The first step in determining if your horse has EIA is a blood test called the “Coggins Test.” This test looks for the presence of antibodies to the EIA virus in your horse’s blood. If your horse has the disease, his body will produce these antibodies as part of its immune response. A negative Coggins test does not guarantee your horse is free of the disease, but it does mean he is not currently infected. Of course, the only way to know for sure is with a biopsy of his bone marrow, spleen or lymph nodes. This is an extremely painful procedure that requires anesthesia. It is done by a veterinarian or an equine surgeon. The results are usually available in seven to ten days.