Bacterial pneumonia in feedlot beef cattle

点击翻译按钮获取中文摘要

Bacterial pneumonia is the most common and economically important disease of Canadian feedlot beef cattle, and is a major reason for preventative use of antibiotics in the beef industry. The disease occurs mainly in the first 2-3 weeks after calves arrive in feedlots, and results from interactions among bacteria, viruses, stress, adverse climatic conditions, and genetic factors. This project encompasses two aspects of this disease: innate immunity against bacterial infection in the lung, and the pathogenesis of a particular form of bacterial pneumonia caused by Mycoplasma bovis. The objective of the innate immunity component of the project is to identify innate immune proteins in the lung and blood that contribute to resistance/susceptibility to bacterial pneumonia. Genetic variation in these proteins will be evaluated for their association with disease susceptibility, and tests to measure these proteins may be of practical benefit to identify calves at increased risk of disease, and permit more focused antibiotic treatment. The second component focuses on Mycoplasma bovis pneumonia, which has recently emerged as a major cause of chronic antibiotic-resistant pneumonia in Canadian beef and dairy calves. The project is an intensive examination of naturally occurring cases of this disease, investigating immune responses and changes in the numbers and genetic type of Mycoplasma bovis bacteria in the lungs of cattle, comparing calves that develop disease to those that remain healthy, and changes that occur prior to disease and during acute and chronic stages of pneumonia. The genotype and antimicrobial resistance of contemporary and archived isolates of Mycoplasma bovis will be compared for differences that may explain the recent emergence of this disease. These results are important to understand how the disease develops, and specifically whether control measures should be directed at the predisposing causes of disease or at virulent strains of Mycoplasma bovis.