United States

Department of

Agriculture

Animal and

Plant Health

Inspection

Service

Program Aid No. 1707

Equine Infectious Anemia: 2001 Update
The U.S. Department of Agriculture (USDA) prohibits

discrimination in all its programs and activities on the basis

of race, color, national origin, sex, religion, age, disability,

political beliefs, sexual orientation, or marital or family

status. (Not all prohibited bases apply to all programs.)

Persons with disabilities who require alternative means for

communication of program information (Braille, large print,

audiotape, etc.) should contact USDA’s TARGET Center at

(202) 720–2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director,

Office of Civil Rights, Room 326–W, Whitten Building, 14th

and Independence Avenue, SW, Washington, DC 20250–

9410 or call (202) 720–5964 (voice and TDD). USDA is an

equal opportunity provider and employer.

Cover photo: What is the chance that these free-ranging

equids are carriers of the equine infectious anemia (EIA)

virus? This photo is used to emphasize that control of EIA

is dependent on finding carriers of the EIA virus through

testing of privately and publicly owned equids and restricting the movement of those found to be test-positive.

(APHIS photo by Ann Czapiewski.)

Photo credits: The photograph on page 7 was taken by

USDA photographer Ken Hammond. The image on page

17 was taken by Carolyn Mason and supplied to APHIS by

the Foundation for Shackleford Horses, Inc., of Beaufort,

NC. That photograph is reproduced by permission of the

Foundation. The picture on page 28 was taken by APHIS

photographer Ann Czapiewski.

Note: The July 2004 reissuance of this publication is

somewhat shorter than the 2001 original and contains new

photographs. Web site references and internal dates have

also been revised.

Issued September 2001

Revised July 2004
By Timothy R. Cordes, D.V.M.,1

Charles J. Issel, D.V.M., Ph.D.,2

Eileen N. Ostlund, D.V.M., Ph.D.,3 and

Beverly J. Schmitt, D.V.M., M.S.4

1

Dr. Cordes is a Senior Staff Veterinarian with the National Animal Health Staff, Veterinary Services,

Animal and Plant Health Inspection Service (APHIS), U.S. Department of Agriculture (USDA),

4700 River Road, Riverdale, MD 20737. He can be reached via the Internet at

Timothy.R.Cordes@aphis.usda.gov or by telephone at (301) 734–3279.

2

Dr. Issel is Wright–Markey Chair of Equine Infectious Diseases, Gluck Equine Research Center,

University of Kentucky, Lexington, KY 40546–0099. He can be reached via the Internet at

cissel@pop.uky.edu or by telephone at (859) 257–1710.

3Dr. Ostlund is Section Head, Equine and Ovine Viruses, Diagnostic Virology Laboratory, National

Veterinary Services Laboratories of USDA–APHIS–Veterinary Services in Ames, IA. She can be

reached via the Internet at Eileen.N.Ostlund@aphis.usda.gov or by telephone at (515) 663–7551.

4Dr. Schmitt is the Chief of the Diagnostic Virology Laboratory, National Veterinary Services

Laboratories of USDA–APHIS–Veterinary Services in Ames, IA. She can be reached via the

Intenet at Beverly.J.Schmitt@aphis.usda.gov or by telephone at (515) 663–7551.

United States

Department of

Agriculture

Animal and

Plant Health

Inspection

Service

Program Aid No. 1707

Equine Infectious Anemia: 2001 Update
4

Introduction

Equine infectious anemia (EIA) has been recognized as a major infectious disease of

equines for more than 150 years. Since 1970, tools have been available to identify

persistently infected carriers of the equine infectious anemia virus (EIAV). Testing of

serum for antibodies to EIAV makes it possible to accurately monitor equines for the

infection. The tests commonly used are the agar gel immunodiffusion (AGID or

Coggins) test and several enzyme-linked immunosorbent assay (ELISA) tests. In many

parts of the world, testing and removal of carriers have become routine and/or required

and have provided a measure of protection against exposure to the virus because

equines are the only known reservoir of infection.

In 1996, the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) published and distributed more than 3,000 copies of a video

brochure package entitled “Equine Infectious Anemia: How To Protect Your Horse.” The

brochure in that package, “EIA: a Status Report on Its Control,” contained much basic

information on the lentivirus that causes EIA and on its transmission and control. The

1996 brochure is

available on the Internet at <http://www.aphis.usda.gov/vs/nahps/equine/eia/eia-1996.pdf>.

