Porcine respiratory disease complex (PRDC) is a common problem in pig production. Pathogens that are frequently involved in PRDC etiology are swine influenza virus (SIV) and A. pleuropneumoniae (Apleuro). The effect of single or dual infection with both pathogens has not been investigated to date.
The aim of the study was to investigate clinical course, immune and acute phase response in pigs single or dually infected with SIV and Apleuro. Thirty seven 7-week-old piglets, randomly allocated to 4 groups (Apleuro; Apleuro +SIV; SIV; control) were used. Humoral response was examined using HI assay (SIV) and ELISA (Apleuro serotype2). Acute phase proteins (App) (CRP, Hp, SAA, Pig-MAP) were examined with ELISA. Pathological changes and pathogens shedding were also recorded.
The most severe symptoms were observed in co-inoculated piglets. All piglets inoculated with SIV developed specific antibodies at 10 dpi, while in dual inoculated animals antibodies were detected at 7 dpi. The concentration of CRP increased only in animals inoculated/co-inoculated with Apleuro. The levels of SAA were elevated from 1 to 2 dpi in all groups as compared to controls. From day 3pi the higher level of SAA was observed only in co-infected pigs. The level of Pig-MAP remained unchanged in SIV- inoculated pigs. In piglets inoculated/co-inoculated with Apleuro significant increase of Pig-MAP were observed between 2 and 7 dpi. At 10 dpi the level of Pig-MAP were still elevated in co-inoculated pigs. The highest and the most prolonged Hp response was observed in Apleuro and Apleuro +SIV groups.
Co-infection with SIV and Apleuro potentiated the severity of SIV-like lung lesions and enhanced virus replication. Enhanced SIV replication contributed to a more severe lesions and stronger humoral and acute phase response compared to single inoculated pigs.
*This work was supported by The National Science Centre (DEC-2014/13/B/NZ6/02566)