Equine Infectious Anemia: The ramifications of a positive test

When a horse receives a positive Coggins Test, it is an industry-wide problem.

Recently, the Michigan Department of Agriculture and Rural Development announced that a horse had received a positive Coggins test in Mecosta County, the first positive horse in Michigan since 2008. As a result of the diagnosis, the 17-year-old grade mare was euthanized. This situation is clearly tragic for the owners of the horse, but it also serves as a reminder as to why regular testing, which is controversial for some, is important to the equine industry.

The Coggins Test is the diagnostic tool for Equine Infectious Anemia (EIA), a disease with no vaccine or cure. Also known as swamp fever, malacial fever, and mountain fever, the death rate of infected equidae (horses, ponies, mules and donkeys, and zebras) ranges from 30-70%. Signs of infection include an intermittent to constant fever from 100-105 degrees F, rapid breathing, sweating, depression and weight loss, although appetite may not be impacted. Equine Infectious Anemia is caused by a virus and is transmitted from horse to horse via biting flies (although not mosquitos), contaminated needles or tools, or blood transfusions. Once a horse is infected it may or may not show signs of the disease and may become a carrier, an animal which appears healthy and may never show signs of the disease, but carries the virus for its entire life. Some horses will also harbor the disease but not show signs until they are stressed. These horses do have the potential to spread the virus to other horses which makes testing critical.

At this time, all 50 states including Michigan require a negative Coggins test for entry. Requirements vary from state to state, with some requiring the test drawn in the past 12 months, 6 months, or in the case of Wisconsin, calendar year. As of July, 2011, Michigan law requires a negative Coggins test drawn in the past 12 months for animals traveling to public events including shows, sales or exhibitions, as well as animals sold which require a change in location. In certain segments of the equine industry, this requirement is somewhat controversial, in that some feel the test does nothing to prevent the disease and that a “negative horse today could be positive tomorrow.” In addition some feel that the burden of the annual cost outweighs any benefit to the individual owner.

It is important to keep in mind that testing is the only way to maintain an “EIA free” herd, whether referring to personal horses or the entire state. By knowing where positive horses are located, public health officials can prevent the spread of EIA and reduce potential impact to the entire industry. Once positive horses are identified and separated from others the transmission of EIA ceases. Hence, regular testing is a responsible part of horse ownership for the greater good.

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