Effect of temperature and salinity on the infectivity pattern of white spot syndrome virus (WSSV) in giant tiger shrimp Penaeus monodon (Fabricius, 1837)

Abstract

White spot disease (WSD) caused by the lethal white spot syndrome virus (WSSV) continues to be the major cause of mortality among farmed tiger shrimp in India and elsewhere, resulting in an annual loss of about 4-6 billion US$. Among the environmental variables, temperature and salinity of the rearing water are considered to be major triggering factors for white spot disease outbreak. In order to characterise the effect of salinity and temperature on the pathogenecity of WSSV infection in giant tiger shrimp Penaeus monodon, a laboratory challenge study was conducted at different levels of temperature (16, 25, 27, 28, 30, 32 and 36 ºC) and salinity (0.5, 5, 10, 15, 30 and 45 g l-1) with virulent white spot syndrome virus. Significant influence of temperature (p<0.05) on the percentage mortality and time until death of shrimp affected by the virus was observed, whereas salinity did not show any effect. Significantly higher survival rate was recorded in animals exposed at 32 ºC (37%) and 36 ºC (14%), 21 days post-challenge (dpc). All the shrimp challenged at other temperature levels, however, died after 21 dpc. These results demonstrated preference of WSSV for lower temperatures and higher survival in temperature ranges of 32 ºC to 36 ºC. The present observation may help to develop a management option to control the WSSV inflicted mortalities by selecting favorable hyperthermic rearing conditions for the shrimp.