Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 22, 1999
Publication Date: N/A
Interpretive Summary: Pneumonia in cattle costs the US cattle industry approximately $1 billion in losses each year. Pasteurella haemolytica is a bacterial pathogen which is the major cause of acute pneumonia in cattle. Treatment with tilmicosin, an antibiotic, temporarily reduced or cured nasal colonization by Pasteurella haemolytica. This is important because treatment would leave fewer bacteria to reach the lungs and to spread to other calves. Both effects should reduce the incidence of acute pneumonia that most often occurs after cattle are shipped to the feedyard.
Calves in 2 separate trials undergoing respiratory tract disease outbreaks after treatment to a feed yard were treated with tilmicosin. Nasal secretions and nasal swabs were examined for the presence of Pasteurella haemolytica to determine the status of colonization. In both experiments, P. haemolytica serotypes A1 and A6 were isolated. Tilmicosin treatment eliminated or markedly reduced detectable colonization in calves for up to 6 days. Tilmicosin treatment reduces the numbers of P. haemolytica in the nasopharynx, leaving fewer to reach the lungs and to spread to other calves. Both effects should reduce the incidence of acute respiratory tract disease at the feedyard for the first several days after arrival, when transported calves are most susceptible.