The Coggins Test


What Is It? | How Is It Performed? | Why Is It Used?

  • The Coggins test is used to detect equine infectious anemia (EIA)—a highly contagious and potentially fatal viral disease of horses.
  • EIA is a reportable disease and is therefore regulated by the United States Department of Agriculture (USDA), but state laws vary. A current, negative Coggins test result is often required to transport horses across state lines.
  • Horses that attend equine events are usually required to show a current, negative test result to participate, even within your home state.
  • The EIA virus is transmitted by certain insects which take blood meals, through contact with infected body fluids or needles and instruments contaminated with infected blood or fluids.

What Is It?

In the 1970s, Veterinarian Leroy Coggins developed the test that bears his name. The Coggins test detects antibodies to the EIA virus. With no vaccine available, the only way to prevent the spread of this highly contagious disease is to identify infected horses and then separate or isolate them from non-infected horses, so the virus is not transmitted. EIA virus is most often spread through biting insects, primarily horseflies and deerflies. It can also be transmitted through saliva and other bodily secretions, shared syringes and any objects contaminated with infected blood or fluids. Infected pregnant mares can pass the virus to their foals. While the USDA estimates that fewer than eight in 100,000 horses become infected with EIA virus, fifty percent do not survive despite treatment.

EIA comes in three forms: acute, chronic, and the inapparent carrier. In the acute form, horses experience fever, lethargy, and loss of appetite, and many die within a few weeks even if they receive aggressive treatment. If they recover, they become chronic carriers and are contagious for life. Chronically infected horses become ill, recover, and then become sick again and never completely recover. They often lose weight and suffer from anemia and swollen limbs. Horses that are inapparent carriers appear healthy but can spread the disease to other horses, or eventually become ill themselves.

How Is The Coggins Test Performed?

To perform a Coggins test, your veterinarian will take a blood sample. The sample is submitted with a form which identifies your horse by its markings and coat color or with a digital photograph. The blood sample and form will be sent to a USDA-accredited laboratory for testing. The Coggins test looks for the presence of antibodies specific for the EIA virus, which an infected horse produces after exposure to the virus. Antibodies are proteins produced by the immune system to help fight infectious diseases caused by organisms such as bacteria or viruses. Lack of these specific antibodies in the blood produces a negative Coggins test result. The test is about 95% accurate; however, if the test result is positive, your veterinarian will send supplemental tests to confirm the results.

Why Is It Used?

The Coggins test is performed to identify infected horses and help prevent the disease from spreading to healthy horses. This testing also helps monitor disease incidence and determine if the disease is becoming more or less prevalent. Therefore, horse owners should have Coggins tests performed annually and test all new horses arriving on their farm. Horse owners are usually required to submit a current, negative Coggins test result when they attend equine events. A current, negative Coggins test result is often required to transport horses across state lines. Most stables require new boarders to provide a negative test result.