Comparison of reverse transcription polymerase chain reaction, immunohistochemistry, and in situ hybridization for the detection of porcine epidemic diarrhea virus in pigs.

Reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and in situ hybridization were compared for the detection of porcine epidemic diarrhea virus (PEDV). Fifteen piglets experimentally infected with PEDV were used in the study. In addition, 94 diarrheic piglets submitted to the Department of Veterinary Pathology in Seoul National University for diagnosis of PEDV infection were used to compare the 3 methods. Antigen and nucleic acid of PEDV were detected in 15/15, 13/15, and 14/15 of the intestinal and fecal samples from the PEDV-inoculated pigs by RT-PCR, immunohistochemistry, and in situ hybridization, respectively. The virus was isolated from 15/15 of the jejunal samples from the PEDV-inoculated pigs. Neither PEDV antigen nor PEDV nucleic acid was detected in the intestinal and fecal samples from mock-infected control pigs. Of the 94 samples, 63 were positive for PEDV by all 3 techniques. Six samples were positive for PEDV by immunohistochemistry and in situ hybridization. Three samples were positive for PEDV by in situ hybridization and RT-PCR. Seven samples were positive for PEDV by RT-PCR. Although RT-PCR identified the presence of PEDV more frequently than the other methods, when only formalin-fixed tissues are submitted, immunohistochemistry and in situ hybridization would be useful methods for the detection of PEDV antigen and nucleic acid.