Colostral transmission of porcine circovirus 2 (PCV-2): reproduction of post-weaning multisystemic wasting syndrome in pigs fed milk from PCV-2-infected sows with post-natal porcine parvovirus infection or immunostimulation

Post-weaning multisystemic wasting syndrome (PMWS) was reproduced in pigs fed colostrum and milk from porcine circovirus 2 (PCV-2)-infected sows and infected post-natally with porcine parvovirus (PPV) or immunostimulated. Pregnant sows were inoculated intranasally with either PCV-2 (n=5) or PCV-2-free PK-15 cell lysates (control, n=10) 3 weeks before the expected farrowing date. Newborn piglets from five of the control sows were introduced to PCV-2-infected sows (n=6 for each sow) and allowed to feed on the colostrum for 12 h and then given 15 ml milk five times a day for 7 days. Newborn piglets from the other five control sows were fed colostrum and milk from their own sows. After 7 days, two piglets from each group were randomly selected to confirm PCV-2 infection. Twenty-one pigs fed by PCV-2-infected sows were randomly divided into three groups and subjected to post-natal PPV infection (group 1), immunostimulation (group 2) or no post-natal treatment (group 3). Twenty-one pigs fed by uninfected sows were also randomly divided and subjected to post-natal PCV-2 and PPV infection (group 4), post-natal PCV-2 infection (group 5) or no treatment (group 6, negative control). Body weight was significantly greater in group 6 than in groups 1, 2 and 4 at 49, 52, 56, 59 and 63 days of age. The typical granulomatous inflammatory reaction and lymphoid depletion of PMWS was observed in the lymph nodes of groups 1, 2 and 4 at 63 days of age. Group 3 had significantly fewer PCV-2-positive cells than groups 1, 2 and 4. In conclusion, PCV-2 shed from colostrum and milk is infectious and reproduces PMWS with post-natal PPV infection or immune stimulation.