Equine Granulocytic Anaplasmosis (EGA) is caused by infection with the rickettsial organism Anaplasma phagocytophilum (formerly Ehrlichia equi). Anaplasmosis is a common, seasonal, non-contagious, tick-transmitted disease of equids observed where the Ixodes tick vector is found. Ixodes scapularis is found in the eastern half of the United States, while Ixodes pacificus is found along the entire west coast. Equine anaplasmosis has been reported in the United States, Canada, South America, Europe, Asia, and North Africa.