In this brochure, we discuss what has been learned about EIA since 1996, what effect

that information has had on determining the best approaches to controlling EIA in the

field, and what additional actions are needed to further the control of EIA nationally. We

have also updated the 1996 bibliography here. We also reiterate and debunk some of

the popular myths about EIA that have led to confusion and overreaction by those forced

to deal with this disease for the first time.
5

At the Federal level, the requirements for testing horses for interstate movement are

explained at Title 9, Code of Federal Regulations (9 CFR), section 75.4. In addition,

9 CFR 75.4 outlines the procedures for the recognition of laboratories and personnel as

qualified to conduct EIA testing. The physical facilities of the laboratory must be inspected, and personnel who perform EIA tests must complete an approved training

course and demonstrate individual proficiency in conducting EIA tests.

Within-State regulations concerning EIA are the jurisdiction of each State, and control of

its spread remains a high priority for most State regulatory agencies. Control is predicated on finding the persistently infected equine carriers of EIAV and controlling their

movement. In many jurisdictions, destruction of the carrier is recommended or mandated. As most of these carriers are without clinical signs suggestive of EIA at the time

the horses are tested, some owners resist testing and/or acting on this recommendation.

Here we attempt to put these issues in perspective and offer several proposals to better

control the spread of EIA.
6

Ten Useful Facts About EIA

1. Equine species (horses, donkeys, mules, etc.) are the only ones in which EIAV

replicates.

2. When equines become infected, they produce antibodies against EIAV.

3. Once infected with EIAV, equines remain infected for life.

4. Some strains of EIAV kill rapidly, and some induce severe chronic disease, but

many field strains present today appear to induce few or no overt clinical signs

of disease in equines.

5. EIAV is a lentivirus and mutates at a high rate.

6. All strains of EIAV are believed to have the genetic potential to induce disease

in equines.

7. EIA is a bloodborne infection: transmission occurs by transfer of blood between

equines.

8. Blood-feeding insects (especially horse flies and deer flies) are important

natural vectors of EIAV.

9. Separating infected from uninfected horses by at least 200 yards is an effective

way to break mechanical transmission of EIAV by insects.

10. Serological testing to identify EIAV carriers is an important tool in controlling

EIA.
7

Figure 2.
8

Popular Myths and Facts About EIA

Myth #1. EIA is a contagious disease.

Facts: EIA is an infectious disease (it is caused by the invasion and multiplication of

the EIAV in tissues of the equine), but it is not thought to be contagious. That is,

the infection is not directly transmitted from one equine to another; it can

spread only with the intervention of vectors, e.g., insects or humans. Many

publications incorrectly refer to EIA as a contagious disease. Perpetuation of

this myth, or imprecise use of the terms “contagious” and “infectious,”

undoubtedly leads to increased fear of the infection and disease. EIA is most

accurately described as a bloodborne infection.

Myth #2. EIAV induces disease and death in a high percentage of infected equines.

Facts: Although EIAV can induce severe disease with a high mortality rate, most field

strains of EIAV found in test-positive carriers today are not associated with overt

clinical disease. EIAV-infected horses usually look healthy. In part, the current

low rate of severe clinical EIA is related to the testing and removal of reactors

with clinical disease over the past 25 years. The EIAV strains with the greatest

potential to induce severe disease have been selected against over the years.
9

Myth #3. EIAV spreads rapidly through a population.

Facts: Transmission of EIAV is predictable only in the sense that infected equines

persistently carry virus in their blood. If enough blood is transferred to a

second equine, the virus will initiate an infection. In the absence of humans,

transmission of EIAV requires the transfer of blood (or possibly other virus-rich

secretions) between equines in close proximity, generally via blood-feeding

insects. The probability and rate of transmission of EIAV in equine populations

are multifactorial but highest when these three conditions are present:

(1) the level of EIAV in the blood is high (i.e., during clinical disease),

(2) blood-feeding vectors are abundant, and (3) equines are crowded. In some

cases, the spread of EIAV from carrier horses has been explosive. In others,

there has been no transmission over periods of years. Transmission of EIAV is

a chance phenomenon. As EIAV mutates at a high rate, for purposes of

disease control every virus strain is assumed to have the potential to initiate

explosive epidemics. Why take chances if horse owners can test and avoid

reservoirs of the infection?
10

Myth #4. Quarantine farms for EIA reactors are dangerous and should not be

permitted.

