Survey of Mycoplasma (Mesomycoplasma) ovipneumoniae, Mannheimia haemolytica, and Pasteurella multocida in pneumonic lungs from sheep slaughtered at 3 abattoirs in New South Wales, Australia

Respiratory disease is common in sheep worldwide. The objective of this study was to use real-time polymerase chain reaction (PCR) on bronchial swabs collected from sheep lungs with gross pathological signs of ovine respiratory complex (ORC) at abattoirs in southeastern Australia to detect 3 common bacterial ovine respiratory pathogens [Mycoplasma (Mesomycoplasma) ovipneumoniae, Mannheimia haemolytica, and Pasteurella multocida]. Mycoplasma ovipneumoniae was the most detected (35% of samples), followed by M. haemolytica (14.9% of samples), and P. multocida (8.1% of samples). The most common combination of infections was M. ovipneumoniae plus M. haemolytica (48 samples, 14.7% of positive samples), followed by M. ovipneumoniae plus P. multocida (21 samples, 6.4% of positive samples), and M. haemolytica plus P. multocida (19 samples, 5.8% of positive samples). There was a weak positive correlation between samples positive for M. ovipneumoniae and samples positive for M. haemolytica (r = 0.14, P = 0.002), a weak positive correlation between samples positive for M. ovipneumoniae and samples positive for P. multocida (r = 0.08, P = 0.002), and a weak-to-moderate positive correlation between samples positive for M. haemolytica and samples positive for P. multocida (r = 0.25, P < 0.001). Further research is needed on management options for ORC in Australian sheep farmed in extensive grazing systems.