Kansas Horse Health Alert: Horses Test Positive for EIA, WNV

Kansas Horse Health Alert: Horses Test Positive for EIA, WNV

A Coggins test screens horses' blood for antibodies that are indicative of the presence of EIA.

Photo: Erica Larson, News Editor

The Kansas Department of Agriculture (KDA) announced Aug. 18 that two potentially deadly equine diseases—equine infectious anemia (EIA) and West Nile virus (WNV)—have been confirmed in horses in that state.

EIA—The Kansas State Veterinary Diagnostic Laboratory (KSVDL) notified the KDA Division of Animal Health (DAH) that a horse in Finney County has tested positive for EIA. The facility was quarantined and all the exposed horses were tested, with five more testing positive. Since the disease is not curable, the affected horses will be euthanized. The remaining horses at the facility will be observed and retested in 60 days.

Equine infectious anemia is a viral disease that attacks horses' immune systems. 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.

There are typically a small number of cases of EIA in the United States every year, although the disease is common in other parts of the world. The disease is controlled in the United States by regular testing before traveling across state lines and/or exhibition. A Coggins test screens horses' blood for antibodies that are indicative of the presence of EIA.

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.

WNV—The KSVDL also informed the KDA-DAH that a horse in Reno County has tested positive for WNV. The horse was euthanized due to the severity of the illness. This is the first reported equine case of WNV in Kansas in 2017.

Health Alert: West Nile Virus

West Nile is transmitted to horses via bites from infected mosquitoes. Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculation; hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia. Equine mortality rate can be as high as 30-40%.

Horse owners should also consult their private practicing veterinarian to determine an appropriate disease prevention plan for their horses. Vaccines have proven to be a very effective prevention tool. Horses that have been vaccinated in past years will need an annual booster shot; in areas with a prolonged mosquito season, veterinarians might recommend two boosters annually—one in the spring and another in the fall. However, if an owner did not vaccinate their animal in previous years, the horse will need the two-shot vaccination series within a three- to six-week period.

In addition to vaccinations, horse owners also need to reduce the mosquito populations and their possible breeding areas. Recommendations include removing stagnant water sources, keeping animals inside during the bugs’ feeding times, which are typically early in the morning and evening, and applying mosquito repellents approved for equine use.

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