Twenty-one horses were humanely euthanized in Texas in May and June of 2024. All 21 horses were admitted to the same equine clinic and placed in the intensive care unit, where they were connected to IV units. Due to the reuse of medical equipment at the Texas equine clinic, the horses had been infected with equine infectious anemia (EIA).
Horses aren’t the only animals that can catch EIA. All equids are susceptible to the virus, including donkeys, mules and zebras.
In Canada, over 25 cases of EIA have been reported as of July, 2025. Four cases in Alberta, one case in British Columbia, one case in Quebec, and 20 cases in Saskatchewan.
The three cases in Alberta happened in the Rocky Mountain House area, while the fourth case was confirmed in the Calgary area. Geographic details of the confirmed cases are not released for privacy reasons.
Dr. Tayler Lesmeister is a veterinarian with Countryside Veterinary Hospital in Olds. She says that EIA is a lentivirus, which means that it stems from a family of viruses that cause chronic and deadly diseases with long incubation periods.
“It’s like HIV in people,” says Dr. Lesmeister. ”It gets into the horse’s DNA and then it’s there. They’ll never clear it.”
The disease is spread primarily through biting insects, such as deer and horse flies. As seen in the 2024 Texas case, spread of the virus is also possible through the use of contaminated medical instruments. Mares can also spread the disease to their foals, which can be infected either in utero or through milk. Breeding also presents risks of the disease spreading.
Foals who were infected through their mothers typically die from EIA within six months.
There are three types of carriers of EIA:
- Asymptomatic, in which equids can carry and spread the disease but show no symptoms of infection.
- Acute, in which the sickness is visible but relatively nonspecific (i.e. lethargy, being off feed, fever and weakness in the hind end).
- Chronic form, where the equid cycles through getting better and getting sick again, and in which symptoms of anemia can be seen.
Once a horse tests positive for EIA, the case is reported to the Canadian Food Inspection Agency (CFIA), which handles food, animals and plants in Canada. The CFIA then adds the case to the equine diseases tracker, which all Canadians are able to access to check for cases in nearby areas.
There is no cure for the disease, including no vaccine or treatment. Therefore, once a case has been confirmed, the CFIA requires for the infected equid to be humanely euthanized.
Dr. Lesmeister explains, “The reason for that is because of the infectiousness of it, the fact that it is not curable. We want to prevent those outbreaks and keep our surveillance system working so that we’re not getting those.” She adds, “Prevention is about preventing exposure.
The CFIA detailed several preventative measures that include the implementation of insect control measures, strict hygiene practices when vaccinating or collecting blood samples, not using the same needle on more than one equine, testing equines as per equine industry requirements, testing equines if they show clinical signs of disease, isolating all new equines until they have been tested for EIA, abiding by the national EIA control program and consulting with a veterinarian if an equid owner suspects an EIA infection.
Dr. Lesmeister says that fly control is also a good preventative measure.
Essentially she says that, “Decreasing your risk of exposure is about all you can do.”
Humans cannot get infected with EIA. However, they can be a transmitter of the virus if those in frequent contact with equids do not follow proper precautionary measures.