Infectious hematopoietic necrosis virus antibody profiles in naturally andexperimentally infected Atlantic salmon Salmo salar

Atlantic salmon Salmo salar naturally and experimentally exposed to infecti ous hematopoietic necrosis virus (IHNV) in British Columbia, Canada, develo ped antibodies against the virus. More than 50% of the fish exposed to IHNV remained seropositive for several months after the IHN epizootic had subsi ded. The virus itself could not be detected in asymptomatic fish once the f ish had recovered from IHN. The persistence of IHNV-specific antibodies in a large percentage of Atlantic salmon, from 4 different populations that su rvived an outbreak of IHN, and the lack of IHNV-specific antibodies in fish with no history of the disease, suggests that serology may be a useful too l for determining previous exposure to the virus. It may be important to de termine whether Atlantic salmon have been infected with IHNV because, altho ugh the virus is difficult to detect in asymptomatic fish, an incidental fi nding suggests it may persist in a small number of fish after the outbreak has subsided. Furthermore, the presence of seropositive fish would be an in dication that the virus may be enzootic at a farm, and such information wou ld thus aid producers with stocking decisions.