Study to Compare the Efficacy of Three Oxytetracycline Regimens for the Treatment of Anaplasma Marginale Carrier Status in Beef Cattle

Abstract

Anaplasmosis is a blood-borne disease of cattle and other ruminants caused by Anaplasma marginale. Animals recovering from clinical anaplasmosis and those treated with therapeutic doses of oxytetracycline remain persistently infected with microscopically undetectable levels of the organism. These animals serve as reservoirs of the disease which can be spread mechanically or through arthropod vectors. Tetracyclines are the only compounds approved for treatment of acute anaplasmosis infections in the United States; however no compounds are approved for eliminating the carrier state. This has contributed to the restricted movement of cattle from endemic areas of the US to anaplasmosis-free territories such as Canada. Anaplasmosis is estimated to cost the US cattle industry $100 million per year, with some estimating the cost of resticted trade to be near $300 million annually. The objective of this study was to compare the effects of three oxytetracycline treatment regimens on eliminating Anaplasma marginale infection from carrier beef steers.