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

Global prevalence of 4 neglected foodborne trematodes targeted for control by WHO: A scoping review to highlight the gaps

BACKGROUND

Foodborne trematodiases (FBTs) are a group of trematodes targeted for control as part of the World Health Organization (WHO) road map for neglected tropical diseases from 2021 to 2030. Disease mapping; surveillance; and capacity, awareness, and advocacy building are critical to reach the 2030 targets. This review aims to synthesise available data on FBT prevalence, risk factors, prevention, testing, and treatment.

METHODS

We searched the scientific literature and extracted prevalence data as well as qualitative data on the geographical and sociocultural risk factors associated with infection, preventive/protective factors, and methods and challenges of diagnostics and treatment. We also extracted WHO Global Health Observatory data representing the countries that reported FBTs during 2010 to 2019.

RESULTS

One hundred and fifteen studies reporting data on any of the 4 FBTs of focus (Fasciola spp., Paragonimus spp., Clonorchis sp., and Opisthorchis spp.) were included in the final selection. Opisthorchiasis was the most commonly reported and researched FBT, with recorded study prevalence ranging from 0.66% to 88.7% in Asia, and this was the highest FBT prevalence overall. The highest recorded study prevalence for clonorchiasis was 59.6%, reported in Asia. Fascioliasis was reported in all regions, with the highest prevalence of 24.77% reported in the Americas. The least data was available on paragonimiasis, with the highest reported study prevalence of 14.9% in Africa. WHO Global Health Observatory data indicated 93/224 (42%) countries reported at least 1 FBT and 26 countries are likely co-endemic to 2 or more FBTs. However, only 3 countries had conducted prevalence estimates for multiple FBTs in the published literature between 2010 to 2020. Despite differing epidemiology, there were overlapping risk factors for all FBTs in all geographical areas, including proximity to rural and agricultural environments; consumption of raw contaminated food; and limited water, hygiene, and sanitation. Mass drug administration and increased awareness and health education were commonly reported preventive factors for all FBTs. FBTs were primarily diagnosed using faecal parasitological testing. Triclabendazole was the most reported treatment for fascioliasis, while praziquantel was the primary treatment for paragonimiasis, clonorchiasis, and opisthorchiasis. Low sensitivity of diagnostic tests as well as reinfection due to continued high-risk food consumption habits were common factors.

CONCLUSION

This review presents an up-to-date synthesis on the quantitative and qualitative evidence available for the 4 FBTs. The data show a large gap between what is being estimated and what is being reported. Although progress has been made with control programmes in several endemic areas, sustained effort is needed to improve surveillance data on FBTs and identify endemic and high-risk areas for environmental exposures, through a One Health approach, to achieve the 2030 goals of FBT prevention.

Prevalence and Associated Risk Factors of Intestinal Parasitic Infections: A Population-Based Study in Phra Lap Sub-District, Mueang Khon Kaen District, Khon Kaen Province, Northeastern Thailand

Intestinal parasitic infections are still a crucial problem among communities in Northeast Thailand. Misuse of antiparasitic drugs and unhealthy food behaviors are known. This study aimed to explore the prevalence, behavioral health factors, and motivation for self-treatment of anti-parasitic drugs in this area. A community-based cross-sectional study was conducted in Phra Lap sub-district, Mu Khon Kaen district, Khon Kaen province, Northeast Thailand, in 2016. A total of 419 participants were recruited to complete a self-administered questionnaire and stool examination. Binary logistic regression was used to assess the association between the risk factor and parasitic infection. Forty-two participants (10%; 95%CI 7.5-13.3) were positive for at least one parasite species. In this community, the most detected intestinal parasite was Opisthorchis viverrini (5.3%), followed by Strongyloides stercoralis (3.1%). A total of 67.5% of the participants had the experience of anti-parasitic drug treatment within previous 1 year, and "Often eat raw food" was the most common reason for the use of anti-parasitic drugs. On multivariate analysis, parasitic infections were significantly associated with male gender (ORadj. 2.42; 95%CI 1.00-5.85), age ≥ 60 years (ORadj. 7.55; 95%CI 1.60-35.76), and often consuming raw food of at least one type (ORadj. 2.37; 95%CI 1.03-5.44). Given these findings, correction of the dietary habit of eating raw fish/meat, which is the most important measure, and limitation of the use of anthelmintic treatment for individuals with stools positive for ova as well as emphasis on sanitary toilets will be implemented for the prevention and control of parasitic infection in endemic communities.

