Evolving Pathogens, Targeted Sequences, and Strategies for Control of Bovine Respiratory Disease

NON-TECHNICAL SUMMARY: Mycoplasma bovis is an emerging infection of high mortality and morbidity in backgrounding and feedlot operations. This project will measure impact of this infection in midwestern farms and study molecular events that lead to septiciemia, polyarthritis, and death in affected calves.

<P> APPROACH: 1. Summary data for diagnostic efforts against Mycoplasma bovis will be shared by IA with MI and SD. This will include numbers of cases examined, and percent positive by diagnostic protocol used. Genotyping of M. bovis strains from outbreaks will be continued. <BR> 2. Molecular events involved in systemic infection by M. bovis will be characterized, including interaction of the mycoplasma with lymphocytes, endothelial cells, and platelets. IA will participate in a M. bovis genome sequencing project to find and characterize virulence genes.
<BR> <BR>
PROGRESS: 2001/10 TO 2006/09<BR>
Iowa worked on several aspects of Mycoplasma bovis infections in cattle. At feedlots, field sampling by nasal swabs compared favorably to tracheal washes in percent recovery and biotypes of M. bovis recovered. A marked skewing towards lack of expression of the surface protein VspA was noted among respiratory tract accessions of M. bovis, as compared to those from mastitis cases. Two ELISA serology methodologies were developed and compared for evaluation of field serum samples. A peptide ELISA targeting the MbLIP peptide of VspL was shown to have lower false negative results than a conventional whole organism ELISA, although both methods yielded similar proportion of false positives. A method was devised to measure antibiotic susceptibility profiles of strains of M. bovis. A survey of 243 M. bovis strains from the entire USA was followed by a survey of 46 strains from the mid-west. In both cases, antibiotics in current use in feedlots were evaluated, and several new antibiotics were shown to be active against the mycoplasma. A survey of Iowa-preconditioned calves indicated that very few beef herds in Iowa were infected with M. bovis, while a comparable survey from Georgia herds showed a higher percentage of infected herds there.
<BR> <BR>
IMPACT: 2001/10 TO 2006/09<BR>
Culture followed by immunoblot detection from nasal swabs to ascertain if beef calves were infected with Mycoplasma bovis at preconditioning proved to be more sensitive than PCR detection from nasal swabs. Detection of M. bovis can now be readily accomplished at preconditioning. This information in turn, can be used to assure that calves arriving from clean Iowa farms (in other words, not infected with M. bovis) receive the appropriate management on arrival at feedlots. The comingling of clean calves with infected calves can be a risk factor for populations of cattle arriving at feedlots, and appropriate management is needed for these calves. New management protocols for arrival at feedlot have not been explored in this study, although the development and testing of methods to define if calves are infected at herd of origin will provide incentive to design these protocols.