United States

Department of

Agriculture

Animal and

Plant Health

Inspection

Service

APHIS 91–55–075

Equine Viral Arteritis

Uniform Methods and Rules,

Effective April 19, 2004
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs

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warrants the standard of any product mentioned. Product names are mentioned solely

to report factually on available data and to provide specific information.

Issued April 2004
Contents

Introduction 5

Part 1: Definitions 7

Accredited veterinarian

Approved laboratory

Approved laboratory tests

Area Veterinarian-in-Charge (AVIC)

Booking

Carrier

Certificate

Cover

Equine

Equine arteritis virus (EAV)

Equine viral arteritis (EVA)

Exposed animals

Herd

Herd of origin

Identification

Official seal

Official test

Permit

Quarantine

Quarantined area

Reactor

Reference laboratory

Seroconversion

Seropositive horse

Seronegative horse

Shedder

State

State animal health official

Vaccination

Virus isolation test

Virus neutralization test

Part II: Recommended Procedures (Minimum Requirements) 11

A. Laboratory Testing—Prescribed Methods 11

B. Approved Laboratories 11

C. Serology 11

D. Virus Isolation 11

E. Testing Procedures 12

3
F. Outbreak Procedures 14

G. Control Procedures 15

H. Movement of Stallions and Semen 17

I. Recommendations for Breed Registries 17

4
Introduction

Equine viral arteritis (EVA) is a contagious disease of equids caused by the equine

arteritis virus (EAV). Although typically not life-threatening to otherwise healthy adult

horses, EVA is of special concern because it can result in abortion in pregnant mares,

illness and death in young foals, and establishment of the carrier state in stallions.

Despite the presence of EAV in many equine populations throughout the world, its

prevalence in any particular country can vary widely depending upon breed.

Notwithstanding the global distribution of the causal virus, confirmed outbreaks of EVA

are reported infrequently.

Ever since the 1984 epidemic on a considerable number of thoroughbred breeding

farms in Kentucky, EVA has significantly impacted international trade in horses and

equine semen. The import control policies of most countries currently deny entry to

carrier stallions and EAV-infective semen because of the associated disease risks.

Currently, the United States is the only major horse-breeding country without an import

control policy for EVA.

Traditionally, the U.S. horse industry has attached relatively little significance to this

disease. Efforts to achieve a greater level of control over dissemination of EAV within

the country’s equine population have been hampered by insufficient awareness of the

disease and its potential economic consequences among many within the Nation’s

horse industry. This was clearly revealed from the findings of the U.S. Department of

Agriculture’s (USDA) National Animal Health Monitoring Systems’ Equine ’98 Study. A

high percentage of individuals responding to that survey had little if any knowledge

about EVA and even less about the reasons or methods for controlling it.

Another finding of major importance to emerge from that study was the very low

seroprevalence of EAV infection in most U.S. horses. Because they have never been

exposed to the virus, the vast majority of the Nation’s horse population could therefore

be considered completely susceptible to natural infection.

Although the international movement of horses has increased over the past 30–40

years, trade in both horses and semen has accelerated considerably during the past

decade as a result of changing economic trends in the horse industry worldwide. The

absence of any restrictions on the import of carrier stallions or EAV-infective semen

into the United States has greatly increased both the likelihood of the virus’ becoming

more widely disseminated in the Nation’s equine population and the risk of economically damaging outbreaks of EVA. This trend has been amply borne out by instances

in which imported carrier stallions or infective semen has been responsible for significant outbreaks of EVA, including abortion in mares and mortality in young foals. Such

importations not only augment the number of carrier stallions in the breeding population at large but also increase the potential for disease outbreaks through the introduction of more highly virulent strains of EAV previously exotic to the country.

This publication, “Equine Viral Arteritis: Uniform Methods and Rules” (UM&R), contains minimum standards for detecting, controlling, and preventing EVA as well as

minimum EVA requirements for the intrastate and interstate movement of equines.

5
It should be noted that these minimum standards and requirments represent a framework for creating a domestic EVA control program. This document should therefore not

be viewed as a final product, but as a work-in-progress that can be modified as science and technology evolve, as more experience in controlling EVA is acquired, and as

resources become available to implement the program.

