Identification of porcine circovirus in tissues of pigs with porcine dermatitis and nephropathy syndrome

Thirty-three pigs affected by porcine dermatitis and nephropathy syndrome, 30 from Spain and three from the USA, were investigated in order to detect porcine circovirus (pcv) in their tissues. A standard in situ hybridisation technique using a specific DNA 317-bp probe based on a well-conserved sequ ence of pcv (which recognises both PCV-1 and PCV-2) was applied to formalin -fixed, paraffin-embedded tissues. Twenty-eight of the 30 Spanish pigs and all three American pigs had pcv in at least one tissue. Viral nucleic acid was detected mainly in lymphoid organs, and especially the lymph nodes. The viral genome was also found, in order of decreasing quantity, in Peyer's p atches, tonsil, lung, spleen, kidney, liver, and skin. Viral nucleic acid w as located mainly within the cytoplasm of monocyte/macrophage lineage cells , including follicular dendritic cells, macrophages, histiocytes and Kupffe r cells. No viral nucleic acid was found in damaged glomeruli or arteriolar walls. In frozen samples available from three Spanish pigs, the virus was identified as type 2 by using the polymerase chain reaction and restriction fragment length polymorphism. Most of the pigs from which serum was availa ble were seropositive against porcine respiratory and reproductive syndrome virus (PRRSV), and PRRSV antigen was detected in the lung of two of the Sp anish pigs. These results suggested that pcv is present in tissues of almos t all pigs affected by PDNS, and PCV has to be considered as a possible age nt involved in the pathogenesis of the syndrome.