The effects of danofloxacin and tilmicosin on neutrophil function and lung consolidation in beef heifer calves with induced Pasteurella (Mannheimia) haemolytica pneumonia

Fajt, V. R., Apley, M. D., Roth, J. A., Frank, D. E., Brogden, K. A., Skogerboe, T. L.,Shostrom, V. K., Chin, Y.-L. The effects of danofloxacin and tilmicosin on neu-trophil function and lung consolidation in beef heifer calves with inducedPasteurella (Mannheimia) haemolytica pneumonia. J. vet. Pharmacol. Therap. 26,173–179.Pneumonia caused by Pasteurella (Mannheimia) haemolytica was induced inweaned beef heifer calves, approximately 6 months of age. Calves were treated at20 h after challenge with therapeutic doses of danofloxacin or tilmicosin.Peripheral blood neutrophils were collected at 3, 24 and 48 h after treatment.The ex vivo effects on neutrophil function, neutrophil apoptosis, and hematolog-ical parameters were examined, as was the effect on percentage lungconsolidation. Neutrophil function assays included random migration underagarose, cytochrome C reduction, iodination, Staphylococcus aureus ingestion,chemotaxis, and antibody-dependent and antibody-independent cell-mediatedcytotoxicity. Apoptosis was determined using a cell death detection kit. Killingwas performed at 72 h after treatment. Statistical comparisons were madeamong the three groups of challenged–treated animals: saline, danofloxacin, andtilmicosin. Comparisons were also made between nonchallenged nontreatedanimals (NCH) and challenged saline-treated animals. There were no significantdifferences for any of the neutrophil function assays or neutrophil apoptosisamong the challenged–treated groups. This suggests that danofloxacin andtilmicosin have no clinically significant effects on neutrophil function orapoptosis. There were also no significant differences in percentage lungconsolidation among the challenged–treated groups. Significant differences werefound between the NCH calves and the challenged saline-treated calves in severalneutrophil assays, which were attributed to effects of P. haemolytica infection.(Paper received 24 August 2001; accepted for publication 12 February 2003)Virginia R. Fajt, Department of Veterinary Diagnostic and Production AnimalMedicine, Iowa State University College of Veterinary Medicine, 1710 Vet Med,PO Box 3020 Ames, IA 50010-3020, USA. E-mail: fajt@iastate.edu