The Montana Department of Livestock (MDOL) reports that multiple horses on a Gallatin County premises have been diagnosed with equine infectious anemia (EIA). EIA was last diagnosed in Montana in 2011 in Carbon County.
Also known as swamp fever, EIA is a potentially fatal viral disease of equines spread by biting insects. No vaccine or treatment is available for the disease, which is characterized by fever, depression, progressive weakness, weight loss, edema (fluid under the skin or in body cavities) and anemia. Not all horses show signs of illness, however, these animals serve as carriers capable of transmitting the disease.
The infected animals were discovered when they tested positive to a screening test required for equine movement into or out of the state. Otherwise known as a Coggins test, the preliminary results were confirmed by the USDA-APHIS National Veterinary Service Laboratories (NVSL) in Ames, Iowa.
Follow-up testing on other equines located at the premises, which is currently under quarantine, is underway. Additionally, MDOL has contacted all horse owners within 200 yards of the affected herd regarding potential exposure and testing requirements.
Due to strict regulations and no available treatment, owners of EIA-infected equines have few options. Infected horses can be placed under a lifetime quarantine with a minimum of 200 yards distance between the quarantined animal and other equines, euthanasia, or donating the animal for EIA-related research.
The incidence of EIA has decreased since Coggins testing began in 1972, with approximately 50 cases of EIA diagnosed in the United States annually. Pockets of the disease continue to be found in populations with limited interstate movement which are rarely tested.