Preventing Equine Infectious Anemia

Spring is upon us, and with that comes the excitement of warmer weather for horse show season. Unfortunately, travelling to horse shows or any event where horses co-mingle also increases the risk of disease transmission to your equine partner. Before show season begins, it is important to consider diseases that may affect your horse and the mitigation strategies available to protect their health. One disease that should concern horse owners is equine infectious anemia.

Equine infectious anemia affects the immune system of horses, donkeys and mules. Affected animals may show no signs of disease, but they can carry the virus for life and be a source of infection for others. Transmission of the virus primarily occurs via biting flies that carry and spread the virus from infected animals to non-infected animals. It cannot be treated and there is no effective vaccination, so prevention strategies are necessary for any owner.

The incubation period between animals becoming infected and showing clinical signs is typically two to four weeks, but can take several months. Clinical signs can include depression, anorexia, weakness, intermittent fever and a loss of co-ordination. Horses showing clinical signs of equine infectious anemia can be even more infectious than those that do not show signs of disease and can lead to widespread infection within a herd. Early detection through voluntary testing can reduce the risk of disease transmission to other horses.

Equine infectious anemia is a reportable disease, meaning that when it is suspected, it must be reported to the Canadian Food Inspection Agency (CFIA). The CFIA administers the National Equine Infectious Anemia Disease Control Program, which is made up of two parts: voluntary testing of animals by owners and mandatory testing performed by CFIA for a suspect case.

Voluntary testing is performed with a blood sample, which must be taken by an accredited veterinarian. A negative test certificate is valid for six months and is often requested prior to attendance at horse shows, and is also required for export of horses to the United States. Although the test only measures one point in time, it is an effective screening tool for equine infectious anemia and has resulted in a number of positive detections in the past. After testing, owners should ensure their animals are only around other negative animals to minimize the risk of becoming infected.

When a positive result is detected, the CFIA is notified and disease control measures will be put in place. These measures include confirmatory testing for the positive animal, testing animals in contact with the positive animal, and a permanent quarantine or euthanasia of the positive animal(s).

In 2018, the CFIA proposed changes to the equine infectious anemia program and carried out public consultation. For more information on the current program and proposed changes, visit the CFIA equine infectious anemia website at and search “equine infectious anemia.”

While there is no vaccine for equine infectious anemia and it cannot be treated, animal owners can prevent infection in healthy animals.

Article by Stephanie Smith, DVM, Animal Health Veterinary Intern, Animal Health Unit, Livestock Branch. Originally published in Agriview, April 2020, Volume 3, Issue 3.