Prevalence and Risk Factors of Opisthorchis viverrini Infection in Sakon Nakhon Province, Thailand

Opisthorchiasis is a parasitic infection caused by the liver fluke Opisthorchis viverrini. This parasite is widely distributed and well documented in Thailand, Lao PDR, Southern Vietnam, Cambodia, and Myanmar. However, its prevalence is a major problem in these countries. Thus, the aim of this study was to determine the prevalence and risk factors of O. viverrini infection from 2017 to 2020 in Sakon Nakhon province, Thailand. Questionnaires were used to interview 320 participants (160 cases and 160 controls) in a random selection of 18 districts across Sakon Nakhon province. Univariate logistic regression was used to identify the factors associated with O. viverrini infection. The overall prevalence levels of O. viverrini infection in Sakon Nakhon province for 2018, 2019, and 2020 were 3.60%, 5.21%, and 7.01%, respectively. Raw fish consumption was a positive risk factor for its infection in endemic areas. Factors associated with O. viverrini infection were the habit of consuming unsafely prepared fish (OR = 6.33, 95%CI = 0.32–0.59), the medical history of O. viverrini examination (OR = 8.93, 95%CI = 5.15–15.47), a history of O. viverrini infection (OR = 3.64, 95%CI = 1.17–1.44), and a history of taking praziquantel (OR = 3.64, 95%CI = 1.17–1.44). These results identified gaps in the epidemiological knowledge of O. viverrini in this region that need addressing to identify and develop innovative methods for prevention, control, and support efforts to permanently overcome O. viverrini infection in endemic regions.

Similarities and differences among the Opisthorchiidae liver flukes: insights from Opisthorchis felineus

The foodborne liver trematode Opisthorchis felineus (Rivolta, 1884) is a member of the triad of phylogenetically related epidemiologically important Opisthorchiidae trematodes, which also includes O. viverrini (Poirier, 1886) and Clonorchis sinensis (Loos, 1907). Despite similarity in the life cycle, Opisthorchiidae liver flukes also have marked differences. Two species (O. viverrini and C. sinensis) are recognized as Group 1A biological carcinogens, whereas O. felineus belongs to Group 3A. In this review, we focus on these questions: Are there actual differences in carcinogenicity among these 3 liver fluke species? Is there an explanation for these differences? We provide a recent update of our knowledge on the liver fluke O. felineus and highlight its differences from O. viverrini and C. sinensis. In particular, we concentrate on differences in the climate of endemic areas, characteristics of the life cycle, the range of intermediate hosts, genomic and transcriptomic features of the pathogens, and clinical symptoms and morbidity of the infections in humans. The discussion of these questions can stimulate new developments in comparative studies on the pathogenicity of liver flukes and should help to identify species-specific features of opisthorchiasis and clonorchiasis pathogenesis.

Prevalence of Opisthorchis viverrini and Its Associated Risk Factors in the Phon Sawan District of Nakhon Phanom Province, Thailand

Background:

Opisthorchis viverrini is one of the endemic helminths in Thailand. Nonetheless, O. viverrini still exist and raise concerns regarding public health. This study aimed to evaluate the current prevalence of O. viverrini infections and underlying risk factors among rural communities in Northeast Thailand.

Methods:

A cross-sectional study was conducted between Sep and Dec 2019 in Phon Sawan district in Nakhon Phanom Province, Thailand. The participants were selected using a voluntary sampling method after the proportional allocation of the total sample size. Demographic data were collected using a standardized questionnaire. One stool sample was collected from each participant and the presence of O. viverrini and other intestinal parasite infections were determined using the modified Kato-Katz technique.

Results:

Overall, 250 participants aged 21 yr or older were enrolled. Overall, the prevalence of O. viverrini and Strongyloides stercoralis was 24% (95% confidence interval [CI]: 18.8–29.8) and 1.2% (95% CI: 0.2–3.5), respectively. Of the positive O. viverrini cases, the parasite rate significantly differed between gender, age group and in those who had a history of eating raw fish and taking the anti-helminthic drug (all P<0.05). Nevertheless, multivariate regression analysis among O. viverrini cases revealed that only being male (adjusted odds ratio [aOR] 1.9 [95% CI: 1.1 – 3.6], P = 0.033) and aged ≥61 yr (aOR 6.7 [95% CI: 1.4 – 32.5], P=0.018) were positively associated with a higher risk of O. viverrini infection.

Conclusion:

Opisthorchiasis and strongyloidiasis are still endemic in this area and there is a need for projects to eliminate these parasites.

