Chemoprophylaxis of vector-borne anaplasmosis with sustained-release boluses

Sustained-release oxytetracycline boluses (20%) delivering 145 to 150 mg/bolus/day were administered to complement-fixation test-negative cattle at dosages of 2.0, 2.5, and 3.0 mg/kg of body weight. Subsequent challenge exposure of cattle with Dermacentor andersoni Stiles infected with Anaplasma marginale Theiler indicated that treatment with the dosage of 2.5 mg/kg prevented clinical anaplasmosis and that treatment with the dosage of 3.0 mg/kg prevented disease infection.