Experimental white spot syndrome virus challenge of juvenile Litopenaeus vannamei (Boone) at different salinities

In recent years, the shrimp industry has turned to inland freshwater culture as one method to avoid problems such as the introduction of possible vectors of viral pathogens into seawater ponds. Our experiments evaluated susceptibility to white spot syndrome virus (WSSV) in Litopenaeus vannamei held under different salinity regimens. Juvenile L. vannamei that were conditioned at salinities of 35, 25, 15, 5 and 2 g L⁻¹ were challenged with WSSV. In order to assess the severity of white spot disease, histological analysis and nested polymerase chain reaction (PCR) tests were carried out on the challenged shrimp every 4 h after 48 h post challenge. The results indicated that significantly more severe infections resulted at 15‰ than at other salinities. Mortality could not be compared due to the sampling design and because severe WSSV infections occurred in all test groups such that few shrimp remained alive in each challenged group at the end of the test. Despite this, the results suggest that salinity may affect the course and outcome of WSSV infections.