Prevalence and Risks of Vibrio parahaemolyticus in Black Tiger Shrimp (Penaeus monodon)

Background: The objective of this study was to determine the prevalence of Vibrio parahaemolyticus and its virulent strains in frozen and unprocessed cultured shrimp as well as their culture environment in Malaysia. The scope of this work was also to assess the risk of acquiring gastroenteritis due to V. parahaemolyticus for local population as a result of consumption of cooked black tiger shrimp and also for Japanese consumption of uncooked shrimp imported from Malaysia. Methods: Frozen shrimps (30 samples), live shrimps (40 samples), sediments (38 samples) and water samples (48 samples) were collected from a shrimp factory and 3 farms respectively. A total of 241 suspected isolates were tested (50: frozen shrimp, 50: cultured live shrimp, 67: sediments and 74: water) targeting the toxR, thermostable direct hemolysin (tdh) and related hemolysin (trh) genes for confirmation of total and pathogenic V. parahaemolyticus. Microbiological risk assessment was conducted in order to estimate the risk of infection using @RISK software (Palisade USA). Results: V. parahaemolyticus was detected in 98% of water samples with densities ranging from 10 to 420 cfu/ml whereas it was 200 to 9000 cfu/g for pond sediments. It was detected in all live shrimp samples with densities ranging from 300 to 8000 cfu/g. 43% of frozen shrimp samples were contaminated with V. parahaemolyticus ranging from 4 to 93 MPN/g. 46.5% of strains were found to be positive for toxR and 8% of the isolates from culture environment possessed the haemolysin tdh gene and trh gene. 7% of frozen shrimp samples were positive for virulent genes. Estimated illness per year is 123 persons (age from 18 to 59 years) for Malaysia and 63 for Japan. Conclusion: This study indicated that pathogenic V. parahaemolyticus strains were present in shrimp culture environment in Malaysia and suggest a probable risk for health of people consuming raw shrimp.