####### **Evaluation of the Exotic Newcastle Disease Status**![](media/image1.png){width="1.1569444444444446in" height="0.8270833333333333in"}

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####### **The Yucatan Peninsula -- Mexico**

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####### **(States of Yucatan, Quintana Roo and Campeche)**

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**National Center for Import and Export**

**Regionalization Evaluation Services**

**December 2001**

**APHIS Evaluation of the Exotic Newcastle Disease Status of the Yucatan
Peninsula, Mexico** **(States** **of Yucatan, Quintana Roo, and**
**Campeche)**

**Introduction**

The Animal and Plant Health Inspection Service (APHIS) has evaluated the
Newcastle Disease (END) status of three Mexican States on the Yucatan
Peninsula. These are Yucatan, Quintana Roo, and Campeche. The evaluation
was conducted to identify any factors that might contribute to the risk
of introducing END virus into the United States through the importation
of poultry or poultry products from the Yucatan Peninsula and to provide
a decision-making tool to help with the determination of the END status
of the region.

The evaluation has been based on a review of documents supplied by the
Mexican Government through the Secretariat for Agriculture, Livestock,
Rural Development, Fisheries and Food Safety (SAGARPA). As part of this
evaluation APHIS conducted a site visit to the Yucatan Peninsula in
March of 2001.

In accordance with its regulations, APHIS evaluated the following
factors:

• Authority, organization and infrastructure of veterinary services;

• Disease surveillance;

• Diagnostic laboratory capabilities;

• Disease outbreak history and disease prevalence;

• Active disease control programs, if any, if the agent is known to
exist in the region;

• Vaccination status;

• Disease prevalence and outbreak history in adjacent regions;

• Separation of the region from regions of higher risks through physical
or other barriers;

• Control of movement of animals and animal products from the regions of
higher risk;

• Livestock demographics and marketing practices; and

• Animal health policies and infrastructure for animal disease control.

A summary of the data relating to each of these factors is provided
below.

**Authority, organization and infrastructure of regional veterinary
services \[2, 4\]**

The Secretariat for Agriculture, Livestock, Rural Development, Fisheries
and Food Safety (SAGARPA) conducts sanitary and phytosanitary programs
in conjunction with State and industry groups under a commission
structure. Examples of programs under authority of SAGARPA and of the
Directorate for Animal Health (DGSA), which operates under SAGARPA, are
(a) animal disease control or eradication activities including
quarantine and movement restrictions, (b) accreditation of professionals
to perform program activities, (c) disease reporting, (d) emergency
response, (e) disease diagnosis, and (f) animal depopulation.
International sea and airport border control for animal and plant and
products is under the authority of SAGARPA and the Directorate for
Phyto- and Zoosanitary Inspection (DGIF).

Each State has a Federal Delegate and other Federal personnel assigned
to conduct the Federal animal health activities in that State. Other
personnel include an Assistant Delegate, as well as DGSA and DGIF
personnel assigned to work in the State. Authority and control for
exotic animals is under the Department of the Environment and Natural
Resources (SEMARNAT).

Specific State or Federal personnel assigned to the regional coordinator
for animal health are as follows:

  ----------------------------------- -----------------------------------
  Campeche                            25

  Quintana Roo                        45 (includes 10 for FMD prevention
                                      and surveillance)

  Yucatan                             16 State and 110 (SAGARPA)
  ----------------------------------- -----------------------------------

Each respective Federal delegate works with the state animal health
officials to administer the joint Federal/State animal health programs.
A peninsular animal health council which is made up of the Federal
regional coordinator, State animal health official, and SAGARPA
delegates. This council meets every few months to evaluate and determine
the funding needs of the animal health activities of the region.
Technical members meet more frequently. For these programs, a
significant joint budget is managed by the regional, Federal and State
officials. Funding levels are supported by industry and State
components.

Examples of activities under joint Federal/State authorities include:

Maintenance of an appropriate animal disease database;

Provision of epidemiological services;

Licensing of pertinent activities;

Inspection activities;

State-specific response to emergency animal disease incursions under the
National Interagency Emergency Animal Disease Response System (DINESA);
and

Indemnification for animals or materials affected by animal disease.

Evaluation: Animal health officials in the Yucatan Peninsula have the
legal authority to enforce END Federal and State regulations and the
necessary veterinary infrastructure to carry out END surveillance and
control activities. No specific factors were identified in the
evaluation that might present a risk to the United States if animals or
products were exported.

