This is a disease of cattle caused by an organism called Anaplasma marginale. This organism is a rickettsia, half way between a virus and a bacteria. It is susceptible to tetracyclines, but cannot be grown in the laboratory. The disease, anaplasmosis, is caused with the body of infected cattle reacts to remove the infected red blood cells and causes a severe anemia.
All cattle are susceptible to infection by A. marginale.
Also, deer, elk, and other ruminants are susceptible to becoming infected. Recently, you may have attempted to purchase vaccines to prevent Anaplasmosis and discovered they are no longer available. Since the first of the year, the two U.S. companies that manufactured and marketed vaccines for the prevention of anaplasmosis nationwide have decided not to continue making these vaccines. Both of these vaccines protect against Anaplasmosis by similar mechanisms. The vaccines contain the organism, Anaplasma marginale, which had been harvested from infected cattle.