Experimental reproduction of severe wasting disease by co-infection of pigs with porcine circovirus and porcine parvovirus.

Colostrum-deprived pigs were infected intranasally with a recent isolate of porcine circovirus (PCV2) and a porcine parvovirus (PPV), both from Canadian pigs with post-weaning multisystemic wasting syndrome (PMWS). Four pigs were inoculated with PCV2 alone, three with PPV alone, five with a combined PCV2/PPV inoculum, and two with a chloroform-treated combined PCV2/PPV inoculum. Pigs were killed 21-26 days after infection and tissue samples examined for gross and microscopical lesions and for the presence of viral antigens. No clinical signs, lesions or viral antigens were detected in two uninfected control pigs or in pigs inoculated with PPV alone. One pig inoculated with PCV2 alone became dull and thin. Mild to moderate histopathological lesions containing PCV2 antigen were detected in lymphoid tissues from the pigs inoculated with PCV2 alone. Pigs given the PCV2/PPV inoculum and the chloroform-treated PCV2/PPV inoculum became dull and two died. Jaundice and hepatomegaly were seen at post-mortem examination of most of the dually infected pigs. The latter showed large amounts of PCV2 antigen in numerous tissues; PPV antigen, which was less abundant, was detected in a few tissues, especially kidney. The lesions were similar to those seen in recently described field cases of porcine PMWS in North America and Europe.