Causative agent: Anaplasma marginale
A. marginale parasitizes the red blood cells of the host animal. It is transmitted between hosts by insect vectors. In the western USA the most common vector is the tick Dermacentor andersoni (9). Anaplasmosis has been experimentally induced in bison (39). 15.7% of bison tested at the National Bison Range in Montana, were positive to Anaplasmosis as determined by a compliment fixation test (39).
Clinical signs:
In cattle, the common clinical signs include anemia, jaundice, emaciation and debility (9). Bison calves experimentally infected with anaplasmosis demonstrated very mild clinical signs that included anemia, mild depression and listlessness (39). It is suggested that bison may be more resistant to anaplasmosis than cattle (39).
Diagnosis:
Anaplasmosis may be diagnosed in bison by examining blood samples for the presence of A. marginale on erythrocytes (39). Blood samples may be submitted to a diagnostic pathology laboratory for a compliment fixation test, detecting of antibodies to anaplasmosis.
Treatment:
There have been no treatment protocols established for treating anaplasmosis in bison. Cattle with anaplasmosis respond well to treatments with long acting tetracyclines (9).
Control:
There have been no control programs reported for anaplasmosis in bison. There are vaccination protocols established for cattle. They do not provide complete protection against anaplasmosis for extended periods of time. Some of the vaccines are associated with serious side affects (9). It may not be advisable to use these vaccines in bison.