An outbreak investigation of food poisoning due to Salmonella spp. in 2 villages, Muangna Subdistrict, Chiangdao District, Chiangmai Province, Thailand, 30 April–16 May 2019

Abstract

Background: On 2 May 2019, Chaiprakarn Hospital received notification of 7 food–poisoning cases in 2 villages, Muangna Subdistrict, Chiangdao District, Chiangmai Province. The objectives of this investigation were to describe outbreak, determine source of outbreak and provide appropriate recommendations.
Methods: Active case finding was done in 2 villages (Moo 1 and Moo 13) by surveyed and interviewed with questionnaire. Suspected case was defined as a person who live in Moo 1 and Moo 13 and presented with diarrhea and vomiting or any of diarrhea or vomiting with at least one of the following symptoms: nausea, abdominal pain, diarrhea, constipation, bloody diarrhea, fever, or headache during 30 April to 3 May 2019. Confirmed case was identify by bacterial isolation from stool samples. Case–control (1:4) study was conducted to identify risk factors by using defined suspected cases and selected controls from persons who live in Moo 1 and Moo 13 and did not have those symptoms. We interviewed cases as well as food handlers about food chain. Environmental study was performed by sanitation survey, residual chlorine test, collected food, water, utensil and rectal swabs from food handlers.
Results: Total 17 cases (4 confirmed cases, 13 suspected cases) were identified from Muangna Village (Moo 1) and Jiajan Village (Moo 13). Attack rate was 532.08 per 100,000 population. Clinical presentations were abdominal pain (100%), diarrhea (100%) following by vomit (76%), nausea (65%), headache (18%), rectal bleeding (12%) and fever (6%). Salmonella enterica subsp. enterica ser.4,5,12:i:–were detected from the stool culture of 4 patients (23.53%) and 2 food handler as carriers. Food (meat salad), cooking pot and cutting plate were identified Salmonella serovar Typhimurium. Northern Thai–style meat salad which served raw was shown as a risk factor from analytic study (OR = 158.67, 95%CI = 24.23–1039.22).
Conclusions and discussions: This food poisoning outbreak caused by Salmonella enterica subsp. enterica ser.4,5,12:i:–from meat salad which were contaminated from food handlers, who also detected same pathogen, through inadequate hygiene during cooking process and consumed uncooked food. Therefore, eating cooked food and hygienic cooking practices could prevent illness and outbreak.