What test is routinely used to diagnose equine infectious anemia?

• A. Indirect fluorescent antibody test
• B. Coombs test
• C. Coggins test
• D. Hemoglobin electrophoresis

Answer: (C)

Detecting exposure to the equine infectious anemia virus relies on identifying antibodies in the horse’s blood. The routinely used test for this is the Coggins test, which is an agar gel immunodiffusion (AGID) assay. In this method, antigen is placed in the center well of an agar plate and the horse’s serum is placed in surrounding wells; if antibodies against EIA are present, they diffuse and form visible lines of precipitation where the antibody and antigen meet, indicating a positive result. Because infected horses typically develop lifelong antibodies, this test serves as a reliable screening tool for routine health checks, movements, sales, and certifications. The other tests listed aren’t standard for EIA diagnosis: they target different conditions or use different principles (for example, the indirect fluorescent antibody test is a different antibody-detection method, while the Coombs test and hemoglobin electrophoresis diagnose other immune or blood disorders).