State veterinarians search for Montana EIA origin
May 28, 2010
Montana Board of Livestock veterinarian this week continued to search for the origin of two cases of rare equine infectious anemia (EIA) in Gallatin County.
During a briefing by Montana Board of Livestock State Veterinarian Marty Zaluski, DVM, and Field Veterinarian Tahnee Szymanski, DVM, several dozen horse owners were briefed on the status of the investigation and up-to-date information on the deadly viral disease at the Gallatin County Fairgrounds.
The infection is sporadic and rare in Montana according to the veterinarians. In 2007, there was a case in Park County, and in 2001 and 2003 there were cases in eastern Montana.
There is no vaccine or treatment for the disease. It is not contagious and cannot be passed to humans.
Dr. Szymanski said two horses had tested positive for the disease after a screening test for EIA that is required for movement into or out of Montana. A third horse on the place tested negative. The initial test was made on April 21by the department’s Veterinary Diagnostic Laboratory in Bozeman and confirmed by the National Veterinary Services Laboratories in Ames, IA.
The investigation has determined that the positive horses had traveled to Utah and to Carbon County, MT last August. They tested negative in 2009. Most of the neighboring horses in the Gallatin Gateway area have been tested, Szymanski said. There are six premises in the immediate area and the animals in those locations tested negative.
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The two positive horses were shipped last week to a USDA laboratory for research. Neither one showed any clinical signs.
The department is looking at 30 horses that were at the Carbon County event and are asking horse owners to test the horses that were present.
Szymanski said there is a possibility that the disease was contracted in Utah because it is more prevalent in that state. The infected horses participated in a trail event in that state. It is also possible for the infection to come from blood transfusions or on contaminated needles, surgical instruments and teeth floats. Equine infectious anemia is a potentially fatal viral disease that is spread mechanically by biting insects like stable, horse and deer flies that feed on blood. EIA may also be passed from a mare to her foal in utero and through contaminated semen.
The disease is characterized by acute and/or chronic recurring clinical signs that include fever, anemia, edema and cachexia. Many horses have very mild or inapparent signs on first exposure and carry the virus subclinically. Szymanski said the owners of these animals are unlikely to realize that they are infected unless serological testing is done. All infected horses, including those that are asymptomatic, become carriers and are infectious for life. Infected animals must be be destroyed or remain permanently isolated from other equids to prevent transmission. Only .003 percent of tested horses nationwide are positive.
Szymanski recommends annual testing and likes to see horses that travel for equine-related event s tested twice a year.
As preventive measure, fly control is important. Some horse owners hang cattle tags on horses and it seems to help keep the insects away, it was reported. Another method reported was to use a spot-on horse fly control product.