AEROSOL VACCINATION OF CALVES WITH PASTEURELLA-HAEMOLYTICA AGAINST EXPERIMENTAL RESPIRATORY-DISEASE

Abstract

Three experiments were conducted on calves in which the efficacy of vaccination with live P. haemolytica in aerosol was tested by challenge with sequential aerosol exposure to bovine herpesvirus 1 and P. haemolytica. Neither single nor multiple aerosol vaccinations protected against the experimental disease. Macroscopically recognizable rhinitis, tonsillitis, tracheitis and pneumonia occurred in controls and vaccinates. In 1 experiment as many as 3 aerosol vaccinations with live P. haemolytica for up to 20 min failed to elicit clinical signs in exposed calves. P. haemolytica was isolated less frequently from tissue of vaccinated calves than from those of nonvaccinated calves. P. haemolytica was isolated from deep nasal swabs of 4/14 vaccinated calves 5 and 6 days after viral exposure. Thus, although bovine herpesvirus 1 vaccination has been shown previously to prevent the experimental disease produced by bovine herpesvirus 1-P. haemolytica, live P. haemolytica vaccination by aerosol apparently will not provide the same protection.