Prevalence, infection intensity and risk factors of Opisthorchis viverrini infection in rural area of Central Thailand

Abstract

Opisthorchis viverrini (OV) infection is a food-borne trematode infection through the consumption of uncooked cyprinoid fish containing infective stage, metacercariae. Adult flukes are living in hepato-biliary system. Infected cases could be unaware of the infection because of asymptomatic clinical presentation and chronic infection is strongly associated with cholangiocarcinoma, which IARC has declared OV to be carcinogenic to human. In Thailand, uncooked cyprinoid fish is popular in the North and Northeastern region as a traditional dish especially Koi pla (Chopped raw fish mixed with spicy herbal ingredients). The study was conducted in Phra-plerng sub district located in Sa Kaeo Province, Central Thailand in 2015 using cross-sectional design. The study areas are combined of Central and Northeastern descendants. Stool specimen was examined with three methods; direct smear, modified Kato-Katz and FECT aimed to measure prevalence and intensity of OV infection. Infection intensity was measured as EPG (eggs per gram) and risk behaviours were assessed by questionnaires. Zero-inflated model was used for zero-excess data from EPG. Study areas comprised of 5 villages with 1267 participants. Overall prevalence of OV infection was 9.4%. The prevalence was significantly higher in Village Moo 9 (P < 0.001) where most of villagers are Northeasterners. Male gender increased risk of acquiring infection (OR = 2.8, 95% CI: 1.1–7.5). Infection intensity showed overdispersion with mean EPG = 3.2 and SD = 28.1. Zero-inflated negative binomial model showed that male gender, increasing age and Koi pla consumption were associated with increasing EPG (P < 0.05). Modelling zero-excess and overdispersion for infection intensity could help shaping more robust analysis. Up-to-date information on risk factors are valuable for targeting intervention to high-risk population.