Simultaneous Detection of Infectious Hematopoietic Necrosis Virus (IHNV) and Infectious Pancreatic Necrosis Virus (IPNV) by Reverse Transcription (RT)-Polymerase Chain Reaction (PCR)

Multiple virus infections have recently been observed during routine examination of salmonid fish.1) Infectious hematopoietic necrosis virus (IHNV) and infectious pan creatic necrosis virus (IPNV) are often isolated together or with other viruses, such as a herpes virus or a retro-like virus.1,2) In case of multiple virus infections, only the virus which replicates most efficiently will be detected. In these cases, other viruses may be detected only after neutraliza tion of the original sample with specific antibody against the virus isolated primarily. Therefore, a rapid diagnosis is needed to detect multiple viruses in culture fluid. Serologi cal tests are rapid but generally lack sensitivity of detection and repeated neutralization assays may be needed to identi fy the isolated viruses. Furthermore, if an antibody against the virus is not available, identification of the virus is difficult. The polymerase chain reaction (PCR) is a rapid and sensitive method for detecting viruses in infected cells, and assays for different viral agents may be performed at the same time.2,3) In this paper, we describe simultaneous detection of IHNV (strain ChAb) and IPNV (strain VR299, West Buxton and Jasper) by reverse transcription (RT)-PCR assay. IHNV (strain ChAb) was isolated in our laboratory from chum salmon Oncorhynchus keta in Hokkaido, Japan. IPNV (strain VR299) was provided by Dr. J. L. Fryer, Center for Salmon Disease Research, Oregon State University, OR, USA and the West Buxton and Jasper strains were provided by Dr. B. J. Hill of The Centre for Environment, Fisheries & Aquaculture Science (CEFAS), UK. All viruses were propagated at 15•Ž in rainbow trout