Susceptibility of Different Marine Fish Fingerlings to Yellowtail Ascites Virus (YAV)

Abstract

The susceptibility of the fingerlings (mean weight 2g) of 5 different marine fish species to Yellowtail Ascites Virus (YAV) was studied by intraperitoneal (IP) injection or immersion (IS) infection methods: yellowtail Seriola quinqueradiata, hybrid of goldstriped amberjack Seriola aureovittata and amberjack Seriola dumerili, Japanese parrotfish Oplegnathus fasciatus, spotted parrotfish Oplegnathus punctatus and red sea bream Pagrus major. The challenge vir`us was grown in RTG-2 cells at 16°C for 3d and its titer was 2×10^7.63 TCID₅₀/ml. The fingerlings were IP injected with 2×10^5.63 TCID₅₀ of culture grown YAV/g fish or immersed for 50 min in seawater containing the same quantity of virus/ml.
Results showed that yellowtail exhibited the highest susceptibility to YAV by both methods of infection followed by Japanese parrotfish, hybrid of goldstriped amberjack and amberjack, whereas spotted parrotfish and red sea bream were not sensitive to the virus. All dead fingerlings exhibited abdominal ascites and clinical symptoms differed among the species. Virus titers in the viscera were little different among the fish species.