The provisions of these methods and rules were approved by the USDA, Animal and

Plant Health Inspection Service (APHIS), Veterinary Services (VS) with recommendations from the United States Animal Health Association, the American Horse Council

(AHC), and the American Association of Equine Practitioners (AAEP). These UM&R

may be amended in the future.

6
Accredited veterinarian

Approved laboratory

Approved laboratory

tests

Certificate

Part I—Definitions

A veterinarian approved by the Deputy Administrator of USDA–APHIS–VS in accordance with provisions of part 161, title 9, Code of Federal Regulations (CFR). An

accredited veterinarian is preapproved to perform certain functions of Federal and

cooperative State–Federal programs.

A State, Federal, or private veterinary diagnostic laboratory that must be approved for

EVA testing by the USDA–APHIS–VS.

Laboratory tests for the diagnosis of EAV infection that are approved by the Office

International des Epizooties (OIE) and USDA–APHIS–VS.

The veterinary official of USDA–APHIS–VS who is assigned by the Deputy

Administrator of VS to supervise and perform the official animal health work of APHIS

in the State or States concerned.

The contracting or scheduling of mares for breeding to stallions by natural service.

A clinically normal stallion that sheds EAV continuously in it’s semen.

An official document issued by a VS representative, State representative, or accredited

veterinarian at the point of origin of a shipment of equines. It includes all of the following:

1. The description, including age, breed, color, sex, distinctive markings, or unique

and permanent forms of identification, when present (e.g., brands, tattoos, scars, or

blemishes), of each restricted equine to be moved;

2. The number of restricted equines covered by the document;

3. The purpose for which the equines are to be moved;

4. The points of origin and destination;

5. The consignor; and

6. The consignee.

To breed a stallion to a mare by natural service.

Any animal in the Family Equidae, including horses, asses, mules, ponies, and zebras.

The organism that causes the disease equine viral arteritis.

A contagious disease of equids caused by equine arteritis virus.

Area Veterinarian-inCharge (AVIC)

Booking

Carrier

Cover

Equine

Equine arteritis virus

(EAV)

Equine viral arteritis

(EVA)

7
8

Official test

Animals in the Family Equidae that have been exposed to EAV by reason of associating with equines known to be infected with the virus.

1. All animals of the Family Equidae, such as horses, asses, or zebras, under common ownership or supervision that are grouped on one or more parts of any single

premises (lot, farm, or ranch); or

2. All animals of the Family Equidae under common ownership or supervision on two

or more premises that are geographically separated but between which equines

have been interchanged or had contact with equines from other premises. It will be

assumed that contact between animals of the Family Equidae on the different

premises has occurred unless the owner can establish otherwise and the results of

the epidemiologic investigation are consistent with the lack of contact between

premises; or

3. All animals of the Family Equidae on common premises, such as community

pastures or grazing association units, but owned by different persons. Other

groups of equines owned by the persons involved that are located on other

premises are considered to be part of a herd unless epidemiologic investigation

establishes that equines from an affected herd have not had the opportunity for

direct or indirect contact with equines from that specific premises.

A farm or other premises where the equines were born or where they have been kept

for 30 days or more before the date of shipping. For the purposes of these UM&R,

herd of origin has the same meaning as place of origin, premises of origin, and farm of

origin.

Any modality that provides a unique and permanent identification of an individual

equine.

A serially numbered metal or plastic strip, consisting of a self-locking device on one

end and a slot on the other end, that forms a loop when the ends are engaged. An

official seal is tamperproof and cannot be reused if opened. It is applied to the doors

of a transport vehicle by a representative of the APHIS AVIC or the State animal health

official. A serially numbered, self-locking button that cannot be reused may be substituted for the metal or plastic-strip type of seal.

The virus neutralization and virus isolation test in cell culture are the official laboratory

procedures currently employed for the diagnosis of EAV infection. The procedures are

described in the OIE Manual of Standards for Diagnostic Tests and Vaccines.

Exposed animals

Herd

Herd of origin

Identification

Official seal
An official document (VS Form 1–27 or comparable State form) issued by a State or

Federal representative or by an accredited veterinarian. The permit must accompany

all EAV carrier stallions and those EAV-exposed equines being moved under official

seal to a specified destination.

The act of placing exposed or infected animals into isolation from other animals to

prevent the transmission of an infection.

A confined area under the direct supervision and control of a State or Federal animal

health official who establishes procedures for the monitoring/recording of all animals

entering or leaving the area. All equines under EVA quarantine are considered to have

been exposed to EAV.

