RESPIRATORY-TRACT DISEASE AND MUCOSAL COLONIZATION BY PASTEURELLA-HAEMOLYTICA IN TRANSPORTED CATTLE

Objectives-To follow incidence of Pasteurella haemolytica (PH) in the upper respiratory tract of healthy carves at the farm and through the marketing process, and to determine the effect of vaccination on PH co lonization of the upper respiratory tract and on the incidence of resp iratory tract disease (RTD). Animals-2- to 5-month-old calves (n = 104 ) from 4 farms. Procedure-Calves were vaccinated with a killed PH sero type-1 product. Nasal secretion and tonsil wash specimens were culture d for PH, and serum antibody was measured by indirect hemagglutination . Calves with RTD were treated with tilmicosin phosphate. Results-At t he feedyard, 73 calves had RTD. The incidence of RTD was significantly related to the farm of origin, and was inversely related to the PH se rum titer at the farm, but was not influenced by vaccination. Isolatio ns of PH serotype 1, however, were reduced by vaccination. The major s erotypes of PH encountered were 1 and 6. Conclusion-Vaccination can re duce the frequency of colonization of the upper respiratory tract by P H.