March 2018
From the State Vet's Office

Considering Coggins Tests

Is it time to strengthen our approach to controlling equine infectious anemia?

The horse industry has quite an impact on Alabama’s economy. If you write the checks related to taking care of your horse, you know what I am talking about. A couple of years ago, I found a figure on the Alabama Horse Council website stating that the horse industry had a direct impact of $563 million on the state’s economy.

The indirect impact, the direct money continuing to affect the economy, is about three times that amount. As a horse owner, I try to do my part to stimulate the economy with my horse-related spending habits.

As a horse owner and State Veterinarian, I have more than a passing interest in keeping equine infectious anemia to the most negligible level we possibly can. The way we currently do that is through Coggins testing of the equine population in our state.

Swamp fever is what they used to call it. That’s because EIA was so prevalent in the coastal areas of the Southeast.

The disease was first diagnosed in France in 1843. Several years later, in 1888, it was diagnosed in North America where it was called equine relapsing fever. The first extensive epidemic reported in the United States was in Wyoming in 1901.

EIA is a retrovirus from the lentivirus family, the same family as the human AIDS virus. However, there is no known threat to humans by the EIA virus. The lentivirus family has the characteristic of possibly having a very long incubation period − the length of time between exposure and infection until the host begins to show signs of illness. That means the virus could be present in an equine host for a long period of time with the animal still appearing completely healthy. While the disease can develop within a few weeks of infection, it most often takes months to years. Since a large majority of infected equines don’t show any apparent signs, it is important to have your horse tested.

The virus is most often transmitted by horseflies feeding on the blood of an infected horse then feeding on an uninfected one. It can also be spread by shared brushes, combs, tack, bits and hypodermic needles.

Once infected, the horse will remain infected for life. The disease itself is manifest in three forms: acute, subacute and chronic that may become fatal.

In the acute disease, the horses, ponies, mules or other equids become very ill. They will have a high fever, possibly swelling in the legs and lower abdomen, be lethargic and simply appear to be very sick.

In the subacute form, the animal will not be as ill as the acute animal. It will be somewhat sick.

Chronic occurs when the horse survives the acute or subacute phase. The chronic animal will have recurring episodes of illness and may recover to only have a later episode. This animal is often on a roller-coaster ride eventually leading to its demise. There is no effective vaccine and no cure.

For years, the diagnosis of the disease was complicated and had some room for error. In 1970, Dr. Leroy Coggins developed a diagnostic test detecting the antibodies to the virus present in an infected horse. The test is called the Coggins test. While it may take up to 60 days for an infected horse to become positive, it is a very good diagnostic test.

In 1973, the U.S. Department of Agriculture made the Coggins test the official test for EIA.

After a horse is officially declared positive, it must be marked with "64A" on the left side of its neck using a cold or hot brand. Then there are three possible dispositions of the horse. First, it may be euthanized or permitted to be slaughtered on a restricted movement permit. The second possibility is to house it in an approved, screened stall periodically inspected to make sure flies are not a transmission factor (nearly impossible). Finally, it may be isolated at least 150 yards from any other EIA-negative horses for the rest of its life (also periodically checked to assure compliance).

Our present regulations concerning EIA require all equines over 6 months old, except those for immediate slaughter, entering the state must be accompanied with a negative Coggins test from within the past 12 months. We also have an event regulation basically saying that anywhere horses are congregated or comingled for any purpose such as trail rides, jackpot roping, horse shows, rodeos and other events are required to have a negative Coggins test. For every event, the person in charge is responsible for ensuring the horses are accompanied by a negative test.

As I look closely at what we are doing to reduce the incidence of EIA to as near zero as possible, I think we may need to look at our regulation from a different perspective. I do not want to diminish the importance of horse owners having their horses tested annually; that must continue. But I believe there is a segment that, for whatever reason, has never been tested for EIA but often comingle with other horses, mules or other equine species. For that reason, I am considering tweaking the regulation to include requiring a negative Coggins test at change of ownership and whenever a horse travels within the state.

Many horse owners believe they can tell if their horse is infected with the virus. In most incidences, that is true. But I have seen horses that appeared to be, well, as healthy as a horse. However, they were carriers of the virus. While we often hear people say they have never been asked to show their negative Coggins test at events, the disease is serious enough that I, along with many other horse owners I have spoken with, will not even participate in an event where the Coggins requirement is not being enforced.

Our diagnostic laboratory in Auburn tests around 8,000 equines per year. It is not the only lab that can perform the test. However, if all the horses tested from Alabama were counted, we are still missing a large number. Our Auburn lab had two positive horses back in early 2016.


If you have thoughts on Coggins testing and how we can better serve the horse industry in this area, I would love to hear your thoughts. Don’t hesitate to be part of the discussion.


Dr. Tony Frazier is the State Veterinarian for Alabama. You can contact him at 334-240-7253.