What Is a Coggins Test for Horses? EIA, Travel and Show Rules

What is a Coggins test for horses?

A Coggins test for horses is a blood test that screens for equine infectious anemia (EIA), a virus with no vaccine and no cure that an infected horse carries for life. A vet draws a tube of blood, an approved lab checks it for EIA antibodies, and the negative result becomes the "Coggins papers" you'll be asked for at shows, sales, boarding barns and state or national borders.

This week showed exactly why that paperwork exists. On Sept. 17, the Canadian Food Inspection Agency (CFIA) confirmed EIA in a horse in Perth East, Ontario. An accredited vet had tested the horse at the owner's request to meet a U.S. export requirement, and it showed no signs of illness when the blood was drawn.

The CFIA placed movement controls on that horse and on contact animals on the farm, where other horses live, and opened an investigation. Those controls stay in place until all disease-response work, including follow-up testing, is finished. Nobody knew the horse was infected until a routine travel test said so, and that is the job the Coggins test does.

Equine infectious anemia: why a healthy-looking horse can carry it

EIA, also known as swamp fever, is caused by a lentivirus that writes itself into the horse's own cells. It infects only equids: horses, ponies, donkeys, mules and zebras. Texas animal health officials note there is no evidence it threatens human health.

Infection usually moves through three stages:

• Acute: fever, dullness and a drop in platelets (the cells that help blood clot), typically 15 to 45 days or more after infection. It can be severe, or so mild nobody notices.
• Chronic: repeated bouts of fever, anemia, weight loss, swelling of the lower legs and belly, and tiny red or purple spots on the gums and other mucous membranes.
• Inapparent carrier: most infected horses end up here within about a year. They look and work normally, but the virus stays in their blood.

Why "no symptoms" doesn't mean "no risk"

That third stage is why "EIA horses no symptoms" is such a common search. A carrier can still pass the virus to other horses through blood, and signs can flare up again later.

Timing matters too. Antibody tests can read negative early in an infection, especially in roughly the first 45 days. A negative Coggins is a snapshot of the day the blood was drawn, not a guarantee for the months after.

New to terms like platelets or mucous membranes? Our glossary and health basics guide explain them.

How horses get EIA: flies, needles and shared blood

EIA spreads through blood, not through casual nose-to-nose contact.

• Biting flies. Horse flies and deer flies are the most efficient carriers, with stable flies playing a smaller role. Their bite hurts, so the horse swishes or stamps, and the fly finishes its meal on the next horse with blood still on its mouthparts.
• People. Reused needles and syringes, shared IV sets, dental and tattoo tools, transfusions from untested donors, illegal blood products and contaminated multi-dose drug vials. USDA says this human-caused spread is now the most common way EIA moves in the United States.

The numbers back that up. U.S. labs ran 1,292,655 EIA tests in 2024 and found 147 positive horses on 63 premises, up from 61 positive horses in 2023.

Texas had 78 of those positives, New Mexico 26, Louisiana 16 and California 15. Nationally EIA is rare: USDA puts prevalence at about 0.004%, down from nearly 4% when U.S. control efforts began in 1972.

When your horse needs a Coggins test

So why do horses need a Coggins test to travel? Because carriers look healthy, and a negative test is the simplest proof a horse isn't bringing EIA into a new barn, show ground or state. Rules come from states, countries, event organizers and barn owners, and they stack on top of each other.

Common times you'll need one:

• Crossing state lines. Most U.S. states require a negative Coggins for interstate travel, usually alongside a certificate of veterinary inspection (CVI, or health certificate).
• Shows, rodeos, trail rides and clinics. Many events want a negative test drawn within the past 12 months. The All American Quarter Horse Congress, which opens Sept. 26 in Columbus, Ohio, also requires a current health certificate for every horse on the grounds starting this year.
• Buying, selling or boarding. Texas, for example, requires a negative test within the previous 12 months for horses 8 months or older that change owners. Texas horses also need one for any assembly (rodeo, trail ride, parade, roping), a racetrack, public riding trails, or life at a boarding, training or breeding facility.
• Crossing a national border. Horses entering the U.S. from Canada need a negative EIA test within 180 days before export, run at a lab approved by the CFIA or at USDA's National Veterinary Services Laboratories (NVSL), plus an official Canadian health certificate. Horses coming from Mexico spend at least 7 days in quarantine at a USDA-approved import facility, where they must test negative for EIA and other diseases.

