Prevent equine infectious anemia (EIA) with regular Coggins testing and biosecurity measures. Stay informed on outbreaks via equine disease updates and protect your horse today.
Ever wondered why horses need a Coggins test? Whether you have a pasture pet or a performance horse, your equine friend must have a negative Coggins test to make sure they do not have equine infectious anemia, which is a non-treatable, contagious, potentially fatal disease that affects equids. People have been aware of EIA for over a century, and it has been reported all over the globe. While this disease is nothing new, a recent outbreak in the United States means that right now is the perfect time to brush up on your knowledge of equine infectious anemia while keeping an eye on equine news.
Is there a current outbreak of EIA?
Yes. As of the writing of this article (June 4, 2025), there is a current outbreak of equine infectious anemia in the United States. In the Equine Disease Communication Center’s National Equine Health Industry Stakeholder Call for the month of May, they reported a total of twenty-one EIA positive horses across four states, those being California, Colorado, Oklahoma, and Texas. According to a news release published on May 30, 2025 by the EDCC it states, "A cluster of EIA-positives that were infected throughout May 2024 and another cluster from mid-June through the end of August 2024 were found to have originated at a Texas equine clinic. The USDA-APHIS has the complete medical history of the 21 horses confirmed EIA positive that were treated at the Texas clinic. All of the EIA-infected horses had been hospitalized in the Intensive Care Unit (ICU) at the clinic and had an IV catheter placed and flushed.
The current investigation indicated the route of the infection identified was EIA-infected blood contamination of heparinized saline in multiple use bottles used repeatedly to flush catheters at the clinic by one or more employees of the clinic. The ongoing re-use of syringes without sterilization in the ICU as a routine procedure caused repeated instances of blood contamination into the bottles.
According to the USDA, it is likely that not all of the exposed horses have been tested. Anyone who is concerned that their horse might have been exposed should contact their veterinarian and have their horse(s) tested.
The next step in the investigation is to compile a more complete list from the clinic’s appointment book of exposed horses that had an IV catheter placed at the clinic in the affected time range while completing regulatory EIA testing of all horses that were potentially exposed. Testing will also be completed on cohorts of any new EIA positive cases."
In a follow up EDCC news release published on June 3, 2025 by Leslie Barlow and Dr. Angela Pelzel-McCluskey it stated that, “ About 1.3 million horses per year are tested for EIA. So far in 2025 there have been 44 EIA positives. In 2024, there were 147 positive cases and 120 of those were in the primary high-risk category of Quarter Horse racehorses which contracted the disease via iatrogenic transmission by unhygienic injection practices of owners and trainers, not veterinarians.”
What is EIA?
EIA is a viral disease that spreads through bodily fluids. This means that horse flies, stable flies, and deer flies are some of the biggest transmitters of EIA (mosquitoes do not transmit EIA according to the article “Equine Infectious Anemia” from the University of Kentucky), but so are iatrogenic transmissions, which are transmissions that result from medical procedures via contaminated surgical equipment or shared/reused needles. EIA causes a wide range of symptoms, and not every infected horse becomes sick, making this typically uncommon disease difficult to recognize. Symptoms include anemia, fever, fatigue, swelling, neurological abnormalities, weight loss, and more. Infected horses can die in a matter of days or weeks, even if they express no symptoms; what is even more concerning, however, are the horses who become asymptomatic carriers of EIA. These horses may recover from their symptoms or never even have symptoms in the first place, but the virus will remain in their systems for the rest of their lives, which can lead to infection in other horses. For this reason, asymptomatic carriers are left with the same options as their symptomatic counterparts despite not appearing sick.
What happens if my horse tests positive?
Firstly, EIA is a reportable disease; it must be reported to all relevant authorities such as state veterinarians and federal animal health entities. If a horse tests positive for equine infectious anemia, owners are required to quarantine every horse on their place within the first
twenty-four hours after infection is confirmed. An APHIS certified veterinarian will then come and test all exposed horses on the property to determine how many have EIA. After that, owners are left with two choices for any infected animals: permanent, strict isolation or euthanasia. Unfortunately, since this disease is so serious and has no cure at this point in time, strong measures must be taken to prevent it from spreading. When it comes to isolation, positive horses must be kept two hundred yards away from all other equids since this is the distance a horsefly can travel and still transmit the live EIA virus. Additionally, very specific and rigid fly prevention protocols must be put in place to keep the infected horse from being bitten. In Florida, there is a sanctuary that takes EIA positive asymptomatic horses, known as the F.R.I.E.N.D.S. Horse Rescue & Sanctuary, that owners may look into. Sadly, though, euthanasia is usually the chosen option because it immediately eliminates the chance that the infected horse will spread the virus any farther.
Why is there no vaccine for EIA?
Vaccines for EIA have been researched before and are being researched now. In China, a live attenuated EIA vaccine was developed and applied with significant success. The National Library of Medicine’s article “Equine infectious anemia virus in China” reports “...in 1978 an attenuated vaccine was successfully developed for equine infectious anemia virus, effectively preventing equine infectious anemia virus in China.” However, this vaccine, while certainly a source of hope, is not USDA-approved because it causes positive tests in vaccinated horses according to an analysis entitled “EQUINE INFECTIOUS ANEMIA TESTING” which was conducted for the House of Representatives in Michigan. Research is still being done in the United States to develop a vaccine for EIA.
How often should my horse be tested for EIA?
The Coggins test, developed by Dr. Leroy Coggins, is what is used to test for equine infectious anemia, and it is generally recommended that horses be tested annually. By contacting their veterinarian, owners can schedule a time for their horse’s blood to be drawn and tested for EIA. Most equine events require a negative Coggins test for entry, and hauling a horse between states often requires one as well. The test needs to be recent, usually meaning it needs to have been run within the last year. Different states have different rules about EIA testing, so make sure to read up on which ones apply to your personal situation as a horse owner. As far as prevention goes, fly control and regular testing for EIA are the main ways you can help prevent your horse from contracting this virus.
EIA is frightening, but this is not the first time there has been an outbreak, and as more and more people in the equine industry work together to stop this disease, we increase our chances that this could be the last. Follow equine epidemiology sites such as the Equine Disease Communication Center for continual coverage of this outbreak, and remember to schedule that Coggins test.
For more information about Equine Infectious Anemia go to https://www.equinediseasecc.org/equine-infectious-anemia
