Shrimp (Penaeus vannamei) survive white spot syndrome virus infection by behavioral fever

Both endotherms and ectotherms may raise their body temperature to limit pathogen infection. Endotherms do this by increasing their basal metabolism; this is called 'fever'. Ectotherms do this by migrating to warmer places; this is called 'behavioral fever'. White spot syndrome virus (WSSV) is the most lethal pathogen of cultured shrimp. This study examined the existence of behavioral fever in WSSV-infected Penaeus vannamei shrimp. Shrimp weighing 15 ± 0.5 g were inoculated intramuscularly with WSSV and kept in a four-compartment system (4-CS) with all the chambers at 27 °C or with a thermal gradient (27-29-31-33 °C). During the first 4 days post-inoculation, 94% of the WSSV-inoculated shrimp died in the 4-CS with a fixed temperature (27 °C), while only 28% died in the 4-CS with a temperature gradient. The inoculated animals clearly demonstrated a movement towards the warmer compartments, whereas this was not the case with the mock- and non-inoculated animals. With primary lymphoid organ cell cultures, it was demonstrated that the increase of temperature from 27-29 °C to 31-33 °C inhibits virus replication. It is concluded that behavioral fever is used by shrimp to elevate their temperature when infected with WSSV. Behavioral fever prevents WSSV infection and mortality.