Food poisoning outbreak caused by Vibrio parahaemolyticus in steamed salted shrimp, Kaengkhro district, Chaiyaphum province, Thailand, 25–27 November 2014

Abstract

Background: On 28 November 2014, the Bureau of Epidemiology (BoE), Ministry of Public Health received a notification from Chaiyaphum provincial health office that a cluster of food poisoning cases visited Keangkhro hospital. Thus joint investigation was conducted to confirm diagnosis and verify outbreak, describe epidemiological characteristics of the outbreak, identify source of outbreak and implement control measures and provide recommendations for further prevention.
Methods: Descriptive study was used for the investigation. We reviewed medical records by semi-structured questionnaire including Demographic data, Onset, signs and symptoms, Water and food consumption, Menu, process of cooking, ingredients, and amount of consumed suspect. Case-control study was conducted to evaluate risk factors among cases and hospital-based control. An environmental study was conducted and collected samples for bacterial culture. Pulse Field Gel Electrophoresis (PFGE) was done to determine linkage between cases, food handler and food.
Results: A total of 99 (13.5/10,000 population) in Kaengkhro district met our case definition. Ninety-five percent showed diarrhea, 80% of abdominal pain. Median of incubation period was 7 hrs. (Range 1–36 hrs.). For multivariate analysis who ate steamed salted shrimp was a risk factor (Adjusted OR = 37. 83, 95%CI = 14. 48 – 98. 86) and dose-response relationship between number of shrimp consumption and food poisoning cases was presented (p-value<0. 001). PFGE revealed linkage between cases food handler and steamed salted shrimp. Undercooked processing and sharing equipment of raw and cooked food were precipitating factor for the outbreak.
Conclusion: The cause of this outbreak might be Vibio parahaemolyticus-contaminated steamed salted shrimp. Adequate cooking including, temperature and duration should be educated to food handler and the public. Reheating for ready-to-eat food should be emphasize to the public before eating especially shrimp and other seafood.