A follow-up study of Opisthorchis viverrini infection after the implementation of control program in a rural community, central Thailand

BACKGROUND: Opisthorchis viverrini infection is still one of the public health problems in Thailand. Our recent cohort study conducted in a rural community in central Thailand showed that the incidence rate of O. viverrini infection in 2002–2004 was 21.6/100 person-years. Conventional control activities including case diagnosis and treatment, hygienic defecation promotion and health education focusing on avoiding raw fish consumption was implemented. This study aimed to re-assess the status of infection after implementation of intervention programs, using both quantitative and qualitative methods in 2007–2009. METHODS: A prospective cohort study was conducted to evaluate the incidence and risk factors of O. viverrini infection. Stool examination methods including wet preparation, Kato and formalin-ethyl acetate concentration technique were performed for the detection of O. viverrini eggs. A standardized questionnaire was used to assess risk behavior. In addition, qualitative information was collected from both O. viverrini negative and positive villagers using focus group discussions. RESULTS: The incidence of O. viverrini infection was 21.4/100 person-years. Consumption of chopped raw fish salad, Koi pla and age 60 years and older were independently associated with O. viverrini infection, similar to our previous study. Findings from the qualitative study, indicated that inadequate knowledge, misbeliefs, and social and cultural mores were important factors leading to the maintenance of risk behaviors. Moreover, unhygienic defecation and insufficient diagnosis and treatment were found to facilitate O. viverrini transmission. CONCLUSION: Although the conventional control program had been used in the study population, the incidence of O. viverrini infection remained the same. Precise and regular health education and promotion targeting the main risk factor, Koi pla consumption, improving diagnosis and treatment, and promoting hygienic defecation should be used in the prevention and control program.