**Type and extent of disease surveillance**

As the three Yucatan Peninsula States are considered to be free of END
by Mexico, surveillance for animal disease must comply with the dictates
of program manuals for END. Annual surveillance is required under
NOM-013-Z00 1994, National Velogenic Newcastle Disease Campaign norms.
In general terms within free States, active and passive surveillance are
performed every year.

*Active Surveillance*

Each year, a census is submitted to the DGSA's risk analysis and
international reporting unit in Mexico City. That unit responds with
instructions for the active surveillance to be performed in each State.
The sample size necessary to identify disease at a specified prevalence
and confidence level is determined using the standard formulas by Cannon
and Roe. Those prevalence and confidence levels are adjusted annually to
increase the ability to identify any disease present and take into
account the number of flocks present in a State. The sample numbers
requested and the final number of active surveillance samples collected
in 1999 and 2000 are shown below (Tables 2 - 3).

Table 2. Surveillance testing in Yucatan Peninsula for Newcastle
Disease, 1999

  -------------- -------------- -------------- -------------- --------------
                 Commercial     Samples per    Backyard       Samples per
                 flocks sampled flock          flocks sampled flock

  Campeche       32             59             299            5

  Quintana Roo   11             59             299            5

  Yucatan        212            29             299            5
  -------------- -------------- -------------- -------------- --------------

Table 3. Surveillance testing in Yucatan Peninsula for Newcastle
Disease, 2000

  -------------- -------------- -------------- -------------- --------------
                 Commercial     Samples per    Backyard       Samples per
                 flocks sampled flock          flocks sampled flock

  Campeche       58\*           59             350            5

  Quintana Roo   20\*           36 - 69        348            5

  Yucatan        225\*          29             356            5
  -------------- -------------- -------------- -------------- --------------

\* = discrepancy in number of flocks may be due to collections from
separate houses on same farm

Selection of flocks for testing is done in the State by program
officials. All commercial flocks are sampled once a year. A commercial
flock is one set up for commerce, with appropriate fencing and
biosecurity to isolate the unit. A "farm" is a grouping of houses that
are together within a single perimeter fence.

The number of backyard flocks to be tested is stratified by municipality
based on census numbers. Up to five birds are sampled from each backyard
flock. The average backyard flock size nationally is about 10 birds.
Within each municipality, official veterinarians select the communities
to be sampled. Different communities are selected each year. The focus
is on communities where there are commercial farms nearby, communities
where there are more chickens, and communities near the borders of the
State. Each owner or household is considered a single flock, whether
birds are confined or mingle with other flocks. Veterinarians test
representative poultry, including chickens (with emphasis on
naked-necked chickens), as well as turkeys and ducks. If the community
was selected for testing the previous year, an effort is made to select
different households than those tested the previous year.

Within the commercial farm sector, each farm is sampled once during the
year. Birds are selected at random from within the selected flocks. On
commercial farms with multiple houses, samples are required from each
house. The total number of samples required on a premises is divided by
the number of houses. For example, in 2000 for END in Campeche, 59
samples were taken from sites with up to 10 houses. If the number of
houses on a premises exceeds 10, then 10 samples are taken from each
house. Birds are selected randomly, although sick birds may be submitted
preferentially if any are present when the sample is taken.

There is also a special high-risk zone in Campeche adjacent to Tabasco;
this zone consists of the area within 50 km from the Tabasco border and
is delineated by peninsular officials, not by the national program.
Additional backyard poultry premises are tested annually from the risk
zone, above the number of samples outlined by the national program. For
END and Salmonella in poultry, samples are collected from approximately
60 extra premises.

*Passive Surveillance*

Cases of concern are reported by and to various personnel. Once a
problem is reported to an official, the mandated response time is 24
hours. Quarantine of a premises is based on presumptive clinical signs
and appropriate samples must be collected. Officials may take more
definitive action when they have certain presumptive results from the
local lab. If the disease suspected is exotic to Mexico, samples go to
one of the national laboratories. However, for END and other poultry
diseases that occur in portions of Mexico, samples generally go to the
regional laboratory first. Positive samples are sent to the national
laboratory in Mexico City to confirm.

Table 4 below shows the levels of passive surveillance samples submitted
to the regional laboratory during 2000.

