Studies on transmission, diagnostics, and immunity to white sturgeon iridovirus (WSIV)

Juvenile white sturgeon (Acipenser transmontanus) known to be asymptomatic for white sturgeon iridovirus (WSIV) infection were stocked at rearing densities of 3, 5, 9, and 13 g 1-1 for 80 d. Fish reared at densities greater than 3 g 1-1 exhibited increasing signs of disease and mortality that suggested a density relationship to disease outbreak. Stress associated with stocking density should be minimized to reduce the risk of outbreaks under culture conditions.; Fertilized eggs from wild Kootenai River white sturgeon broodstock were disinfected with various concentrations of iodine and hatched using Kootenai River or dechlorinated municipal water to investigate vertical transmission. Density manipulation was utilized to induce WSIV disease in individuals harboring virus, and it was shown that fish reared on municipal water were not infected with WSIV while siblings and other groups reared on river water tested positive for infection. Therefore, horizontal transmission appears to play a significant role in viral transmission. Vertical transmission did not occur and results suggest that not all wild broodstock will produce WSIV-positive progeny.; Non-lethal sampling of pectoral fin tissue by histopathology or PCR for WSIV detection was compared to lethal sampling of head tissue. Weekly sampling of white sturgeon challenged with WSIV (Abernathy isolate) by co-habitation as well as survivors showed early detection by the lethal method, but under typical screening situations it appears that the likelihood of detecting WSIV infected individuals was equal between lethal and non-lethal methods. Asymptomatic carriers of WSIV (Kootenai River isolate) were readily detected by lethal and non-lethal histopathology, but PCR results were negative using primers developed against a Sacramento River isolate. Depending on virus isolate, it appears these non-lethal methods can be effective and may minimize the need to euthanize large numbers of fish for WSIV screening.; Enzyme linked immunosorbant assays (ELISA) were developed to monitor specific antibody responses in serum and cutaneous mucus in white sturgeon immunized with WSIV or fluorescein isothiocyanate conjugated to keyhole limpet hemocyanin (FITC:KLH). Serum and mucus antibody titers were highest at 12 and 15 wk post-immunization, respectively, in fish responding to immunization. Immunoglobulin in the mucus was confirmed by Western blotting using a monoclonal antibody.