Outbreaks of pleuritis and peritonitis in calves associated with Pasteurella multocida capsular type B strain.

Abstract CASE HISTORY: Three dairy calf-rearing properties experienced high mortality in calves during 2008 and 2009. Affected calves were aged 13–18 weeks (Farm I), 6 months (Farm II), and 2–11 weeks (Farm III), and the mortality rate was 22/175 (13%), 5/80 (6%), and 60/900 (7%), respectively. CLINICAL AND LABORATORY FINDINGS: Affected calves rapidly became moribund, were in respiratory distress, and had a fever (40–41°C). Post-mortem examination of nine calves revealed fibrinopurulent pleuritis, pericarditis, and peritonitis. This was confirmed histopathologically on tissues from three calves, one from each farm; aggregates of small Gram-negative coccobacilli were evident on Gram stain. Pasteurella multocida was cultured from tissues from affected calves on the three farms, and PCR of DNA extracted from tissue samples amplified cap-sular type B-specific DNA. Multi-locus sequence typing (MLST) demonstrated that all capsular type B isolates belonged to the same sequence type (ST), ST62, but did not belong...