title: Effects of vaccination of calves against induced Haemophilus somnus pneumonia.
abstract: The efficacy of a killed whole-cell Haemophilus somnus bacterin against induced H somnus pneumonia was examined in 10-week-old male calves. Twenty calves were assigned to 1 of the 3 following groups: group 1, nonvaccinated controls (n = 4); group 2, vaccinated once (n = 8); and group 3, vaccinated twice 14 days apart (n = 8). The serum antibody response to vaccination and challenge exposure was evaluated by the bacterial agglutination test and solid-phase immunoassay (SPIA). Vaccinating calves twice, 14 days apart, significantly (P less than 0.05) reduced the severity of clinical signs of pneumonia and gross lesions. Deaths occurred in 1 of 4 nonvaccinated controls, 1 calf vaccinated once, and none of the calves vaccinated twice, 14 days apart. Postvaccination bacterial agglutination titers measured 14 days after the final vaccination were not significantly different between groups 2 and 3, but SPIA titers were significantly (P less than 0.05) higher in groups 2 and 3, compared with those in group 1. The less severe clinical signs of pneumonia observed in group-3 calves, compared with those in calves in groups 1 and 2, were significantly (P less than 0.01) correlated to higher SPIA titers, indicating the protective value of vaccinating twice.
authors.affiliation: Department of Pathology, Ontario Veterinary College, University of Guelph, Ontario, Canada.
authors.forename: S C
authors.initials: SC
authors.lastname: Groom
authors.forename: P B
authors.initials: PB
authors.lastname: Little
mesh_terms: D000372:Agglutination Tests; D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis; D001428:Bacterial Vaccines / Q000276:immunology; D002417:Cattle; D002418:Cattle Diseases / Q000473:pathology / Q000517:prevention & control*; D006190:Haemophilus / Q000276:immunology; D006192:Haemophilus Infections / Q000473:pathology / Q000517:prevention & control / Q000662:veterinary*; D007118:Immunoassay; D008168:Lung / Q000473:pathology; D008297:Male; D011014:Pneumonia / Q000473:pathology / Q000517:prevention & control / Q000662:veterinary*; D014611:Vaccination / Q000662:veterinary*
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines