Summary

Equine Infectious Anemia (EIA), also known as swamp fever or horse malaria, is a lifelong viral disease of horses that affects red blood cells, platelets, and multiple organs. The virus infects white blood cells and persists mainly in the spleen and liver. EIA is spread through blood transfer, most commonly by biting flies such as horseflies and deerflies, but also through contaminated needles or equipment, natural breeding, and from mare to foal. Clinical signs range from acute illness with high fever, anemia, and lethargy to chronic disease with weight loss, limb or abdominal swelling, intermittent fever, and ongoing anemia. Some horses become inapparent carriers with no visible signs but remain infectious. There is no cure or vaccine. Control relies on routine testing using the Coggins test, movement regulations, insect control, and strict biosecurity. Horses testing positive must be permanently quarantined or euthanized.