarely dipp ed below 300 ppm (which is well above the effective concentration according to the label) . Similarly, c oumaphos levels at the line dipping vats were rarely found to be

below 200 ppm. Pollution levels and pH tests were conducted a t the required frequency and all were within target ranges . Similarly, acaricide c oncentration was checked, recharges conducted, and dip ping vat contents replaced according to the protocol. The documentation was complete and matched what was provided in the animal movement log books, the supervisors’ reports, the laboratory submission and report forms

, and any recommended adjustme nts to dip ping vat procedures or contents were quickly acted upon by the dip ping vat inspectors [54]

.

During the 2011 site visit it was determined that the turnaround time for receipt of acaricidal solution analysis result s from the CENAPA laboratory generally took three weeks, and sometimes longer than four weeks. Although on

- site inspectors and supervisors made the necessary corrections to the solutions based on laboratory results, the delay in receipt of laboratory resu lts meant that the dip ping vat solution often had already received a number of recharges or, in some cases, complete replacement by the time the findings and associated recommendations were received, rendering the

recomm endations practically useless [54]

.

The dip ping vats used at the quarantine stations and line dipping vats are designed for use by cattle and are n o t appropriate for horses and small ruminants. These animals are therefore treated using spray equipment rather than the dipping vats. Organophosphates are used in the spray equipment and the equipment is cleaned and flushed with clean water after each use. Any unused solution is discarded after use [56, 60]

.

When treating an animal with spray equipment

, one liter of solution per 100 kg of weight

is prepared and applied so that each animal becomes thoroughly wet. The solution is applied to the animal’s entire body, particularly difficult to reach areas such as the base of the tail, t he ears, the groin

, and inside the legs. As with the dip ping vats, dates of

treatment, number of a nimals treated, and the name and amount of the product used are recorded in the register [56]

.

Controls on hay and other forages entering Sonora Because hay and other forages can harbor ticks and other pests, the government of Sonora regulat es the importation of these products

. Most livestock in Sonora are kept on
pasture; therefore there is little demand for imported hay and forages for livestock feeding. F orage materials that are used for Sonoran livestock generally originate from

within the State and seeds used to sow these crops are acquired primarily f rom the United

St ates and must comply with phytosanitary (plant health) requirements [56]

.50 When importation of forage is necessary, requirements contained in the Official Mexican

Standa rd NOM

- 044

- FITO

- 1995, which spells out the phytosanitary requirements and specifications for the import of nuts, vegetable products

, and vegetable byproducts , must
be followed. Additionally, in 2000, USDA APHIS performed a risk assessment and site

visit f or the importation of hay from the Mexicali region of Baja California to the United

States. The evaluation determined that there was no risk of importing tick

- infested Sudan hay (the major crop in this region), but that opportunities existed for contact o f cattle with some other forage crops. Therefore, hay from this area was allowed entry into the United States provided it was accompanied by certification stating that no potential tick

- infested animals were allowed access to the hay pasture during produc tion or harvesting [77, 78]

.

Movement of infested w ildlif e into Sonora The most likely avenue for movement of Rhipicephalus

- infeste d wildlife into Sonora is via the southern border of Sonora due to that area’s proximity to tick

- infested regions of Mexico. Although cattle are the preferred host for Rhipicephalus ticks, other hooved animals, including white

- tailed deer have also been f ound to harbor these ticks. While

white

- tailed deer have been demonstrated to maintain Rhipicephalus tick populations in previously infested cattle ranges, other wildlife species have not been implicated in the

maintenance of these ticks to date [79, 80]

.

If infested wildlife were to be come established in Sonora it is likely that the ticks would also be present on cattle in the region. Because of the intensive surveillance and pre

emptive treatment measures performed by local and special livestock inspectors and at dipping vats and quar antine stations in the southern portion of Sonora (the buffer zone), it is likely that infestation of cattle or other livestock would be detected by inspectors, quarantine station officials or members of the brigades. In addition, the currently infested

a reas that are adjacent to Sonora, in both Sinaloa and Chihuahua

, are currently undergoing eradication and control programs for Rhipicephalu s spp., and livestock in these areas are currently subject to similarly rigorous inspection and treatment regimens.

Illegal movement of livestock into Sonora Another concern is the possibility that livestock could be smuggled into Sonora, effectively bypassing the control measures in place at the border stations. This is unlikely due to the mountainous terrain along Sonora’s border with Chihuahua, the narrow geographic border with Sinaloa

, which possesses very few easily navigable access roads, and targeted distribution and locations of inspection facilities along the border with

Chihuahua and Sinaloa. In addition, d ocumentation checks are performed at the many inspection stations along the interior roads in Sonora and livestock inspector s conduct an annual inventory of all animals located on premises in their zone and verify the origin of the animals, which increases the likelihood that smuggled animals would be detected subsequent to their entry into Sonora. Any violations in movement or documentation would likely be detected and would result in fines and possible forfeiture of livestock, providing a strong negative incentive for attempting illegal movement. It can be expected that these measures would be sufficient to both deter and detect illegal

movement of livestock infested with Rhipicephalus spp. ticks.51 Discussion The system of transit guide s, tick inspecti on, and dipping or spray treatment associated

with animal movement i nto and within Sonora has proven successful in preventing the

introduction of Rhipicephalus spp. ticks into Sonora from other States or from the buffer zone region in southern Sonora. T he procedure s for entry into Sonora include tick inspection and treatment of all animals, as well as verification of information contained in all required movement documents as specified under the Animal Health Federal Law and

NOM

- 019

- ZOO

- 1994. These proced ures are strictly followed by the inspection personnel and, in the event that ticks are detected on any animals, on

- site q uarantine is imposed until elimination of the tick(s) is accomplished and investigation of the origin of

the animals is conducted

. Pe rsonnel involved in the documentation and livestock inspections, as well as th ose manning th e dipping vat stations

, were found to be knowledgeable and professional during the multiple site visit reviews

.

Although the possibility that livestock could be smuggled into Sonora, allowing them to bypass the inspection and dipping procedures required upon entry, cannot be entirely excluded, this is unlikely due to the presence of multiple inspection and dipping stations located along most of the navigable roads into Sonora, such as line baths, quarantine stations, and zoosanitary cord stations and routine inventory audits conducted by local livestock inspectors.

Because Sonora is adjacent to some tick

- infested regions it is possible that wildlife harboring Rhip icephalus spp. ticks could enter into Sonora, most likely in the buffer zone area. Because these ticks prefer cattle hosts, it is likely that any ticks would move to

cattle and be detected and/or treated as a result of enhanced surveillance and treatment measures in place in the buffer zone.

Facilities at the various inspection and dipping facilities were found to be in good overall condition, possessing all necessary infrastructure. Significant improvements to the facilities have been made in response to previous site visit recommendations

.

The inspectors at the dip ping vat facilities were knowledgeable

, professional , and

conscientious. S upervisors were likewise knowledgeable and respons ive to issues requiring correction

. Routine actions, such as aeration of the dip ping vat solution, maintaining records of animal movement

, and management of acaricidal solution were carried out as required in Federal and State regulations and procedures . Record keeping

was excellent and documents from different sou rces (i.e. lab results, monthly reports, and registries) were consistent with each other.

The concentration of a caricid e in the dip ping vat solution and pH levels were improved from previous site visits, with most sample results in the effective ra nge; however the

concentration levels were still highly variable from one sample to the next, possibly due to the delay in receipt of sample analysis results and the implementation of recommended changes after several re

- charges and possibly replacement of dip ping vat solution had already occurred, causing a boomerang effect.52 T he lengthy turnaround time for receipt of results of acaricidal solution analysis is cause

for concern as this could potentially result in the treatment of cattle with inadequate a nd ineffective acaricidal solution for a prolonged period of time before the deficiency c ould be recognized

. However, the speed and accuracy with which inspectors and supervisors representing the different types of dipping vat stations were observed to co rrect deficiencies in acaricidal solution when these deficiencies were noted significantly mitigated this concern.

8. Livestock demographics and marketing practices in the region

As of the 2010 livestock inventory, there were over 1.5 million cattle re siding in the State

of Sonora. Most cattle farms in Sonora consist of beef operations , with a small number

of dairy or mixed operations. Sonora’s 2010 livestock inventory also identified over 51,000 sheep, 22,000 goats , 73,000 horses, mules, and donkeys, and 400 farmed deer. The livestock were recorded as residing on over 46,000 premises [20, 71]

.

The primary market for Sonoran cattle is export . The vast majority of Mexican exports (over 99.9%) are destined for the U nited States

, with a few doz en head going to Central American countries or Micronesia each year [54, 73]

.

