Influence of geographic, knowledge and behavioral factors on Opisthorchis viverrini infection in the Northeast of Thailand

Objective:To determine the influence of geographic,knowledge and behavioral factors on Opisthorchis(O.)viverrini infection in the Northeast of Thailand.Methods:This cross-sectional study was conducted by using four datasets of years 2016 and 2017.Generalized linear mixed model was employed to analyze association between geographic,knowledge and behavioral factors and O.viverrini infection.Results:Totally there were 1885 participants.The prevalence of O.viverrini infection was 10.03%.Geographic factors that showed statistically significant association with O.viverrini infection in the Northeast region were featured by at least a dam and reservoir(Adj.OR=4.21,95%CI:2.49-7.13,P<0.001),at least a weir(Adj.OR=1.74,95%CI:1.09-2.77,P=0.020),>50 dogs and cats per village(Adj.OR=3.40,95%CI:2.17-5.31,P<0.001),and rice fields covered>50%of its areas(Adj.OR=1.91,95%CI:1.04-4.01,P=0.036),as well as low to moderate levels of knowledge(Adj.OR=1.60,95%CI:1.32 to 1.94,P<0.001),consumed raw fish(Adj.OR=1.90,95%CI:1.02 to 3.52,P=0.040)and consumed processed raw fish(Adj.OR=3.03,95%CI:2.20 to 4.18,P<0.001).Other significant covariates were gender and age of the respondents.Conclusions:O.viverrini infection still remains a public health problem of the Northeast of Thailand.Geographic and demographic factors,knowledge,and consumption behaviors of raw fish products are significantly associated with O.viverrini infection.

Examining ecosystem(dis-)services on liver fluke infection in rural Northeast Thailand

Background The direct reliance of humans on and their interactions with freshwater ecosystems in the Lower Mekong Basin have given rise to parasitic infections,which is particularly prevalent in Northeast Thailand where raw fish consumption is practiced.This study examined the interactions between environments,ecosystem(dis-)services,human raw fish consumption habits,and raw fish dish sharing on liver fluke infection risk.Method Water fecal contents and the first intermediate snail host were sampled between June and September of 2019.One hundred twenty questionnaires were surveyed in two villages of different environmental surroundings,one next to a river and the other located inland,in Northeast Thailand.Multivariate regression analyses using linear mixed effect models assessed the influence of social,behavioral and perceptual factors on raw fish consumption frequency,willingness to avoid consumption and liver fluke infection status.Social network analysis compared the degree of raw fish dish sharing between the villages and assessed the probable influence of connections to fish procurement locations and sharing activities on liver fluke infection risk.Results High abundance of the first intermediate snail host and presence of fecal contamination in water could endanger both villages to ecosystem disservices of parasitic transmission.The river-side village relied more on provisioning ecosystem services than the inland village(29.7%vs.16.1%of villages)to consume raw fish as their main source of protein.Males in both villages(64.5 and 40.4 days/year for the respective villages)are also likely to consume koi pla and pla som,higher risk fish dishes,more frequently than females(4.1 and 4.3 days/year for the respective villages).The consumption habits of both villages were driven mostly by deriving cultural ecosystem services.Participation in raw fish dish sharing activities significantly reduced the odds of an individual being willing to avoid the consumption(Odds ratio=0.19).Network analysis suggested that river-side villagers had a more direct raw fish dish sharing interaction and they procured fish from multiple locations;these characteristics might potentially account for more liver fluke infected households in the village.Conclusion Villagers’raw fish consumption is driven by deriving cultural ecosystem services,and the geographic settings of the villages potentially affect villagers’fish procurement locations and infection risk.The findings underscore the linkages between villagers and their surrounding ecosystem environments as pertinent determinants for foodborne parasitic disease risk.

Accuracy of a new rapid diagnostic test for urinary antigen detection and assessment of drug treatment in opisthorchiasis

Background Screening for opisthorchiasis,a parasitic worm infection affecting many millions of people in Southeast Asia,has traditionally relied on faecal egg examination such as the formalin-ethyl acetate concentration technique(FECT)and Kato-Katz method.Although the urinary enzyme-linked immunosorbent assay(ELISA)has been used more recently,we developed a urinary antigen-based rapid diagnostic test(RDT)to simplify diagnosis and as a point-of-care testing(POCT)and field applications for surveillance and control of opisthorchiasis.Methods A urinaryOpisthorchis viverrini(OV)-RDT was developed using immunochromatographic methodology with a specific monoclonal antibody against OV.The diagnostic performance of the urinary OV-RDT was compared to that of quantitative faecal FECT and urinary antigen ELISA(n=493).Cross-reactivities of urinary OV-RDT with other helminthiases coexisted withO.viverrini were determined(n=96).A field trial in the application of urinary OV-RDT was compared with urinary antigen ELISA at baseline screening and assessment of drug treatment outcomes in opisthorchiasis(n=1629).The McNemar chi-square,Kruskal-Wallis and Cohen’s kappa coefficient(κ-value)tests were used for statistical analyses.Results Urinary OV-RDT had sensitivity of 94.2%and specificity of 93.2%,compared to faecal FECT.Urinary OV-RDT had high diagnostic agreement(Kappa=0.842-0.874,P<0.001)and quantitative correlation with urinary antigen ELISA(Kruskal-Wallis tests=316.2,P<0.0001)and faecal FECT(Kruskal-Wallis tests=362.3,P<0.0001).The positive rates by OV-RDT,ELISA and FECT were 48.9%,52.5%and 49.3%,respectively.Cross-reactions of urinary OV-RDT with other helminthiases were few(2%).Field trials of urinary OV-RDT yielded comparable prevalence ofO.viverrini between urinary OV-RDT(53.2%)and urinary antigen ELISA(54.0%).OV screening showed high diagnostic agreement(kappa>0.8,P<0.0001)between urinary OV-RDT and urinary antigen ELISA.The cure rates of opisthorchiasis at 1 month post-praziquantel treatment determined by urinary OV-RDT(86.6%)and urinary antigen ELISA(80.5%)were similar(P>0.05).Conclusions The urinary OV-RDT test has high potential as a new tool for screening and evaluating treatment outcomes in opisthorchiasis.The ease of sample collection and simplicity of urinary OV-RDT may facilitate mass screening,control and elimination of opisthorchiasis,thereby contributing to a reduction in the disease burden in Southeast Asia.

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.

Repeated praziquantel treatment and Opisthorchis viverrini infection:a population-based cross-sectional study in northeast Thailand

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 hepatobiliary 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%C/:0.74-2.21),and more than three times was 1.86(95%C/: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.viverrni and increases the risk of CCA.

Correction to:Repeated praziquantel treatment and Opisthorchis viverrini infection:a population-based crosssectional study in northeast Thailand

In the original publication of this article[1],there is an error in the section of‘Ethics approval and consent to participate’at the end of the article,the correct Ethics reference number should be HE551404 rather than HE591067.