Prevalence of Opisthorchis viverrini Infection in Nakhon Ratchasima Province,Northeast Thailand

Background: Opisthorchis viverrini infection is a serious public-health problem in Southeast Asia especiallyin Lao PDR and Thailand. It is associated with a number of hepatobiliary diseases and the evidence stronglyindicates that liver fluke infection is the major etiology of cholangiocarcinoma. Objectives: This study aimed todetermine actual levels of Opisthorchis viverrini infection in Nakhon Ratchasima province, Northeast Thailand.Methods: A cross-sectional survey was conducted during a one year period from October 2010 to September2011. O. viverrini infection was determined using a modified Kato’s thick smear technique and socio-demographicdata were collected using predesigned semi-structured questionnaires. Results: A total of 1,168 stool sampleswere obtained from 516 males and 652 females, aged 5-90 years. Stool examination showed that 2.48% wereinfected with O. viverrini. Males were slightly more likely to be infected than females, but the different was notstatistically significant. O. viverrini infection was most frequent in the 51-60 year age group and was found tobe positively associated with education and occupation. Positive results were evident in 16 of 32 districts, thehighest prevalence being found in Non Daeng with 16.7%, followed by Pra Thai with 11.1%, Kaeng SanamNang with 8.33%, and Lam Ta Men Chai (8.33%) districts. Conclusion: This study indicates that O viverrini isstill a problem in some areas of Nakhon Ratchasima, the patients in this study bing suitable for the purpose ofmonitoring projects.     

MTHFR Polymorphisms and Opisthorchis viverrini Infection: a Relationship with Increased Susceptibility to Cholangiocarcinoma in Thailand

Opisthorchis viverrini (OV) infection is the major risk factor for cholangiocarcinoma (CCA).Methylenetetrahydrofolate reductase (MTHFR) is an important enzyme in folate metabolism. Change in MTHFRactivity may influence both DNA methylation and synthesis, crucial steps in carcinogenesis. This study aimed toinvestigate the association between MTHFR polymorphisms and OV infection with CCA risk in a high-incidencearea of Thailand. A nested case-control study within cohort study was carried out: 219 subjects with primaryCCA were matched with two non-cancer controls from the same cohort on sex, age at recruitment and presence/absence of OV eggs in stool. At the time of recruitment information on consumption of foodstuffs potentiallycontaminated by OV was obtained by questionnaire. MTHFR polymorphisms were analyzed using PCR withhigh resolution melting analysis. Associations between variables and the risk of CCA were assessed usingconditional logistic regression. Risk of CCA was related to consumption of a dish of raw freshwater fish (Koi-Pla) with clear dose-response effects, and there were joint effects on CCA risk between MTHFR polymorphismsand consumption of dishes containing raw- and/or semi-raw freshwater fish. This study provides evidence tosupport a relationship of increased susceptibility to CCA in individuals with MTHFR variants, especially forthose individuals who have OV infection or consume semi-raw freshwater fish (acting either as a source of OVor of pre-formed nitrosamine). Folate may play an important role in OV-related cholangiocarcinogenesis byupsetting the balance between DNA methylation and synthesis in the folate pathway.     

Opisthorchis viverrini Infection Among People in the Border Areas of Three Provinces,Northeast of Thailand

Opisthorchis viverrini is still a serious problem in Northeastern and Northern Thailand. Active surveillance is required to determine updated data for further prevention and control planning. Therefore, this study aimed to examine the prevalence and risk factors for O. viverrini in three provinces, Northeastern Thailand. A cross-sectional survey was conducted during October 2015 to March 2016 at Kaeng Sanam Nang district of Nakhon Ratchasima province, Waeng Noi district of Khon Kaen province, and Khon Sawan district of Chaiyaphum province, Thailand. Stool samples were examined by using a modified Kato-Katz Thick smear technique. From a total of 978 participants screened, O. viverrini infection was found in 1.74%, the majority opf positive cases being male (6.62%), age group 51-60 years old (4.21%), educated at primary school (8.43%), occupied with agriculture (9.62%),having an income <4,000 baht per month (4.82%), and living in Khon Sawan district (8.43%). Participants had a high knowledge level (42.43%), good attitude level (34.76%), and fair level (38.04%). The present study indicates the O. viverrini infection rate is low, but elderly males with primary school education involved in agriculture are still frequently effected particularly in Khon Sawan district. Therefore, this risk g roup requires behavior modification and continued monitoring.     

