Surveillance of WSSV Carriers in Shrimp Farms

Possible carrier samples (wild shrimps and wild crabs) were collected inside and outside the farms using the convenience sampling method. In each sampling, five carriers from each species were pooled as one sample. In this study, the sites of carrier collection were divided into two categories: (1) Inside the farms and surrounding areas, and (2) outside the farms. Inside the farms and the surrounding areas, possible carrier samples were collected at night in reservoirs, inlet canals, drainage ponds, and communal canals (15 stations × 3 seasons × 60 carriers = 2,700/5 = 540 pooled samples). The specimens sampled were banana shrimp (Fenneropenaeus merguiensis, n = 21), jinga shrimp (Metapenaeus affinis, n = 16), banded snapping shrimp (Alpheus euphrosyne, n = 2), dwarf prawn (Macrobrachium equidens, n = 53), whiteleg shrimp (Litopenaeus vannamei, n = 12), green tidal crabs (Varuna yui, n = 208), and mangrove crabs (Episesarma spp., n = 228). Outside the farms, possible carriers were collected from water sources along the coastline of Rayong Province (11 stations × 3 seasons × 60 carriers = 1980/5 = 396 pooled samples). The samples consisted of banana shrimp (n = 9), Jinga shrimp (n = 8), dwarf prawn (n = 25), whiteleg shrimp (n = 1), green tidal crabs (n = 187), and mangrove crabs (n = 166). In total, 936 pooled samples were sent to a DOF laboratory for WSD detection using nested PCR.