Experimental Model for Porcine Circovirus and Porcine Parvovirus Coinfection of Specific-Pathogen-Free Pigs

Porcine parvovirus (PPV) coinfection has been shown to increase the incidence and severity of porcine circovirus 2 (PCV2) associated disease in gnotobiotic and in colostrum-deprived pigs. PPV and PCV2 coinfection is also common in the grow-finish pigs in the field today. The objectives of this study were to determine the interactions between PCV2 and PPV in conventional SPF pigs and to determine whether PPV vaccine has an effect on the coinfection. Seventy-two, 6-week-old conventional pigs were inoculated either with PCV2, PPV, both PCV2 and PPV, or sham-inoculated. Before inoculation, 56 pigs were vaccinated twice with a PPV killed-virus vaccine. Clinical signs due to postweaning multisystemic wasting syndrome (PMWS) (fever, respiratory disease, jaundice, weight loss) were seen in both coinfected groups, vaccinated as well as nonvaccinated. The majority of pigs in the PCV2, and in the PCV2/PPV-inoculated groups had mild-tosevere lymphoid depletion with histiocytic replacement of follicles, and mild lymphohistiocytic interstitial pneumonia. The majority of pigs in the PCV2/PPV-coinfected groups also had mild-to-severe lymphoplasmacytic interstitial nephritis and hepatitis. There were no statistical differences between the two coinfected groups (vaccinated and non-vaccinated) in terms of clinical disease, and macroscopic and microscopic lesions. The results indicated that PPV and PCV2 coinfection resulted in increased severity of clinical disease and lymphoid lesions typical of PMWS and that a PPV-vaccination was not able to prevent PMWS in PCV2/PPV-coinfected pigs.