Any horse, ass, mule, pony, or zebra that has been subjected to an officially approved

laboratory test that is confirmed positive for antibodies to EAV.

The national reference laboratory for the serological testing of EAV infection is the

diagnostic virology laboratory in Ames, IA, a part of USDA–APHIS–VS’ National

Veterinary Services Laboratories (NVSL). As designated by OIE, the international

reference laboratory for all laboratory diagnostic tests for EAV infection is the M. H.

Gluck Equine Research Center at the University of Kentucky in Lexington, KY.

The development of neutralizing antibodies to EAV in response to natural infection with

EAV or to the administration of EVA vaccine.

A horse that has a serum neutralizing antibody titer of 1:4 or greater to EAV using the

virus neutralization test.

A horse that has a serum neutralizing antibody titer less than 1:4 to EAV using the

virus neutralization test.

A term used to refer to a carrier stallion that has been determined to have EAV present

in its semen and is capable of transmitting the infection to other equines through the

act of breeding either by natural service or the use of artificial insemination.

Any State of the United States and the Northern Mariana Islands or any other territory

or possession of the United States. The District of Columbia, Puerto Rico, the U.S.

Virgin Islands, and Guam are other examples of the latter category.

The chief sanitary health official in each State responsible for disease control and

eradication programs affecting livestock and poultry.

An equine that has been vaccinated with an approved EVA vaccine and for which the

vaccination status has been kept current in accordance with the manufacturer’s

recommendations.

Permit

Quarantine

Quarantined area

Reactor

Reference laboratory

State

State animal health

official

Seroconversion

Seropositive horse

Seronegative horse

Shedder

Vaccinate

9
Virus neutralization (VN)

test

Isolation of EAV should be attempted in cultures of the RK–13 cell line (ATCC CCL37).

Suspensions of appropriate tissues or fluid specimens from suspect cases of EAV

infection are inoculated onto monolayer cultures of RK–13 cells either in 25-cm2

 flasks

or multiwell plates in accordance with the procedures prescribed in the OIE Standards

Manual for Diagnostic Tests and Vaccines. Inoculated cultures are incubated for 5 to 7

days at 37 °C and examined microscopically for viral cytopathic effect. In the absence

of visible cytopathic changes, culture supernatants are subcultured onto fresh cell

monolayers and incubated for an equivalent period at 37 °C. The identity of any virus

isolates must be confirmed using reference EAV antiserum.

An assay for determining serum neutralizing antibodies to a particular virus, in this

case EAV. Serial twofold dilutions of serum are tested against a standard quantity of

an approved reference strain of EAV. The antibody titer is expressed as the highest

serum dilution that neutralizes 75 percent of the standard quantity of virus. An antibody titer of 1:4 or greater is considered positive in the EVA VN test.

10

Virus isolation test
Part II—Recommended Procedures (Minimum Requirements)

Laboratory tests to detect EAV or EAV antibody should be conducted according to the

methods for international trade prescribed by the OIE. These methods are published

in the chapter on EVA in the current OIE Manual of Standards for Diagnostic Tests and

Vaccines. The manual is available at

<http://www.oie.int/eng/normes/mmanual/A_summry.htm>.

USDA–APHIS–VS maintains a list of laboratories approved to conduct serological

testing for EAV. The proficiency of approved laboratories is subjected to periodic

evaluation by NVSL. The current list of approved laboratories can be viewed at

<http://www.aphis.usda.gov/vs/nvsl/labcertification.htm>.

1. Collecting samples—Serum samples are examined for the presence of antibodies

to EAV in a VN test. Clean, nonhemolyzed, separated serum is required. Blood

samples should be collected into a Vacutainer® tube without anticoagulant.

Following clot formation, the blood collection tube should be centrifuged and the

serum transferred to a new sterile tube. Serum must be shipped to the testing

laboratory on ice packs.

2. Supporting documentation needed—The purpose for testing (e.g., diagnostic,

surveillance, prevaccination) and a clinical history, including EVA vaccination status

and vaccination dates, must be provided to the testing laboratory. A single serum

sample is sufficient to screen for the presence of EAV antibodies in a healthy horse.

A VN titer of 1:4 or greater is considered positive for EAV serum antibodies.

When samples are submitted for diagnostic purposes, paired sera are required.