Table 4. Total numbers of samples run for Newcastle disease diagnosis
(program and other), 2000

  ----------------------- ----------------------- -----------------------
  State                   Number of flocks        Number of samples
                          represented             

  Campeche                470                     3,003

  Quintana Roo            387                     4,457

  Yucatan                 598                     15,053
  ----------------------- ----------------------- -----------------------

Evaluation: APHIS concluded that authorities in the Yucatan Peninsula
are conducting an adequate level of END surveillance to detect the
disease if it were to be reintroduced into the peninsula.

**Diagnostic Lab Capabilities**

There are two laboratories that provide veterinary diagnostic services
to the poultry industry in the Yucatan Peninsula. One is a small
regional laboratory located in Chetumal in the State of Quintana Roo and
the second is a full service regional laboratory located in Merida,
Yucatan. The Yucatan Regional Laboratory in Merida meets the Office of
International Epizootics recommendations for equipment and training. An
APHIS team visited the lab in 2001 and deemed the facilities and
personnel adequate for the END surveillance program. Any samples that
test positive at the Yucatan lab are sent to the central laboratories in
Mexico City (CENASA) for confirmation, and tissues of any suspect
animals are sent to the Exotic Animal Disease Commission (EADC)
Laboratory in Mexico City for virus isolation. The laboratory in
Chetumal provides general microbiological services to local producers
but does not conduct diagnostic tests for program diseases.

The laboratory in Merida also provides support for hazard analysis and
critical control point (HACCP) programs for Federally inspected (TIF)
processing plants in the region. The laboratory does not have an
official quality assurance program in place; however, some monitoring of
equipment is being performed.

Tests for END are conducted using chick embryos from commercial sources.
The plate hemagglutination test (HA) is used to test for the presence of
the virus. Isolates of Newcastle Disease virus (NDV) are identified by
the plate hemagglutination-inhibition (HI) test with END virus-specific
antiserum. Time of embryo death is the only determinate used to
pathotype END virus isolates. Suspect virulent isolates are forwarded to
the CENASA or EADC laboratories in Mexico City for characterization. Of
the 3,482 samples tested in 2000, no isolations of END virus were made.
One isolation of a lentogenic strain of END virus was made in 1999. The
isolate was not forwarded to CENASA or EADC laboratories for
characterization.

Evaluation: APHIS concluded that the laboratory capabilities and
infrastructure on the Yucatan Peninsula are sufficient to support the
END surveillance activities. However, the APHIS site visit team has made
recommendations for improved functioning of the diagnostic procedures
and capabilities within the regional laboratory in Merida.

**Disease Outbreak History and Disease Prevalence**

The government of Mexico recognized Yucatan as free of END in July 1996.
The last reported focus was detected and eradicated in May 1984.
Similarly, Quintana Roo was declared free in December of 1997, the last
focus having been detected and eradicated in September 1990. Campeche
was recognized as free in December 1997. There is no history of END in
Campeche.

Evaluation: No cases of END were reported on the Yucatan Peninsula for
several years. Based on the evidence produced by Mexico and the results
of the site visit, APHIS considers that the authorities on the Yucatan
Peninsula are engaged in adequate and capable disease detection and
reporting activities.

**Disease Control Program**

Mexico established the National Campaign Against Velogenic Newcastle
Disease in 1994. A decree published in the Federal Official Daily
established the program as general, mandatory, and permanent throughout
the entire country (NOM-013-ZOO-1994). The campaign is conducted at
three levels; State, region, and zone. The campaign includes the
following operational phases:

\(1\) Control phase -- includes the following requirements: control of
movement of poultry and poultry products and avian equipment; an
adequate epidemiological surveillance system; a campaign promotion
program; and verification of primary and multiplier breeders.

\(2\) Intensive control phase -- includes the following requirements:
control of movement of poultry and poultry products and avian equipment;
an adequate epidemiological surveillance system; a campaign promotion
program; diagnostic infrastructure; verification of primary and
multiplier breeders; and progressive verification of farms of commercial
layers, broilers, fighting cocks, wild fowl, song and ornamental birds,
either in production or rearing.

\(3\) Eradication phase -- includes the following requirements:
recordkeeping of movement of poultry and poultry products and avian
equipment; an adequate epidemiological surveillance system; a campaign
promotion program; absence of END on farms of commercial layers,
broilers, fighting cocks, wild fowl, song and ornamental birds, either
in production or in rearing, that is corroborated through taking samples
of the size estimated by the department; and whenever dealing with
primary breeders, compliance with the guidelines to obtain proof of
freedom from END.

