Fish sharing as a risk factor for Opisthorchis viverrini infection:evidence from two villages in north-eastern Thailand

Background:Foodborne trematodiasis(FBT)is a significant global health problem,with the liver flukes Opisthorchis viverrini,O.felineus,and Clonorchis sinensis contributing to half of the global burden of FBT.North-eastern Thailand where O.viverrini is endemic and un-cooked fish dishes remain an integral part of the food culture has the highest reported incidence of opisthorchiasis,including associated cholangiocarcinoma.Both food sharing and eating practices are potentially important factors in FTB,suggesting an important role for the social ecology of disease transmission in these rural communities.Methods:Two rural Thai-Lao villages that were part of a 12-village project in Northeastern Thailand were selected for detailed investigation of O.viverrini infection risk associated with sharing of raw fish dishes among households.The project included screening individuals for infection and cholangiocarcinoma,a household questionnaire,and offering treatment options for positive individuals.Social network mapping was used to construct raw fish dish-sharing networks and create a proxy variable capturing variability in the degree of food sharing(DFS),measured as the number of different households with which each household shared fish dishes.Measures of associations between DFS,O.viverrini infection,the frequency of raw fish consumption,and the number of raw fish dishes consumed were generated using binary logistic regression,proportional odds ordinal logistic regression,and Poisson regression.Results:The results showed that the probability that a household has members infected with O.viverrini increased by~7%(P<0.01)for each additional household included in its network.Moreover,the frequency and number of types of raw fish dishes consumed increased significantly as the DFS increased.Of the two villages,that with the highest infection prevalence(48%versus 34.6%)had significantly higher social connectivity overall(P<0.001).Conclusions:Our findings suggest that the social ecology of human settlements may be key to understanding the transmission dynamics of some FBT.In the case of O.viverrini in Thai-Lao communities,for which food sharing is a traditional practice supporting social cohesion,food sharing network mapping should be incorporated into community-based interventions.These should encourage fish dish preparation methods that minimize infection risk by targeting households with high DFS values.

Thinking beyond Opisthorchis viverrini for risk of cholangiocarcinoma in the lower Mekong region:a systematic review and meta-analysis

Background:Cholangiocarcinoma(CCA)is a fatal bile duct cancer associated with infection by the liver fluke,Opisthorchis viverrini,in the lower Mekong region.Numerous public health interventions have focused on reducing exposure to O.viverrini,but incidence of CCA in the region remains high.While this may indicate the inefficacy of public health interventions due to complex social and cultural factors,it may further indicate other risk factors or interactions with the parasite are important in pathogenesis of CCA.This systematic review aims to provide a comprehensive analysis of described risk factors for CCA in addition to O.viverrini to guide future integrative interventions.Main body:We searched five international and seven Thai research databases to identify studies relevant to risk factors for CCA in the lower Mekong region.Selected studies were assessed for risk of bias and quality in terms of study design,population,CCA diagnostic methods,and statistical methods.The final 18 included studies reported numerous risk factors which were grouped into behaviors,socioeconomics,diet,genetics,gender,immune response,other infections,and treatment for O.viverrini.Seventeen risk factors were reported by two or more studies and were assessed with random effects models during meta-analysis.This meta-analysis indicates that the combination of alcohol and smoking(OR=11.1,95%CI:5.63-21.92,P<0.0001)is most significantly associated with increased risk for CCA and is an even greater risk factor than O.viverrini exposure.This analysis also suggests that family history of cancer,consumption of raw cyprinoid fish,consumption of high nitrate foods,and praziquantel treatment are associated with significantly increased risk.These risk factors may have complex relationships with the host,parasite,or pathogenesis of CCA,and many of these risk factors were found to interact with each other in one or more studies.Conclusions:Our findings suggest that a complex variety of risk factors in addition to O.viverrini infection should be addressed in future public health interventions to reduce CCA in affected regions.In particular,smoking and alcohol use,dietary patterns,and socioeconomic factors should be considered when developing intervention programs to reduce CCA.