Contamination with Vibrio parahaemolyticus and Its Virulent Strains in Seafood Marketed in Thailand, Vietnam, Malaysia, and Indonesia from 2008 to 2011

Abstract

Infections with virulent strains of Vibrio parahaemolyticus are frequently reported in Southeast Asia. This is due to frequent contamination of seafood by virulent strains. In this study conducted from 2008 to 2011, fish, shrimp, squid, crab, and molluscan shellfish were purchased from provinces in Thailand and three other Southeast Asian countries and examined for the prevalence of three genetic markers of V. parahaemolyticus (species-specific gene: toxR gene, virulence genes: tdh and trh genes). An enrichment culture of seafood was examined for these markers using PCR methods. Molluscan shellfish showed a high frequency of contamination in Thailand. The shellfish harvested from the coastal zone of the Gulf of Thailand were significantly more contaminated with virulence genes (0 to 36.1%) than those from the Andaman Sea (0 to 6.7%). The seafood purchased from three other Southeast Asian countries was positive for the three markers of V. parahaemolytcus at differing frequencies. The virulence markers (tdh and trh markers) were frequently detected in molluscan shellfish from Vietnam (17.9 and 8.0%, respectively), Malaysia (11.1 and 16.7%), and Indonesia (9.1 and 13.6%). These data suggest that the molluscan shellfish sold in markets in Southeast Asia are highly contaminated with virulent strains of V. parahaemolyticus.