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A Coggins Test for Equine Infectious Anemia is required for transporting a polo pony from one state to another.

The Federal government requires a Coggins Test before a polo pony can be imported.

A Coggins Test on a polo pony is required as proof that the horse is free of the Equine Infectious Anemia disease.


The Coggins Test is a blood test that checks for Equine Infectious Anemia (EIA) antibodies in a horse's blood. It is used to diagnose a contagious disease that affects horses worldwide.

It is also known as Swamp Fever because it occurs more on the Gulf Coast of the United States where humidity and temperature are favorable for transmission of the disease.


The first case of EIA was recorded in France in 1843. North America reported its first case in 1888 in Wisconsin, where it was known as Equine Relapsing Fever. In 1901 Wyoming was the site of the first extensive epidemic in the U.S. An epidemic in 1947 at Rockingham Park Racetrack in New Hampshire resulted in 77 horses either dying outright or requiring euthanization.

Dr. Leroy Coggins of Cornell University developed the first accurate laboratory procedure for diagnosing EIA in 1970. The test does not detect the virus itself, but it does detect the presence of antibodies in the blood. Scientists all agree that the presence of antibodies is proof of infection by the virus. The U.S. Department of Agriculture made the Coggins Test the official test for EIA in 1973.

EIA is a viral disease that infects horses, ponies, mules, and donkeys. Once infected, the animal is infected for life. There is no effective vaccine and no known cure.

Studies to develop an effective vaccine have been disappointing. However, researchers have recently grown more interested because the EIA virus is closely related to the human immunodeficiency virus (HIV).

State Laws

Most laws dealing with EIA are established at the state level. Most states generally require at least a health certificate and a negative Coggins Test for a horse to enter the state. A few states require Coggins Test within the last six months, but most will accept results from the last twelve months.

Some states also require a Coggins Test before the sale of a horse.

Testing Procedure

A federally accredited veterinarian fills out a form that positively identifies a horse. Blood samples are drawn and sent to an accredited state laboratory.

If the test is negative the owner receives a certificate stating the Coggins Test results.

If the test is positive, state authorities are notified, the farm is quarantined, the horse is separated from other horses, and retested.

If the second test confirms that the horse is infected, then all exposed horses are tested. Some states consider any horse within three miles exposed, while other states consider a horse within 200 yards or less exposed.

Because a horse which has been exposed to the disease can take up to 45 days to develop antibodies, exposed horses are retested every 30 to 60 days until no positive results are found.


EIA is transmitted primarily by bloodsucking insects.

Horseflies and deer flies are more likely to be involved with the spread of EIA than mosquitoes for two reasons. First, their mouth parts hold more infected blood. Second, their bites are more painful which makes it likely that a horse will tail swish or twitch to interrupt their feeding.

This is the problem: the virus is transmitted to other horses when the horsefly starts a meal on an infected horse and completes it on an uninfected one.

Most horses that are infected do not die. They will show very few symptoms and quickly become asymptomatic carriers who are still capable of spreading the disease. Animals that are currently showing signs of disease have larger amounts of virus in their blood than asymptomatic carriers, but both can spread the disease.

EIA is not contagious to people and is not directly contagious from horse to horse. It can only be spread via contaminated blood. The most likely way this occurs is via blood sucking insects such as horseflies, deer flies, and less frequently mosquitoes.

The virus can also be spread by blood contaminated needles or surgical instruments.


To help protect polo ponies from exposure:

  • Test all horses for EIA at least annually.
  • Stable owners should require a current negative Coggins Test before introducing a new horse.
  • Never use syringes on multiple horses.

Signs of EIA

In the acute or early form, the horse will be depressed, uncoordinated and feverish. Horses are rarely anemic during this stage. This phase may last several days and is the stage during which the horse is most likely to transmit the disease to nearby horses.

The second phase is characterized by weight loss, recurring fevers and general weakness. Anemia is likely to be present, and mares can abort during this stage.

If horses survive the first two stages, they enter the final or chronic stage, where they often appear normal. An owner may report that a horse is a poor keeper, and the animal may be mildly anemic. Infected mares can transmit the disease to their foals.

Coggins Test Positive Results

A polo pony that tested positive can be dealt with in three ways. First, the polo pony can be euthanized. Second, it can be sent to a recognized research facility or slaughterhouse. Third, the horse can be permanently identified with a tattoo or brand, and quarantined at least 200 yards from any other Equids for life.