Comparison of virus isolation, reverse transcription-polymerase chain reaction, immunohistochemistry, and in situ hybridization for the detection of porcine reproductive and respiratory syndrome virus from naturally aborted fetuses and stillborn piglets

Virus isolation, reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and in situ hybridization methods were compared for t he detection of porcine reproductive and respiratory syndrome virus (PRRSV) . Seven aborted fetuses and 6 stillborn piglets naturally infected with PRR SV were used in the study. Viral antigen and viral nucleic acid were detect ed in macrophages and dendritic cells in the spleen, tonsil, lymph nodes, a nd thymus; in macrophages of Liver, heart, and lung; and in endothelial cel ls and myocytes of the heart, Viral antigen and viral nucleic acid were mos t consistently detected in the spleen. Of the 13 samples, 6 were positive f or PRRSV by all 4 techniques. Four (31%) samples were positive for PRRSV by RT-PCR, in situ hybridization, and virus isolation. Two (15%) samples were positive for PRRSV by virus isolation, RT-PCR, and in situ hybridization. One (8%) was positive for PRRSV by virus isolation and RT-PCR. The RT-PCR i dentified the presence of PRRSV more frequently than the other methods. How ever, when only formalin-fixed tissues are submitted, immunohistochemistry and in situ hybridization would be useful methods for the detection of PRRS V antigen and nucleic acid.