####### **Evaluation of the Classical Swine Fever 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 Classical Swine Fever 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
Classical Swine Fever (CSF) 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 CSF virus into the United States through the
importation of swine or swine products from the Yucatan Peninsula and to
provide a decision-making tool to help with the determination of the CSF
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 site visits to the Yucatan Peninsula in
November 1996 and March 2001 \[1, 2\].

In accordance with its regulations \[3\], 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.
There is a peninsular animal health council 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
(Dispositivo Nacional de Emergencia de Sanidad Animal) (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 CSF Federal and State regulations and the
necessary veterinary infrastructure to carry out CSF 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 \[2\]**

As the three Yucatan Peninsula States are considered to be free of CSF
by Mexico, surveillance for animal disease must comply with the dictates
of program manuals for CSF. Annual surveillance is required under
Nom-037-Z00 1995, National CSF Campaign norms \[3\].

*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 herds 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 Classical Swine
Fever, 1999

  -------------- -------------- -------------- -------------- --------------
                 Commercial     Samples per    Backyard herds Samples per
                 herds sampled  herd           sampled        herd

  Campeche       5              59             299            5

  Quintana Roo   38             59             299            5

  Yucatan        211            29             299            5
  -------------- -------------- -------------- -------------- --------------

Table 3. Surveillance testing in Yucatan Peninsula for Classical Swine
Fever, 2000

  -------------- -------------- -------------- -------------- --------------
                 Commercial     Samples per    Backyard herds Samples per
                 herds          herd                          herd

  Campeche       5              59             348 scheduled, 1 - 5
                                               961 sampled    

  Quintana Roo   35             59             347            5

  Yucatan        238            29             405            5
  -------------- -------------- -------------- -------------- --------------

Selection of herds for testing is done in the State by program
officials. All commercial herds are sampled once a year. Animal are
selected at random from within the selected herds. The number of
backyard herds to be tested is stratified by municipality based on
animal census numbers. Up to five animals are sampled from each backyard
herd or all animals if less than five. The average backyard swine herd
nationally is three to eight pigs. For any farm that is said to be
empty, an official goes to the farm to verify this information. If any
empty farm is later repopulated, it must be sampled.

Sampling has been intensified in high risk regions. There is a special
high-risk zone in Campeche adjacent to Tabasco; this zone consists of
the area within 50 kilometers from the Tabasco border and is delineated
by peninsular officials, not by the national program. Additional
backyard swine premises are tested annually from the risk zone, above
the number of samples outlined by the national program. For CSF and
pseudorabies, samples are collected from approximately 60 extra
premises.

*Passive surveillance*

Reportable diseases in Mexico include Newcastle disease (ND), avian
influenza (AI), avian salmonelloses, CSF, pseudorabies, brucellosis,
tuberculosis, rabies, cattle ticks, and varroa mites in bees, as well as
exotic List A and many list B animal diseases. In the Yucatan Peninsula,
animal health eradication activities for the cited diseases began in
1992 with eradication programs for salmonella, ND and AI in poultry and
CSF and pseudorabies in swine.

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. If the disease
suspected is exotic to Mexico, samples go to one of the national
laboratories; this is the case for vesicular signs or screwworm samples.
If the disease suspected is a program disease, samples generally go to
the regional laboratory first. Positive samples are sent to the national
laboratory in Mexico City to confirm. Officials may take more definitive
action when they have certain presumptive results from the local lab.
Tables 4 shows the levels of passive surveillance samples submitted to
the regional laboratory during 2000.

Table 4. Total numbers of samples run for classical swine fever
diagnosis (program and other), 2000

  ----------------------- ----------------------- -----------------------
  State                   Number of herds         Number of samples
                          represented             

  Campeche                1,035                   2,091

  Quintana Roo            383                     3,734

  Yucatan                 643                     8,689
  ----------------------- ----------------------- -----------------------

In regions, States or areas under eradication or free of CSF, the
Federal and State government, as well as swine owners or producers and
accredited veterinarians, have responsibility for maintaining
epidemiological surveillance for CSF.

Mexico is currently seeking to eradicate pseudorabies. Blood samples
collected for the pseudorabies campaign are also tested for CSF, thus
providing additional surveillance. In addition to the active sampling
from annual surveillance, passive surveillance also resulted in an
additional 8,689 samples representing 643 different herds. There have
been no positive tests confirmed from either passive or active
surveillance in the State of Yucatan.

Evaluation: All three States are conducting active and passive
surveillance. APHIS concluded that authorities in the Yucatan Peninsula
are conducting an adequate level of surveillance to detect the disease
if it were to be reintroduced into the peninsula. While there was no
specific information presented that would show that any wild swine on
the peninsula are free of CSF, backyard herds (which may be exposed to
wild swine) are actively monitored in the Yucatan Peninsula and have
been free of this disease for many years.

**Diagnostic Lab Capabilities \[2\]**

Two laboratories provide veterinary diagnostic services to the swine and
poultry industries in the Yucatan peninsula. One is a small regional
laboratory located in Chetumal in the State of Quintana Roo. 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 facilities and personnel adequate for
the CSF surveillance program in Yucatan.

