Officials at the California Department of Food and Agriculture (CDFA) confirmed a 5-year-old Quarter Horse mare as positive for equine infectious anemia (EIA). The result came from routine testing for her return to the racetrack. Equine infectious anemia is a viral disease that attacks horses’ immune systems. The virus is transmitted through the exchange of body fluids from an infected to an uninfected animal, often by blood-feeding insects such as horseflies. It can also be transmitted through the use of blood-contaminated instruments or needles.