수온 변화가 넙치(Paralichthys olivaceus)의 VHSV 감염성 및 스트레스 반응에 미치는 영향

Abstract

This study investigated the relationship between temperature-induced stress and susceptibility to viral hemorrhagic septicemia virus (VHSV) in olive flounder. To assess stress levels, changes in plasma cortisol, glucose, and lactate concentrations were measured following temperature shifts. When fish reared at 17℃ were transferred to 10℃ or 20℃, olive flounder exhibited a transient increase in stress during the initial period of the experiment. In the VHSV challenge study, mortality and stress responses were monitored following abrupt temperature changes. When the temperature was reduced from 20℃ to 15℃, the mortality rate was similar to that of fish maintained at 15℃, whereas the highest mortality occurred when the temperature was sharply lowered to 10℃. Furthermore, in the VHSV-uninfected group, stress levels gradually decreased after the temperature change, while in the VHSV-infected group, stress tended to increase over time. However, since stress remained high at the time of peak mortality, this change was considered to result from VHSV infection rather than temperature stress alone. Taken together, these findings suggest that rather than temperature-induced stress directly influencing VHSV-related mortality, water temperature itself may act as a direct factor affecting mortality due to VHSV infection. Notably, no mortality was observed when the temperature was increased from 10℃ to 15℃, indicating that even under the low-temperature conditions conducive to VHSV outbreaks, a moderate temperature rise may reduce VHSV pathogenicity.