Marketing and movement patterns of cattle

As discussed above , in section 7 , the majority of cattle entering Sonora from other states are destined for further States, many to the domestic feedlots in Mexicali Valley

, Baja

California. Of cattle that are destined to remain in Sonora, most are intended for feeding for feeding (57

- 73% between 2008 and 2011), while a few ar e used for breeding

, working, exhibition, or other purposes [54, 61]

.

M ost of the steers that are exported from Sonora go to the United States for feeding (90%) or to the States of Chihuahua or Baja California. A pproximately 30% of heifers are exported to the United States as spayed heifers for feeding, w hile the remainder are kept as replacement heifers or used for feeding within Sonora

, Chihuahua, Baja

California or Sinaloa [20]

.

The main auction market in Sonora operates twice a week and is located in the UGRS

corrals in Hermosillo. The market trades in all livestock and operates under the oversight

of the UGRS, w hich maintain s detailed records of the sales and movements of animals marketed through this auction. Most of the cattle marketed through the UGRS auction

market are used for slaughter within Sonora with the rest going to Chihuahua or Sinaloa [2 0]

.

Animal identification required for movement Sonora’s herd identification pro gram was started in 1997. The program is mandatory for

any livestock moving off of their premises of origin and uses yellow metal ear tags imprinted with “SON” for Sonora f ollowed by a five digit number, with the first two digit s signifying the municipality and the last three the premises of origin of the animal

.53 This coding system allows for a unique number to be assigned to each herd in Sonora.

All cattle that are moved in Sonora are required by State Law to be identified with a herd of origin ear tag

. L ivestock inspector s will only issue transit guide s for cattle that have appropriate identification [54, 56]

.

Sonoran cattle may also utilize the National Cattlemen’s Association tag ( Sistema Nacional de Identificacion Individual de Ganado

, or SINIIGA ) . This tag costs more than the Sonora tag, but it provides access to subsidies and other benef its provided by the Cattlemen’s Association. This tag also provides a distinct code for the premises of origin, but is recognized across Mexico. Its first two digits are the letters “MX”, followed by a numerical code for the State of origin (Sonora’s cod e is “26”) and then 8 additional digits denoting the specific premises [54]

.

Other tags used to denote test status for tuberculosis and brucellosis are recorded on the transit guide and other documents if present . The offic ial test tags are serially numbered and may be required for certain movement purposes, but they do not identify the premises of origin and may not be substituted for Sonora or SINIIGA tags [54]

.

Annual Livestock inventor y Sonora ’s livestock inspectors are responsible for conducting an inventory of all livestock premises and stock within their livestock zone each year. The inspectors use their knowledge of the local livestock industry as well as information from transit g uides acquired by livestock farms to help insure that all livestock owners respond to the survey

. They also verify that the numbers of stock provided are accurate (for instance

, the

number of new natural additions should be consistent with the number of b reeding females on the farm, purchased additions or sales should align with the number of animals listed on transit guides leaving and entering the farms, etc.) [81]

.

The inventory includes the number of livestock on each farm by age, se x, and production type, as well as the brand and ear notch pattern associated with each farm. The survey is conducted every Novemb er. Livestock owners that do not provide the information will

be in violation of the State and Federal law and may be fined accordingly. Additionally, animals will not be allowed to leave the premises (for sale, slaughter, export, etc.). If necessary, the livestock inspector may follow up with an on

- farm visit if there are any discrepancies or concerns about the veracity of t he data on the inventory form or if the form was not provided. And the information submitted on the inventory can also help inform the livestock inspector when issuing transit guides to ensure consistency of the

information [ 54]

.

The annual inventory report is compiled by each livestock inspector

. The owner keeps the original of the form and one copy each goes to the livestock inspector, the Livestock

Committee , and the State offices where the information is compiled. Fu nding for the annual inventory is derived from fees paid by cattle farmers to the Livestock Association for movement, export and slaughter of cattle . The results of the inventory can be used at the local level to verify that improper or illegal movement o f livestock has not occurred, as it would be detected on inventory checks [54, 63]

.54 Export of livestock to the U nited S tates
The number of ca ttle exported to the U nited States from Sonora varies each year, ranging

from 200,000 to almost 300,000 between 2007 and 2010 . The majority of these cattle, in excess of 90%, originate from the northern area of the State, outside of the buffer zone ( see T able 1 ) [54]

.

Table 1 . Cattle exports to the U nited S tates from Sonora, by origin

Year Northern

Sonora % Southern

Sonora % Total

2007

- 2008 197,449 93.13% 14,572 6.87 % 212,021

2008

- 2009 210,882 91.93% 18,509 8.07 % 229,39 1

2009

- 2010 256,480 91.41% 24,092 8.59 % 280,572

2010

- 2011 214,663 93.38% 15,207 6.62 % 229,870

Source: [61]

Sonora has three ports on the border with the U nited S tates : San Luis Rio Colorado , near the border with Baja California; Nogales, located centrally on the border; and Agua Prieta, located near Chihuahua. Currently, o nly Sonoran cattle ar e exported through

Sonora’s U.S. ports

. See Table 2 for a break down of cattle exports to the U nited S tates by port [54]

.

Table 2 . Cattle exports to the U nited States by port and type

Year SLRC Nogales Agua Prieta Total

9/2008

- 8/2009 18,937 123,826 86,628 229,391

9/2009

- 7/2010* 20,392 161,802 89,968 272,162

* partial year

Source: [60]

Most cattle exported to the United States from Sonora use the export corrals owned by the UGRS to congregate and process cattle prior to export. The corrals are also used as a

feed l ot for congregating and assembling groups of animals of similar types and sizes prior to exporting them as lots. Only Sonoran cattle are allowed to use these corrals, and their owners must be members of the cattlemen’s association. Cattle undergo spay or castration surgery while at the corrals, and may receive brucellosis and tuberculosis testing and identification placement . The cattle also typically receive an injection of ivermectin shortly after arrival . If cattle come from the buffer zone of Sonora they receive an inspection for ticks (although they are not given additional dipping after leaving the buffer zone and receiving dipping at the Bahuises station and also the line dip bath). Cattle usually spend between 21

- 30 days at the corrals, which is enough time for testing to be completed and spay or castration incision to heal. Occasionally cattle may be kept for up to 180 days for feeding and fattening [54]

.

Whether or not cattle are exported through the UGRS corra ls, they must all adhere to the same export requirements. The first step in the process is for the owner to have the cattle55 intended for movement tested for tuberculosis and brucellosis and to acquire tags denoting their test status (they must test negati ve for required tests in order to be moved). The owner must also procure a transit guide and certificate of origin prior to moving off of their premises and must have either the yellow SON or SINIIGA premises ear tags applied to all cattle that will be mo ved. If the cattle are coming from the southern part of Sonora (south of the Guasimas quarantine station) they must also have been inspected

and treated for ticks prior to moving to the corrals [54]

.

The export facility h as its own livestock inspection office

, which is separate from the system of livestock inspectors located in local livestock zones throughout Sonora. Instead, this counts as one of the Centers of Livestock Inspection for High Movement (or CIGAMs) and it i s staffed by employees of the State of Sonora. The inspectors check animals upon arrival for proper documentation and brands, presence of premises ear tags, and verify the number, sex, and type of animals. At the export corrals, they receive a n ear tag d enoting sterilization after spay or castration has been completed as well as a blue

metal SAGARPA ear tag denoting brucellosis testing , which is an individually, serially numbered tag required for all cattle exported to the U nited S tates . All identificati on tags (premises, testing, spay/castration, export, etc.) are linked together in the database by the inspector. The inspector also verifies that appropriate testing has been conducted, dipping certificate is present if required, and that the export healt h certificate (zoosanitary certificate) has been procured. Once the animals are ready to proceed for export the inspector at the corrals will issue another transit guide for movement to the border [54]

.

The re is another C IGAM inspection station located at the corrals immediately preceding

the U.S. port . The inspector at this station checks to make sure that the appropriate

documentation accompanies the animals and has not expired

, verifies that the information

contained i n the documentation matches the animals (i.e. number of head, brand and tag numbers, etc.), verifies that tuberculosis and brucellosis testing has been conducted with negative results, and checks to make sure that a dipping certificate is present if one is required. The inspector also performs a cursory visual inspection of animals in the load.

If any documentation is missing the inspector will check with the owner, and will refuse the load if proper documentation cannot be supplied. If ticks or evidence of disease is detected on inspection the load will also be refused. Once the load has been approved the inspector cancels the final transit guide and forwards the cancelled document to the State offices where they will be entered into the electronic data base and used to verify that the

animals have arrived at the port . Only then are the cattle allowed to proceed for USDA inspection [54]

.