Facts: There is no scientific basis for the fear of acquiring EIA from known test-positive

equines in safe quarantine (>200 yards from other equines). The chance of

acquiring the virus by commingling with untested equines in an area where only

1 in 10,000 equines is infected is significantly greater than the chance of

acquiring it from the quarantined equine directly, maybe more than a millionfold

greater. When fear subsides and logic prevails, quarantine farms might become

acceptable alternatives to mandated destruction.

EIA continues to challenge horse owners because they cannot tell if the equines they

encounter have ever been tested for EIA or—if they have been tested—with what

other horses theirs have commingled since the test. If infected equines commingle

with healthy ones, nobody knows for sure how likely it is that the infection will be

transmitted.
11

The following are suggestions on how to reduce significantly the risk of acquiring EIA in

the United States. The remainder of this brochure is devoted mainly to discussing these

actions.

1. Promote and implement the adoption of effective, permanent methods to identify

individual equines.

2. Encourage State programs to enhance the public understanding of EIA.

3. Develop novel cooperative programs that promote areawide testing of equines.

4. Consider the establishment of quarantine farms to permit the safe containment of

EIAV-infected equines.

5. Obtain a better understanding of the biological risks of EIAV transmission, and then

apply this knowledge to develop quantitative risk-assessment models on which to

base regulatory decisions.

Implementing these five suggestions will help the horse industry find solutions to

problems such as:

How can EIA control methods be modified to maintain or increase surveillance for EIA

and give a higher benefit-to-cost ratio to the industry? Can science do a better job of

finding reservoirs of EIAV that have not been tested? How can veterinarians and

government regulations better serve the equine community in relation to EIA?
12

EIA Literature

The vast majority of articles published on EIA and EIAV during the past 8 years (found

by searching the National Center for Biotechnology Information’s “PubMed” Web site at

http://www.ncbi.nlm.nih.gov) focus on understanding the basic molecular aspects and

control of viral replication, generally in cell cultures in the laboratory. Much of the

research was conducted because EIAV is genetically related to the human immunodeficiency virus (HIV), not because EIAV causes infections in horses.

There still are modestly funded efforts to define how EIAV causes disease in horses, to

identify the immune effectors that help horses control viral replication, and to produce

safe vaccines that would protect horses against EIAV infection if exposed. Developing a

vaccine is tricky because some of the disease signs in infected horses are related to

immune responses (immunopathology) shown to be stimulated by some experimental

vaccines.

In the past 8 years, several groups have demonstrated that the genetic material of EIAV

can be found persistently and sometimes in relatively high levels in test-positive horses

without clinical signs of EIA. Such horses are called inapparent carriers. These data

provide clear evidence that these inapparent carriers should be isolated or quarantined

once their test status is verified.

EIAV as a virus

is better known

today, and the

genesis of some

of the clinical

signs is better

understood, but

control strategies are essentially unchanged

since 1972.
13

Realities and Surprises

Since 1980, on average, 1 million equine samples have been tested for EIA each year in

a major surveillance effort by industry, veterinarians, and regulatory agencies. In spite

of this, the National Animal Health Monitoring Systems’ survey of the equine industry

reports that 58 percent of owners in the Midwestern States have never heard of EIA,

and only 12 percent of equines in the West are tested for it. The same survey also

reports that EIA is perceived as the most important viral infectious disease of equines

nationally.

EIA appears to be of greatest concern in areas of the country where the infection has

occurred historically at highest frequency (States in the Southeast) or where regulations

have helped to inculcate a sense of urgency about EIA control (States in the Northeast).

For example, a review of the surveillance statistics reported for fiscal year 1998 reveals

the significance of State regulations. In that period, more than 179,000 equine samples

were tested in the Northeastern States, and only 3 test-positive horses were found.

Extensive testing, comprehensive regulations, and aggressive followup on new infections for the past 25 years have significantly reduced the risk of contacting a testpositive equine in the Northeast. State regulations are available at the Web site

http://www.aphis.usda.gov/vs/sregs.

