넙치에서 체중별 VHSV 최소 감염 농도와 환경 요인별 생존능 분석을 통한 수평 전파 위험 평가

Abstract

Viral hemorrhagic septicemia virus (VHSV) is one of the most devastating viral pathogens in olive flounder (Paralichthys olivaceus) aquaculture. However, quantitative data on its minimum infectious dose (MID) and environmental stability remain limited. This study determined the MID of VHSV in relation to fish body weight and evaluated the effects of environmental factors on viral persistence in seawater. Immersion challenges were performed using fish weighing 10, 100, and 200 g, each exposed to 10^3 –10^5 copies mL－1 of VHSV. Mortality occurred only in the 10 g group at viral concen- trations ≥10⁴ copies mL－1, with 45% cumulative mortality. At 10^5 copies mL－1, viral loads and infection rates in spleen tissues decreased with increasing weight, with infection detected in 91%, 45%, and 27% of the 10, 100, and 200 g groups, respectively. Logistic regression analysis confirmed a significant decline in infection risk with higher body weight. Across all groups, the minimum in- fectious dose required to induce VHSV infection was estimated to be ≥ 10^3 copies mL－1. Environmental stability assays showed that VHSV infectivity decreased rapidly at higher water temperatures and under natural sunlight, whereas lower temperatures and elevated FBS concentrations prolonged viral survival. The virus was inactivated within 1–2 days at ≥18°C, within 90 min under sunlight exposure, and after 3–5 days depending on the FBS concentration (0–25%). These findings demonstrate that smaller fish are more susceptible to VHSV infection and that viral persistence depends strongly on temperature, sunlight, and organic matter, providing a basis for assessing horizontal transmission risk in aquaculture.