Comparison of Three Oral Chlortetracycline Treatment Regimens for Persistent Anaplasma marginale Carrier Clearance

Anaplasma marginale causes the most prevalent tick-transmitted disease of cattle. Once infected, a lifelong carrier state persists to function as a disease reservoir enabling subsequent vector infection or production equipment contamination. Despite reports of successful carrier clearance, no antimicrobial compound is labeled for disease elimination. In the absence of an efficacious vaccine, a validated antimicrobial regimen for persistent A. marginale elimination is urgently needed. Three oral chlortetracycline (CTC) treatments were evaluated for carrier clearance in cattle persistently infected with a Virginia isolate of A marginale.