Approximately 30 distinct Mycoplasma species have been isolated from cattle, but only a few are pathogenic and can cause serious respiratory diseases. Consequently, this study aimed to identify Mycoplasma spp. infections in cattle with bovine respiratory disease (BRD), considering factors such as animal demographics, concurrent infections with other pathogens, post-mortem clinical findings and histological examinations, and seasonality. A total of 326 samples were collected from 322 cattle that had died from BRD in Northwestern Italy. A total of 54 animals (16.8%) tested positive for Mycoplasma spp., and Mycoplasma bovis (n = 22, 40.7%) and Mycoplasma dispar (n = 13, 24.1%) were the most frequently detected species among the examined cattle. Among positive cattle, those aged five months or younger were approximately five times more likely to be infected by Mycoplasma dispar than by Mycoplasma bovis compared to those older than five months (proportional incidence ratio: 5.1, 95% CI 1.2-21.2). The main bacterial pathogens identified in cattle exhibiting co-infection was Pasteurella multocida, whereas the main viral pathogens were BRSV and BoHV-1. Histopathological investigations predominantly revealed catarrhal bronchopneumonia or purulent catarrhal bronchopneumonia among the examined cattle. Finally, Mycoplasma hyopharyngis, a species isolated from the pharyngeal and nasal cavities of pigs so far, was detected for the first time in the pneumonic lung of a bovine infected with BRD. Further investigations are necessary to thoroughly characterize its host range and pathogenic potential.
Keywords: BRD; Mycoplasma hyopharyngis; Mycoplasma spp.; Ureaplasma spp.; co-infections; seasonality.