Primary surveillance for CSF is carried out by serologic monitoring
using the Immunoperoxidase test (IPT). Samples with equivocal or
positive results are further tested by the ELISA test to confirm the
specificity of the antibody. This approach is consistent with serologic
methods used in the United States for CSF. Any samples that test
positive at the Yucatan laboratory 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.

Evaluation: APHIS concluded that the laboratory capabilities and
infrastructure on the Yucatan Peninsula are sufficient to support the
CSF surveillance activities although the team felt that some
improvements might be in order. Although the APHIS site visit team made
recommendations for improved functioning of the diagnostic capabilities
within the regional laboratory in Merida, team members did not consider
the issues addressed to be critical.

**Disease Outbreak History and Disease Prevalence \[2\]**

The government of Mexico recognized Yucatan as free of CSF in April
1995. The last case was detected and eradicated in August 1982.
Vaccination was discontinued in 1993. Similarly, Quintana Roo was
declared free in June 1996, the last case having been detected and
eradicated in 1980. Vaccination was suspended in 1994. Campeche was
recognized as free in December 1997, following detection and elimination
in July 1995 of a suspicious case based on clinical findings. This case
was not confirmed to be CSF. The last outbreak preceding this case had
been detected and eradicated in 1989. The last CSF vaccine used in this
region was in September 1995 in one municipality in Campeche, in
response to the July 1995 suspected case.

Evaluation: No cases of CSF were reported 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. No
specific factors were identified as a source of risk under this factor.

**Disease Control Program**

Mexico started the National Campaign for the Control and Eradication of
CSF in March of 1980. A decree published in the Federal Official Daily
established the program as general, mandatory, and permanent throughout
the entire country. The campaign was updated in 1992. The country is
divided into three types of zones defined by CSF status:

\(1\) Control zone -- includes Mexican States where CSF is enzootic.
Procedures applied include: vaccination, control of movement of swine
and swine products, epidemiological surveillance, and reporting and
follow-up of disease outbreaks.

\(2\) Eradication zone -- includes Mexican States where CSF has not
occurred for 12 months and procedures described for control zones have
been followed. Additionally the following must be enforced: suspension
and prohibition of the use, distribution, and marketing of CSF vaccines;
strict control of interstate movement of swine and swine products; and
epizootic surveillance.

\(3\) Free zone - free status is granted to Mexican States in which CSF
has not occurred for 24 months and the procedures for eradication have
been followed and applied. Serological sampling must be carried out at
least every 12 months.

Movement among these zones is controlled. Live hogs from control zones
are prohibited entry into free zones. Garbage feeding of swine is
prohibited by law in free zones in Mexico. However, this prohibition is
not enforced for backyard pigs.

Evaluation: CSF is considered to be 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, as well as ongoing animal movement controls, and an
emergency response system to respond if CSF were again detected in the
States. However, one risk factor identified is the lack of enforcement
of the prohibition of garbage feeding for backyard pigs.

**Vaccination Status \[2\]**

Vaccination was discontinued in Yucatan in 1993, in Quintana Roo in
1994, and in September 1995 in one municipality in Campeche.

Evaluation: According to Federal regulations, vaccination for CSF is
only practiced in States with active control programs and where
outbreaks of the disease are being reported. Vaccination is prohibited
in regions declared free by the Mexican Government. Mexico has declared
all three States on the Yucatan Peninsula as free of CSF. Therefore,
APHIS accepts that vaccination for CSF is not currently practiced on the
Yucatan Peninsula, and that vaccinated pigs (in which clinical signs of
disease might be masked making disease detection difficult) do not
constitute a risk factor.

**Disease status of adjacent regions \[2\]**

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.

Tabasco is a control State for CSF. Tabasco had four foci of CSF in
2000, all of which were controlled using task forces. These were in
Tenosique (three outbreaks in August and October 2000) and Emiliano
Zapata (September 2000). This is out of a total of 12 cases in all of
Mexico for 2000.

As mentioned, the Yucatan Peninsula shares borders with Belize and
Guatemala. Although the United States considers both countries to be
affected with CSF, officials of the Regional International Organization
for Agricultural Health (OIRSA) informed APHIS that CSF has not been
described in Belize since 1988; it is a notifiable disease and
vaccination is prohibited. There apparently has been no evidence of
titers in serologic surveillance conducted.

In Guatemala, CSF is more commonly reported in the southern portion of
the country, a region not adjacent to Campeche. There were 38 cases and
55 cases reported during 1998 and 1999, respectively. In the Petén
region which abuts Campeche, an outbreak associated with the State of
Tabasco was reported recently (November 2000) and was rapidly
eliminated. In survey work in the Petén, serologic titers have been
dropping off as vaccination has declined due to eradication efforts and
prohibition of vaccination since 1999.

Evaluation: Although there are continuing CSF outbreaks in adjacent
Mexican States and adjacent countries, APHIS considers that the control
point activity (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 CSF. 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 \[2\]**

The State of Yucatan is northwest of Qunitana Roo. 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 four outbreaks of CSF in 2001, all of
which were quickly controlled.