The first sample is collected as early in the clinical course of the infection as

possible, and the second sample is collected 14–21 days after the first. The two

samples are examined together in the same VN test. Demonstration of

seroconversion or a fourfold or greater rise in antibody titer between the first and

second sample is significant and confirmatory of recent infection.

3. Repeating blood collection—Occasionally, sera will be encountered that cause

nonspecific toxic changes to the cell monolayers. These changes can interfere with

interpretation of VN results at the lower serum dilutions. In cases where the

problem cannot be overcome by the laboratory, it may be necessary to repeat blood

collection from the horse in question and submit the new serum sample to the

testing laboratory. The test setup schedule of the laboratory determines the turn

around time for receiving VN test results, which is normally 5–7 days.

1. OIE reference laboratory—Isolation of EAV in cell culture is a specialized

procedure. Attempts to perform this test should be limited to veterinary diagnostic

laboratories with experience and expertise in working with EAV. The OIE reference

laboratory for EVA in North America is under the direction of Dr. Peter J. Timoney. It

is located at the Department of Veterinary Science, 108 Gluck Equine Research

Center, Lexington, KY 40546–0099. [Telephone: (859) 257–4757, ext. 81085;

Fax: (859) 257–8542; E-mail: ptimoney@uky.edu).] Laboratories wishing to

provide virus isolation for EAV are urged to contact Dr. Timoney or Dr. William

McCollum to obtain a panel of semen samples for evaluation and to confirm their

competency in the isolation of EAV.

A. Laboratory Testing—

Prescribed Methods

B. Approved Laboratories

C. Serology

D. Virus Isolation

11
2. Maximizing accuracy—To maximize the accuracy of attempted virus isolation, care

must be taken in sample selection and handling during shipment to the laboratory.

Submitters should contact the receiving veterinary diagnostic laboratory to

coordinate sample selection, handling and processing, and expedient shipment of

samples collected for EAV isolation attempts. For example, use of heparin is

contraindicated when collecting whole blood samples as is the use of disinfectants

in cleansing the external genitalia of stallions before collecting a semen sample. In

conjunction with attempted virus isolation, the EAV serostatus of each horse being

tested for virus should be determined (see the section entitled “Serology” above).

3. Virus isolation samples—In the case of suspected outbreaks of EVA, samples for

virus isolation include nasopharyngeal and conjunctival swabs immersed in virus

transport media, unclotted blood using EDTA or sodium citrate as an anticoagulant,

and semen from stallions considered to be possible carriers of the virus. When EVA

is suspected as a cause of mortality, a variety of tissues collected at necropsy

should be examined. It is advisable to consult OIE in determining what tissues

should be sampled. In instances of suspected EVA abortion, fetal and placental

fluids and tissues should be submitted.

4. Semen samples—To determine the virus-shedding status of seropositive stallions,

the sperm-rich fraction of semen must be submitted. Semen from at least two

ejaculates should be submitted for evaluation. The preferred sample size is

5–10 mL of unextended raw semen. Less preferable is 5–10 mL of extended fresh

cooled semen. When frozen semen is the only sample available, at least two straws

per ejaculate should be submitted to the laboratory. Virus isolation attempts may

require more than one cell-culture passage. The normal turnaround time for EAV

isolation testing is 10–14 days.

1. Test before breeding—Before being used for breeding, stallions should have a blood

sample collected and tested for antibodies to EAV. Stallions that are seronegative

should be vaccinated with an approved EVA vaccine. EVA-vaccinated stallions

should not be exposed to EAV-infected animals and should not be used for breeding

within 28 days after their initial vaccination. Stallions should be annually

revaccinated against EVA.

2. Seropositive stallions—It is recommended that the following procedures be followed

when stallions test positive for antibodies to EAV.

a. If the stallion’s owner can document that the animal was seronegative for

antibodies to EAV before being vaccinated for EVA, the procedures listed under

E.1 should be followed. A valid EVA vaccination certificate is needed to

document the stallion’s negative prevaccination antibody status.

b. If the stallion’s owner cannot document that an antibody titer to EAV was the

result of vaccination, one of the two procedures listed below should be followed.

E. Testing Procedures

12
(1) Breed the stallion to two mares that are negative for EAV antibodies. Test

mares must be tested approximately 28 days after breeding for the presence

of antibodies to EAV. A negative test result on the two test mares will qualify

the stallion for breeding. The stallion will be classified as a seropositive

nonshedding stallion.

