Molecular detection of respiratory coinfections in pig herds with enzootic pneumonia: a survey in Brazil.

Mycoplasma hyopneumoniae is the primary etiologic agent of swine enzootic pneumonia (EP), in which the immune response is reduced, making pigs susceptible to secondary infections. We surveyed commercial pig herds in Brazil for viral and bacterial respiratory coinfections that could complicate EP. Over a 2-y period (2015-2016), we found that 854 of 2,206 pigs (38.7%) were positive for M. hyopneumoniae in herds from various production systems in 3 Brazilian regions (Central-West, Southeast, South). We collected samples of 321 lungs positive for M. hyopneumoniae from 169 farms to also screen for Pasteurella multocida, Actinobacillus pleuropneumoniae, Glaesserella parasuis, influenza A virus (IAV), and porcine circovirus 2 (PCV2) by real-time PCR. The prevalence of pathogens found in addition to M. hyopneumoniae varied: P. multocida (141; 43.9%), G. parasuis (71; 22.1%), PCV2 (50; 15.6%), IAV (23; 7.2%), and A. pleuropneumoniae (18; 5.6%). G. parasuis was more frequent in farrowing or nursery herds (48.7%) than in breeding and fattening herds (10% and 18.6%, respectively; p < 0.01); A. pleuropneumoniae was found only in herds on farrow-to-finish and fattening farms.