Anaplasmosis: a regional serologic survey and oral antibiotic therapy in infected herds.

A test and treatment program was conducted in northern Idaho and southeastern Washington to detect bovine reactors to Anaplasma marginale and to achieve anaplasmosis-free status in the herds tested. Of 3,920 cattle tested, 214 (5.5%) were reactors; 110 of the reactors (from 7 herds) were tested after being treated orally for 45 days with chlortetracycline or oxytetracycline at a calculated daily dosage of 11 mg/kg of body weight, and all were seronegative. Two reactors refused to eat the medicated feed and were seropositive at retest. In untreated herds, the prevalence of reactors remained constant. It was concluded that a test and treatment program would have to be continued for several years to achieve an anaplasmosis-free status in cattle herds of the area.