Colocalization of porcine reproductive and respiratory syndrome virus and porcine circovirus 2 in porcine dermatitis and nephrology syndrome by double-labeling technique.

Simultaneous detection of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus 2 (PCV2) was achieved by a double-labeling technique using a combination of immunohistochemistry and in situ hybridization in five pigs with naturally occurring porcine dermatitis and nephropathy syndrome (PDNS). Both PRRSV and PCV2 were isolated from a homogenate of pooled skin and kidney from three pigs. PRRSV RNA was demonstrated by reverse transcription polymerase chain reaction (PCR) in skin, kidney, lymph node, and tonsil homogenates from all pigs. PCV2 DNA was demonstrated by PCR in kidney, lymph node, tonsil, liver, and lung homogenates from all pigs. For double-labeling studies, the tissue samples were processed sequentially, first by immunohistochemistry and then by in situ hybridization. The most consistent and intense staining for PRRSV and PCV2 was in the kidney, lymph node, and tonsil. PRRSV antigen and PCV2 DNA were also detected in the skin. This morphologic study is the first to confirm the presence of both PRRSV and PCV2 in the same tissues in pigs with naturally occurring PDNS.