Bovine Anaplasmosis is an infectious disease of adult cattle caused by the hemotrophic rickettsial parasite Anaplasma marginale. Cattle of all ages may become infected with Anaplasma marginale, but clinical disease increases in severity with age. Anaplasmosis is rarely observed in calveslessthan sixmonths of age. Cattle over three years of age are most susceptible and have the highest mortality rate (30-50%). Anaplasmosis is a cyclical disease with outbreaks occurring every five to seven years. The American National Cattlemen's Association has considered anaplasmosis as a major disease problem with annual losses and disease control estimated to be $300 million