The use of a short and a long acting oxytetracycline for the treatment of Anaplasma marginale in splenectomized calves.

Twenty splenectomized Afrikander/Simmentaler cross animals were used. Eight of these were naturally infected with Anaplasma marginale while 12 were infected artificially. When the packed cell volume was reduced to between 24% and 20% during the post splenectomy relapses or primary infections, six animals were treated with a single injection of 20 mg/kg of long acting oxytetracycline (LA) and seven animals were treated on two successive days with 10 mg/kg of short acting oxytetracycline (SA). The remaining seven animals served as untreated controls. Both drugs were effective in controlling A. marginale reactions. No deaths occurred in the group of animals treated with oxytetracycline LA and they showed a longer relapse interval and higher blood levels of oxytetracycline compared to those treated with oxytetracycline SA. A single death occurred in the latter group. Four deaths occurred in the control group which also had the shortest relapse interval.