Coggins is the name of the test that is used to check blood for the virus that causes the disease. The disease is called Equine Infectious Anemia (EIA for short). This disease is caused by a virus that infects red blood cells of horses, mules, donkeys, and zebras. The infected animal's body responds to the virus by mounting an immune response to the infected red blood cells, destroying them and causing the horse to become anemic (low red blood cell count). An anemic horse is depressed, lethargic, loses weight, and easily gets sick from other diseases. About one-third to one-half of infected animals develop clinical symptoms and suffer from fever, dramatic weight loss, or swelling around the chest and legs. Some die. Others will demonstrate no symptoms and are referred to as "inapparent carriers". In some cases, chronically infected horses display a variety of symptoms when subjected to work, stress or travel, but they may recover when allowed to rest. These symptoms are very similar to HIV, therefore some people call EIA "horse AIDS".

Equine Infectious Anemia is spread by blood transfer from an infected horse to a healthy horse. Blood-sucking insects (i.e. horseflies, mosquitoes) are the main carriers. Blood contaminated needles, syringes, etc. can also act as carriers.

Testing a horse for EIA involves drawing blood, filling out the proper paper work, and submitting the sample to a laboratory for testing. There are local laboratories than can provide test results in 24 - 48 hours. A negative result indicates that the horse is not infected. A positive Coggins test means that the horse is infected with the EIA virus.

If a horse tests positive, the Texas Animal Health Commission requires that it be 1) quarantined for life, 2) euthanized, 3) sold for slaughter, or 4) donated to an approved research facility.

The State of Texas has required horse owners to test their horses yearly when they are traveling to all assemblies of horses (shows, rodeos, grand entries, trail rides, ropings, etc). Most shows require a Coggins test to be no more than one year old. Also, a Coggins test is required when you travel from state to state for any reason. It is also required that a horse have a negative Coggins test prior to sale