Metaphylaxis with tildipirosin did not inhibit effectiveness of an experimental monovalent vaccine of live, attenuated Mannheimia haemolytica administered intranasally to dairy calves
DOI:
https://doi.org/10.21423/bovine-vol54no2p145-152Keywords:
bacterial vaccine, Mannheimia, interference, tildipirosin, immunization, lung lesions, bovine respiratory disease modelAbstract
The objective of this study was to evaluate the effect of tildipirosin on the efficacy of a concurrently administered experimental vaccine against Mannheimia haemolytica. The experimental vaccine was developed for intranasal (IN) administration and contained the same live, attenuated, streptomycin-dependent Mannheimia haemolytica, at the same titer as in commercial product(s). Eighty-eight 14-week-old Holstein or Holstein-cross male calves from a single source were randomly assigned (using a 2 x 2 factorial design) to 1 of 4 treatment groups (22 head per group) as follows: 1) experimental vaccine (VAX) (IN); 2) VAX (IN) + tildipirosin subcutaneously (SC); 3) placebo vaccine (PLBO) (IN) as negative control; and 4) PLBO (IN) + tildipirosin (SC). Seventy days after enrollment, 84 calves were challenged with virulent M. haemolytica. Clinical assessment of each calf was recorded daily after challenge. There was no significant (P > 0.05) effect of any experimental treatment on clinical signs. Seven days after challenge, the calves were euthanized, a percent lung lesion score (LLS) was assigned to each, and samples of lung were submitted for isolation of M. haemolytica. There was no significant (P = 0.51) effect of tildipirosin on LLS for calves vaccinated with VAX or those vaccinated with PLBO; however, VAX resulted in significantly (P = 0.046) lower LLS. Under the conditions of this study, concurrent administration of tildipirosin and IN live, attenuated, streptomycin-dependent M. haemolytica vaccine with the same antigen as used in this study did not interfere with the efficacy of the vaccine.