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What Is a Coggins Test and Why My Horse Needs One? 5 Reasons

Last updated: December 30, 2022

By: Miles HenryFact Checked

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As we were loading our horses, I asked my daughter to ensure we had Coggins test certificates in the truck. My grandson overheard our conversation and said he’ll check, but what are they?

The Coggins test detects Equine Infectious Anemia(EIA), a disease not unlike HIV, but in horses. It is a rare disease, but it is also incurable. There are no vaccines to prevent it, and it can be passed from one horse to another via fly bites. A negative Coggins certificate is required for horses.

Coggins tests are vital in the battle against infectious diseases, and it’s critical to understand what’s involved if you own a horse.

Why would a horse need a Coggins test?

Why horses need a Coggins test is a question every new horse owner should ask… and find the answer for. It is one of many things that need to be done before buying or selling a horse, amongst other reasons. It is a requirement in all fifty states, and there are time limits before a purchase.

Coggins tests for Equine Infectious Anemia (EIA), which is a highly infectious disease. It causes lethargy, and edema, and keeps horses from eating; some horses die right away, but most become asymptomatic carriers. When that happens, they need to be kept away from other horses at all costs.

Picture of a vet drawing blood to run a Coggins test,

There are several approved tests for this disease. The Coggins test, however, is recognized as the most definitive of the group. It was developed in 1970 by Leroy Coggins, a veterinarian specializing in horses.

There are several reasons for having this test done. As mentioned, it must be done before buying or selling a horse. However, those aren’t the only reasons. A great deal of caution is needed, mainly where the disease is the most prevalent.

Picture of a truck and horse trailer at a horse farm near a horse and rider,
Featherlite commercial shoot, Mill Run Farm near Marshall, VA, 2 June, 2013.


If you plan to go to shows or other events with your horse, the grounds will require a current Coggins test to show that your horse is safe to be around other horses.

Some states have a thirty-day period after a negative test result, but quite a few have only five days. It’s best to check with your local authorities to ensure the length of time you have before you need another test.

You can check out my article here, which details how to prepare for a long trip with your horse. It provides some useful information and a checklist of things you will need to have before taking off on your excursion.


The necessity of a negative Coggins for comingling horses is both for moving a new horse into your herd or bringing a horse to a boarding facility.

Most boarding facilities would need it even if it weren’t a state requirement. Equine boarding facilities typically carry liability insurance, and most carriers require all horses present with a negative Coggins.


It isn’t necessary to have a Coggins test if you are moving nearby, but any move over seventy-five miles requires one. It’s even more critical if you use a moving service, as they may have other horses in the trailer. As with boarding facilities, their liability insurance will require it.

Signs of illness

While it is rare, it may be wise to have this test done if the horse shows the disease’s symptoms. Your vet will most likely recommend it, but if you don’t live in the areas most likely to have the virus present, you may have to ask for it.

Where is the disease more likely?

While it could crop up anywhere under the right conditions, it is most prevalent along the Mississippi River valley and in the Southeastern United States. This is because the disease involves blood-sucking insects that like a warm climate.

That does not mean those are the only places. The disease is worldwide, although the Gulf States, including Saudi Arabia, don’t appear to have any cases. That said, there have been outbreaks in Tennessee and Pennsylvania in the past.

In the United States, the gulf coast is the most frequent area of infection. The hot, humid weather is perfect for breeding insects, and it is hard to stamp them out. Because it can infect ponies, mules, and donkeys as well, it is even more challenging to control.

One of the top places in the world for this disease is in Brazil. It is estimated that around fifty percent of the horses are carriers. This isn’t good for the horse population of that country, nor the surrounding countries.

Picture of an underweight two-year old horse.

What if my horse tests positive?

The choices aren’t good. In most areas, a positive Coggins test requires immediate euthanasia. The horse puts too great a risk on other equines in the area. However, there is a possibility that an isolated horse might be allowed to live.

If that happens, the horse can never be around other horses again… unless they are also positive for Equine Infectious Anemia. At this point, that seems unlikely to happen, and it would be in the horse’s best interest to be put down.

Horses are social animals. They need to be in groups to be happy. A horse forced to live alone would probably go into a decline just for that reason. Even though the immediate death rate is thirty percent, it truly is a death sentence for the horse.

How can I prevent it?

There are a lot of steps that can help prevent the disease. Most horse owners do them instinctively, but they should be mentioned.

Waste removal

Waste removal is vital because insect vector is the primary means of spreading the disease; removing debris and manure is an essential first step in prevention. Stalls, paddocks, and pastures should be cleared daily if not more frequently.


Contact your local vet or animal health officer for a list of approved insecticides for equine use. You and your horse will appreciate it, as the flies bite both humans and horses. The bites hurt and can become infected.


Good drainage is a must. This applies everywhere the horse may go, and in humid regions, it must be all of the property. Some insects breed in standing water.

Disposable needles

Many horse owners give their horses standard injections, such as vaccinations. Sharing needles is as bad for horses as it is for humans. Never share a needle between horses. The rule is “one horse, one needle.”

Sanitize equipment

As with injections, some horse owners use dental tools on their horses. All such equipment should be completely sanitized between horses.

Isolate new horses

New horses should be kept separate from the herd for the first forty-five days. At the end of the forty-five days, another Coggins test will assure you that the horse is safe to comingle with the others.

Follow government guidelines

Keep your horse vaccinations current and have your horse vet checked at least once a year. When you notice a problem, don’t let it linger because, most of the time, it won’t go away on its own.

For example, we think of diarrhea as a minor inconvenience. However, if it persists in horses, it could be fatal. There is a lot to know if you own a horse, so rely on knowledgeable horse people and don’t be shy about calling a vet.

Below is a YouTube video about the equine Coggins test.

YouTube video

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