양식 동남아산 뱀장어, Anguilla bicolor의 Anguillid herpesvirus-1 (AngHV-1) 감염증

Abstract

양식 동남아산 뱀장어 Anguilla bicolor에 아가미의 출혈 및 간장의 충혈을 특징으로 하는 질병의 원인을 조사한 결과 Anguillid herpesvirus (AngHV-1) 의 감염이 확인되었다. 병어는 병리조직학적으로 아가미의 상피세포의 증생과 모세혈관의 출혈, 간장의 공포변성 및 중심정맥의 충혈이 관찰되었다. 병어를 <TEX>$35^{\circ}C$</TEX>에 10일간 승온 사육한 결과 아가미의 형태가 건강어의 아가미와 유사한 형태로 회복되었으며, 폐사율도 10%로 승온 처리가 폐사율 감소에 효과적인 것으로 나타났다. Diseased eel (Anguilla bicolor) displayed severe hemorrhages in the gills, and congestion and swelling in the liver. During the epizootic, the water temperature was <TEX>$28^{\circ}C$</TEX> and the morality rates were about 5%. No parasites were found on the gills and skin. Bacteria were not cultured from any internal organs using TSA or SS agar at <TEX>$28^{\circ}C$</TEX> for 48 hrs. Histopathologically, the gills showed epithelial hyperplasia in the base of secondary gill lamellae and hemorrhages in the capillaries. Some cells in the proliferated interlamellar epithelia exhibited marginal hyperchromatosis. And severe vacuolated changes in the parenchymal cells and congestion in the central veins were observed in the liver. The specific amplicon (396 bp) was detected from gills and opercula of affected eel PCR using Anguillid herpesvirus-1 (AngHV-1) -specific primer sets HVAPOLVPSD (5-'GTG TCG GGC TTT GTG GTG C-3') and HVAPOLOOSN (5'-CAT GCC GGG AGT CTT TTT GAT-3'). Sequencing analysis of the amplicon demonstrated that this gene was 99% homologous to the AngHV-1 sequence deposited in GenBank. This is the first report of AngHV-1 outbreak in the farmed shortfin eels (A. bicolor) in Korea. When diseased fish were maintained for 10 days at water temperatures of <TEX>$32^{\circ}C$</TEX> and <TEX>$35^{\circ}C$</TEX>, the cumulative mortalities were 100% and 10%, respectively. Even though the AngHV-1 genome in the gills from the eel kept at <TEX>$35^{\circ}C$</TEX> was detected using PCR, the structure of gill filaments was similar with that of normal fish. Increasing the water temperature to <TEX>$35^{\circ}C$</TEX> was an effective way to diminish the mortality of AngHV-1 affected eel.