An outbreak investigation of Salmonella food poisoning in 2 villages, Wachirabarami district, Phichit province, June 2021

Abstract

On June 10, 2021, the Situation Awareness Team (SAT) of the Office of Disease Prevention and Control Region 3, Nakhon Sawan (ODPC3) was notified by the Situation Awareness Team (SAT) of Phichit Provincial Health Office (PPHO) that there were 36 patients having fever, vomiting and diarrhea in two villages of Wachirabarami district, leading to the investigation to confirm an outbreak, study epidemiological features, determine the sources and routes of transmission and risk factors, and to recommend control and prevention measures. The study included active case finding in the two villages, inspecting the cooking process, and collecting samples from the patients, food handlers, water and foods to test for causative pathogens. A case was defined as any food handlers or villagers who had at least one of these symptoms: diarrhea, abdominal pain or cramp, fever, watery stool, fatigue, nausea, vomiting or headache, and mucous stool between June 7-10, 2021. A retrospective cohort study was conducted to determine the risk factors and source(s) of outbreak. The results found that 54 (87.10%) of the 62 persons developed the symptoms. The main clinical manifestations were diarrhea (92.59%), abdominal pain or cramp (75.93%) and fever (72.22%). A total of three patients were hospitalized. Rectal swabs for culture were taken from 7 cases, two of whom were found to have Salmonella serovar Bredeney. Eating spicy minced pork salad with raw pig blood was significantly associated with the disease (adjusted odd ratio = 65.12, 95% confidence interval 5.61-755.30). Salmonella serovar Bredeney was also identified from this food sample. In addition, enterotoxin A produced methicillin-susceptible Staphylococcus aureus was found in this food sample. Environmental investigation discovered an unhygienic cooking process of this pork salad; Staphylococcus aureus was detected from the food handler’s hand swabs and Bacillus cereus group identified in water used for cooking. In summary, this food poisoning outbreak with a high attack rate was caused by Salmonella serovar Bredeney from eating spicy minced pork salad with raw pig blood. As a key disease prevention and control measure, food handlers are recommended to follow hygienic cooking process and members of the public are advised to consume only freshly cooked and well-cooked foods, as well as avoiding eating raw or undercooked foods in order to prevent food poisoning