Or:

(2) Collect semen from the stallion and submit it to a laboratory approved for the

isolation of EAV. A negative virus isolation result qualifies the stallion for

breeding. The stallion will be classified as a seropositive nonshedding

stallion. This stallion will be eligible for EVA vaccination and should be

annually vaccinated against the disease.

c. The farm’s veterinarian must document all vaccinations and submit an EVA

 vaccination certificate to the State Veterinarian within 7 days of the vaccination

 date.

(1) Before a stallion receives its first EVA vaccination, a blood sample must be

collected, either very shortly prior to or at the time of vaccination.

(2) A stallion’s prior EVA test history will establish how the EVA UM&R will be

applied in determining the stallion’s breeding status.

d. When a shedding stallion is approved for breeding by the State

Veterinarian, the procedures listed next should be followed.

(1) The owner or agent of a mare booked to a carrier stallion, or seeking such a

booking, must be notified in writing by the stallion’s owner or agent that the

animal is classified as a carrier of EAV. A written copy of the booking

confirmation must be sent to the State Veterinarian.

(2) The carrier stallion must be housed, handled, and bred in a facility isolated

from noncarrier stallions.

(3) A carrier stallion can be bred to a mare that was vaccinated against EVA at

least 21 days before breeding or that has an antibody titer to EAV from

previous natural exposure to the virus.

(4) A carrier stallion can be bred to a seronegative mare that can be kept in total

isolation from other seronegative equines for 3 to 4 weeks after breeding.

(5) A mare with clinical signs of EVA should not be bred until it has been

 documented that she is seropositive for antibodies to EAV.

13
1. Notification of State Veterinarian—When an EVA outbreak is suspected, the farm or

attending veterinarian should immediately contact the State Veterinarian. In

jurisdictions where EVA is not a reportable disease, a self-imposed quarantine

should be implemented immediately on the affected premises to restrict further

spread of the infection.

2. Farm outbreaks—For a quarantine to be maximally effective, immediate restrictions

must be imposed on the movement of all horses associated with the premises.

Take these actions as soon as you suspect an outbreak:

a. Promptly isolate all affected horses.

b. Notify the farm or attending veterinarian immediately.

c. In consultation with the farm or attending veterinarian, seek laboratory

confirmation of a diagnosis as soon as possible.

d. In the case of abortion or death in a newborn foal, place the placenta, fetus, or

 foal in a leakproof bag, keep cold (not frozen), and dispatch to the nearest

 qualified diagnostic laboratory.

e. Disinfect the stall, any equipment, or other potentially contaminated facilities

 using a phenolic disinfectant. After treatment with disinfectant, dispose of any

 bedding by composting in an area away from other horses.

f. Using the antiseptic recommended by the farm or attending veterinarian, wash

down the hindquarters and tail of any mare that has aborted and isolate her from

other horses for 4 weeks.

g. Restrict movement of horses onto and off the affected premises.

h. Suspend breeding and training operations until the outbreak is over and notify

 owners of mares on the affected premises. Mares affected with EVA can be

 safely bred later in the same breeding season once they have fully recovered

 from the disease and once the outbreak has run its course.

i. Monitor horses at weekly intervals to check for any additional spread of the virus.

 If no further clinical cases of EVA or serologically confirmed cases of infection

 have occurred for 3 consecutive weeks, the outbreak can be considered over,

 and all movement restrictions can be lifted.

j. Vaccinate all at-risk horses.

3. Racetrack outbreaks—Measures to be taken in the event of an EVA outbreak at

a racetrack, equestrian event, or horse show are broadly similar to those

recommended for dealing with an outbreak on a breeding farm. Major emphasis

should be placed on isolating animals, restricting movement in and out of the

14

F. Outbreak Procedures
facility, and vaccinating all at-risk animals at the earliest opportunity. However, EVA

outbreaks at racetracks may involve conflicting interests. Measures to restrict the

spread of infection at such venues often interfere with racing and frequently do not

find favor with track management, trainers, and owners. In addition to the steps

outlined for farm outbreaks, implement these specific measures as soon as an EVA

outbreak is suspected at a racetrack:

a. Isolate all affected horses.

b. Prohibit the movement of horses between barns that have housed affected

horses.

c. Restrict the movement of horses stabled in such barns other than for racing or

training.

d. Establish temporary, sanitized stabling facilities for ship-ins.

e. Require that a health certificate accompany all horses coming to the track.

f. Require a 48-hour departure slip from the State Veterinarian and require the

certifying veterinarian to contact the jurisdiction of the horse’s destination for

approval to return home.