Despite our

collective efforts

over 25 years,

EIA is still an

unknown or an

enigma to many

owners. To

most, it represents a problem

only when it

knocks at their

door.
14

Regulations, Laws, and Challenges

Once an accurate test to identify carriers of EIAV became available, the Infectious

Diseases of Horses Committee (IDoHC) of the United States Animal Health Association

(USAHA) formulated recommendations for the control of EIA. Those recommendations

have been used by most authorities interested in promulgating regulations or laws to

control the infection. In 1997, a set of guidelines for EIA control was drawn up by a

working group from the IDoHC. These guidelines were adopted by USDA and used in

the brochure “Equine Infectious Anemia, Uniform Methods and Rules, Effective January

1, 1998” to help standardize control recommendations in different jurisdictions. A

revised version of the publication, under the same title but showing an effective date of

March 1, 2002, was published in March 2002. It is available for download from the Web

in .pdf format at <http://www.aphis.usda.gov/oa/pubs/eiaumr.pdf>.

In 1993, Louisiana made regulatory history by taking the bold step of requiring permanent identification and annual EIA testing of all equines. Although Louisiana authorities

estimate that fewer than 40 percent of equines are actually tested every year, the public

has responded favorably to the increased emphasis on EIA control. Finding methods to

increase compliance beyond 40 percent remains a formidable challenge.

During the past 5 years, Arkansas and Texas have enacted dramatic changes in State

regulations following Louisiana’s lead. Besides identification and testing, Louisiana law

also requires the destruction of test-positive equines (or removal to a research facility) and

the quarantine and testing of equines that have been within 200 yards of the reactor.

Legislation passed in Arkansas in 1997 requires that every equine have an EIA test

annually and whenever there is a change of ownership. The law also mandates
15

destruction of each reactor (or removal to a research facility) and requires State authorities to quarantine and test all equines that have been within 440 yards of the reactor.

In 1999, and after appropriate public debate, the legislation was modified further to

broaden a good-neighbor provision. In Arkansas, any horse owner can now request

that the State authorities verify that any other owner had tested their equines during the

past year. If no evidence of a current test is produced, then the State is mandated to

test the animals. This provision is novel, and time will tell if it increases compliance and

goodwill among owners or has the opposite effect.

The regulations in Texas are similar in that they require testing for congregation and for

change of ownership, as well as requiring State authorities to perform traceback testing

on all equines within 200 yards of reactors. The number of samples tested for EIA

increased dramatically after these regulations were adopted.

In summary, three States where EIA has occurred frequently in

the past have instituted comprehensive regulations or laws that

require testing each year and when there is a change of ownership. Regulations for EIA and other equine diseases change

frequently, so we advise a careful review of individual State

requirements before moving equines to another State.
16

Distribution of EIA

Since testing for EIA was initiated, the vast majority of new cases have been found each

year in the area we have designated the Hot Zone. In the past 5 years, some anomalous case distributions have been noted, mostly in groups of horses on specific

premises or in specific regions being tested for EIA for the first time. For example, the

increased rate of positive tests in 1998 in Indiana was traced to 32 new cases on

1 farm; in Arizona to 15 new cases on 1 premises; and in Utah to 127 new cases found

in free-roaming horses.

Results from two free-roaming populations of horses in diverse geographic areas

deserve further discussion. In North Carolina in 1996, EIA was discovered in horses on

Shackleford Banks, a barrier island in the Cape Lookout National Seashore, managed

by the National Park Service. On the first testing of this isolated, insular, free-roaming

population, 41 percent (76/184) of the horses were reactors. If the 10 test-positive foals

of reactor mares are subtracted, the reactor rate of the population drops to 38 percent.

In Utah in 1998, reactor rates in one hot area were similar to those seen in North

Carolina. There the rate was 49.5 percent (53/107) and 44 percent if the test-positive

foals of reactor mares are subtracted.

In both of these cases, it appears that EIA had been present in the population for years

and had stabilized, as the rate of infection increased with age. In both cases, the EIA

test-positive rate was exceptionally high in mature stallions: 88 percent (16 of the 18

dominant herd stallions) on Shackleford Banks and 89 percent (17 of 19 stallions >3

years of age) in the index area in Utah.
17

Figure 3—Horses on the Outer

Banks of North Carolina represent

a unique national resource. EIA was found on Shackleford Banks for the first time in 1996. Removal

of test-positive horses and

repeated annual testing since

1998 suggest that EIA has been

eradicated from this population.

