Forty horses from one Clarksville, Ark., farm have died or been euthanized after testing positive for equine infectious anemia (EIA), according to Arkansas State Veterinarian George Pat Badley, DVM.
"The first positive came in about two to three weeks ago," Badley explained, adding that testing on the entire herd began after two horses on the property died and were subsequently confirmed as EIA-positive. "When we got one that tested positive, we sent the blood off to Ames, Iowa, (to the USDA's National Veterinary Services Laboratory for confirmation) and it tested positive, too. That's when we found the (rest of the) positives, when the private veterinarian went back and tested the blood on all the horses." The farm was quarantined after the initial positive test results were returned.
Of the 80 horses residing on the property, a total of 40 horses tested EIA-positive and were euthanized, Badley confirmed. The remaining horses are under veterinary observation, however at this point all have tested negative for EIA.
"We have one herd that has a lot of positives in it," Badley said. "These horses don't show and the owner hasn't sold any for quite some time, either. It's pretty much a closed herd.
This year "the owner has taken additions in," he noted. "The latest addition, which arrived about four to six months ago, had a negative test when it arrived there. Then (when the outbreak) happened, it was one of the positives."
Badley noted that all the horses at that horse's farm of origin had current negative Coggins tests, but the animals were retested at the state's expense and were confirmed as negative.
Although state veterinary officials believe this to be an isolated and contained incident, they are working to determine the source of the disease and confirm whether or not the virus has spread from the property. State animal health officials have tested 13 horses residing at a nearby facility (all of these horses were at least a quarter mile away from the index property), and all test results have been negative at this point, Badley noted.
He also said that blood for Coggins tests had not been drawn on the affected farm's complete herd for several years: "Arkansas has a law that says every horse is supposed to be tested once a year, but that's in a perfect world and it doesn't happen. So we now believe that the disease was there for quite a while and has been brewing."
Additionally, he stressed that this incident is not related to another isolated situation that occurred two to three months ago in Van Buren County, Ark., in which five horses on three premises in close proximity tested positive for EIA. Badley noted that the five horses were all in contact with each other prior to testing positive for the disease.
"There are some reports that try to tie the two separate events together and it makes it (the scope of the scenario seem) much worse if you do that, but these events are completely unrelated. They do not have anything to do with each other epidemiologically. The horses had never even seen each other." Epidemiology is the study of the causes, distribution, and control of disease in populations.
Equine infectious anemia is a viral disease that attacks horses' immune systems and is most commonly detected with the Coggins test. The virus is transmitted through the exchange of body fluids from an infected to a noninfected animal, often by blood-feeding insects such as horseflies, and more rarely through the use of blood-contaminated instruments or needles. Once an animal is infected with EIA, it is infected for life and can be a reservoir for the spread of disease. Obvious clinical signs of the disease include progressive loss of condition along with muscle weakness and poor stamina. An affected horse also could show fever, depression, and anemia.
TheHorse.com will continue to provide updates should more information become available.
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