Equine Infectious Anemia Testing and Risk

Despite the fact that infection with equine infectious anemia (EIA) virus is found in fewer and fewer horses every year, U.S. horse owners continue to pay in excess of $50 million annually for required testing (Coggins tests). In 2006, the USDA reported fewer than 200 new cases, 66 of them on one premises. In other words, owners are paying on average about $250,000 to find each positive horse or about $500,000 for each infected premises.

Is the expense of testing appropriate to the risk? It is not. But the current system of testing has reduced the threat of EIA from more than 10,000 cases each year (with many clinical cases in the early 1970s) to the number today, almost all of whom are inapparent carriers. It has been a tremendous success story. Because of that, regulators of animal disease within states are hesitant to make changes without guidance or pressure from the horse-owning public.

In view of such success, can we relax about EIA and not test? No, but we can reduce testing costs to the industry while simultaneously reducing risk--and we should.

Analysis of the origin of new cases on a national scale is needed to establish risk estimates for horses. Some states have made changes: New Jersey reduced the requirement for testing from each year to every two years for resident horses; Washington and Oregon have agreed to waive testing for resident horses moving within their two states while retaining a requirement for horses entering from other states. When the USDA was asked to estimate savings by adopt-ing only regional requirements for EIA, it found an annual savings of $10 million. Substantial savings could be made by reducing testing intervals in low-risk areas.

Can we accurately estimate the risk of acquiring EIA in all 50 states? No, but horses in active show/racing/competition circles are essentially living in an EIA-free world because of their high testing rates. It can be argued that reduced testing in that population would have no effect on the number of new cases of EIA.

The USDA National Surveillance Unit is currently working to develop rough statistical estimates of expected EIA preva-lence rates across the nation, based on population estimates, numbers of horses tested for EIA, numbers of positive cases found over time, etc. These estimates will have ranges because the figures they're based on won't be accurate, but they can be valuable as predictors until firmer figures are compiled. If it turns out that contiguous states have similar risks for EIA, strong arguments for regional requirements can be made.

When will such changes occur? Regulators of animal disease-- state veterinarians in most cases--have told us they will not change until horse owners tell them changes are desired.

EIA was a hot topic in 2006, when it was discovered officially for the first time in Ireland. It is thought that the virus was brought to Ireland in plasma collected from horses in Italy and imported for prophylactic treatment of foals to help prevent foal pneumonia. The infection appears to have spread on a breeding farm and was not recognized until veterinarians were apprised of an outbreak of EIA in Italy associated with plasma administration. By the time EIA was suspected and testing was done on foals and on a dead mare, EIA had been transmitted to horses at several farms and to horses hos-pitalized where the mare was euthanatized. Overall, 28 cases of EIA were reported in Ireland in 2006.

This is a good example of what can occur if EIA is ignored or assumed not to be present. Active surveillance is required to prevent outbreaks of this type. We must not assume that we are free of this infection. Freedom requires responsibility and continued vigilance against a disease. In Ireland veterinarians are prohibited from testing horses brought in from other major trading partners, as they all are assumed to be free of the infection.

In the United States, if we wish to reduce testing costs to the industry, we must implement sound strategies that include increased surveillance of horses at higher risk, e.g., those not tested earlier or those changing ownership. We should also adopt enhanced isolation/segregation/quarantine standards to prevent introduction or to break transmission not only of EIA virus, but also equine herpesvirus-1 (EHV-1), equine viral arteritis (EVA), etc.

We are part of a global equine community and are subject to introduction of numerous agents of disease, many for which vaccines or effective treatments are not available. We must be prepared and remain vigilant. With EIA, this can be done more efficiently and less expensively with smarter testing.

Charles J. Issel, DVM, PhD, is the Wright-Markey Chair of Equine Infectious Diseases at the University of Ken-tucky's Gluck Equine Research Center. For more information on Issel's vision for EIA testing, visit www.TheHorse.com/ViewArticle.aspx?ID=8787.

About the Author

Charles Issel, DVM, PhD

Charles J. Issel, DVM, PhD, is the Wright Markey Chair of Equine Infectious Diseases at the Gluck Equine Research Center at the University of Kentucky. He has studied equine infectious anemia since 1974 while on the faculty at Louisiana State University (until 1990) and at UK. Issel bred Thoroughbreds in Louisiana prior to working at UK.

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