Blood Levels of Oxytetracycline After the Use of a Long-Acting Formulation to Eliminate the Carrier State of Bovine Anaplasmosis

Abstract

The purpose of this paper is to present data on the blood plasma levels of oxytetracycline which resulted when cattle were injected intramuscularly (IM) once a week with a strengthened and improved formulation of oxytetracycline containing 200 mg/ml of base drug. One injection of this formulation has been reported to have an inhibitory effect on the parasitemia in acute anaplasmosis equivalent to three daily injections of oxytetracycline containing 50 mg/ml (2). Also, the former formulation has been recently reported to effect the elimination of the carrier state of bovine anaplasmosis when administered IM at seven-day intervals (3).

The use of tetracycline drugs at relatively high dosage levels for varying periods of time has been an accepted procedure for eliminating A. marginale infection. Either prolonged feeding of chlortetracycline or daily injection of oxytetracycline have been used for this purpose in a number of earlier studies. The present study suggests that the use of a long-acting oxytetracycline will effectively eliminate the carrier state of sensitive strains of A. marginale. Also, the present study shows that in a limited ·number of cattle, detectable blood levels were present in 10 of 12 cattle seven days after one treatment with the long-acting formulation of oxytetracycline. It will be necessary to further evaluate the use of this treatment regimen to determine if similar results can be achieved under field conditions.