\(4\) Free phase -- includes the following requirements: at least 12
months in the eradication phase, and epidemiological testing that
validates the animal sanitary situation; and animal health emergency and
epidemiological surveillance systems. A region can be declared free only
by accord from the Minister of Agriculture, Livestock, and Rural
Development and must be published in the Official Federal Gazette.

Evaluation: END is considered an exotic disease on the Yucatan
Peninsula. Therefore, while there are no active disease control
programs, the States do maintain both active and passive disease
surveillance, ongoing animal movement controls, and an emergency
response system to respond if END is again detected in the States.

**Vaccination Status**

Vaccination for END with lentogenic vaccine strains or inactivated virus
is allowed in areas in Mexico considered free of the disease.
Vaccination is carried out according to the Mexican Norms
(NOM-013-ZOO-1994, National Velogenic Newcastle Disease Campaign). In
the industry, as an example, the vaccination program in broilers used by
the CRI'O, the third largest broiler producing company in the Yucatan
located near Merida, consisted of a full dose of B1 END virus and
infectious bronchitis virus (IBV) administered by spray at the hatchery.
The birds are also given an injection of Marek's vaccine at the
hatchery. Between 10 and 14 days the birds are given a second
vaccination consisting of a half-dose B1 END virus and IBV administered
by course spray. No other vaccinations are given.

Evaluation: According to Mexican Federal regulations, vaccination
against Newcastle disease is practiced in commercial poultry farms in
all States in Mexico. APHIS concluded that vaccination against Newcastle
disease is currently being practiced on the Yucatan Peninsula, and that
vaccinated poultry do not constitute a significant risk factor for
introducing END into the United States.

**Disease status of adjacent regions**

Yucatan is bordered to the west by Campeche, and by Quintana Roo to the
east and south. Tabasco is the only Mexican State bordering the Yucatan
Peninsula and shares the western border of the peninsula. The State of
Campeche shares its southern border with Guatemala and the State of
Quintana Roo shares its southern border with both Guatemala and Belize.

The State of Tabasco is in the control phase for END; thus they have had
active cases and still vaccinate. There were three foci of END infection
in Tabasco in 2000, out of 50 in all of Mexico.

The United States considers the countries of Belize and Guatemala as
affected with END. Officials of the Regional International Organization
for Agricultural Health (OIRSA) informed APHIS that Belize has gone
without reporting a case of END for several years, and that there are
very few poultry in the Petén region of Guatemala bordering the Yucatan
Peninsula. Cases are more likely to be reported in southern Guatemala.
There were 48 and 69 cases reported in 1998 and 1999 respectively.
Guatemala apparently is entering into an eradication program for several
poultry diseases including END, low path AI, salmonellosis, and
laryngotracheitis.

Evaluation: Although there are continuing END outbreaks in adjacent
Mexican States and adjacent countries, APHIS considers that the control
point activities (described in the section, "Control of Animal
Movement") in place between the Yucatan Peninsula and the neighboring
State and countries is sufficient to substantially reduce the risk from
END. In addition, eradication activity for diseases considered exotic is
diligent and sufficient to rapidly control outbreaks of the type
observed in the past.

**Degree of separation from areas of higher risks**

The State of Yucatan is northwest of Qunitana Roo and Campeche sits to
the west, with Guatemala and Belize located south and southwest. The
Gulf of Mexico lies to the north, the Caribbean to the east, and the
Hondo River to the south bordering Belize. Quintana Roo is separated
from Guatemala by the Calakmul Biosphere rain forest and Belize by the
Hondo River. The border between Campeche and the State of Tabasco
follows a river for a significant distance. In Campeche's southern part,
bordering Guatemala, sits the Calakmul Biosphere Reserve. This is a
natural rain forest protected by the Mexican government. All roads
crossing the border have checkpoints. Yucatan has no direct contact with
any area of higher risk.

Evaluation: The area of higher risk closest to the Yucatan Peninsula is
the State of Tabasco, which had three outbreaks of END in 2000. APHIS
concluded that the peninsula had sufficient separation from areas with
higher risk.