Risk factors for Opisthorchis viverrini Infection in Nong Khai Province,Thailand

Background: Opisthorchis viverrini (OV) infection is the main risk factor for cholangiocarcinoma and is oftenfound in Northeastern Thailand. The prevalence of OV infection and the incidence of cholangiocarcinoma aremajor public health problems in this region. Objectives: The objectives of this study were to identify factorsassociated with OV infection among people in Nong Khai Province in order to develop a prevention programmein the community. Materials and Methods: The data were collected in July 2013. Stool specimens were examinedfor intestinal parasites within hours after collection using a normal saline wet preparation and the modified Kato-Katz technique. A case-control study was conducted to collect information about demographic data, the habit ofeating unsafely prepared fish, the safe disposal of waste food, and the practice of defaecating in fields. Structuredquestionnaires were used to interview 351 participants (117 cases and 234 controls) in a random selection of 30villages across Nong Khai Province. Multiple logistic regression was used to identify risk factors for OV infection.Results: In the multivariate analysis, the results showed that the factors which had a statistically significantassociation with OV infection were the habit of consuming unsafely prepared fish (ORadj=5.17, 95%CI=2.49-10.74), the similar habit of family members (ORadj=3.25, 95%CI=1.63-6.49) , a history of O. viverrini infection(ORadj=5.64, 95%CI=2.10-15.18), a history of taking praziquantel (ORadj=5.66, 95%CI=3.11-10.29), and theunsafe disposal of waste food (ORadj=2.1, 95%CI=1.10-3.80). Conclusions: The findings of this study highlightthe features on which a community programme should focus in order to reduce the prevalence of opisthorchiasisand incidence of bile duct cancer.     

Review and Current Status of Opisthorchis viverrini Infection at the Community Level in Thailand

Opisthorchis viverrini is remains a public health problem in Thailand, particularly in the northeast andnorth regions which have the highest incidences of chonalgiocarcinoma (CCA). O. viverrini causes the diseaseopithorchiasis, and its has been classified as a group 1 biological carcinogen. Humans, dogs, and cats becomeinfected with O. viverrini by ingesting raw or undercooked fish containing infective metacercariae. The firsthuman cases of O. viverrini infection were reported in Thailand 100 years ago, and it’s still a problem at thecommunity level. Based on data for the year 2009, more than 6 million people were infected with O. viverrini.Associated medical care and loss of wages in Thailand costs about $120 million annually. This review highlightsthe current status of O. viverrini infection in communities of Thailand through active surveillance for the fiveyears period from 2010 and 2015. A total of 17 community-based surveys were conducted, most in the northeastregion. Some 7 surveys demonstrated a high prevalence over 20%, and the highest was 45.7%. Most commonlyinfection was found in age group of 35 years and older, males, and agricultural workers. Although, the nationalprevalence may be decreasing but the results show that the O. viverrini infection is still high in communities ofthe northeast region. Therefore, the focus in populations living in northeast Thailand should be screening ofinfection and changing their eating behavior.     

Re-Examination of Opisthorchis viverrini in Nakhon Ratchasima Province,Northeastern Thailand,Indicates Continued Needs for Health Intervention

Opisthorchis viverrini infection is associated with cholangiocarcinoma particularly in the cases of chronic or re-infection. This presents a serious health problem in northeastern and northern Thailand. A community base approach is required for surveillance. Therefore, in a pilot project, re-examination of O. viverrini infection was conducted in the 3 districts of Nakhon Ratchasima province, Thailand, during June and October 2015. A total of 355 participants from a 194,152 population, was selected through multi-stage sampling. O. viverrini infection was determined using modified Kato Katz thick smear technique. Participants were 229 males and 126 females, and aged ≥30 years old. Prevalence of O. viverrini infection was 2.25% (8/355 participants). O. viverrini infection was slightly higher in females (3.17%), and age group between 41-50 years (4.49%). Mueang Yang district had a highest of O. viverrini infection rate (2.82%), and followed by Bua Yai (2.48%), and Chum Phuang (1.84%), respectively. O. viverrini infection rate was increased from year 2012 to 2015 particularly in Bua Yai and Mueang Yang. These re-examinion results indicate that opisthorchiasis is still problem in community of Nakhon Ratchasima province, therefore, the provincial-wide scale is need required. Furthermore health education is need intervened in the infected group, and screening of cholangiocarcinoma is urgently concerned.     

