WHITE SPOT SYNDROME VIRUS IN FROZEN SHRIMP SOLD AT MASSACHUSETTS SUPERMARKETS

One of the most damaging viral diseases affecting the shrimp aquaculture industry is white spot disease (WSD) caused by white spot virus (WSSV), which causes high morbidity and mortality rates in penaeid shrimp and other crustaceans. The rapid spread of WSSV within wild and cultured stocks of shrimp may be caused by unregulated processing, disposal of infected imported shrimp, or the use of contaminated broodstock. The risk of introducing this virus to cultured and wild shrimp and other native species of crustaceans in the United States warrants investigation. The aim of this study is to determine the prevalence of WSSV in frozen commodity shrimp sold at four stores in the Boston area belonging to different supermarket chains. Samples from two size classes were collected in two different batches a month apart. Polymerase chain reaction was used to amplify a portion of the WSSV genome using a commercial PCR kit (ShrimpCare, DiagXotics). WSSV positive samples were visualized by electrophoresis and amplified product of selected samples was sequenced. Results showed a range of 0% to 38.7% for WSSV prevalence rate in the test populations, with an overall prevalence of 4.7%. Significant (P < 0.001) differences in WSSV prevalence were observed between shrimp from the two batches purchased a month apart, the two size classes, and the four test stores. Country of origin seemed to dominate the results. Sequence analysis confirmed the presence of WSSV genome in PCR-positive samples. Results provide preliminary evidence that an appreciable proportion of the shrimp sold in Massachusetts' supermarkets are carrying WSSV, and this constitutes a substantial risk of importation of this virus into the local environment. Further investigation is necessary to determine the risk of release of this virus into native fresh and marine water environments in Massachusetts and throughout the United States.