Reduction of Reinfection Rates with Opisthorchis viverrini through a Three-Year Management Program in Endemic Areas of Northeastern Thailand

To clarify the reinfection profile associated with risk factors of opisthorchiasis, we conducted an epidemiological study on the chemotherapeutic effects on reinfection with O. viverrini in the endemic areas of Northeastern Thailand for 3 years. A total of 3,674 fecal samples were collected from participants in villages of 5 provinces. They were examined microscopically using a modified technique of formalin ethyl-acetate concentration. Egg-positive residents were reexamined year (2018) by year (2019) after treatment with a single dose (40 mg/kg) of praziquantel. Health education was provided to the participants yearly. The egg-positive rate of O. viverrini was 14.3%, and was highest (22.2%) in the 20–30 year-old group in 2017. The egg positive rate was 15.3% in dogs and 11.4% cats. Human reinfection rate was 15.5% and 6.3% in next 2 years, and was highest (23.2%) among the fishermen. Relative risk factors of reinfection were significantly higher for males, over 40-year-old age, or working as fishermen or farmers, and eating uncooked fish within the preceding year. A significant difference resulting from a health education program was observed in the third year. Therefore, health education and sustainable surveillance for opisthorchiasis should be maintained to decrease the risk of reinfection.

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 hepato-biliary 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% CI: 0.74–2.21), and more than three times was 1.86 (95% CI: 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. viverrini and increases the risk of CCA.

Electronic supplementary material

The online version of this article (10.1186/s40249-019-0529-5) contains supplementary material, which is available to authorized users.

Risk factors for Opisthorchis viverrini infection in Nakhon Phanom, Thailand, where the infection is highly endemic

Background

Opisthorchiasis caused by Opisthorchis viverrini is a serious health issue in the Mekong basin region, resulting in a high prevalence of cholangiocarcinoma. Nakhon Phanom province had the highest prevalence of O. viverrini infection in Thailand at 60% of the surveyed population in 2009, despite the attempted control of opisthorchiasis for >50 years. Knowing risk factors for O. viverrini infection in Nakhon Phanom may lead to improved control and prevention of opisthorchiasis.

Objectives

To determine risk factors for O. viverrini infection in Nakhon Phanom.

Methods

We conducted a cross-sectional survey in Nakhon Phanom province from February to March 2014. The community was selected using a stratified random sampling method, and then, participants were selected by systematic random sampling. Individuals ≥15 years old were included. Knowledge of O. viverrini infection, and attitudes and practice to avoid it were assessed using a questionnaire. O. viverrini infection was determined by stool examination with a formalin–ether concentration method. Factors associated with the infection were determined using multivariate logistic regression analysis.

Results

Of the 134 participants, 75 (56%) were infected with O. viverrini. In the multivariate logistic regression analysis, 3 independent factors were associated with O. viverrini infection: age ≥ 55 years, odds ratio (OR) adjusted 6.36 (95% confidence interval (CI) 1.28–31.66); consumption of chopped raw-fish salad (koi pla), OR adjusted 28.74 (95% CI 3.59–230.24); and perceived susceptibility, OR adjusted 0.15 (95% CI 0.03–0.74).

Conclusions

Age ≥ 55 years, consuming koi pla, and perceived susceptibility were independently associated with O. viverrini infection in Nakhon Phanom.

Detection of Risk Groups for Carcinogenic Liver Fluke Infection by Verbal Screening Questionnaire Using a Mobile Application

The carcinogenic liver fluke, Opisthorchis viverrini, is a serious health problem in Southeast Asia where infection is associated with cholangiocarcinoma, a major cause of death in Thailand. This cross-sectional study aimed to screen for O. viverrini infection among a Thai rural population of 560 individuals from Nakhon Ratchasima, Khonkaen, and Chaiyaphum provinces with a verbal screening test with a mobile application (OvApp). Faecal samples were also processed with a mini-parasep sf parasite faecal concentrator. The infection rate of O. viverrini was found to be 2.86%. The majority of infections were detected in males aged 41–50, with primary school being their highest education level, and who were engaged in agricultural occupations. In screening for O. viverrini infection, the OvApp had a high sensitivity (87.5%), specificity (94.6%), negative predictive value (98.9%), and accuracy (98.6%). The positive predictive value was 70.0% for the OvApp. The observed agreement was substantial for this application (k-value = 0.64) indicated that it is a potentially useful tool for decreasing the cost of large-scale O. viverrini screening.

