양식어류에서의 감염성 바이러스 검출과 질병발생과의 상관관계 분석

Abstract

Virus monitoring in cultured marine fish were conducted in Tong-yeong of Korea during ten month from 2013. March to 2013. December. In total, about 800 fish samples of 4 marine fish species at fifteen aquaculture farms were divided into 280 groups. Fish species belonged to rock fish (Sebastes schlegeli), red sea bream (Pagrus major), rock bream (Oplegnathus fasciatus), black sea bream (Acanthopagrus schlegelii). Target viruses, Iridovirus and viral nervous necrosis virus, were detected by nested PCR. The Iridovirus were detected at 0.0 ~ 42.9 % for ten month and the detection rate was low with an 0.0 % in May and high with an 42.9 % in October. Iridovirus were detected from the 4 species of fish. But Viral nervous necrosis virus were detected from the 1 species of fish, rock fish. Comparing with prevalence of VNNV seasonally, Virus were detected in May, June and August only. The detection rates of VNNV in May, June and August were 6.7 %, 10.0 % and 10.7 % respectively. From september to October 2013, there was mass mortality of rcok bream (St. 10), The rate of mortality was more than 90 % and the causes were assumed to be rapidly rising water temperature in September. Despite the high mortality caused by the virus in rock bream, no mortality is occurred in rock fish and red sea bream. But through the nested PCR, persistent infections were confirmation in rock fish. And the detection rate increased by rising of water temperature. For histopathological observations, the spleen of symptomatic infected rock bream showed local necrosis and enlarged cells around the splenic pulp. and derived virus of symptomatic infected rock bream was injected in PMF cell line and rock bream of length 5~6 ㎝. cell lines were incubated at 25 °C and observed every3days for the appearance of cytopathic effect (CPE) up to nine days. And test of infectivity in rock bream challenged with derived virus were determined by measuring the mortality. According to result of sequencing analysis, the virus extracted from spleen of the rock bream and rock fish were appeared subgroup II of megalocytivirus. This study was performed to survey the prevalence of fish disease viruses in marine fish sampled for Fish Care project & Control Center for Aquatic Animal Disease. And we assumed the relation between prevalence of viruses and occurrence disease in aquaculture farm. Thus we provide a significant information to establish a warning system for the occurrence of fish diseases.