As news of a Montgomery County horse testing positive for EIA has been circulating this week, a lot of Equiery readers have been posting questions as to what the virus is, how a horse becomes infected and how they may or may not be treated. We hope we are able to answer a few of your questions here.

Please note, as of this morning (July 13), the case in Montgomery County is still under investigation and no new information has been released from the Maryland Department of Agriculture. All neighboring farms have been notified by MDA and the case farm will remain in quarantine until the 60-day hold period is lifted, as long as no other horses on the farm test positive during the hold period. The horse infected was euthanized earlier this week. In addition, according to Jason Schellhardt of the MDA Public Health Office, the origin of the virus in the infected horse is under investigation. “This virus is very rare for our area and is more common along the Gulf Coast. We are currently investigating where the horse could have been infected.”

Equine Infectious Anemia (EIA) is a blood borne virus, typically transferred by biting flies or infected needles that effects horses, donkeys and mules. EIA is closely related to the human immunodeficiency virus (HIV), but is not known to effect human health. The disease is characterized by fever, anemia, jaundice, depression, edema and chronic weight loss. However, EIA is often difficult to differentiate from other fever-producing diseases.

Categorized as a retrovirus, “EIA contains genetic RNA material which it uses to produce DNA. This DNA is then incorporated into the genetic makeup of the infected cells,” according to the United States Department of Agriculture. The clinical symptoms are a result of inflammatory and immune responses to the virus, where the horse’s system continuously produces antibodies that will never successfully eliminate the virus. Instead, they unintentionally attack the cells with viral particles attached, which cause damage to the kidneys, liver, spleen, lymph nodes, bone marrow and brain.

According to the MDA Public Health Office, the virus can take on three stages. The “carrier” phase is a horse that has low levels of the virus in its system but can still transmit the virus. These horses, as in the Montgomery County case, may not show any symptoms. A horse in the “chronic” phase will look thin and unhealthy and will spike a fever. The “acute” phase is fatal. Unfortunately, there is no successful way to treat EIA and there is no vaccination against it. For horses that are infected and survive the virus, the only options are a lifetime of quarantine or euthanasia.

According to USDA, only one horse fly out of six million is likely to pick up and transmit EIA from carrier horses. Insect transmission of EIA is dependent on the number of insects, the density of the horse population, the number of time the insect bites the same and other horses, the amount of blood transferred between horses and the level of virus obtained in the blood meal.

The Coggins is a blood test that detects antibodies to EIA showing either a negative or positive test result. While there is a misconception that the purpose of a Coggins is simply to ensure your horse is free to travel, it is a most important screening to ensure your horse’s health status and avoid the spread of EIA.