Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/1999
Publication Date: N/A
Interpretive Summary: Isolates of Mannheimia haemolytica, the most common causative bacterial agent responsible for pneumonia in cattle, were collected in the Upper Midwest United States to determine the most prevalent serotypes in the area. This would help in determining vaccination strategy for the bacterium, since there is evidence that cross-protection among certain serotypes may be lacking. Although serotype 1 was the most prevalent, at least 4 other serotypes were found frequently enough to warrant consideration.
Technical Abstract: Mannheimia (Pasteurella) haemolytica biotype A serotype1 (A1) is the primary bacterial agent responsible for the clinical signs and pathophysiologic events in bovine pneumonic pasteurellosis. The goal of this study was to determine the prevalence of other serotypes of M. haemolytica biotype A organisms obtained from the upper Midwest diagnostic laboratories. A total of 147 M. haemolytica isolates were collected from Minnesota, South Dakota, and Michigan. Isolates were tested against M. haemolytica antisera obtained from the National Animal Disease Center, Ames, Iowa. Results indicated that M. haemolytica serotype 1 represented approximately 60%, serotype 6 represented 26%, and serotype 2 represented 7% of the total examined isolates. In addition, 7% of the isolates were serotype 9, 11, or untypable. This finding suggests that M. haemolytica serotypes other than serotype 1 can be isolated from the lung lesions of diseased cattle and seem to be capable of causing the pathologic changes observed in the lung with pneumonic pasteurellosis.