EVA Confirmed In Kentucky

An outbreak of equine viral arteritis (EVA) was confirmed on one Thoroughbred farm on March 20. Kentucky State Veterinarian Don Notter was notified about mid-day.

The outbreak appears to be restricted to one barn of mares at Crystal Springs Farm in Paris, Kentucky, with no evidence of transmission off the farm. Appropriate restrictions have been put in place. The source of the infection has not been identified, but officials have begun epidemiologic studies.

Two states--Kentucky and New York--have specific control programs for equine viral arteritis (EVA), a highly contagious venereal disease that can cause mares to abort and a high percentage of infected stallions to be persistent shedders of the virus in their semen. These control programs are regulated by law in those states, and require horse owners to follow protocols for breeding. Symptoms of the disease include fever, respiratory illness, ocular inflammation, edema (swelling, especially of the limbs), birth of weak or sick foals, and abortion. This virus can be passed by sexual contact or through respiratory inhalation.

The good news is that EVA is a very manageable disease. There's a modified live virus vaccine that can prevent a horse from getting EVA. The bad news is that outbreaks continue to occur in populations of horses which haven't been vaccinated.

"Major features of the current EVA control programs are the identification of carrier animals in a breeding stallion population and annual vaccination of all at-risk breeding stallions at least 28 days before the start of each breeding season," said Dr. Peter Timoney, head of the Gluck Equine Research Center in Kentucky and a leading authority on EVA. Stallions should be sero-negative (not have antibodies for the disease) prior to vaccination. He added that teaser stallions should be vaccinated against EVA on an annual basis, and first-season stallions should be checked for the carrier state before being used for breeding. Mares should be vaccinated prior to breeding. It has been noted by researchers that vaccination of weanling colts is effective in preventing establishment of the carrier state later in life. As many as 25%-55% of natural seropositive stallions are confirmed to be long-term carriers of the disease.

There has been an increasing number of confirmed occurrences of EVA in recent years, according to researchers, and many of the outbreaks reached epidemic proportion and involved abortion.

About the Author

Kimberly S. Brown

Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.

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