CANYON COUNTY, Idaho — The Idaho State Department of Agriculture is warning of an infectious illness that affects horses after a horse in the Treasure Valley tested positive for the disease. 

The virus, known as equine infectious anemia or EIA, was diagnosed in a horse that had recently been transported from Washington to its home in Canyon County. The illness is typically spread by biting insects, but used needles or other equipment contaminated with the blood of an infected horse can also pass the infection from one horse to another.

EIA can be fatal, and causes symptoms including low-grade fever, lethargy, weight loss, yellowing of body tissues, anemia, swelling in limbs, and weakness. Signs of the disease can be subtle, and sometimes go unnoticed, according to the ISDA.

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The virus can not be transmitted to humans.

There is no vaccine currently available to guard against EIA. Idaho requirements mandate that any horse that tests positive for the disease be isolated from other horses for the rest of its life. 

Laboratory analysis for the antibodies to EIA - known as a Coggins test - can determine whether a horse is infected. A negative Coggins test is required  

The Coggins test is the most commonly used laboratory analysis for the antibodies to EIA. All states require that horses have a negative Coggins test before they can be moved from one state to another. 

"Horse owners are strongly encouraged to incorporate an annual Coggins test into their animal health regimen regardless of whether they travel interstate," ISDA State Veterinarian Dr. Bill Barton said in a release. "Horses that acquire EIA are infected throughout their lives and will remain a source of infection to other horses in close proximity, so Coggins tests are incredibly important to managing the spread of EIA."