Abstract
BACKGROUND: Opisthorchis viverrini infection is highly prevalent in northeast Thailand. This liver fluke is classified as a carcinogen due to its causal links with cholangiocarcinoma (CCA) development. Although treatment with praziquantel (PZQ) effectively cures O. viverrini infection, the prevalence remains high due to the traditional consumption of raw fish. Therefore, re-infection is common in the endemic community, leading to severe hepato-biliary morbidities including the fatal CCA. In this study, we evaluate the association between the frequency of previous PZQ treatment and current O. viverrini infections among Thai adults living in the endemic area of northeast Thailand. METHODS: This study includes all participants who were screened for O. viverrini infection in the Cholangiocarcinoma Screening and Care Program (CASCAP), northeast Thailand. History of PZQ treatment was recorded using a health questionnaire. O. viverrini infections were diagnosed using urine antigen detection. Associations between PZQ and O. viverrini were determined by adjusted odds ratio (aOR) and 95% confidence interval (CI) using multiple logistic regression. RESULTS: Among participants, 27.7% had previously been treated once with PZQ, 8.2% twice, 2.8% three times, and 3.5% more than three times. Current O. viverrini prevalence was 17% (n = 524). Compared with participants who never used PZQ, the aOR for infection among those who used the drug once was 1.09 (95% CI: 0.88-1.37), twice was 1.19 (95% CI: 0.85-1.68), three times was 1.28 (95% CI: 0.74-2.21), and more than three times was 1.86 (95% CI: 1.18-2.93; P = 0.007). CONCLUSIONS: The population with a frequent history of PZQ use and still continued raw fish consumption showed high levels of repeated reinfection with O. viverrini. They were infected, treated and re-infected repeatedly. These findings suggest that certain participants continue raw fish consumption even after previous infection. This is a particular problem in highly endemic areas for O. viverrini and increases the risk of CCA.