Case Report: Identification of Pathogenic Porcine Circovirus in Pigs with Post-Weaning Multisystemic Wasting Syndrome in Taiwan

An outbreak of post-weaning multisystemic wasting syndrome (PMWS) characterized by progressive weight loss and dyspnea was observed in weaning pigs at a 660-sow continuous- flow operation in central Taiwan in 1999. The disease was observed mainly in weaning and growing pigs. The histopathologic findings in the PMWS pigs were bronchointerstitial pneumonia and granulomatous lymphoadenitis, with unique large, multiple, basophilic ＂botryoid＂ intracytoplasmic inclusions forming within the histiocytes of the lymph node. These findings resemble those in pigs with PMWS recently reported in North America and Europe. Ultrastructurally, porcine circovirus (PCV)-like particles were observed in mesenteric lymph nodes from the ultra-thin sections and homogenates preparations using transmission and scanning electron microscopy respectively. PCV nucleotides were also amplified by a polymerase chain react ion (PCR) from the lymph nodes, lungs, spleen, and tonsils. This study verifies that outbreaks of PMWS have occurred in Taiwan.