Co-infection analysis of bacterial and viral respiratory pathogens from clinically healthy swine in Eastern China.

Porcine respiratory disease complex (PRDC) is one of the most challenging health concerns for pig production worldwide. The aim of the present study was to determine the prevalence of pathogens associated with PRDC, including porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) and bacterial agents, such as Streptococcus suis, Haemophilus parasuis and Actinobacillus pleuropneumoniae, in clinically healthy pigs in Eastern China. Molecular detection revealed positive single-pathogen detection rates of 59.9%, 27.2%, 52.3%, 33.2% and 0.4% for PCV2, PRRSV, S. suis, H. parasuis and A. pleuropneumoniae, respectively. Co-infection with more than one pathogen was frequently detected in these samples, with PCV2/S. suis, H. parasuis and PCV2/H. parasuis mixed infection rates of 35.4%, 33.2% and 21.6%, respectively, and PCV2/S. suis/H. parasuis and PRRSV/PCV2/S. suis co-infection rates of 21.6% and 6.2%, respectively. These results suggest that mixed infections are prevalent among PRDC cases in swine, which may pose a greater threat to the health of herds compared with single-pathogen infections.