Postweaning multisystemic wasting syndrome induced after experimental inoculation of cesarean-derived, colostrum-deprived piglets with type 2 porcinecircovirus

Cesarean-derived, colostrum-deprived pigs (n = 23) were inoculated intranas ally and subcutaneously with a low cell culture passage of type 2 porcine c ircovirus. In 11 pigs, a persistent fever that lasted 7-17 days began 12-15 days after inoculation with virus. Additional signs of disease in those 11 pigs included depression (11 of 11 pigs), palpable enlargement of inguinal , prefemoral, and popliteal lymph nodes (11 of 11), icterus (6 of 11), and hyperpnea (2 of 11). The remaining 12 pigs had fever that occurred intermit tently for 2-4 days between days 12 and 20 postinoculation. Overt signs of disease in those pigs were limited to palpable enlargement of inguinal and popliteal lymph nodes (9 of 12 pigs). When compared with control pigs of si milar age, the average daily rate of weight gain for all pigs inoculated wi th virus was less over a 2-week period that be-an 2 weeks post inoculation. At postmortem examination, lymph node enlargement was seen in 14 of 14 pig s euthanized between days 20 and 28 postinoculation. Lymph node enlargement was especially prominent in pigs that developed a persistent fever. Micros copic lesions noted in pigs that developed a persistent fever included cell ular depletion in lymphoid tissues; hepatic cell necrosis; and lymphogranul omatous inflammation of lymph nodes, Peyer's patches of the intestine, live r, kidney, and heart. Virus was isolated with varying frequency from nasal, rectal, or tonsil swab specimens, buffy coat, serum, urine, and lung lavag e fluid obtained antemortem or postmortem. Virus was isolated from or viral DNA was detected in a variety of tissues obtained postmortem up to 125 day s postinoculation. Antibody against type 2 porcine circovirus usually was d etected in serum between 15 and 20 days postinoculation; however, antibody against virus was not detected in serum from 4 pigs euthanized 20-24 days p ostinoculation. Direct contact with pigs inoculated with virus 42 days prev iously resulted in transmission of virus to 3 of 3 control pigs.