In Canada, EIA testing is voluntary under the CFIA program, though owners are strongly encouraged to test when the industry requires it or their vet recommends it. That's how the Perth East case surfaced: through an export requirement.

Rules change, so check before you haul. Outside the U.S. and Canada, ask your vet and your country's animal health authority (in Mexico, that's SENASICA). Getting ready for a first show? Our show prep guide covers the rest of the checklist.

How the Coggins test works (and what it costs)

1. Book your vet. In the U.S., an official EIA sample is drawn and submitted by an accredited veterinarian, who completes USDA form VS 10-11.
2. The lab runs the test. About 400 USDA-approved labs use one of two methods: the agar gel immunodiffusion (AGID) test, the original "Coggins" described by Dr. Leroy Coggins at Cornell in 1970, or an ELISA. In 2024 labs used both at nearly equal rates, and every U.S. positive is confirmed by the National Veterinary Services Laboratories.
3. You get the papers. The completed VS 10-11 identifies your horse, so check the description matches before you file it. Keep a copy in the truck or trailer and a photo on your phone.

Timeline: results aren't instant, so don't leave the blood draw for the week of the show. Spring is the crunch: March, April and May were the busiest months for EIA testing in 2024.

Cost: prices vary by region and practice. As one example, a Virginia equine practice lists $80 for a Coggins and $70 for an out-of-state health certificate. Ask whether a farm-call fee is added, and pair the draw with spring vaccines to save a trip.

How long it's good for: 12 months is the most common window (Texas and the Quarter Horse Congress both use it), but check each state or event rule. Some barns, sellers or vets want a more recent test; that same Virginia practice asks for a Coggins dated within six months for pre-purchase exams, or it draws a new one.

What happens if a horse tests positive

A positive Coggins doesn't start a treatment plan; it starts a regulatory process. There is no antiviral cure and no vaccine.

• In the U.S., a confirmed positive horse must be permanently isolated and quarantined, or euthanized. A horse that is kept must live at least 200 yards from other equids. In Texas, every horse on the same premises is quarantined and tested, and positive horses that aren't euthanized get a permanent "74-A" freeze or hot brand on the left shoulder or neck. They may never leave the property except with approval to go to a diagnostic or research facility, and most are euthanized.
• In Canada, horses confirmed positive are ordered destroyed, and owners may qualify for compensation of up to C$2,000 per horse. Horses on the same farm must test negative before they can leave, and animals in contact with the positive horse within 30 days of sampling are tested too.

That's what the Perth East farm is working through now: an investigation, testing of stablemates and a hold on movement until the CFIA finishes. It's also why the test matters for everyone else. Finding one silent carrier protects every horse that would have shared its pasture, its flies or a careless needle.

Your Coggins checklist: what to do now

Before any trip, show or sale:

• Find your horse's current Coggins and check the draw date against the event or state rule.
• Get a health certificate if you're crossing state lines, and check the destination's entry rules before you load up.
• Keep paper and digital copies with the horse.

Buying or bringing home a new horse:

• Ask for a current negative Coggins, and consider a fresh draw during the pre-purchase exam.
• Keep newcomers separate for a while and ask your vet whether a follow-up test makes sense, since a very recent infection may not show up yet.
• First horse? Start with our get started guide.

Every day in the barn:

• One new needle and syringe per horse, every time, and never go back into a multi-dose bottle with a used needle.
• Never use blood or blood products from an unknown source.
• Cut down on biting flies: manage manure, drain standing water, and use fly sheets, masks and repellent in fly season. Our care guide covers daily routines.
• Barn managers: ask every boarder for a current Coggins.

What to watch next

• Follow-up testing of the other horses on the Perth East farm. The Equine Disease Communication Center (EDCC) alert on the case cites the CFIA, so watch it for updates.
• Fall show, rodeo and sale season, when papers get checked at the gate.
• EDCC alerts for your own state or province, so you know when EIA turns up nearby.