Fluorescent Antibody Test for the Rapid Diagnosis of Infectious Hematopoietic Necrosis

Abstract

A fluorescent antibody test (FAT) was developed for the rapid detection of infectious hematopoietic necrosis virus (IHNV). Both polyclonal and monoclonal antisera prepared against IHNV were evaluated. Test variables investigated included type of fixative, dilution rate of antibody reagents, staining time, and type of fluorescent conjugate that would be optimal for detection of IHNV. Specificity tests of the FAT indicated no cross-reactivity of the two antisera with other viruses or with cell lines of salmonid and nonsalmonid origin. All strains of IHNV tested, which included different electropherotypes, those isolated from selected salmonids at different life stages, and those from different geographic regions, reacted with both antisera. The FAT has been used for the detection of IHNV in blood smears and organ imprints from clinically infected juveniles, and in IHNV-infected cells in ovarian fluid from adult carriers. With this FAT, IHNV was detected after 48 h in cell lines inoculated with infected fish tissue. The test was equal in sensitivity to the plaque assay method and required less time to obtain a definitive diagnosis.