1. Vaccine—It has been possible to develop effective programs for the prevention and

control of EVA based on the known characteristics of the causal agent and

epidemiology of the disease. This infection can be controlled by minimizing or

eliminating direct or indirect contact with various secretions, excretions, or tissues of

infected horses. An important adjunct to the success of existing EVA control

programs is the availability of a safe and effective vaccine against the disease

(ARVAC®, Ft. Dodge Animal Health).

2. Nonbreeding farm settings—The goal of current control programs is to restrict the

dissemination of EAV in breeding horse populations in order to prevent outbreaks of

EVA-related abortion or illness and death in young foals and establishment of the

carrier state in stallions and postpubertal colts. Even though EAV has sometimes

been known to cause widespread outbreaks of disease at venues such as race

tracks, horse shows, sales, and equestrian events, currently there are no control

programs specifically directed at preventing the spread of the virus in nonbreeding

farm settings.

15

G. Control Procedures
3. Specific measures—Critical to the effectiveness of EVA prevention and control

programs is the observance of sound management practices that can help minimize

the risk of spreading this and various other equine infectious diseases. All control

programs developed so far highlight the uniquely important role of the carrier

stallion in the epidemiology of EVA. Such animals are the primary reservoir of the

virus and serve as long-term sources of infection, transmitting EAV to susceptible

mares either through natural cover or by artificial insemination. The following

specific preventive measures can help minimize the spread of EAV in breeding

horse populations:

a. Isolate all new arrivals and horses returning from other farms, sales, or race

 tracks for 3 to 4 weeks.

b. If at all possible, segregate pregnant mares from other horses and maintain

 mares in small groups based on anticipated foaling dates until they have foaled.

c. Before each breeding season, blood-test all new breeding stallions for the

 presence of antibodies to EAV.

d. Have the semen of any antibody-positive, nonvaccinated stallion laboratory-

 tested to identify any carrier animals.

e. Annually vaccinate all noncarrier breeding stallions at least 4 weeks before the

 start of each breeding season.

f. Physically isolate any EAV-carrier stallions.

g. Observe strict hygienic precautions when breeding or collecting semen from

 carrier stallions to avoid the risk of inadvertent transfer of infection through

 indirect contact with virus-contaminated objects.

h. Restrict breeding EAV-carrier stallions to vaccinated mares or mares that have

 previously tested positive for naturally acquired antibodies to the virus.

i. Vaccinate EAV antibody-negative mares against EVA at least 3 weeks before

 breeding to a known carrier stallion or with virus-infective semen.

j. For 3 weeks after they have been bred to a carrier stallion, isolate mares

 vaccinated for the first time against EVA from all but known EAV antibody-

 positive horses. It is especially important to avoid contact between such mares

 and other pregnant mares to which the virus can be spread by the respiratory

 route.

k. In breeds or areas in which there is a high prevalence of EAV infection, vaccinate

all immature male foals between 6 and 12 months of age against EVA as advised

by your veterinarian. If implemented over a period of years, such a program of

targeted vaccination would greatly reduce the number of carrier stallions and

largely eliminate the primary reservoir of EAV.

16
H. Movement of Stallions and Semen

l. Determine the infectivity status of semen used for artificial insemination,

especially if imported from abroad. When breeding mares with EAV-infective

semen, adopt the same precautions as recommended for mares bred by natural

cover to a carrier stallion.

4. Voluntary protocol available—A voluntary, industry-driven protocol to assist

breeders in preventing the spread of EVA was developed by a working group

convened by the AHC in 1996. The guidelines, released in August 1997, were

widely endorsed and are available at the Council’s Web site:

 <http://www.horsecouncil.org>. Click on the Equine Health Advisory box.

5. Vaccination debate—Because outbreaks of EVA are sporadic and infrequent in

settings such as racetracks, horse shows, sales, and veterinary clinics, it is

debatable whether a more widespread policy of vaccination against EVA would be

justified. Implementation of such a program of prophylactic vaccination would have

repercussions on international trade with certain countries that currently debar the

import of horses seropositive for antibodies to EAV.

