Comparative efficacy and duration of immunity of commercial Pasteurella haemolytica vaccines

Abstract

Nursing crossbred calves on range were assigned to 6 groups. Five of these groups were vaccinated with different commercially available Pasteurella haemolytica A1 (PHA1) vaccines. Calves in group 6 were not vaccinated and served as controls. At 83 and 97 days postvaccination the protection of 5 calves from each group was challenged by transthoracic inoculation of live, highly pathogenic PHA1. Based on survival of challenged calves and lung lesion size there were significant differences in protection compared to controls in one or more comparisons of LeukoTox M,LeukoTox 1and Presponse HM. Overall, vaccination with two of the bacterin-toxoids, LeukoTox Mand LeukoTox 1 (American Animal Health),resulted in 70 percentage point reductions in mortality. Reduction in mortality from Presponse HM (American Home) was 40 percentage points; from OneShot (Pfizer), 30 percentage points. Once PMH (Bayer) did not protect. Lung lesions were significantly smaller in calves vaccinated with LeukoTox M, LeukoTox 1 and Presponse HM compared to controls. In general, lung lesion size paralleled mortality in protection tests. Antibody titers measured by cell-associated agglutination tests and cytotoxin neutralization assays were not strongly indicative of protection suggesting that other immune mechanisms also are involved in duration of immunity.