Discussion

Sonora ’s herd identification system appears to be an effective way to tr ack animals back to their herd and municipality of origin, allowing inspectors to determine the origin of livestock and thus their compliance with tick inspection and treatment requirements . In combination with the transit guide system and annual inventor y, the identification program is an important and effective tool in Sonora’s tick control and identification

arsenal.56 Export requirements for livestock intended for export to the United States provide another layer of checks and balances in the assuranc e that Sonoran livestock destined for

the United States have received tick inspections and treatment as appropriate based on their origin and movement patterns.

9. Tick surveillance in the region

Routine surveillance Tick inspections are regularly perfor med on livestock moving through and within Sonora

as a part of routine movement requirements , particularly in livestock moving from or through the buffer zone or entering Sonora from other Mexican States

. Although livestock moving entirely within the nort hern tick

- free portion of Sonora are not required to receive a scratch inspection for ticks prior to movement, they do undergo a thorough health evaluation in order to receive a transit guide, which would potentially detect an

infestation. Additional insp ections are conducted at inspection and dipping stations encountered along transit routes as described in the preceding sections

.

During 2010, over 70,000 head of livestock moving with Sonora, most of them cattle

, were inspected for ticks at one of Sono ra’s internal quarantine stations (not including Bahuises, which primarily captures livestock moving north from the buffer zone and is addressed below)

.

Inspections are also conducted on all animals presented for slaughter within Sonor a as part of their ante

- mortem evaluation

. Sonora administers a v eterinary i nspection s ervice in 24 slaughterhouses within the state, which account for the slaughter of 92% of the

cattle population

. A visual check for ec toparasite s is conducted by slaughter plant

official s a s part of the ante

- mortem inspection procedure at these slaughter plants

. In the

event that ticks are detected on animals intended for slaughter , the livestock inspector assigned to th e slaughterhouse is informed, the tick(s) i s collected and submitted to the

C ENAPA laboratory, and the State authorities are informed of the submission through the regional supervisor [20, 60]

.

National tick surve y A tick survey is conducted across Mexico each year. Although the primary objective of the survey is to identify Rhipicephalus spp

. ticks, all detected ticks are collected and submitted for analysis. Livestock premises are selected based on a sampling scheme developed by the Department of Epidemiology and Risk Analysis of the DGSA. The study design incorporates a 9 9 % confidence level of detection among herds at a prevalence of 1% and a within herd detection confidence level of 9 5 % and a prevalence of 10%. Premises containing at least 60 head of cattle are eligible for selection, based on random sampling. Sixty head , selected randomly, a re sampled from within each herd. During the 2010 sampling year, 479 livestock pre mises were targeted for sampling in

Sonora , with 481 premises actually sampled (two additional premises were sampled in Bacoachi municipality) . All of Sonora’s 72 municipalities were represented in the study [62, 71 , 82]57 A number of ticks were identified on Sonoran cattle during the 2010 study; however

none were Rhipicephalus spp. (it was this study that found Rhipicephalus microplus in 4 herds in the buffer zone in 2009). Ticks found during the 2010 survey includ ed : Ot obius megnini on 252 premises; R h iphicephalus sanguineus on two premises; Amblyomma cajennense and A. maculatum on one premises each; and Dermacentor albipictus on six premises [62]

.

Enhanced s urveillance in the buffer zone

A dditional surveillance activities for Rhipicephalus spp. ticks are conducted w ithin

Sonora’s buffer zone

. Approximately 181,000 of Sonora’s 1.5 million cattle reside in the

buffer zone. The extra measures are implemented due to th e region’s proximity to potentially infested areas , particularly in those municipalities and premises immediately adjacent to potentially

- infested areas [71]

.

Both active and passive surveillance measures are carried out in t he bu ffer zone

. P assive

surveillance activities are conducted in much the same manner as in the rest of Sonora, consisting primarily of tick inspection by local livestock inspectors or line dipping vat or quarantine station officals as a component of livestock movement. The difference in the

buffer zone is that tick

- related movement requirements are more stringent than in the rest

of Sonora

. All livestock moving within the buffer zone must receive an inspection for ticks as part of their movement requirements , and if departing the buffer zone for the northern part of Sonora they must also receive a tick inspection and treatment at the Bahuises quarantine station , located at the northernmost edge of the buffer zone . I n addition, livestock moving from areas adj acent to the tick

- infested regions of Sinaloa and

Chihuahua must also receive a n inspection and treatment at one of the line dipping vats

before mov ement, and if leaving the buffer zone are also subject to an additional inspection and treatment at the Bahu ises quarantine station . Approximately 3 0% of cattle

in the buffer zone reside in this area and thus are subject to two tick inspections and treatments prior to movement out of the buffer zone [20, 54]

.

Between 11,000 and 12,000 head of livestock were inspected annually at line dipping

vats in the buffer zone from 2008 to 2010 either as part of their movement requirements within the buffer zone or in preparation for moving out of the buffer zone. Almost all of the inspected animals were cattle, with a few horses included

. Additionally, approximately 47 ,000 lives tock ( again, mostly cattle , but also including a few horses, sheep, and goats ) originating from the buffer zone were inspected and treated at the Bahuises quarantine station during 2010

. There is some overlap between livestock inspected at the line dip ba th facilities and those inspected at the Bahuises quarantine station for those animals moving out of the buffer zone from higher risk areas, which requires two inspections. L ivestock from the buffer zone are also subjected to ante

mortem inspection for ti cks and other ectoparasites upon presentation for slaughter as are those in the rest of Sonora [20, 54]

. Error! Not a valid link. Active surv eillance for Rhipicephalus spp. ticks in the buffer

zones consists of a number of supplemental activities, including routine inspection and treatment for ticks on high risk premises and inspection and treatment of any livestock within the perifocal zone of previously infested premises by livestock inspectors

. These58 c attle also receive routine injection s with ivermectin (in a formulation labeled for tick control) two to three times per year, particularly if they will be in pasture and inaccessible

for tick inspection for part of the year. High risk premises consist of properties that are adjacent to or straddle the border with Sinaloa or Chihuahua ; there are currently 66 of these premises in the buffer zone , representing approximately 31,000 head of cattle. In addition to movement inspections, cattle residing on high risk premises are also inspected

on

- farm at least once a year, with any quarantined premises inspected every 21 days [54, 62, 71]

.

There are six special livestock inspectors , directly employed by Sonora, that team up in pairs and form brigades to conduct the active surveillance activities on high risk premises (in addition to 64 regular livestock inspectors in the buffer zone). The special inspectors all have porta ble chutes and treatment equipment that they can carry with them in order to conduct tick inspections and treatments on

- farm. In premises that straddle the border with Sinaloa, they also work alongside Sinaloan employees to assure that tick inspection

and control activities are conducted on both sides of the border [54, 62]

.

Discussion

Routine s urveillance for Rhipicephalus spp. ticks practiced throughout Sonora is comprised of several overlapping activities, including gene ral health inspections performed by local livestock inspectors prior to movement of livestock off of the farm, more rigorous tick inspection b y livestock inspector s prior to certain types of mov e ment

, inspections while in transit at quaran tine stations or line dipping vats

, ante

- mortem inspection at slaughter

, and annual nationwide tick surveys

.

Supplemental measures employed in the buffer zone include additional tick inspection opportunities for livestock during movement, both at the Bahuises quarantine station at the northern perimeter of the buffer zone and at the line dipping vats located within the buffer zone. The increased density of inspection and dipping stations located in the buffer zone, along with supplemental dipping requirements create a m ore robust passive surveillance program than is practiced throughout the rest of Sonora. Enhanced on

- farm inspections and treatment of animals on high risk, quarantined, and nearby premises are also conducted two to three times throughout the year.

The o verlapping surveillance measures used to detect ticks in Sonoran livestock are well organized and implemented and appear to be effective, as has been demonstrated by the periodic identification of ticks in Sonora’s buffer zone.

10. Diagnostic laboratory capacity

The National Center for Animal Health Verification Services ( CENAPA), located in

Morelos

, Mexico, is the national reference laboratory for parasitic diseases and residues

. It operates under the DGSA within SENASICA. Currently, this is the only laboratory used by Sonora in the identification of ticks collected from livestock and the analysis of acaricidal solution. The laboratory was created in 1976 as the National Animal Parasitology Center in order to provide support to the National Campaign against Cattle59 Tick. It has since been restructured, and currently includes offices overseeing ectoparasites and hematophagous flies, hemoparasites and helminthes, animal feeds and medicines, and toxic residues [83]

.

In October 2000 the United Nations Food and Agriculture Organization declared

CENAPA as the Reference Center for the Resistance of Ticks to Pesticides for Central

A merica and the Caribbean. The purpose was mainly to provide diagnostic services for

the detection of resistance in Rhipicephalus spp. ticks, as well as training of Mexican,

Central American and Caribbean technicians on resistance [83]

.

