Effects of a sustained-release oxytetraycline bolus for anaplasmosis carriers

Abstract

Pairs of cattle with experimental anaplasmosis were given oxytetracycline at 1.0, 1.5 or 2.0 mg/kg as a 20% sustained-release bolus. Blood samples, collected weekly for 120 days after treatment were examined for complement fixating (CF) antibodies, packed cell volume, and patent infections. In a second experiment groups of 3 cattle with natural infections were similarly dosed at 1.5, 2.0, 2.5 or 3.0 mg/kg twice at an interval of 60 days. Blood samples were collected weekly for 180 days after the first treatment. Pooled blood samples (175 ml), collected from each treatment group were treated with neoarsphenamine and injected i/v into splenectomized calves. Sustained-release boluses reduced CF titres at all dose levels. One naturally infected group became CF negative. However, calves inoculated with blood from these animals developed anaplasmosis indicating that Anaplasma had not been eliminated.