EIA Exposure in Colorado

On May 9, 2017 the National Veterinary Services Laboratory (NVSL) confirmed that a 5-year-old racing quarter horse in Colorado tested positive for Equine Infectious Anemia (EIA) and was thereafter euthanized. Since the original report, two additional horses from the same location and three additional horses from a separate location tested positive and were euthanized. The remaining horses at these facilities in Fort Lupton, CO (Weld County) are currently under a 60-day quarantine, but despite this quarantine, we still have concerns.

How is EIA spread?

EIA is a viral disease most often spread by bloodsucking insects. It can also be spread through inappropriate use of needles, or other equipment used between susceptible equine animals such as horses, mules, and donkeys. This equine-specific virus is closely related to the HIV-1 virus that causes AIDS in people; both viruses are classified as retroviruses. Once an animal is infected with EIA, it is infected for life and can be a reservoir for the spread of disease. Therefore, an infected horse must be euthanized or quarantined for life. EIA is not transmissible to people.

What are the symptoms?

We want to start by stating that none of the positive horses in Fort Lupton had clinical signs of EIA. Infected horses may not appear to have any clinical signs of the disease, although it can cause high fever, weakness, weight loss, an enlarged spleen, anemia, weak pulse and even death.

How do we test for EIA?

The test for EIA is commonly called a Coggins test. A Coggins test screens horses’ blood for antibodies that are indicative of the presence of EIA, and most U.S. states require horses to have proof of a negative Coggins in order to travel.

Most of our patients receive a Coggins once per year, however if you have been in the Fort Lupton/Weld County area recently, we encourage you to test your horse again around 45 days after travel. The incubation period for the disease is between 10 – 45 days, and because horses may show no clinical signs, this test will ensure that you horse did not contract EIA through a local insect.


In summary, EIA is most often spread through bloodsucking insects. These insects may spread the disease to horses outside of the affected stable in Fort Lupton, CO by flying off the property. If you travel in the Weld County area, we recommend a Coggins test around 45 days after returning home. Your horse may not show clinical signs, yet be positive for the disease. This disease does not affect humans, but requires euthanasia or indefinite segregation in horses.

Visit these trusted sites to learn more:

Equine Disease Communication Center

Colorado Dept. of Agriculture News Release

EIA Fact Sheet – Center for Food Security & Public Health

TheHorse.com EIA Article

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