The Ectoparasite and Diptera Office of CENAPA conducts activities related to ticks, bloodsucking flies, and bees. This office provides speciation of preserved ticks as well as the acaricide resistance profile of live ticks that are submitted by livestock inspectors, quarantine officials and other animal health personnel in Sonora. This office also conducts testing of acaricide samples to determine their effectiveness, conducts biological verification of acaricide effectiveness in order to license their use in Mexico,

and maintains references strains of Rhipicephalus spp. ticks. In addition, staff from this office provide training to field staff in the detection of ticks and maintenance of acaricide

solution [83]

.

An important function of this office is evaluating and monit oring changes in the acaricide resistance of ticks submitted by field personnel throughout Mexico in collaboration with the National Campaign against Cattle Fever Ticks in order to identify zones that are believed to be at high risk for the development of resistance to the various acaricides currently in use in Mexico. Methodologies used in the characterization of resistance include the Adult Immersion Technique (AIT), Larvae Package Technique (LPT) and Stone’s Technique . For analysis of acaricide levels ultraviolet/visible spectrophotometry is used for coumaphos and high resolution liquid chromatography is used for a mitraz [60, 83]

.

Employee training in the analysis of acaricide sam ples is provided by a number of sources, including suppliers of analytical equipment, employees at other similar laboratories (usually international laboratories) that perform the same functions, and national laboratory agencies, including the Mexican labo ratory accreditation agency, National Center of Standards and Measurements, and Department of Labor. Quality assurance audits are provided by external agencies, including the Mexican Accreditation and Standardization and Certification agencies. The audit s take place on an annual basis [71]

.

During multiple site visit s conducted by APHIS it was noted that the turnaround time for receipt of laboratory results for acaricide solution evaluation was cause for concern. In

some of the quarantine stations evaluated during the 2011 site visit, results were not received until up to 30 days after the sample was collected. Part of this delay was reportedly due to transport time to the laboratory [54, 60, 63, 72]

.

D iscussion60 A lthough the ability of the CENAPA laboratory to provide tick speciation and characterization services and evaluate acaricide solution samples appears to be sufficient, the delay in receipt of laboratory results, particular ly the analysis of acaricide samples, is a significant concern due to the potential that cattle could be treated with inadequate acaricidal solution for extended periods of time without the knowledge of inspectors (although, as mentioned previously, dippin g vat management practices greatly mitigated this concern) . The APHIS evaluation team recommended that either additional laboratory facilities or improved policies are needed in Sonora to more quickly and effectively return laboratory analysis results for tick dipping solutions used at tick dipping stations and quarantine stations in Sonora.

11. Emergency response capacity

Sonora contains a State Emergency Group for Animal Health ( Grupos Estatales de Emergencia en Salud Animal , or GEESA) which includes members from Federal, State and private sectors trained in various disciplines in animal health. This group is responsible for organization and training of personnel at all levels to respond to multiple animal health emergencies, not just those related t o Rhipicephalus spp. tick incursions and also with organization and oversight of emergency response activities. Personnel from several different areas of animal health with different backgrounds are included in the response team. The scope of the group i ncludes surveillance, diagnosis, and movement control of not only animals, but also products, byproducts, vehicles, and people. The group currently consists of 32 members [20, 54, 60]

.

All emergency response individuals (including recent veterinary graduates) receive training from GEESA at different levels based on their experience and the amount of responsibility they would have during an animal health emergency. The first level of training provides instruction on the recognition of exotic animal diseases plus information on the planning documents and operations of the emergency response system. This training is broa dly targeted to all recent or imminent veterinary graduates. The next three levels of training include additional information combined with tabletop exercises and involve increasingly specific and complex information designed for

individuals with increasi ng levels or responsibility in the event of an animal health emergency. The final two levels are intended for new and returning GEESA members. A specific tabletop exercise for Rhipicephalus spp. ticks is included in the training of

GEESA members [60]

.

The d irector of t he GEESA is the regional coordinator for the United States

- Mexico

Commission for the Prevention of Foot

- and

- Mouth Disease and Other Exotic Animal Diseases ( Comision Mexico

- Estados Unidos para la prevención y control de la fiebre aftosa y otras enfermadades exoticas , or CPA)

. The CPA operates within the DGSA of

SENASICA as part of the National System for Emergencies in Animal Health ( Dispositivo Nacional de Emergencia de Sanidad Animal , or DINESA). The mission of the CPA has expanded beyond foot and mouth disease since its inception and its

functions currently include the prevention, detection, control and eradication of exotic pests and emerging diseases of animals, as well as the protection public health. The CPA61 prepares and maintains contingency plans and procedural documents on the control and eradication of exotic diseases and implements emergency operations through DINESA. It also oversees laboratories that are involved in the detection of emerging and exotic diseases and pests, promotes disease det ection and reporting activities, and provides training and technical updates to staff at various levels of emergency response. DINESA responds to a broader range of animal health concerns, including endemic disease events and natural disasters involving a nimal health consequences [20, 84, 85]

.

The funding for response to incursions of Rhipicephalus spp. ticks in Sonora is derived from contributions made by Federal, State, and private partners. As of 2010

, the amount available in this fund was estimated at approximately $1,160,000 MX p esos (approximately $100,000 USD) . Additional funds could also be made available by the Federal government as needed [20, 60]

.

Sonora’s rapid and effective response to the most recent incursion s of Rhipicephalus spp. ticks into the buffer zone indicate that th eir emergency response syst em is able to respond quickly in containing and controlling the infestation.

Discussion Sonora appears to have an adequate system for responding to tick incursions . The State

run GEESA has ample participation from individuals within many Federal and St ate agencies as well as different sectors of private industry. Training is applied broadly in a way that incorporates different levels of participation into reporting and response

activities. Evidence of th e effectiveness of Sonora’s emergency response c apabilities with respect to Rhipicephalus spp. tick incursions has been demonstrated with in the

buffer zone in re cent years

.

C onclusions

APHIS concludes that t he likelihood that Sonora is currently infested with or will be come infest ed with Rhipicephal us spp. ticks is very low

.

The northern region of Sonora is desert

- like in climate and does not support the survival

of Rhipicephalus tick spp. eggs

. Consequently , this area has historically remained naturally free of Rhipicephalus spp. ticks

. The sout hern tip of Sonora, near its border

with Sinaloa

, comprises a buffer zone, which is similar to the permanent tick quarantine

buffer zone in South Texas in that it possesses a suitable climate for tick survival and occasionally experiences tick incursions.

Sonora has demonstrated that it has the infrastructure, personnel, and legal framework to prevent tick incursions into the free area through its program of routine tick inspection and dipping during movement from areas at risk for tick infestation

. Inspe ction stations are strategically located along major transportation routes that enter into and traverse the State. The transit guide system requires identification of livestock during movement, linking tick inspection and treatment requirements to the ori gin and destination of livestock, ensuring that appropriate control measures are applied to all livestock engaged62 in transit. Furthermore, this system, in combination with the annual livestock census

, helps ensure that animals are not moved illegally, eva ding tick inspection and treatment procedures. An important component of Sonora’s successful eradication program is its

Federal

- State

- private partnerships, which have been instrumental in accomplishing and maintaining Sonora’s Rhipicephalus

- free status.

Four infestations of Rhipicephalus spp. ticks have been detected in Sonora since

eradication was declared by SAGARPA in 1972 ; however, all occurred exclusively within Sonora’s buffer zone, were detected before the infestation became widespread,

and were co ntained and controlled within time frames established by SAGARPA. Movement controls and additional tick inspection and dipping requirements are in place for livestock that move from the buffer zone into the historically tick

- free region of

Sonora. These controls have so far been able to restrict any incursions to the buffer zone.

If Rhipicephalus spp. ticks were to enter into Sonora, internal inspection requirements could be expected to detect these ticks on Sonoran livestock. Surveillance efforts have proven effective at detecting tick incursions in the buffer zone in a timely manner.

Surveillance for Rhipicephalus spp. ticks is multi

- pronged and comprehensive, and

includes routine surveillance through an integrated system of tick inspection tied to

mo vement, an annual tick survey directed by SAGARPA, and active inspections in high

risk areas within the buffer zone.

The most significant concern identified by APHIS is the delay in receipt of dip ping vat acaricide analysis results at quarantine station s and line dipping vats . Laboratory analysis turnaround times evaluated during the 2011 site visit often exceeded three weeks from submission of sample to receipt of results. A mitigating factor is the adherence of dip ping vat personnel to routine dip pin g vat maintenance, including recharging and replacing the dip ping vat contents. In the case of high volume quarantine stations, these procedures may have been conducted multiple times before dip ping vat analysis results were received, limiting the exposur e of cattle to inadequate acaricidal solution, if it were present. Results reviewed in the dip ping vat registries indicated that overall levels of acaricidal solution concentration were maintained within the effective range. However,

d espite the responsi veness of dip ping vat personnel in conducting routine maintenance activities and undertaking recommended adjustments to the dip ping vat solution, APHIS

has concerns that this delay could potentially result in personnel unknowingly applying

ineffective acar icidal solution to cattle for an extended period of time.

