Viability of white spot syndrome virus (WSSV) in shrimp pond sediments with reference to physicochemical properties

The white spot syndrome virus (WSSV), the causative agent of white spot disease (WSD) of shrimp, has emerged as a single most critical pathogen causing severe epizootics, inflicting significant economic loss to the global shrimp aquaculture industry. It can be transmitted vertically from infected broodstock to post-larvae and horizontally by cannibalism, invertebrate carriers, water, and sediment. Shrimp pond sediment represents an important reservoir of WSSV. The viability of WSSV in sediment is the most vital parameter in the transmission of WSD in the freshly stocked ponds. The physicochemical properties of sediment influence the viability and infectivity of WSSV. The objective of this study was to determine the viability of WSSV with reference to the physicochemical properties of pond sediment under farm conditions. The viability of WSSV in sediment samples from three WSSV-affected ponds with different soil types was examined using polymerase chain reaction (PCR), quantitative PCR, and infectivity studies. The soil characteristics, such as texture, pH, organic carbon (OC), electrical conductivity (EC), and moisture content were examined to unravel their relationship with the viability of WSSV. The WSSV could be detected in these shrimp pond sediments by PCR up to 35 to 52 days. However, it was revealed that the WSSV was infective up to 21 and 32 days in sandy clay loamy soil and 25 days in sandy loamy soil, suggesting the infectivity of WSSV was prolonged in sandy clay loamy soil. Further, the viability of WSSV was found to be dependent on the moisture content of the pond sediment and independent of organic carbon, pH, and electrical conductivity. These observations reinforce the adoption of best management practices (BMPs) like sun-drying of ponds for at least 3–5 weeks between the crops to achieve biosecurity and ensure successful culture.