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

Simultaneous detection of porcine reproductive and respiratory syndrome vir us (PRRSV) and porcine circovirus 2 (PCV2) was achieved by a double-labelin g technique using a combination of immunohistochemistry and in situ hybridi zation in five pigs with naturally occurring porcine dermatitis and nephrop athy syndrome (PDNS). Both PRRSV and PCV2 were isolated from a homogenate o f pooled skin and kidney from three pigs. PRRSV RNA was demonstrated by rev erse transcription polymerase chain reaction (PCR) in skin, kidney, lymph n ode, 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, lymp h node, and tonsil. PRRSV antigen and PCV2 DNA were also detected in the sk in. This morphologic study is the first to confirm the presence of both PRR SV and PCV2 in the same tissues in pigs with naturally occurring PDNS.