Although APHIS has concerns about the delay in the turnaround time for acaricide analysis results from dipping vats, Sonoran officials and inspectors appear to maintain appropriate acaricidal con centrations in the dipping vats . This factor, when combined with Sonora’s low environmental suitability for cattle fever ticks, excellent detection and response capabilities, and overlapping movement control procedures, results in the finding of a ve ry lo w likelihood that Sonora would become infested with Rhipicephalus spp. ticks and that imported Sonoran cattle would introduce these ticks into the United

States.63 

## Exposure Assessment

In accordance with the OIE, an exposure assessment consists of describ ing the biological pathway(s) necessary for exposure of animals and humans in the importing country to the hazards released from a given risk source and estimates the probability of the exposure occurring [25]

. APHIS’ regulatory authority only extends to animal health ; therefore the exposure assessment will focus on the exposure risks to animals

.

The importation of cattle into the United States from Mexico is currently permitted provided the cattle are subject to mitigations contained in 9 CFR 93.427, among others. The regulatory action proposed in this document recommends the removal of the

r equirement for tick dipping at the U.S. border port as written in Part 93.427(b)(1) of the CFR for cattle originating from Sonora. The proposed change will only affect the legal importation of cattle; therefore, this is the only pathway that will be addre ssed in the exposure assessment. Other possible pathways, including movement of illegal and stray

cattle infested with Rhipicephlaus spp. ticks, movement of infested wildlife, and importation of tick

- infested animal by

- products and animal feed are not aff ected by the proposed action and will not be discussed further.

For purposes of this exposure assessment, a release event or outbreak is defined as an

infestation of Rhipicephlaus spp. ticks in one animal in the U.S. domestic cattle population outside th e permanent (or temporary) tick quarantine zone in Texas

. Alternatively, an outbreak could be defined as the diagnosis of bovine babesiosis in one animal in the domestic cattle population outside the tick quarantine zone. Cases of

bovine babesiosis and R hipicephlaus spp. ticks found during routine import procedures (i.e. scratch inspections at the port, quarantine facilities, etc.) or on livestock within the

tick quarantine zone will not be considered an outbreak.

Legal importation of cattle infested wit h Rhipicephlaus spp. ticks

In order for an outbreak to occur in U.S. cattle as a result of legal importation of infested cattle under the proposed regulations, multiple failures in both Sonora n and U.S. tick

detection and treatment measure would have to occur , and the cattle would have to end up in a suitable environment for tick survival

. First, infested cattle originating from

Sonora would have to be selected for export to the United States without being detected

. T ick inspection measures required at Sonoran inspection stations and as a component of

Sonoran livestock movement requirements would then have to fail, as would any tick treatments required during movement to the U.S. border. On arriving at the U.S. border
port, the infested cattle would hav e to pass a scratch inspection without detection of the

ticks. Following importation, the infested cattle would have to be transported within the

United States to a n environment that favors the survival of Rhipicephlaus spp

. ticks (refer

to the Hazard Ide ntification for further details)

. An adult female tick would have to feed sufficiently to produce eggs , drop from the imported animal and find a suitable

environment to lay the eggs, and produce viable larvae , all in close enough proximity to

U.S. cattle in order for the larvae to attach to a domestic cattle host.64 Based on the historic endemic range of Rhipicephlaus spp

. ticks, climatic conditions, and general movement patterns of Mexican cattle, exposure of the U.S. cattle population to

fever ticks , if they were imported on cattle from Sonora, would most likely occur in the southern United States. However, the variability of seasonal weather patterns, possible climatic changes, and livestock movement pa tterns within the United States could create
suita ble microclimates outside these parameters and allow pockets of Rhipicephlaus spp

. ticks to survive in unexpected or unprecedented regions of the United States.

Approximately one million cattle are exported into the United State from Mexico per year. Catt le enter through various ports in Arizona, New Mexico and Texas. Although cattle from Mexico are shipped all over the United States, most end up in s tates where large amounts of cattle feeding occur s such as California, the central United States, and

the s outhwest [86]

. Thus, Mexican cattle could be commingled with domestic herds in regions that could sustain the life cycle of Rhipicephlaus spp

. ticks. Sonora exported an average of 240,000 head of cattle to the United States per year between 2007 and 2010.

Due to the many overlapping tick prevention and detection measures in place in Sonora, as well as at the U.S. border ports, combined with environmental and transmission requirements for successful movement of ticks to the domestic cattle pop ulation, APHIS

considers the likelihood of an outbreak of Rhipicephlaus spp. ticks in domestic livestock resulting from the legal importation of undetected infested cattle from Sonora to be low

.65 

## Consequence Assessment

In accordance with the OIE, the consequence assessment consists of describing the relationship between specified exposures to a biological agent and the consequences of those exposures. Direct consequences include animal morbidity and mortality, production losses, and public health cons equences while indirect consequences include surveillance and control costs, trade losses, and adverse consequences to the environment [25]

. This consequence assessment will consider both direct and indirect consequences of introducing the hazard under con sideration in to the United States.

For purposes of this consequence assessment, an outbre ak is defined as an infestation of Rhipicephalus (= Boophilus ) spp

. ticks in one animal in the U.S. domestic cattle population outside the tick quarantine z one. Alternatively, an outbreak could be defined as the diagnosis of bovine babesiosis ( B. bovis or B . bigemina) in one animal in the domestic cattle population outside the tick q uarantine z one.

Biological consequences Direct consequences of an outbreak need to consider the biological consequences of a Rhipicephalus spp

. tick infestation or bovine babesi osis. It is assumed that the U.S. domestic cattle population is a naïve, or non

- endemic population, with a general lack of immunity to B. bigemina and/or B. bovis

. If the cattle are found to be infested with Rhipicephalus spp

. ticks in the absence of bov ine babesiosis, morbidity and mortality are expected to be low. Although tick infestations can cause some morbidity, especially in the very young and immunodeficient, death is uncommon. Severe tick infestations can cause anemia, poor growth, decreased mil k production, and damage to hides and skin.

In contrast, bovine babesiosis can cause significant morbidity and mortality in fully susceptible populations. Morbidity is expected to be greater than 50% with older animals

more affected than calves. Simila rly, mortality rates will also be greater than 50%, perhaps approaching 90%

, with B. bovis generally resulting in a more severe infection. Animals that do survive can remain persistently infected and can contribute to persistence

of the disease if Rhipice phalus spp

. ticks are also present. Additionally, those that survive have a slow recovery and production losses associated with severe weight loss, drop in milk production, and abortion can be expected. If bovine babesiosis becomes endemic in the populat ion, morbidity and mortality rates will subsequently drop as cattle can develop lifelong resistance to a species after infection [26, 87]

.

Although the biological cons equences of infestation of U.S. cattle with Rhipicephalus spp. ticks are low, if the infestation were to lead to infection of the U.S. cattle population

with bovine babesiosis , the consequences would be high, particularly in the early stages

of the outbrea k while the majority of cattle are susceptible to acute infection.

Public health consequences66 Although public health is not under the authority of APHIS, public health consequences will be briefly mentioned. Neither B . bovis nor B

. bigemina are believe d to be zoonotic, so transmission of the infection to people is not a concern [26]

.

Exposure to the acaricid e chemicals , however, can result in public health concern s

. Coumaphos is an organophospate that can cause acute toxicity to humans via

cholinesterase inhibition. It can be fatal if swallowed and may be absorbed through the skin, mucous membranes and throu gh inhalation [88]

. Increased occupational exposure of animal health personnel to coumaphos during an outbreak of Rhipicephalus spp. ticks

or bovine bab esiosis in the United States would be expected. The general public could be exposed through ground and water contamination . However, p ersonal protective

measures a nd pesticide disposal protocols could be expected to mitigate both of these exposures. Pers onal protective equipment guidelines are stated in VS Memo 556.1 Supplemental No. 11 titled, Use of Personal Protective Equipment (PPE) when Using Permitted Pesticides for the Control and Eradication of Cattle Ticks

. Disposal guidelines

are stated in VS M emo 556.1 Supplement No. 10 titled, Procedures for Storage and Disposal of Permitted Pesticides

.

Additionally, depending on the size of the outbreak, there may be psychosocial effects on farmers and the farming community as a result of loss of livestock and revenue associated

with outbreak control measures. Loss of animals, particularly expensive or rare breeding stock, disruption to business due to quarantine measures and movement restrictions,

economic burden s from revenue losses, and stress of uncerta in financial future can result in increased stress and distress in people during animal disease outbreaks.

