Opisthorchis felineus infection, risks, and morbidity in rural Western Siberia, Russian Federation

Author summary Opisthorchis felineusis a trematode (liver fluke) that infects the hepatobiliary systems of humans in endemic regions. The infection may lead to severe liver and bile duct diseases, making it a public health issue in endemic communities like Western Siberia. Yet, little information is available from this region about its epidemiology. We aimed to assess the current prevalence ofO.felineusinfection along with associated risk factors and morbidity in one district in rural Western Siberia. We conducted a cross-sectional community-based study in the Shegarskiy district, Tomsk Oblast, Russian Federation. All household members (>= 7 years) present on the survey day were enrolled (n = 600). Two stool samples per person were examined for helminth eggs. We interviewed study participants to determine risk factors using a questionnaire. An abdominal ultrasonography examination was performed to assess liver and bile duct pathology. In total, 488 persons completed assessments. We found a highO.felineusinfection prevalence of 60.2%. Women and older study participants had a higher risk of infection. The consumption of river fish, particularly stock, smoked, frozen and raw fish; and fishing activities increased the risk of infection. Study participants with a higher socio-economic status had a lower risk of infection. The ultrasonography showed that participants with infection had an increased risk of gallbladder stones and bile duct pathologies. Our study provides valuable information aboutOpisthorchisinfection prevalence, its risk factors and morbidity in rural Siberia. The results will be useful for developing a multidisciplinary, community-based control program againstOpisthorchisinfection in endemic regions.Background The liver fluke,Opisthorchis felineus, is widely distributed throughout Europe and large parts of the Russian Federation. In Western Siberia, information about opisthorchiasis is lacking although infection may lead to severe liver and bile duct diseases. We aimed to assess the current prevalence ofO.felineusinfection along with associated risk factors and morbidity in rural Western Siberia. Methods We conducted a community-based, cross-sectional study in the rural Shegarskiy district, Tomsk Oblast, Russian Federation. All household members (>= 7 years) present on the survey day were enrolled (n = 600). Two stool samples per person were examined for helminth eggs, using PARASEP (DiaSys Ltd, UK). The number of eggs per gram (EPG) of feces was recorded. Each study participant was interviewed to determine risk factors, using a pre-tested questionnaire. An abdominal ultrasonography examination of liver and bile ducts was performed with a mobile, high resolution ultrasound device. In total, 488 persons completed assessments (two stool samples, completed questionnaires); of those, 436 individuals had an US examination. Results We observed a prevalence ofO.felineusinfection of 60.2%. Significant risk factors for infection were the consumption of river fish (odds ratio [OR] 2.4, 95% CI 1.52-3.95, p<0.001), particularly stock fish (OR from multivariable analysis [mOR] 3.2, 95% CI 2.63-3.80, p<0.001), smoked fish (mOR 1.5, 95% CI 1.24-1.72, p<0.001), frozen fish (mOR 1.6, 95% CI 1.29-2.02, p<0.001), and raw fish (mOR 1.4, 95% CI 1.05-1.84, p = 0.022); and fishing activities (mOR 1.2, 95% CI 1.03-1.43, p = 0.019). Women had a higher risk of infection than men. Infection was associated positively with age and negatively with socio-economic status. The respondents' general awareness of opisthorchiasis was quite high (93.2%), but their knowledge about infection transmission and prevention was insufficient. Children aged 7-18 years old had a lower level of awareness compared to adults. The abdominal ultrasonography results demonstrated a strong association betweenO.felineusinfection and gallbladder stones (mOR 2.8, 95% CI 1.33-6.04, p = 0.007) and periductal fibrosis of intrahepatic bile ducts (mOR 1.9, 95% CI 1.08-3.46, p = 0.026). Conclusion O.felineusinfection is highly prevalent in rural regions of Western Siberia, and associated with severe hepatobiliary pathology. Identified risk factors will be used to develop a comprehensive targetedO.felineusinfection control program.