Influence of temperature on Betanodavirus infection in Senegalese sole (Solea senegalensis)

- Horizontal transmission of Betanodavirus in Senegalese sole has been demonstrated.
- Subclinical infection can be established at 16 °C for long periods of time.
- After a temperature increase (above 18 °C) subclinically infected fish develop VER.

In this study Senegalese sole juveniles were experimentally infected with a reassortant Betanodavirus strain at three different temperatures: 22 °C, 18 °C and 16 °C by bath challenge and cohabitation. The results obtained showed that virus virulence decreased by reducing the water temperature. At 22 °C mortalities reached 100%, at 18 °C they ranged from 75 to 80% and at 16 °C only 8% of the fish died. In addition, horizontal transmission was demonstrated regardless of the rearing temperature. At 16 °C active viral replication was detected up to 66 days post-infection, but no signs of the disease were observed and only a very low level of mortality was recorded. The increase in water temperature from 16 to 22 °C caused a quick rise in the viral load and a subsequent outbreak of mortalities. These findings demonstrate that this reassortant Betanodavirus strain can cause a persistent infection in Senegalese sole at low temperatures (16 °C) for long periods of time, and when temperature increases the virus is able to trigger an acute infection and provoke high mortalities.