A Rhipicephalus spp

. tick outbreak would be expected to be isolated , with relatively limited numbers of producers affected and control measures wo uld not likely include destruction of infested animals. Additionally, current measures could be expected to mitigate human exposure to pesticides used to treat the tick infestation.

Economic consequences It is likely that movement restrictions would be imposed in the event of a domestic

infestation with Rhipicephalus spp. ticks , involving affected herds as well as neighboring and epidemiologically linked herds. In addition, enhanced surveillance, inspection and

treatment measures would likely be undert aken by livestock authorities. Implicated

s tate(s) may also be subject to movement restrictions or additional requires for entry into

unaffected s tates

, including additional inspections and/or dipping requirements. International trading partners could be expected to apply restrictions on live cattle from the United States and associated products, at least temporarily

.

Although difficult to accurately predict, the economic impact of a single outbreak is likely to be significant. In a report from the Agri cultural and Food Policy Center at Texas A&M University, analysts constructed a model to forecast the economic impact of

a relatively small Rhipicephalus spp

. tick outbreak outside of the tick quarantine zone i n Texas as well as a more extensive outbreak w ith in the historic tick range of the United

States

. The annual cost for the small outbreak (defined as 3 infestations) in Texas was67 estimated at $123 million the first year and $93 million per year for subsequent years. For

a 500 cow

- calf herd, producer c osts in the first year were estimated at $250 per head

. Extending the outbreak to the 14 states that comprise the historic range of Rhipicephalus

spp

. ticks would conservatively cost over $1.2 billion in the first year [89]

.

The FY 2010 budget for the Cattle Fever Tick Eradication Program was $13.1 million. Even a relatively small outbreak would far exceed the budgetary resources needed to

control and eradicate Rhipicephalus spp

. ticks. The burden of additional funding for surveillance, dipping and inspections, in demnity, new dipping facilities, acaricide acquisition and disposal mechanisms , etc. would likely be borne by producers, State Governments, and APHIS. Additional revenue losses from trade restrictions, both domestic and international, would be expected to cause additional damage the U.S. cattle industry.

Environmental consequences Environmental consequences resulting from a Rhipicephalus spp

. tick outbreak would

result primarily from the use of additional acaricide in an effort to control the infestatio n. If bovine babesiosis were to result from the infestation, increased consequences may also occur as a result of increased carcass disposal due to livestock mortalities.

For acaricide disposal, human and animal exposure to spent dip ping vat coumaphos in the environment (ground and water sources as well was dietary sources) are mitigated by U.S. regulations

. Currently, bioremediation (aerobic microbial degradation) of spent dip ping vat water followed by storage in shallow, concrete lined evaporation po nds is required to be employed at U.S. Cattle Fever Tick Eradication Program dip ping vats in the disposal of spent coumaphos solution [88, 90, 91]

. Disposal guidelines are stated in VS Memo 556.1 Supplement N o. 10 titled, Procedures for Storage and Disposal of

Permitted Pesticides

. Because of these regulations the environmental impact of disposal of spent dip ping vat acaricidal solution would likely be low.

M ortalities would be expected to occur in the event of exposure of U.S. cattle to bovine

babesiosis , at least initially, as this population is considered to be fully susceptible to B. bigemina and B. bovis

. In addition, increased dipping of cattle as part of the enhanced tick control measures could be exp ected to lead to a small amount of morbidity and mortality in treated cattle, particularly young or weak animals, potentially as a result of drowning, aspiration pneumonia, or toxicity.

Disposal of the additional carcasses could potentially have an eff ect on air quality (if incineration is used) or ground water (if burial is used). However, the expected number of additional mortalities is expected to be low. In addition, both State and Federal regulations would govern incineration and burial, likely m inimizing or eliminating the effect of carcass disposal on air quality and ground water contamination, so the ultimate impact to the environment could be expected to be low.68 

## Risk Estimation

Risk estimation consists of integrating the results from the release assessment, exposure assessment, and consequence assessment to produce an overall measure of risk associated with the hazards identified at the outset of the evaluation. Thus, risk estimation takes into account the whole risk pathway from hazard identified to the unwanted event [25, 92]

.

APHIS concludes from the release assessment that t he likelihood that Sonora is currently

or will become infested with Rhipicephalus spp. ticks is very low. This is due in part to

the historical absence of Rhipicephalus spp. ticks from Sonora as a result of its climate, as well as its robust inspection, t reatment, and movement programs, which are largely

successful due to the coordinated involvement of Federal, State, and private entities in Sonora’s tick eradication and prevention programs . Given th at APHIS considers the risk

of Rhipicephalus spp. tick i nfestation in Sonora to be very low, APHIS consequently

concludes that removal of the requirement that Sonoran cattle receive a dipping vat

treatment at the Sonoran port of entry into the United States is not likely to result in the exposure of U.S. cattle to these ticks.

APHIS concludes from the exposure asse ssment that the risk of Rhipicephalus spp. ticks reaching the U.S. cattle population is low. Sufficient exposure would require the

occurrence of a number of sequential adverse events following the importation of

undetected Rhipicephalus

- infested cattle into the United States . These would include a

failure of tick mitigations applied at the U.S. border ports, transport of imported cattle to an environment that could support the survival and replicat ion of these ticks, and contact
of the resulting larval ticks w ith domestic cattle. The combined risk of release and exposure is, therefore, extremely low.

T he consequences of Rhipicephalus spp. ticks entering into the U nited S tates , resulting in

a tick outbreak would likely result in the implementation of a control campaign, which could be costly, especially if it becomes extensive. In contrast, if the tick infestation

resulted in a resurgence of bovine babesiosis in the indigenous cattle populatio n , the additional consequences in terms of cattle morbidity and mortality could be significant. Additionally, movement restrictions within the United States, as well as export trade losses, could be expected to add to these consequences

.

In summary, alth ough the consequences of an outbreak of Rhipicephalus spp. ticks in the

U

. S

. cattle population could be costly, especially if associated with bovine babesiosis,

APHIS considers the risk of Rhipicephalus

- infested cattle entering the U nited S tates from

Sonor a resulting in exposure to U

. S

. cattle , even with the removal of the tick dipping requirement at the U.S. border port, and subsequent transmission of bovine babesiosis to

the U

. S

. cattle herd to be very low.69 

## References

1. Graham, O.H. and J.L. Hourrigan, Eradication Programs for the Arthropod Parasites of Livestock. Journal of Medical Entomology, 1977. 13 (6): p. 629

- 658.

2. Duhaime, R., NAHSS Outlook

- Surveillance Requirements of Cattle Fever Tick

Outbreak , APHIS/VS/CEAH/NCAHS/NSU , Editor. 2009.

3. USDA APHIS, Controlling Cattle Fever Ticks , in APHIS Factsheet . 2002.

4. Bram, R.A. and J.H. Gray (1979) Eradication

- an alternative to tick and tick

borne disease control . Ticks and tick

- borne disease: selected articles from the

World Animal Review Volume

, 5. ARS. The continuing fight against cattle ticks . 2006 [cited 2011 July]; Available

from: http://www.ars.usda.gov/is/AR/archive/jun06/ticks0606.htm

. 6. Ev erett, C. Fever Tick Quarantine in South Texas . 2011 [cited 2011 July];

Available from: http://www.texasdeerassociation.com/article_info.php?articles_id=297

. 7. Pelzel, A., Cattle Fever Tick Surveillance in Texas , in NAHSS Outlook . 2005.

8. CFSPH. Rhipicephalus (Boophilus) microplus

- Center for Food Security and Public Health, College of Veterinary Medicine, Iowa State University . 2007 [cited; Available from: http://www.cfsph.iastate.edu/Factsheets/pdfs/boophilus_microplus.pdf

. 9. CFSPH. Rhipicephalus (Boophilus) annulatus

- Center for Food Security and Public Health, College of Veter inary Medicine, Iowa State University . 2007 [cited; Available from: http://www.cfsph.iastate.edu/Factsheets/pdfs/boophilus_annulatus.pdf

. 10. USDA APHIS, 2011 Denver CO BNC Tick Minutes

- The Binational Boophilus spp. Tick Committee, . 2011.

11. TAHC. Press Release: TAHC Releases the Remainder of the Olmal Temporary Preventative Quarantine Area in Starr and Hidalgo Counties

- July 26, 2011

. 2011 [cited July 2011]; Avail able from: http://www.tahc.state.tx.us/news/pr/2011/2011July_StarrHidalgoFeverTickQuara ntineRelease.pdf

. 12. Durham, S., Ridding the Texas

- Mexico Border of Cattle Fever Ticks. Agricultural Research Magazine, 2010. 58 : p. 18

- 19.

13. Fears, R., Money to Fight Fever Ticks , in The Cattleman . 2009, Texas and Southwestern Cattle Raisers Association,.

14. George, J.E., Use and abuse of Ivermectin: Selectio n of acaricide

- resistant cattle fever ticks United States

- Mexico Binational Tick Committee Meeting, Reno,

Nevada. , in The Binational Boophilus spp. Tick Committee . 2008.

