Cross-sectional study of calves from Norwegian dairy herds with enzootic pneumonia: pathogen occurrence, antimicrobial resistance, culture result interpretation, and sampling site agreement
Abstract
Enzootic pneumonia in calves is associated with pathogens such as Pasteurellaceae bacteria and Mycoplasmopsis bovis. Some of these bacteria are commensals in healthy calves, complicating culture interpretation, discouraging laboratory diagnostic use, and limiting knowledge of their impact. This study aimed to investigate the occurrence and antimicrobial resistance pattern of respiratory pathogens in calves from dairy herds with enzootic pneumonia. Culture results between upper and lower airway sites in healthy and diseased calves were also compared to evaluate their diagnostic value. A cross-sectional study was conducted on 131 calves (72 healthy and 59 diseased) from nine Norwegian dairy herds. Nasal swabs (NS), nasopharyngeal swabs (NPS), and serum were obtained from each calf, and bronchoalveolar lavage (BAL) from 113 calves. At the calf level, Pasteurella multocida was present in 60%, Mannheimia haemolytica in 55%, and Histophilus somni in 3%. At the sampling site level, from NS, NPS, and BAL, P. multocida was detected in 47%, 45%, and 27%, and M. haemolytica in 46%, 37%, and 8%, respectively. H. somni was detected in ≤ 2% per site. P. multocida appeared as pure culture in 73% (22/30) of positive BAL cultures. Serum antibodies to M. bovis were not detected. Most Pasteurellaceae isolates were susceptible to penicillin and other common pneumonia antimicrobials (disc diffusion). The exceptions were penicillin-resistant M. haemolytica isolates in two calves. Logistic…
How strong is the evidence?
Evidence Hub reads this as a cross-sectional. Its evidence level is 4 of 5 (Low · observational). Observational designs can show an association but not prove cause.
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