Association between Praziquantel and Cholangiocarcinoma in Patients Infected with Opisthorchis viverrini: A Systematic Review and Meta-Analysis

Background: The liver fluke, Opisthorchis viverrini, and the associated incidence of subsequentcholangiocarcinoma (CCA) are still a public health problem in Thailand, and praziquantel (PZQ) remainsthe antihelminthic drug of choice for treatment. Evidence in hamsters shows that repeated infection and PZQtreatments could increase the risk of CCA. However, the existing evidence in humans is inconclusive regardingincreased risk of CCA with frequency of PZQ intake. Objectives: To investigate the relationship between numberof repeated PZQ treatments and CCA in patients with O viverrini infection. Materials and Methods: The reviewedstudies were searched in EMBASE, MEDLINE, ProQuest, PubMed and SCOPUS from inception to October,2012 using prespecified keywords. The risk of bias (ROB) of included studies was independently assessed by tworeviewers using a quality scale from the Newcastle-Ottawa Scale (NOS). Risk effect of PZQ was estimated as apooled odds ratio (OR) with its 95% confidence interval (95%CI) in the random-effects model using DerSimonianand Laird’s estimator. Results: Three studies involving 637 patients were included. Based on the random effectsmodel performed in two included studies of 237 patients, the association between PZQ treatments and CCA wasnot statistical significant with a pooled OR of 1.8 (95%CI; 0.81 to 4.16). Conclusions: The present systematicreview and meta-analysis provides inconclusive evidence of risk effect of PZQ on increasing the risk of CCA andsignificant methodological limitations. Further research is urgently needed to address the shortcomings foundin this review, especially the requirement for histological confirmation.     

The Carcinogenic Liver Fluke Opisthorchis viverrini among Rural Community People in Northeast Thailand: a Cross- Sectional Descriptive Study using Multistage Sampling Technique

Opisthorchis viverrini infection is a serious public health problem in Southeast Asia especially in the northeast and north of Thailand. Therefore, a cross-sectional survey using multistage sampling was conducted from the rural communities of Surin province, Thailand, during September 2013 to July 2014. O. viverrini infection was determined using Kato’s thick smear technique. Socio-demographic, information resources, and history data were collected using predesigned semi-structured questionnaires. A total of 510 participants completed interviews and had stools collected. Some 32 (6.47%) participants were infected with O. viverrini. The rate was slightly higehr in males (6.61%) than females (6.32%). High frequencies were found in the age groups 61-70 (19.4%) and 71-80 years (19.4%), those involved in agriculture (10.5%), and in primary school (10.3%). The distribution of high infection was found in Tha Tum (16.7%) and Sankha district (16.7%), followed by Samrong Thap (13.3%), Si Narong (13.33%), and Buachet district (13.33%). Chi-square testing indicated that age (61-70 and 71-80 year old), education (primary school) and occupation (agriculture), were significantly associated with O. viverrini infection (p-value<0.05). Of 72.6% participants who had past histories with stool examination, 17.0% of them had been infected with O. viverrini and 43.2% treated with praziquantel. This finding confirmed that O. viverrini is still a problem in Surin province, Thailand, and therefore, interventions are urgently required for mass treatment and health education implementation.     

Ultrasonography as a tool for monitoring the development and progression of cholangiocarcinoma in Opisthorchis viverrini/ dimethylnitrosamine-induced hamsters

Cholangiocarcinoma (CCA) is the most common cancer in northeastern Thailand. At present, effective diagnosis of CCA either in humans or animals is not available. Monitoring the development and progression of CCA in animal models is essential for research and development of new promising chemotherapeutics. Ultrasonography has been widely used for screening of bile duct obstruction in CCA patients. In this study, we preliminarily investigated the applicability of ultrasonography to monitor the development and progression of CCA in Syrian golden hamsters (n=8) induced by Opisthorchis viverrini (OV)/dimethylnitrosamine (DMN) administration. Ultrasonography and histopathological examination of hamsters was performed at week 0, 20, 24 and 28 of OV infection or at the start of water/Tween-80 administration to controls. The ultrasonographic images of liver parenchyma and gallbladders of OV/DMN-induced CCA hamsters showed sediments in gallbladder, thickening of gallbladder wall, and hypoechogenicity of liver parenchyma cells. The ultrasonographic images of liver tissues were found to correlate well with histopathological examination. Although ultrasonography does not directly detect the occurrence of CCA, it reflects the thickening of bile ducts and abnormality of liver tissues. It may be applied as a reliable tool for monitoring the development and progression of CCA in animal models in research and development of new promising chemotherapeutics for CCA.     