**Control of Animal Movement from High Risk Areas**

There is a system of interstate and zonal agricultural and animal health
check points operating throughout Mexico. SAGARPA generally has overall
authority for these activities. The Mexican National Agricultural
Quarantine System represents the strategic base for implementations of
foreign and domestic quarantine services. These services focus on
preventing the entry of exotic diseases and pests; assisting in the
prevention and the control and eradication of such diseases, if they
should occur; and supporting the phytozoosanitary campaigns at the
national levels to maintain zones that are free of diseases and pests.

The primary means for preventing reintroduction of END into the Yucatan
Peninsula is through regulations controlling the movement of land and
air traffic. Movement of birds and bird products that enter the
peninsula are subject to zoosanitary certificates issued by local
organization under SAGARPA's control. All movements of birds and
products from control and eradication zones are under restrictions
specified in the Mexican norms (NOM-013-ZOO-1994, National Velogenic
Newcastle Disease Campaign; NOM-005-ZOO-1993, National Avian
Salmonellosis Campaign; and NOM-044-ZOO-1995, National Avian Influenza
Campaign).

The border check points between Campeche and Tabasco (Peninsula -
Tabasco Quarantine Cordon) provide 24-hour inspection and control. All
roads that traverse the border between these two States are tightly
monitored and controlled by officials from SAGARPA, peninsular
governments, and law enforcement and military personnel from Campeche,
Quintana Roo, and Yucatan, as well as from the State of Tabasco. Animal
and plant products detected during vehicle searches are confiscated and
incinerated. Movement of livestock and poultry between States is
prohibited without proper movement authorization/documentation and the
transport of unauthorized live animals from Tabasco is strictly
prohibited.

There are two international airports on the peninsula; the International
Airport at Meridia and the International Airport at Cancun. There are
two national airports in Campeche and Quintana Roo. The site visit team
visited the International Airport at Meridia, Yucatan. Program officials
inspect incoming domestic flights, including passengers, cargo and
vessels for unpermitted agricultural products, including food wastes and
stores.

The maritime port of Progreso primarily handles grains. Animals and
animal products are allowed entry if the proper health certificate and
permit requirements are met. There are four full-time inspectors,
including two veterinarians.

Evaluation: A system of permits, inspection, quarantines and treatments
is in place to control animals and animal products. Officials on the
Yucatan Peninsula have the authority, procedures, and infrastructure to
effectively enforce such a system. APHIS was unable to identify specific
limitations in the system that might pose risk to the United States.

**Livestock Demographics and Marketing**

In recent years the Yucatan Peninsula has seen a significant growth in
production of poultry, swine, and cattle. In 2000, the State of Yucatan
produced 82,099 metric tons of broilers, 76,530 metric tons of eggs, and
1,512 metric tons of turkey meat. The peninsula has evolved into an
agriculture exporting region, supplying poultry products to other parts
of Mexico as well as foreign markets. Disease control and surveillance
programs are in place for each of the above species as well as for bee
pests. For poultry, control programs target END, avian influenza, and
salmonella.

Site visit team members reviewed census information for poultry in the
States on the Yucatan Peninsula. The population and proportion of
chickens on commercial and backyard premises, based on the 2000 census,
is shown in Table 1. These do not reflect production figures. Rather
they are the population on premises at the beginning of 2000.

**[Table 1. Poultry population and proportion on commercial farms, 2000
census]{.underline}**

  ----------------------- ----------------------- -----------------------
  State                   Commercial farms /      Backyard farms /
                          poultry / percent birds poultry / percent birds
                          of total                of total

  Campeche                30 / 1,243,181 / 82.1 % 21,595 / 271,500 /
                                                  17.9%

  Quintana Roo            2 / 2,139,706 / 92 %    25,639 / 185,212 / 8 %

  Yucatan                 226 / 13,000,000\* / 92 58,501 / 1,132,828 / 8
                          %                       %
  ----------------------- ----------------------- -----------------------

\* = 1999 figures

About 60 percent of the poultry production is for regions outside the
peninsula. Most of the birds and poultry products that come into
Quintana Roo and Campeche originate in the State of Yucatan. A site
visit was made to the third largest broiler producing company in the
Yucatan, located near Merida. This was a first-class operation that
would rival the best production facilities in the United States.
However, it appeared that many operations consisted of two to six house
units with passive air systems and chicken houses often located close to
heavily traveled roads. Most houses appeared to be 15 or more years of
age.

Industry leaders demonstrated awareness of animal disease control
measures to ensure maintaining a healthy and productive animal industry.
Industry groups contribute funds to develop and improve sanitary
operations to maintain the status of their respective States.