15. George, J.E., J.M. Pound, and et al., Chemical control of ticks on cattle and the resistance of these parasites to acaricides Parasitology, 2004. 129 Suppl : p. S353

- 66,.70 16. Miller, R.J., R.B. Davey, and J.E. George, First Report of Organophosphate

Resistant Boophilus microplus (Acari: Ixodidae) within the United States of

America. Jour nal of Medical Entomology, 2005. 45 (2): p. 912

- 917.

17. Rosado

- Aguilar, J.A., R.I. Rodriguez

- Vivas, and et al., Development of amitraz resistance in field populations of Boophilus microplus (Acari: Ixodidae) undergoing typical amitraz exposure in the Mexic an tropics. Veterinary Parasitology, 2008. 152 (3): p. 349

- 353.

18. Aguilar, J. Ticked 2010 [cited 2010 February]; Available from: http://www.texastribune.org/stories/2010/feb/01/ticke d

. 19. Messenger, M., Cattle Fever Eradication Program National Update in United States Animal Health Association 2010 Annual Meeting, Minneapolis, Minnesota

. 2010.

20. SAGARPA, REQUEST FOR THE RECOGNITION, BY THE UNITED STATES
DEPARTMENT OF AGRICULTURE, OF THE STATE OF SONORA AS A REGION FREE FROM TICK OF THE GENUS Boophilus spp. 2002.

21. SENASICA, CAMPAÑA NACIONAL CONTRA LA GARRAPATA Boophilus

SPP. , in Presented during May 2011 site visit . 2011.

22. SENASICA. National Campaign against Boophilus tick spp . (Campaña Nacional contra la Garrapata Boophilus spp.) . 2011 [cited 2011 July]; Available from: http://www.senasica.gob.mx/?id=803

. 23. NCIE. List of USDA

- Recognized Animal Health Status of Countries/R egions Regarding Specific Livestock or Poultry Diseases, or Acceptable Commodities 2011 [cited 2011 July]; Available from: http://www.aphis.usda.gov/import_export/ animals/animal_disease_status.shtml

. 24. SAGARPA, Official Mexican Standard NO M

- 019

- ZOO

- 1994 (National Campaign against the Tick, Campaňa Nacional contra la Garrapata Boophilus spp.) , Mexico, Editor. 1995.

25. OIE. Terrestrial Animal Health Code 2010 Volume 1, Section 2, Chapter 2.1,

IMPORT RISK ANALYSIS . 2010 [cited 2011 July]; A vailable from: http://www.oie.int/index.php?id=169&L=0&htmfile=chapitre_1.2.1.htm

. 26. CFSPH. Bovine Babesiosis: Center for Food Security and Public Health, College of Vet erinary Medicine, Iowa State University . 2005 [cited; Available from: http://www.cfsph.iastate.edu/Factsheets/pdfs/bovine_babesiosis.pdf

. 27. Kahn, C.M., ed. The Merck Ve terinary Manual . 9 ed. 2008, Merck & Co., Inc.: Whitehouse Station, NJ.

28. Cantu, A., et al., Immunologic and molecular identification of Babesia bovis and Babesia bigemina in free

- ranging white

- tailed deer in northern Mexico. Journal

Of Wildlife Diseases , 2007. 43 (3): p. 504

- 507.

29. Bock, R.E., T.G. Kingston, and A.J. De Vos, Effect of breed of cattle on innate resistance to infection with Anaplasma marginale transmitted by Boophilus microplus. Australian Veterinary Journal, 1999. 77 (11): p. 748

- 751.

30. Zintl, A., et al., Possible mechanisms underlying age

- related resistance to bovine

babesiosis. Parasite Immunology, 2005. 27 (4): p. 115

- 120.

31. Brown, W.C., et al., Immune control of Babesia bovis infection. Veterinary Parasitology, 2006. 138 (1/2): p. 75

- 87.71 32. Fahrimal, Y., W.L. Goff, and D.P. Jasmer, Detection of Babesia bovis carrier cattle by using polymerase chain reaction amplification of parasite DNA. Journal of Clinical Microbiology, 1992. 30 (6): p. 1374

- 1379.

33. Howell, J.M., et al., Persistent ly Infected Calves as Reservoirs for Acquisition and Transovarial Transmission of Babesia bovis by Rhipicephalus (Boophilus) microplus. Journal of clinical microbiology JCM, 2007. 45 : p. 3155

- 3159.

34. Oliveira

- Sequeira, T.C.G., et al., PCR

- based detection of Babesia bovis and Babesia bigemina in their natural host Boophilus microplus and cattle. International Journal for Parasitology, 2005. 35 (1): p. 105

- 111.

35. Smith, B.P., ed. Large Animal Internal Medicine . 1990, C.V. Mosby St. Louis,

MO.

36. Dalgliesh , R.J. and N.P. Stewart, Some effects of time, temperature and feeding on infection rates with Babesia bovis and Babesia bigemina in Boophilus microplus

larvae. International Journal for Parasitology, 1982. 12 (4): p. 323

- 326.

37. Dalgliesh, R.J., N.P. Stew art, and L.T. Mellors, Some effects of temperature on the life

- cycles of Babesia bovis and Babesia bigemina in the tick Boophilus microplus. Australian advances in veterinary science, 1979: p. 73

- 74.

38. Estrada

- Pena, A., Climate Warming and Changes in Hab itat Suitability for Boophilus microplus (Acari: Ixodidae) in Central America. Journal of Parasitology, 2001. 87 (5): p. 978

- 987.

39. Ouhelli, H. and E. Schein, Effect of temperature on transovarial transmission of Babesia bigemina (Smith and Kilborne, 1893 ) in Boophilus annulatus (Say, 1821). Veterinary Parasitology, 1988. 26 (3

- 4): p. 229

- 235.

40. Riek, R.F., The life cycle of Babesia bigemina (Smith and Kilborne, 1893) in the tick vector Boophilus microplus (Canestrini). Australian Journal of Agricultural Research, 1964. 15 (5): p. 802

- 821.

41. Sutherst, R.W., A.S. Bourne, and I.D. Sutherland, Production and survival of eggs of the cattle tick Boophilus microplus (Canestrini) (Acarina: Ixodidae) in the wet and dry tropics of north Queensland. Australian Jour nal of Entomology,

1999. 38 (4): p. 340

- 347.

42. Estrada

- Peña, A., et al., The Known Distribution and Ecological Preferences of the Tick Subgenus Boophilus (Acari: Ixodidae) in Africa and Latin America. Experimental and Applied Acarology, 2006. 38 (2): p. 21 9

- 235.

43. Estrada

- Peña, A., Z. Garcia, and H.F. Sanchez, The distribution and ecological preferences of Boophilus microplus (Acari: Ixodidae) in Mexico. Experimental & Applied Acarology, 2006. 38 (4): p. 307

- 316.

44. Estrada

- Peña, A. and J.M. Venzal, High

- resolution predictive mapping for Boophilus annulatus and B. microplus (Acari: ixodidae) in Mexico and Southern

Texas. Veterinary Parasitology, 2006. 142 (3/4): p. 350

- 358.

45. George, J.E., R.B. Davey, and J.M. Pound, Introduced ticks and tick

- borne

diseas es: the threat and approaches to eradication. The Veterinary Clinics Of North America. Food Animal Practice, 2002. 18 (3): p. 401.

46. Davey, R.B., L.M. Cooksey, and J.L. Despins, Survival of larvae of Boophilus annulatus, Boophilus microplus, and Boophilus hybrids (acari: ixodidae) in different temperature and humidity regimes in the laboratory. Veterinary Parasitology, 1991. 40 (3

- 4): p. 305

- 313.72 47. Estrada

- Peña, A., et al., A retrospective study of climatic suitability for the tick Rhipicephalus (Boophilu s) microplus in the Americas. Global Ecology & Biogeography, 2005. 14 (6): p. 565

- 573.

48. Smith, E.I., Tick Eradication in the South. Jl. American Vet. Med. Assoc., 1920.

57 (4): p. 423.

49. CENAPA. Current situation of tick resistance in Mexico . in United States

– Mexico Binational Boophilus spp. Tick Committee Meeting . 2008. Reno, NV.

50. Rodriguez

- Vivas, R.I., et al., Prevalence and potential risk factors for organophosphate and pyrethroid resistance in Boophilus microplus ticks on cattle ranches from the State of Yucatan, Mexico. Veterinary Parasitology, 2006. 136 (3

- 4): p. 335

- 342.