A Large Scale Study of the Epidemiology and Risk Factors for the Carcinogenic Liver Fluke Opisthorchis viverrini in Udon Thani Province,Thailand

Opisthorchis viverrini infection and cholangiocarcinoma are serious problems in South East Asia. This study aimed to find the prevalence of opisthorchiasis in various hosts in Udon Thani Province. Total fecal samples were collected from 14,766 participants. The epidemiological data collected and analysed included prevalence and intensity of infection. Odds ratios (OR) were calculated to determine the associations between cross sectional data and to predict possible risk factors. The prevalence of O. viverrini infection in Udon Thani Province averaged 15.3% (eggs per gram (epg.) = 48.9 and range; 12-1,320), with differences between villages (range; 3.8%-79.8%). An age-dependence for infection was observed to increase from ages 25 to 50 years and then decrease for older participants. A univariate analysis identified risk parameters including age (p = 0.040; OR = 3.9 (95% CI = 1.2-7.5)), education (p<0.0001; OR = 7.3 (95% CI = 1.8-21.6)) and eating habits (p = 0.032; OR = 1.6 (95% CI = 0.5-3.7)). Interestingly, most participants were not aware of treatments such as praziquantel (p< 0.0001; OR = 3.5 (95% CI = 1.4-11.6)), had no history of parasitic treatment (p = 0.486; OR = 1.5 (95% CI = 0.5-3.5)) and had eaten raw fish (p = 0.04; OR = 7.4 (95% CI = 1.5-18.6)). Liver fluke infection in dogs (18.1%, epg. = 44.7, range; 32-96) was significantly higher than in cats (11.0%, epg. = 117.8, range; 44-372) (p<0.05). A positive association between O. viverrini infection in dogs and their owners was found. In addition, cyprinid fish dominantly infected by metacercaria including Henicorhynchus siamensis (27.7%), Cyclocheilichthys repasson (21.9%), Hampala dispar (14.1%), and Barbonymus gonionotus (6.9%). This study provides basic information required for the development of future effective and sustainable strategies to reduces infection rates, mainly by providing health education and encouraging behavioural changes.     

Prevalence of OV Infection in Yasothon Province,Northeast Thailand

A liver fluke, Opisthorchis viverrrini (OV), is the major cause of the high incidence of cholangiocarcinoma in Thailand. The prevalence of OV infection remains high in various parts of the country, especially in Northeast Thailand and particularly in wetland rural areas where a large proportion of the community work in agricultureand continue the traditional practice of eating raw or uncooked cyprinoid fish products. The national control program seems to have had little impact in many of these areas, and it has been difficult to make precise assessments of the overall effectiveness of the program. This paper is the first report of prospective research project designed to monitor the impact of the national control program in rural communities located in a northeastern province and at high risk of OV infection. The participants in this initial survey were 1,569 villagers, aged 20-65 years, living in two subdistricts of Yasothon Province. Stool examinations showed that 38.68% were infected with OV. Males were slightly more likely to be infected than females, but the difference was not statistically significant. Infection was found to be positively associated with age in both males and females. The preliminary data indicate that the population selected for study is suitable for the purpose of the monitoring project.     

The Carcinogenic Liver Fluke Opisthorchis viverrini is a Reservoir for Species of Helicobacter

There has been a strong, positive correlation between opisthorchiasis-associated cholangiocarcinoma andinfection with Helicobacter. Here a rodent model of human infection with Opisthorchis viverrini was utilized tofurther investigate relationships of apparent co-infections with O. viverrini and H. pylori. A total of 150 hamsterswere assigned to five groups: i) Control hamsters not infected with O. viverrini; ii) O. viverrini-infected hamsters;iii) non-O. viverrini infected hamsters treated with antibiotics (ABx); iv) O. viverrini-infected hamsters treatedwith ABx; and v) O. viverrini-infected hamsters treated both with ABx and praziquantel (PZQ). Stomach,gallbladder, liver, colonic tissue, colorectal feces and O. viverrini worms were collected and the presence ofspecies of Helicobacter determined by PCR-based approaches. In addition, O. viverrini worms were cultured invitro with and without ABx for four weeks, after which the presence of Helicobacter spp. was determined. In situlocalization of H. pylori and Helicobacter-like species was performed using a combination of histochemistry andimmunohistochemistry. The prevalence of H. pylori infection in O. viverrini-infected hamsters was significantlyhigher than that of O. viverrini-uninfected hamsters (p≤0.001). Interestingly, O. viverrini-infected hamsters treatedwith ABx and PZQ (to remove the flukes) had a significantly lower frequency of H. pylori than either O. viverriniinfectedhamsters treated only with ABx or O. viverrini-infected hamsters, respectively (p≤0.001). QuantitativeRT-PCR strongly confirmed the correlation between intensity H. pylori infection and the presence of liver flukeinfection. In vitro, H. pylori could be detected in the O. viverrini worms cultured with ABx over four weeks. Insitu localization revealed H. pylori and other Helicobacter-like bacteria in worm gut. The findings indicate thatthe liver fluke O. viverrini in the biliary tree of the hamsters harbors H. pylori and Helicobacter-like bacteria.Accordingly, the association between O. viverrini and H. pylori may be an obligatory mutualism.     

