Effect of High Water Temperature on Betanodavirus Infection of Fingerling Humpback Grouper Cromileptes altivelis

Fingerling humpback grouper Cromileptes altivelis, experimentally infected with a betanodavirus (RGNNV genotype), were kept at 27°C, 31°C or 35°C for 14 days. The numbers of dead fish in ten fish at each water temperature were five at 27°C, two at 31°C and one at 35°C. The coat protein gene of the virus was detected by RT-PCR from four survivors at 27°C, two survivors at 31°C, but not from survivors at 35°C. Histopathologically, vacuolation in the retinal tissues wasobserved in three survivors at 27°C, but not in survivors at 31°C or 35°C. These results suggest that high water temperature inhibits the viral proliferation in fish.