ISOLATION OF PORCINE CIRCOVIRUS-LIKE VIRUSES FROM PIGS WITH A WASTINGDISEASE IN THE USA AND EUROPE

Samples of lung, liver, kidney, pancreas, spleen, and lymph node from pigs with postweaning multisystemic wasting syndrome from California ( USA) and samples of mesenteric lymph nodes from similarly diseased pig s from Brittany (France) were examined by light microscopy, in situ hy bridization (ISH), and/or virus isolation. Whole genomic probes for po rcine circovirus (PCV) and chicken anemia virus (CAV) were used for IS H. Tissue homogenate supernatants were inoculated onto PK/15 cells for virus isolation, and the presence of viral antigen and viral particle s was verified by indirect immunofluorescence, ISH, and electron micro scopy. Histologic examination of lung from pigs from California reveal ed interstitial pneumonia, alveolar epithelial hyperplasia, and basoph ilic nuclear and cytoplasmic inclusions in mononuclear cell infiltrate s and various pulmonary epithelial cells. Granulomatous lymphadenitis with syncytial cells typified the lesions seen in the pigs from France . PCV-like nucleic acid was detected by ISH in lung, pancreas, lymph n ode, kidney, and liver in pigs from California. Positive signal was al so obtained in lymph node sections from pigs from France. Probes for C AV were consistently negative. PK/15 cell cultures inoculated with lun g preparations from diseased California pigs and mesenteric lymph node preparations from pigs from France had positive fluorescence by indir ect staining for PCV using pooled polyclonal pig sera and hyperimmune rabbit serum and had variable staining with a panel of 7 monoclonal an tibodies specific for cell culture contaminant PCV. PCV-like nucleic a cid was also detected by ISH in cell cultures. Cytopathic effect was n ot observed. Electron microscopic examination of inoculated cell cultu res revealed 17-nm viral particles morphologically consistent with PCV . No other virus particles were observed. Although genomic analysis fo r the definitive identification of these viral isolates remains to be done, the evidence provided strongly suggests that these tissue isolat es are closely related to, although antigenically distinct from, the o riginal PCV cell culture contaminant.