The Shackleford horse population

remains at risk of acquiring EIA,

however, mainly from untested

horses on the mainland or other

barrier islands that could swim to

Shackleford during storms. The risk can be eliminated only by

testing and maintaining segregation from all known carriers.
18

These data suggest that stallion behavior plays a role in increasing the risk of EIAV

transmission between horses. The most obvious behavior to be investigated is the

combative behavior between stallions associated with establishing and defending

harems.

In both of these populations, most test-positive horses were inapparent carriers. In

Utah, however, two stallions appeared to have signs of the chronic form of EIA, and one

died during its first day of captivity. Also, EIA appeared to decrease reproductive

success in the Utah group. The rate of foaling in the test-positive group of mature

mares was 52 percent (12/23) compared to 87 percent (13 of 15) in test-negative mares

from the same area.

In order to find

EIA, horses must

be tested for it.

Undertested

areas may have

carriers, and

transmission

may be slow or

epidemic. In two

free-roaming

horse populations, about

40 percent of

animals tested

positive for EIA.
19

Foals and EIA: the Possibilities and the Realities

In many jurisdictions, young foals are exempted from testing if the mare has tested

negative for EIA. If mares test positive, their foals will generally be test-positive as well.

In these cases, the foals could be infected or merely carrying passive antibodies to

EIAV obtained in colostrum. The risk of transmission to the foal is assumed to be higher

if the mare has recently experienced clinical signs of EIA. When the mare is a stable

inapparent carrier of EIAV, field studies have shown that a high percentage (>90 percent) of foals can be raised uninfected, even when weaned at 5 to 8 months of age in

areas with high populations of insect vectors. Recent studies in Oklahoma have

extended scientific knowledge on this subject. Over 3 years, more than 97 percent of

the foals of test-positive Choctaw or Cherokee bloodlines have been raised free of the

infection.

In foals of test-positive mares, declining levels of antibody to EIAV and sensitive polymerase chain reaction tests showing no viral RNA are good indicators that the foals are

not infected. These foals should be in isolation or quarantine from all sources of EIAV

for at least 60 days before release.
20

Accuracy of Testing

In order to control EIA effectively, the most accurate tests available must be used. The

agar gel immunodiffusion (AGID), or Coggins, test has been approved since 1972. Are

better tests available today?

The answer is a qualified no. It is true that, to give a positive result, the AGID assay

requires more antibody than an ELISA test. The AGID test for EIA, though, is the only

serologic test whose results correlate positively with results of the horse inoculation test,

which tests for the virus itself. Together, the AGID and ELISA tests for EIA give veterinarians and owners better options. By using more than one type of test, owners can

essentially maximize the advantages and minimize the disadvantages of each individual

test. The next several paragraphs cover the advantages and disadvantages of the AGID

test and the ELISA test.
21

1. The AGID test is specific, and nonspecific reactions can be distinguished from

EIAV-specific reactions.

2. The AGID test correlates with the virus content measured by the horse inoculation

test.

3. The AGID test has international acceptance.

4. There has been nearly 30 years of experience with the AGID test.

1. The AGID test requires skilled, subjective interpretation of results.

2. Results are not available for at least 24 hours.

3. The end-user must make up plates with agar, and errors can lead to decreased

accuracy of test results.

Advantages of the

AGID Test

Disadvantages of the

AGID Test
22

Disadvantages of

ELISA Tests

1. All ELISA test kits available today incorporate the same virus-specific antigen as

in the AGID test; one test kit also includes an additional virus-specific antigen.

2. ELISA tests are easier to interpret than the AGID test.

3. Results can be calculated objectively if assay color development is measured with

a spectrophotometer.

4. ELISA tests are more rapid than the AGID test; results are available within

minutes.

1. The ELISA method can be less specific than the AGID test in that false-positive

results may occur. Positive ELISA results MUST be confirmed with an AGID test.

2. ELISA tests are more expensive per sample.

3. ELISA results are not accepted in some States or for international travel [as of

July 2004].