51. Santamaria, V.M., et al. Analisis de la situacion Actual ediante el monitoreo de susceptibilidad a ixodicidas en Boophilus microplus de 1993 a 1999 y medidas preventivas pa ra retardar la resistencia al amitraz en Mexico. in IV Seminario Internacional de Parasitologia Animal: Control de la Resistancia en Garrapatas y Moscas de Importancia Veterinaria y Enfermedades que transmiten . 1999. Puerto Vallarta, Jalisco, Mexico.

52. S oberanes, C.N., et al., First case reported of Amitraz resistance in the cattle tick Boophilus microplus in Mexico. Tecnica Pecuaria en Mexico, 2002. 40 (1): p. 81

- 92.

53. APHIS, Site Visit Report (Report of the Review of the State of Sonora for recognition of the state as a region free of Boophilus spp. and the elimination of the dipping requirement for cattle being exported to the United States) . 2002.

54. USDA APHIS, Observations, presentations and discussions conducted during the May 2011 site visit . 201 1.

55. SAGARPA, Federal Law on Animal Health (Ley Federal de Salud Animal)

, Mexico, Editor. 2007.

56. SAGARPA, INFORMATION REQUESTED BY APHIS, PREVIOUS OT THE

VISIT FOR THE RECOGNITION OF HTE STATE OF SONORA AS A REGION FREE OF CATTLE FEVER TICK (BOOPHILUS SPP). 2006.

57. USAHA. Report of the Committee on Parasitic Diseases (Fragoso) . in United

States Animal Health Association . 2006.

58. SAGARHPA, Sonora’s Livestock Law (Ley de Ganaderia para el Estado de Sonora) , Sonora, Editor. 2005.

59. SENASICA. SERVICI O NACIONAL DE SANIDAD, INOCUIDAD Y CALIDAD

AGROALIMENTARIA

- Portal de Obligaciones de Transparencia . 2011 [cited 2011 July]; Available from: http://portaltransparencia.gob.mx/pot/estructura/showOrganigrama.do?method=sh owOrganigrama&_idDependencia=08210

. 60. SAGARPA, Additional questions for the Evaluation of the Rhipicephalus (Boophilus) spp. Tick Eradication Program of the Sta te of Sonora, Mexico . 2010.

61. SAGARHPA, CRUCE DE GANADO POR EL ESTADO DE SONORA (CATTLE CROSSING THE STATE OF SONORA) , in Presented during May 2011 site visit

. 2011.

62. Comite, Situación Actual del Programa de Vigilancia de la Garrapata Boophilus

spp. e n el Estado de Sonora. , in Presented during May 2011 site visit . 2011.73 63. USDA APHIS, Report of the Second Site Visit to the Mexican Stateof sonora in Recognition of the State as a Region Free of Boophilus species Ticks . 2006.

64. SAGARHPA, yaSonora Garr ap.Booph Ver.2006.ppt, presented at The Binational Boophilus spp. Tick Committee, 2006 . 2006.

65. USDA APHIS, 2009 Aguascalientes BNC Tick Minutes

- The Binational Boophilus spp. Tick Committee . 2009.

66. SAGARPA, Recognition of Baja California as Free Tic k Fever Zone by USDA

. 2008, United States

– Mexico Binational Boophilus spp. Tick Committee Meeting, Reno, NV, Feb. 6, 2008.

67. SAGARPA, Recognition as Free Cattle Fever Tick's Zones in Mexico

- Chihuahua, Coahuila . 2008, United States

– Mexico Binational Boophilus spp. Tick Committee Meeting, Reno, NV, Feb. 6, 2008.

68. CEFPPS, CAMPAIGN AGAINST Boophilus spp TICKS IN THE STATE OF SINALOA (CAMPAÑA CONTRA LA GARRAPATA BOOPHILUS SPP EN EL
ESTADO DE SINALOA) , in Presented during May 2011 site visit , Comité E statal de Fomento y Protección Pecuaria del Estado de Sinaloa A.C., Editor. 2011:

Sinaloa.

69. SAGARPA, Cattle Fever Tick's Advance from Baja California Sur, Durango and

Sinaloa States . 2008, United States

– Mexico Binational Boophilus spp. Tick

Committee Meeting, Reno, NV, Feb. 6, 2008.

70. SAGARPA, USDA/APHIS

- SAGARPA/SENASICA MEETING, HELD IN SAN LUIS POTOSI RELATED TO SONORA STATE'S REQUEST TO BE

RECOGNIZED AS FREE FROM BOOPHILUS SPP TICK. , in Transcript . 2006?

71. SAGARPA, SAGARPA/SENASICA/DGSA response to APHIS site visit follow

- up questions of September 13, 2011 . 2011.

72. USDA APHIS, Site Visit Report (Report of the Review of the State of Sonora for recognition of the state as a region free of Boophilus spp. and the elimination of the dipping requirem ent for cattle being exported to the United States) . 2002.

73. GTA. Global Trade Atlas . 2011 [cited 2011 July].

74. SAGARPA, Recognition of Sonora as Free Tick Fever Zone by USDA . 2008,

United States

– Mexico Binational Boophilus spp. Tick Committee Meet ing, Reno, NV, Feb. 6, 2008.

75. SAGARPA, Response to the Observations Carried Out by USDA (post 2006 site visit) . 2008.

76. SAGARHPA, Operating Manual for Quarantine Stations using Amidines (Manual de Operación de Estación Cuarentenaria con Amidina) , Sono ra, Editor.

2009.

77. USDA APHIS PPQ, Animal Products Manual. [cited 2011 July 20]; Available from: http://www.aphis.usda.gov/import_export/plants/manuals/ports/apm.shtm l

. 2010.

78. USDA APHIS VS, Review of the tick eradication and control program relative to hay production and export in northern Mexico. March 2000. 2000.

79. Pound, J.M., et al., Evidence for role of white

- tailed deer (Artiodactyla: Cervidae) in epizooti ology of cattle ticks and southern cattle ticks (Acari: Ixodidae) in reinfestations along the Texas/Mexico border in South Texas: a review and update. . J Econ Entomol, 2010. 103 (2): p. 211

- 218.74 80. Samuel, W. and M. Pybus, Parasitic diseases of wild mam mals , ed. Wiley

Blackwell. 2001.

81. APHIS, Report of the Second Site Visit to the Mexican Stateof sonora in Recognition of the State as a Region Free of Boophilus species Ticks . 2006.

82. SAGARPA, Tamaño de Muestra para la Vigilancia Epidemiológica de la Garrapata Boophilus spp. en la Población Bovina de Baja California. Dirección General de Salud Animal (DGSA), Information gathered via USDA personnel on the official site visit to Baja California February 22

- 26, 2010 . 2009.

83. SENASICA. CENAPA

- National A nimal Health Verification Services Center

. 2010 [cited 2011 July]; Available from: http://senasica.bio.com.mx/default.asp?idioma=2&id=811

. 84. SENASICA. Dispositivos de Emergencia (E mergency Operations)

- SAGARPA,

SENASICA . 2011 [cited 2011 July]; Available from: http://www.senasica.gob.mx/?id=537

. 85. SENASICA. CPA

- La Comisión México Americana para la Erradicación de la Fiebre Aft osa (Mexico

- United States Commission for the Prevention of Foot

- and

Mouth Disease and Other Exotic Animal Disease) . 2011 [cited 2011 July];

Available from: http://www.senasica.gob.mx/?id=813

. 86. Skaggs , R., et al., Live Cattle Exports from Mexico into the United States: Where Do the Cattle Come From and Where Do They Go? , in Choices

- American Agricultural Economics Association . 2004. p. 25

– 30.

87. Spickler, A.R., J.A. Roth, and et al., eds. Emerging an d Exotic Diseases of

Animals . 3rd ed., ed. I.S.U. Institute for International Cooperation in Animal Biologics, College of Veterinary Medicine, Ames, IA.,. 2008.

88. EPA. United States Environmental Protection Agency. R.E.D. Facts: Coumaphos. August 1996 [cited; Available from: http://www.epa.gov/oppsrrd1/reregistration/REDs/factsheets/0018fact.pdf] . 1996 [cited.

89. Anderson, D.P., et al., Economic Impact of Expand ed Fever Tick Range

, A.a.F.P.C.

- T.A.M. Univeristy, Editor. 2010.

90. Personal Communication. Matthew Messenger, USDA APHIS, Ruminant Health Programs, Tick Program Entomologist. 2011.

91. Mulbry, W., E. Arhens, and J. Karns, Use of a Field

- Scale Biofilter f or the Degradation of the Organophosphate Insecticide Coumaphos in Cattle Dip

Wastes. . Pesticide Science, 1998. 52 (3): p. 268

- 274.

92. OIE. Terrestrial Animal Health Code

- 2007 PART 1, SECTION 1.3, RISK

ANALYSIS 2007 [cited 2007 August]; Available from : http://www.oie.int/eng/normes/mcode/en_titre_1.3.htm

.