1. Official health certificate—Equines entering a State from another State or from

another country should be accompanied by an official health certificate stating that

they are free from clinical signs of an infectious disease (which by inference

includes EVA).

2. Seropositive stallions or EAV-infective semen—Breeding stallions and equine

semen entering a State from another State or another country should be tested for

EAV within 90 days of entry. This means that stallions must be tested serologically,

and seropostive stallions must have their semen tested by virus isolation. Carrier

stallions (those in which EAV has been isolated from their semen) and EAV-infective

semen must be certified. These results appear as a certifying statement—

written on the health certificate—that the consignee has been advised and

consents to the shipment. Vaccinated mares can be bred to infected stallions

or inseminated with semen from an infected stallion.

3. Permit—All carrier stallions and EAV-infective semen entering a State should be

moved only on a permit issued by the State Veterinarian. All parties associated with

the movement of carrier stallions and EAV-infective semen into or within the State

should be made aware that these animals may be subject to quarantine at any time.

4. Regulations—States should develop regulations allowing for the interstate

movement of carrier stallions and EAV-infected semen.

1. EVA education: publication of articles—Breed registries should take a leadership

role in educating their members about EAV. Breed registries should publish articles

that

a. Explain what EVA is, how it is spread, and why it is important to breeders;

b. Advise mare owners how to prevent abortion and neonatal disease;

I. Recommendations

for Breed Registries

17
c. Explain that breeding a shedding stallion is entirely manageable and

 how to breed such a stallion safely;

d. Explain why an effective EVA control program benefits the breed registry's

members;

e. Educate mare owners to ask stallion owners about the EVA status of their

 stallions;

f. Educate prospective stallion buyers to ask for EVA testing at the time of

purchase; and

g. Explain how to prevent the carrier state in stallions.

2. EVA education: additional avenues—Breed registries should also publicize and

distribute other available educational material such as EVA breeding guidelines

(AAEP or AHC) and the USDA video and CD on EVA; distribute information on

testing, laboratories, and testing protocols; and invite speakers to annual meetings

and breeders’ group meetings to explain the disease and answer questions.

3. Safe breeding practices—Breed registries should promote safe breeding practices

by encouraging

a. Testing of breeding stock to determine immune status;

b. Vaccinating to control and eliminate EVA;

c. Vaccinating seronegative stallions, mares, and immature colts; and

d. Properly using and managing carrier stallions.

4. Raising awareness—Breed registries should raise awareness and foster discussion

about EVA by

a. Encouraging open dialog between stallion and mare owners;

b. Encouraging buyers of imported stallions to test before or at the time of import to

 identify carrier stallions;

c. Encouraging buyers of domestic stallions to test them as part of the prepurchase

 examination;

d. Encouraging mare owners to ask stallion owners about the stallion’s EVA status

 before breeding; and

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e. Reducing the stigma attached to EVA by emphasizing that the disease is

 manageable, that it can be prevented through a vaccination program, and that

 carrier stallions can be used safely.

5. Testing—Breed registries should require mandatory testing of all breeding stallions

as a condition of registration. Although voluntary adherence to breeding guidelines

is helpful and desirable, it will not solve all of the problems. A registry can prevent

many problems by using its influence and control over the registration process to

require testing as a condition of registration. This eliminates any singling out of

carrier stallions and tends to discourage deception. In particular, breed registries

should take these actions:

a. Publish the EVA status of all active breeding stallions. On the basis of test

 results, status categories would include (1) serologically negative,

 (2) serologically positive but negative for virus in the semen (nonshedder),

 (3) serologically positive and positive for virus in the semen (carrier), and

 (4) serologically negative and subsequently vaccinated annually.

b. Require annual testing of all nonvaccinated stallions.

c. Recommend vaccination for all nonshedding stallions (after proof of negative

 test).

d. In the case of vaccinated stallions, require proof of annual vaccination booster

 for all active breeding stallions.

e. Keep a list of which stallions recognized by the registry are EAV-carrier

 stallions.

f. Notify mare owners of carrier stallions through publications or in response to

 direct inquiry.

6. Developing regulations—Breed registries should work with local horse groups and

government authorities to develop State, national, and import regulations.

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