Advantages of ELISA

Tests
23

1. Increased accuracy and power are obtained by using several antigens (similar to

the confirmatory tests for HIV).

2. The impact of the majority of human errors is minimized.

The AGID test remains the test of choice for EIA, and because it has been correlated

with viral presence, it will remain the standard against which all other tests are compared. Thus, if a positive reaction is noted in an ELISA assay, it must be confirmed by

an AGID test before a positive result is released and acted upon. In the vast majority of

cases, there is agreement between test results from all available kits.

Sometimes discordant test results occur. Discordants are results that differ from test to

test, e.g., between ELISA and AGID, from laboratory to laboratory, from test run to test

run with the same test method in the same laboratory, or between two samples from the

same animal. When discordant results are seen, which test or tests should be used as

the definitive test? And most importantly, are differences in test results related to

biological phenomena or to differences in human performance?

All licensed kits are standardized to an equivalent sensitivity, but when comparing any

two tests, interpreters sometimes come to different conclusions. These occur most

often when samples have reactions that are near the cutoff point in ELISA or at the limit

of detection in AGID.

Advantages of Having

More Than One Type of

Test for Diagnosis

of EIA
24

A frequent biological reason for divergent test results is that the horse in question has

very low levels of antibody against EIAV. The horse may have recently been exposed

and is just beginning to produce antibodies. Rarely, inapparent carriers have consistently low antibody levels against EIAV, suggesting a low level of viral replication and low

stimulation. In both cases, the end result is the same: the antibody level is so low that it

escapes detection in some routine tests. The next most common reason for divergent

test results is that the horse has been exposed to a related agent that cross-reacts with

antigens of EIAV. Low levels of specific antibodies would result primarily in falsenegative AGID reactions, while nonspecific antibodies would result primarily in falsepositive ELISA results. Fortunately these types of reactions have been observed at a

very low rate.

In order to minimize human errors in testing, USDA–APHIS–Veterinary Services (VS)

mandates that, prior to receiving approval to conduct EIA tests, a technician must have

specific training and must demonstrate individual competence. This governmental

oversight is outlined in 9 CFR 75.4. In addition, APHIS monitors laboratory performance

through annual proficiency tests which must be completed with accuracy by all

approved laboratories. Nonetheless, human errors in testing for EIA and reporting the

results can occur at multiple points. First, a technical error could have been made in

testing the sample. For example, errors in preparing agar for the AGID test or in washing ELISA test wells may lead to incorrect results. Second, the technician may be

uncomfortable or unwilling to interpret and report as positive a sample with a very weak
25

AGID test reaction. Third, loss of sample integrity could occur by cross contamination or

mislabeling. When laboratories are testing large numbers of samples, consistent attention to detail is required to ensure that all tests are properly conducted and reported.

For samples with positive reactions, many laboratories confirm the initial reaction by

testing the sample a second time as originally run and also in other approved types of

tests before issuing the positive test report. We recommend collecting a second sample

from each reactor to confirm the accuracy and reproducibility of test results. This is

important to ensure the integrity of the first report, especially to minimize the impact of

human error.

Biologically false-negative reactions in EIA testing are extremely

rare. The number of EIAV-infected horses estimated to be

reported falsely as negative is less than 1 percent of the number

of reactor horses found each year. The number of false reactions

can be decreased if diagnosticians capitalize on the strengths of

the available tests for EIA. The impact of these false-negative

equines is thought to be significantly lower than that of the millions of equines that remain untested.
26

Risks of Acquiring EIA (from highest to lowest)

• Never testing for EIA

• Acquiring a new animal

• Adding a new animal to the facility or band without a

test

• Commingling with animals with unknown test status

• Being within 200 yards of animals with unknown test

status

• Adding a new animal with an old negative test but

whose contacts were untested

• Being near safely quarantined reactors but at a distance greater than 200 yards

Checks and cross-checks are used to minimize the impact of inaccurate reports.

Repeat confirmation testing of positives should be mandatory. Continued education of

diagnosticians should be required; this should include the routine submission of

challenging samples to be tested blindly and reported.
27

Most new cases of EIA found in the United States each year are in or have originated

from equines that have never been tested for EIA. Eventually, through attrition, the

untested reservoirs of EIA will be discovered. The period of time required to reach that

goal can be reduced significantly through the design and application of industrywide

standards and cooperative programs.

