Last updated: November 6, 2026
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If you’ve bought a horse, hauled to a show, or pulled into a racetrack stable gate, somebody has probably asked to see your Coggins. If you’re new to horses, it’s fair to wonder what that piece of paper is and why everyone wants it.
Here’s what happens during the test, when you’ll need the paperwork, and why a healthy-looking horse can still carry EIA.
Table of Contents
What Is a Coggins Test?
Your vet draws a blood sample, fills out the official paperwork, and sends it to a USDA-approved lab. The test looks for antibodies the horse makes against the EIA virus, not the virus itself. The paperwork describes the horse, so the result belongs to that horse and no other. In Louisiana, the horse has to be permanently identified before an official test, by a microchip, lip tattoo, or brand, according to the Louisiana Administrative Code.
Labs run one of two tests. The ELISA picks up antibodies earlier, and the AGID, or agar gel immunodiffusion test, is the confirmatory test, according to the American Association of Equine Practitioners. The AGID is the original Coggins test, named for Dr. Leroy Coggins, who developed it in the 1970s, according to the LSU AgCenter. Horsemen often call either test a Coggins.
The lab work itself is quick. LSU says an AGID takes about a day and an ELISA can be done in under an hour, but the sample still has to get to the lab and the results back to your vet. Don’t wait until the morning you haul to get it done.
When Does a Horse Need a Coggins Test?
The rules come from the states, and shows, tracks, and barns can set their own on top of that. A Coggins isn’t automatically good for 12 months everywhere. These are the times you’re most likely to need a current negative test.
Crossing state lines. Most states want a negative EIA test before a horse comes in. Louisiana requires one within the past 12 months, according to the Louisiana Department of Agriculture and Forestry. Check with the state veterinarian where you’re headed before you load up. A Coggins is one item on the list when you prepare a horse for a long trip.
Shows, rodeos, sales, and racetracks. In Louisiana, horses moving to fairs, shows, sales, rodeos, racetracks, and other places where horses gather need a test within 12 months, and the grounds will ask to see it. Check the event’s own rules before you leave home.
Buying or selling. When a horse changes hands in Louisiana, LDAF says the Coggins must be current within six months of the sale. Even where a test isn’t required, don’t bring a new horse home without seeing a current negative Coggins.
Boarding. Most boarding barns require a current negative Coggins before a horse moves in.
Living in Louisiana. Every horse that lives in Louisiana has to be tested at least every 12 months, whether it leaves home or not. Nursing foals under seven months old traveling with their dams are exempt from the movement and sale testing rules, but not from the annual test, according to the state code.
What Is Equine Infectious Anemia?
EIA is a viral disease that affects horses, donkeys, and mules, and it’s found nearly worldwide. There’s no treatment and no approved vaccine in the U.S., according to the AAEP. Once a horse is infected, it carries the virus for life.
It spreads through blood. Horse flies and deer flies carry it from horse to horse on their mouthparts, and people spread it with shared needles, syringes, IV sets, dental tools, and blood transfusions. The AAEP says the virus can survive for up to 96 hours on a needle.
Most infected horses never show obvious signs, and that’s what makes EIA so dangerous. A horse can look perfectly healthy and still carry the virus. When it does cause illness, an acute case can bring fever, going off feed, or sudden death, and a chronic case can bring weight loss, weakness, anemia, and swelling in the legs, chest, and belly. The old name for it is swamp fever.
A horse can also test negative for the first several weeks after it’s infected, before it makes enough antibodies for the test to find. If a horse has been exposed, your vet may recommend testing again later rather than trusting one early negative.
What Happens if a Horse Tests Positive?
A positive screening result isn’t necessarily the final diagnosis. Your vet and state animal health officials will decide what confirmation testing is needed. Once a horse is confirmed, it carries the virus for life, so the choices are euthanasia or lifetime quarantine at least 200 yards from other horses, and some states require euthanasia, according to the AAEP.
Louisiana is one of the strict states. The owner can ask for a confirmation retest, but a positive horse is quarantined at the owner’s place and has to be destroyed or sold for immediate slaughter within 20 days, according to the state code. The one exception is a mare at least 270 days pregnant or nursing a foal no more than 120 days old, which can be kept in quarantine at least 200 yards from other horses until the foal dies or reaches 120 days. Horses on the same place or within 200 yards are quarantined, too, until they test negative at least 30 days after the positive horse is gone. The rules differ from state to state, so work with your vet and the state veterinarian.
What Recent U.S. Cases Show
EIA is uncommon now, but it hasn’t gone away. In 2024, labs ran almost 1.3 million EIA tests in the U.S. and found 147 positive horses, according to the USDA. Texas had the most with 78, followed by New Mexico with 26 and Louisiana with 16.
The bigger story is where the cases came from. Of those 147, 120 were current or former Quarter Horse racehorses and 5 were Thoroughbred racehorses. The USDA tied them to reused needles, syringes, and IV sets, untested blood transfusions, and contaminated drug vials, some of it in unsanctioned racing that crosses over with sanctioned racing. Another 10 horses were suspected or confirmed to have been moved illegally from Mexico.
In that report, contaminated needles, equipment, and blood products accounted for most of the cases with a known source. Fly control still matters, but it can’t make up for reusing injection equipment.
How to Protect Your Horse From EIA
The AAEP recommends these steps.
One horse, one needle and syringe. Use a new sterile needle and syringe for every injection, and a new IV set for every treatment. Never put a used needle or syringe back into a medication bottle.
Use only licensed blood products. Untested blood transfusions have spread EIA.
Clean and disinfect shared equipment. Wash blood and dirt off dental, tattoo, and surgical tools with soap and water, then disinfect them between horses. A quick wipe isn’t enough.
Fight the flies. Muck stalls regularly, get rid of manure properly, run fans, and use fly spray. Fly masks and boots help, too.
Test new horses. If you don’t know a horse’s EIA status, have it tested before it joins your barn. If a horse runs a fever, goes off feed, or seems dull, call your vet. Those signs have plenty of causes, but they shouldn’t be ignored.
About Miles Henry
Racehorse Owner & Author | 30+ Years in Thoroughbred Racing
Miles Henry (legal name: William Bradley) is a professional horseman based in Folsom, Louisiana. He holds Louisiana Racing License #67012 and has spent over three decades managing Thoroughbreds at premier tracks including Fair Grounds, Delta Downs, and Evangeline Downs.
Expertise & Hands-On Experience: Beyond the track, Miles has decades of experience in specialized equine care, covering everything from hoof health and nutrition to training protocols for Quarter Horses, Friesians, and Paints. Every guide on Horse Racing Sense is rooted in this “boots-on-the-ground” perspective.
30 of their last 90 starts
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