Risk Factors for Cholangiocarcinoma in the Lower Part of Northeast Thailand: a Hospital-based Case-control Study

Background: Cholangiocarcinoma (CCA) is the most common cancer in Northeast Thailand. It is also acrucial health problem for Thai people. Various risk factors for CCA have been identified in the upper partof Northeast Thailand, but no similar studies of risk factors have been conducted in the lower parts of theregion. This study aimed to investigate factors associated with CCA in the resident population. Materials andMethods: A hospital-based case-control study was conducted during 2009-2012 with the recruitment of 123 CCAcases and 123 non-CCA patient controls, matched for sex, age and residential area. Information was collectedby interview with a structured questionnaire. Blood samples were collected for assays of anti-OV antibodies.Associations between various personal factors, dietary habits, family history, the presence of anti-OV antibodiesand CCA were analyzed using multiple conditional logistic regression. Results: Patients who consumed rawmeat (beef, pork) and alcoholic beverages ≥3 times per week had a higher risk of CCA than non-consumers(ORadj=4.33; 95%CI=1.14-16.35 and ORadj=2.13; 95%CI=1.00-4.55, respectively). Patients who had a familyhistory of cancer had a higher risk than those who did not (ORadj=4.34; 95%CI=1.80-10.43). Also, patients whohad anti-OV antibodies (AU>23.337) had a higher risk than those whose anti-OV antibodies were below thecut-off (AU≤23.34) (ORadj=3.09; 95%CI=1.04-9.16). Conclusions: As is the case in the upper part of NortheastThailand, OV infection is a crucial risk factor for CCA in people who live in lower part of the region. Similarly,a family history of cancer and the consumption of alcohol are risk factors for CCA.     

Ultrasound Screening for Opisthorchis viverrini-associated Cholangiocarcinomas: Experience in an Endemic Area

In Thailand, liver cancer is the most common malignancy in males and the third most common among females. Inthe Northeast region, cholangiocarcinoma (CHCA) is the prevalent type, with Opisthorchis viverrini (OV), an endemicliver fluke, being considered the cause. We evaluated the role of ultrasound (U/S) for cholangiocarcinoma screeningas part of a larger cohort to characterize the linkage between liver fluke infestation and CHCA in Khon Kaen(Northeast Thailand). Most people (77%) had normal U/S findings while only 0.5% had suspected CHCA; thus, U/S should be used primarily for those with the highest risk, presenting symptoms and/or being OV positive.     

Cholangiocarcinoma in Experimental Hamsters with Long-standing Opisthorchis viverrini Infection

Liver fluke infection of Opisthorchis viverrini (O. viverrini) is closely associated with several hepatobiliarydiseases including cholangiocarcinoma (CCA), but no reports have described these diseases in chronic andlong-standing experimental opisthorchiasis in hamsters more than 10 months of age. A longer period of infectioncould induce different pathological lesions. To prove the hypothesis, we therefore sequentially investigatedhistological changes of the hepatobiliary system in 4 groups of hamster: O. viverrini infection (OV group) for upto 20 months, O. viverrini infection combined with short-term DMN (OV+DMN group) until 7 months, longtermtreatment with DMN (DMN group) to 7 months and normal control group for up to 20 months. Pathologicalchanges in hamsters of the OV group gradually increased. Induction of CCA in this study was apparent with allthree protocols. Importantly, this is the first report of CCA-induction in hamsters solely with long-termopisthorchiasis for up to 20 months. Although the histopathology of CCA in the OV group showed some differencesin appearance from the OV+DMN and DMN groups, overall, O. viverrini itself can really induce CCA. Inaddition, this study confirms the previous studies both in vitro and in vivo on of effects of parasites and theirmetabolic products inducing cell proliferation, resulting in cholangiocarcinogenesis.