Evaluation: The poultry industry is well organized. For both economic
and health reasons, the poultry industry on the Yucatan Peninsula is
committed to the production of quality products and maintaining END free
status. No factors were identified in this category that might pose risk
to the United States if poultry or poultry products were to be exported.

**Policies and infrastructure for animal disease control**

Mexico has an established national system for surveillance and reporting
of exotic animal diseases through the United States - Mexico Commission
for the Prevention of Foot and Mouth Disease and other Exotic Animal
Diseases (CPA). If a positive case of an exotic disease is detected, the
National Interagency Emergency Animal Disease Response system (DINESA)
becomes activated. One of this system's most important activities is to
set up the State Animal Health Emergency Groups (GEESA). The function of
a GEESA is to act quickly, effectively, and in an organized way in the
event of an animal emergency. As part of GEESA, veterinarians take
additional training in foreign animal diseases and participate in field
exercises.

Official diagnosis of disease is done by members of DINESA and follows
any State emergency animal disease response team (GEESA) investigation.
The GEESA structure may be described as a loosely organized response
group under the direction of the regional coordinator. DINESA is
described officially in a specific program document.

The GEESA members orally place holds on any suspect farms as soon as a
suspected emergency condition is observed. These holds are converted
into quarantines upon laboratory confirmation by the regional
coordinator or other DINESA official. An official report by EADC and the
risk analysis and international organizations unit (UAROI) follows to
the OIE and trading partners within the designated OIE time frame. After
laboratory confirmation, official quarantines for diseases considered
exotic to the region are enforced. All movements entering and leaving
the farm are investigated and a survey is conducted in the affected
zone. Quarantines are released by regional officials, with the
concurrence of State officials once the disease is considered
eradicated. This is done in accordance with specific program norms.

Evaluation: END in not known to exist on the Yucatan Peninsula.
According to Mexican regulations, in the event of any cases of END in a
free zone, a sanitary slaughter policy would be implemented with
cleaning and disinfection of affected premises. APHIS was unable to
identify specific limitations in this system that would pose a risk to
the United States.

**[Conclusions:]{.underline}**

1\) END has not been confirmed in any part of the Yucatan Peninsula
since 1990, despite ongoing surveillance.

2\) Vaccination for END is practiced freely on the peninsula.

3\) Authorities in the Yucatan Peninsula maintain effective movement
controls on poultry and poultry products from areas of higher risk to
prevent the reintroduction of END.

4\) All three States maintain a surveillance system capable of rapidly
detecting END if it were reintroduced.

5\) The Yucatan Peninsula has the laws, policies, and infrastructure in
place to detect, respond to, and eliminate any occurrence of END.

6\) Given the virulent nature of the disease in a naive population, and
the level of ongoing surveillance, the likelihood of END virus being
present on the peninsula is low.

**Bibliography**

1\) Site Visit Report, Yucatan Peninsula, Newcastle Disease; States of
Campeche, Quintana Roo, and Yucatan, March 25-31, 2001.

2\) Regionalization Final Rule; Importation of Animals and Animal
Products. 62 FR 56000- 56026.

3\) Ministry of Agriculture and Rural Development, Official Mexican
Standard NOM-013- ZOO-1994, National Velogenic Newcastle Disease
Campaign.

4\) Ministry of Agriculture and Rural Development, Official Mexican
Standard NOM-001- ZOO-1993, Official Mexican Emergency Standards
establishing the mandatory National Newcastle Disease Campaign and
official declaration of the State as free zone.

5\) Ministry of Agriculture and Rural Development, Official Mexican
Standard NOM-046- ZOO-1996, National Epidemiological Surveillance
System.

6\) Request for the recognition of the State of Yucatan as a
risk-classified region for exportation of poultry products to the United
States of America. Comision Nacional de Sanidad Agropecuaria, Direccion
General de Salud Animal, Mexico, August, 1998.

7\) Information on Quintana Roo State as free of Velogenic Newcastle
Disease and Avian Salmonellosis. Comision Nacional de Sanidad
Agropecuaria, Direccion General de Salud Animal, Mexico, August, 1998.

8\) Information on Campeche State as free of Velogenic Newcastle Disease
and Avian Salmonellosis. Comision Nacional de Sanidad Agropecuaria,
Direccion General de Salud Animal, Mexico, August, 1998.