**Control of Animal Movement from High Risk Areas \[2, 4\]**

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 primary means for preventing
reintroduction of CSF into the Yucatan Peninsula is through regulations
controlling the movement of land and air traffic. Observations made by
site visit team members verified effective implementation of these
controls.

Interstate checkpoints are manned at all times. Military personnel are
commonly located at these crossing points and provide support. Movement
of live hogs from control zones into free zones is not allowed, thus
avoiding the greatest source of risk. Products and byproducts from
eradication zones and control zones are not allowed to move to free
zones unless they originate in Federal facilities with a current
registration, and with authorization by the General Division of Animal
Health to market their products and byproducts into CSF free zones.
Products must be moved in vehicles sealed with metal straps.

As part of a system of sanitary barriers within Mexico, the border check
points between Campeche and Tabasco 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 were observed being
confiscated and are 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 un-permitted agricultural products, including food wastes
and stores. Because most domestic flights originate from areas not yet
declared free of CSF, food served on airplanes is not allowed to contain
pork.

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

Animals can be brought into the Yucatan Peninsula only from disease-free
zones of Mexico. Permits specify that the pigs must come in via a
specified route through low risk States; the greatest problem is the
State of Tabasco due to more frequent disease findings. To address this,
the programs have set up a system requiring that animals must transit
Tabasco within an approved time limit. This is clocked at more northerly
check points, then again by the program at the Yucatan Peninsula barrier
check point. Swine are then allowed movement only to approved farms.
These farms may be rented out to the importer industry group for 30-day
quarantine and releasing tests.

Pork products from States of lower health status may be imported only if
they meet time and temperature processing requirements (68.9 C for 30
minutes or 80.5 C for three minutes) and if they originate from an
approved TIF (federal) plant.

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 patterns \[2\]**

In recent years the Yucatan Peninsula has seen a significant growth in
production of poultry, swine, and cattle. Commercial herds represent
several major companies. The site visit team had the opportunity to go
to one of the large commercial farms and a swine processing plant. Both
followed strict biosecurity measures. The team also visited the only
USDA-approved Federal (TIF) swine processing plant near Merida, Yucatan.
The current capacity of this plant is about 500,000 head per year, and
the plant exports eight to nine containers (22 tons/container) of pork
meat per week to Japan and Korea. The plant is expected to increase
capacity to 850,000 head per year by 2002 to meet the growing export
market.

The table below shows census information for swine within theYucatan
Peninsula. The population and proportion of swine that are on commercial
and backyard premises, based on the census from early 2000, are shown in
Table 1. These do not reflect production figures. Rather they are the
population on premises at the beginning of 2000.

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

  ----------------------- ----------------------- -----------------------
  State                   Commercial farms /      Backyard herds / swine
                          swine / percent swine   / percent swine of
                          of total                total

  Campeche                5 / 6,612 / 4.6 %       31,607 / 137,174 / 95.6
                                                  %

  Quintana Roo            38 / 29,179 / 26.3 %    13,450 / 137,174 / 73.7
                                                  %

  Yucatan                 252 / 500,000 / 85.8 %  8,786 / 82,672 / 14.2 %
  ----------------------- ----------------------- -----------------------

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 swine industry is well organized. For both economic and
animal health reasons, the swine industry on the Yucatan Peninsula is
committed to the production of quality hogs and maintaining CSF free
status. The eradication of CSF from the peninsula was largely due to the
dedication and persistence of the industry and to its willingness to
work with animal health officials to ensure that the disease is not
reintroduced. No factors were identified in this category that might
pose risk to the United States if swine or swine 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 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.

Contingency funds are not available in case of an outbreak of CSF.
However, if a problem should arise, special contributions would be made
by producers and the State and Federal governments to conduct control
and eradication activities.

Evaluation: CSF in not known to exist on the Yucatan Peninsula.
According to Mexican regulations, in the event of any cases of CSF in a
free zone, a sanitary slaughter policy without vaccination 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 \[4\].

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

1\) Classical Swine Fever has not been confirmed in any part of the
Yucatan Peninsula since 1989, despite extensive and ongoing
surveillance. A suspicious case based on clinical signs was detected in
1995 in Campeche, but never confirmed.

2\) No vaccination for CSF has occurred on the peninsula since 1995, so
clinical signs of disease should not be masked in vaccinated animals.

3\) Authorities on the Yucatan Peninsula maintain effective controls on
animal movements from areas of higher risk to prevent the reintroduction
of CSF.

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

5\) To APHIS' knowledge, CSF has not been linked to wild swine in
Mexico.

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

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

**Bibliography**

1\) Review of the State of Yucatan for Consideration of Classical Swine
Fever (CSF) -- Low Risk Status, November 14, 1996.

2\) Site Visit Report, Yucatan Peninsula, Classical Swine Fever; States
of Campeche, Quintana Roo, and Yucatan, March 25-31, 2001.

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

4\) Ministry of Agriculture and Rural Development, Official Mexican
Standard NOM-037- ZOO-1995, National Classical Swine Fever Campaign.

5\) Hog Cholera. In Foreign Animal Diseases, United States Animal Health
Association, p. 273-282, 1998.