In-situ hybridization for the detection of porcine circovirus in pigs with postweaning multisystemic wasting syndrome.

In-situ hybridization with a non-radioactive digoxigenin-labelled probe was used to detect porcine circovirus (PCV) in formalin-fixed paraffin wax-embedded tissues from 10 weaned pigs with naturally occurring postweaning multisystemic wasting syndrome (PMWS). A 530 base pair DNA fragment from an open reading frame 1 was generated by the polymerase chain reaction. By in-situ hybridization, a distinct positive signal was detected in all 10 pigs. The morphology of host cells was preserved despite the relatively high temperature required in parts of the incubation procedure. Positive cells typically exhibited a dark brown to black reaction product, mainly in the cytoplasm but occasionally in the nucleus, without background staining. Particularly consistent and intense labelling for PCV occurred in the lymph nodes. Virus was also detected in macrophages of the liver, spleen, Peyer's patches, lung and tonsil, in hepatocytes and in renal tubular epithelial cells. The abundant presence of PCV strongly suggested that PCV plays an important role in PMWS.