baquiloprim and Pneumonia

After administration of a bolus containing 0.8 g baquiloprim and 7.2 g sulphadimidine to six calves, plasma concentrations of these compounds exceeded MICs for Pasteurella haemolytica from about 3 hours to at least 48 hours. Experimental infection of three calves with 2.8 x 10(10) P. haemolytica type A1 organisms by the endobronchial route resulted in extensive pneumonic lesions, and smaller, similar lesions were found post mortem in two other calves which had received the same inoculum. Nine similar calves were also infected in the same manner after dosing six hours previously with a bolus providing doses of 4 mg/kg baquiloprim and 36 mg/kg sulphadimidine. Four of these calves received a second bolus 48 hours later. In contrast to the undosed calves, the treated calves exhibited few symptoms of respiratory disease following infection, and their temperatures remained normal. The mean temperatures of the control calves were significantly elevated for several days after infection. At post mortem examinations 6 days after infection, lung lesions were insignificant in all the dosed calves. P. haemolytica was isolated from the lungs of all 5 control calves but not from any treated animal. The combined dose of 40 mg/kg baquiloprim and sulphadimidine was the minimum recommended for use of the bolus in the field, and the results therefore predict efficacy when used in outbreaks of respiratory infection in calves associated with this organism.

Topics: Administration, Oral; Animals; Anti-Bacterial Agents; Body Temperature; Cattle; Drug Therapy, Combination; Female; Lung; Mannheimia haemolytica; Pasteurella Infections; Pneumonia; Pyrimidines; Sulfamethazine