Isolation and PCR detection of Mycoplasma spp. in calves with respiratory disease from selected dairy herds in central Mexico

Among the microorganisms involved in bovine respiratory disease (BRD), certain Mycoplasma species have been associated with the severity and chronicity of infections. This study aimed to determine the frequency of Mycoplasma species in calves with respiratory disease from selected dairy herds in the states of Hidalgo and Mexico, located in Central Mexico. Nasal swabs were collected from 150 clinically affected calves from dairy herds: 35 from Melchor Ocampo, State of Mexico (Herd A); 30 from Actopan, State of Hidalgo (Herd B); and 85 from 3 herds in Tizayuca, State of Hidalgo (Herds C, D, and E). Samples were analyzed by culture and PCR targeting the uvrC gene of Mycoplasma bovis and the rpoB gene of Mycoplasma dispar and Mycoplasma bovirhinis. Specifically, M. bovis was more frequently detected in Herds A and B, with PCR positivity rates of 57.7% and 33.3% and corresponding culture positivity rates of 51.4% and 23.3%, respectively. In contrast, M. dispar predominated in Herds C, D and E, with PCR positivity rates ranging from 30% to 48% and corresponding culture positivity rates ranging from 26.6% to 36.6%. M. bovirhinis was detected at low frequencies across all herds. Sequencing analysis confirmed the identity of the detected species. The detection of M. bovis in some clinically affected calves in this study is consistent with previous evidence recognizing it as an important respiratory pathogen in cattle, whereas the detection of M. dispar and M. bovirhinis may reflect opportunistic behavior or their presence as part of the respiratory microbiota, although their role in bovine respiratory disease remains unclear.