Detection of rainbow trout antibodies to infectious pancreatic necrosis virus by an immunoassay

An enzyme-linked immunosorbent assay (ELISA) for the detection of infectious pancreatic necrosis virus (IPNV) antibodies in rainbow trout Oncorhynchus mykiss was assessed. There was close agreement between the results of the ELISA and a neutralisation test for detecting IPNV antibody when fish sera were tested by both methods. The differences between the ELISA and virus neutralisation are most likely because antibodies against different virus epitopes reacted in the 2 techniques. The sample correlation coefficients of ELISA absorbance values and neutralisation titres for 2 different populations of fish were -0.42 and 0.78. Reasons for those differences are discussed. Combined data from 4 different IPNV positive fish groups showed that virus was isolated from 29.9 % (32/107) of the fish, whereas more than twice that number were antibody positive by the ELISA. All the virus positive fish were also antibody positive by the ELISA and/or neutralisation. Although the ELISA did not detect all virus positive individuals, it potentially has a role in detecting rainbow trout populations previously exposed to IPNV.