Because of the low risk of acquiring EIA in closed herds where all horses have tested

negative for it, testing at frequent intervals may seem unnecessary but is arguably

prudent.

The horse industry should require a negative test for all changes of ownership, have the

States inform the public of the rule, and enforce penalties on those sellers who ignore it.
28

Figure 4—
29

Final Word: Federal Involvement in EIA Control

This brochure covers what the authors have learned about EIA since 1996 and what

might be done to further control EIA at the State level. However, involvement at the

Federal level merits discussion. USDA–APHIS–VS remains committed to the national

EIA control program and proposes to improve the program as follows:

1. Provide the most current EIA educational materials, including:

• A regularly updated version of this EIA brochure,

• A regularly updated version of the EIA Uniform Methods and Rules (UM&R),

• A current edition of the EIA video, and

• A current EIA laboratory guide.
30

2. Improve national EIA surveillance by

• Accounting for quarantined EIA reactors,

• Increasing the frequency and accuracy of laboratory reporting,

• Improving tracking system(s) for out-of-State testing, and

• Incorporating portions of the UM&R into the Code of Federal Regulations.

VS is open to suggestions from the horse industry, State regulatory officials, and other

interested parties concerning what more USDA can do to control EIA in the United

States.
31

Acknowledgments

The authors wish to thank the following for their cooperation, support, and dedication in

helping increase public knowledge about EIA and its control:

Dr. Carey Floyd of the Oklahoma Department of Agriculture,

Dr. Becky McConnico of Louisiana State University,

Students and faculty associated with the chapter of the American Association of Equine

Practitioners at the College of Veteriary Medicine at Oklahoma State University (especially Matt Lampe, who volunteered for numerous EIA projects and activities in Oklahoma and Utah),

Dr. Mike Marshall, Utah State Veterinarian,

Jim Lekas of Vernal, UT, and

Members of the Foundation for Shackleford Horses, Inc., in Beaufort, NC.

We also thank the producers of ELISA test kits for EIA (IDEXX Labs, Centaur, Inc., and

Synbiotics Corporation) for their continued support of the EIA control program activities,

especially for supplying reagents for the awareness and testing exercises in Utah and

Oklahoma.
32

Selected References

Campbell, C. L. 1971. Communication on infectious diseases of horses: a prospectus on

equine infectious anemia with guidelines—1971. In: Proceedings of the United States

Animal Health Association; 24–28 October 1971; Oklahoma City, OK. Richmond, VA:

United States Animal Health Association: 249–261.

Coggins, L.; Norcross, N. L.; Nusbaum, S. R. 1972. Diagnosis of equine infectious

anemia by immunodiffusion test. American Journal of Veterinary Research 33(1): 11–18.

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Tissue sites of persistent infection and active replication of equine infectious anemia

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Since 1996, USDA–APHIS–VS has published several documents on the subject of EIA and

is maintaining the most important of these on the World Wide Web. Our original black-andwhite brochure, “Equine Infectious Anemia: Status Report on Its Control, 1996” (APHIS

91–55–032), is available in .pdf format at <http://www.aphis.usda.gov/nahps/equine/eia/eia1996.pdf>. We encourage readers of the 2001 brochure on EIA to download this older

publication, which contains a great deal of basic information on the disease that has not

been repeated in the 2001 pamphlet or the 2004 revision of it. Finally, users who need a

short, easily photocopied document about EIA may find APHIS’ factsheet on this subject

helpful. It can be viewed at http://www.aphis.usda.gov/lpa/pubs/fsheet_faq/_notice/

fs_aheia.html and printed from a .pdf version at the blue hotlink at the bottom of that Web

page.

Readers looking for more technical information on the detection and control of EIA and the

transportation of equines that have tested positive for the disease may wish to consult

“Equine Infectious Anemia: Uniform Methods and Rules, Effective March 1, 2002” (APHIS

91–55–064). This publication can be downloaded at <http://www.aphis.usda.gov/oa/pubs/

eiaumr.pdf>.

—Timothy R. Cordes, D.V.M.

—Charles J. Issel, D.V.M., Ph.D.

—Eileen N. Ostlund, D.V.M., Ph.D.

—Beverly J. Schmitt, D.V.M., M.S.
36