Submitted to: United States Animal Health Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/19/2000
Publication Date: N/A
Technical Abstract: To contain production costs and offer the hope of good efficacy, our research has focused on the construction and testing of modified-live vaccine strains of Pasteurella (Mannheimia) haemolytica, P. multocida, and Haemophilus somnus. Genetic deletions are introduced into target genes in a manner which leaves no residual foreign DNA and which reassembles the target gene(s) to yield immunogenic but non-functional product(s). As reported last year to this committee, a modified-live Pasteurella haemolytica vaccine has proved efficacious when administered either parenterally or orally and appears to protect cattle within 3 days after eating hay top-dressed with vaccine. An intranasal formulation was administered last fall to low-risk calves at the point of first assembly. Good antibody response was elicited but no mortality and low morbidity yielded no statistical differences between vaccinates and controls in regard to performance. An ovine serotype 2 intranasal vaccine was administered to bighorn sheep where some animals were directly vaccinated and others were simply commingled with vaccinates. Both direct and indirect vaccinates seroconverted and resisted virulent challenge better than a single unvaccinated control, encouraging results considering the high susceptibility of this species to pneumonic Pasteurellosis.