Epidemiology of Opisthorchis viverrini Infection

Opisthorchiasis in the Lower Mekong Subregion is a parasitic disease caused by the liver fluke Opisthorchis viverrini. This parasite has a well-documented distribution in Thailand, Lao PDR, Cambodia, Myanmar and Southern Vietnam. In this chapter, we describe the current knowledge of the epidemiology of O. viverrini infection, highlighting advances in control efforts made in the last four decades in Thailand and identifying ongoing gaps in our epidemiological knowledge which need to be filled to support efforts to permanently overcome the heavy morbidity and mortality burden caused by these parasites within their endemic regions.

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% C = 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 and Factors Associated with Opisthorchis viverrini Infection in Khammouane Province, Lao PDR

Opisthorchis viverrini (OV) liver flukes are common parasites found in central and southern Laos and constitute a major public health problem in the country. Laos people continue to have the habit of extensively consuming raw or half-cooked fish which are intermediate hosts. This study aimed to study the prevalence and factors associated with OV infection in the population of Thakek district, Khammouane Province. This cross-sectional analytic study covered 237 subjects who filled out structured questionnaires. Fecal examination for OV infection was performed by Kato's thick smear method. Data analysis was carried out using STATA Version 10.0. Multiple logistic regression was applied. The results showed that the infection rate of OV was 54.8 %. Factors associated with OV infections were gender, a habit of defecation in fields and raw fish (goi bplaa dip) consumption. Opisthorchiasis and associated cholangiocarcinoma development thus appear to remain as important concerns in Laos.

Detection of the Carcinogenic Liver Fluke Opisthorchis viverrini Using a Mini Parasep SF Faecal Parasite Concentrator

The Mini Parasep SF fecal parasite concentrator (MPSFC) is a new modification of the closed concentration system, which can easily be adopted in any routine clinical pathology laboratory. Here we describe our experience with the system in diagnosing Opisthorchis viverrini. A total of 199 fecal samples was submitted for routine examination in the clinical pathology laboratory of Suranaree University of Technology hospital, Nakhon Ratchasima province, Thailand, during August to October 2015. Out of all samples examined, 10 (5.03%) were positive with intestinal parasites including O. viverrini (2.01%), followed by Strongyloided stercoralis (1.51%), Hookworm (0.5%), Taenia spp. (0.5%), and Entamoeba coli (0.5%). Regarding the distribution of intestinal parasites in relation to the methods used, and found that 4 samples (2.01%) were positive using the direct wet smear method while 10 (5.03%) were positive with the Mini Parasep SF method; the difference was statistically significant (X2-test = 116.506, p-value =0.001). Mean time for processing using the Parasep system was 6.03 min/ sample, the conventional direct wet smear method at 0.3 min/sample. Cost per test, conventional direct wet smear method costing less than the Parasep method at USD 0.74/sample versus USD 1.47/sample. This first report of O. viverrini detection using MPSFC indicates that Parasep concentration test is useful in the routine laboratory, increasing the yield of parasites as compared to direct microscopy, but with greater processing time and cost. Further comparisons between the Parasep concentration test and common methods for O. viverrini detection are required, particularly concerning use in epidemiological surveys.

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 and north regions which have the highest incidences of chonalgiocarcinoma (CCA). O. viverrini causes the disease opithorchiasis, and its has been classified as a group 1 biological carcinogen. Humans, dogs, and cats become infected with O. viverrini by ingesting raw or undercooked fish containing infective metacercariae. The first human cases of O. viverrini infection were reported in Thailand 100 years ago, and it's still a problem at the community 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 highlights the current status of O. viverrini infection in communities of Thailand through active surveillance for the five years period from 2010 and 2015. A total of 17 community-based surveys were conducted, most in the northeast region. Some 7 surveys demonstrated a high prevalence over 20%, and the highest was 45.7%. Most commonly infection was found in age group of 35 years and older, males, and agricultural workers. Although, the national prevalence may be decreasing but the results show that the O. viverrini infection is still high in communities of the northeast region. Therefore, the focus in populations living in northeast Thailand should be screening of infection and changing their eating behavior.

Opisthorchis viverrini infections and associated risk factors in a lowland area of Binh Dinh Province, Central Vietnam

Opisthorchiasis caused by Opisthorchis viverrini is a major public health problem in the Mekong Basin in South East Asia. It is associated with cholangiocarcinoma, a fatal cancer of the bile duct, which is very common in some areas of Thailand and Lao PDR. Although there is evidence of opisthorchiasis in the central and Southern provinces of Vietnam, data are scarce and Vietnam is often not considered an opisthorchiasis endemic area in the international literature. We conducted a cross-sectional survey in June 2015 in a lowland rural area of Binh Dinh Province in Central Vietnam to investigate the apparent prevalence of O. viverrini infection in the population and the associated risk factors. A total of 254 stool samples were collected and examined by the Kato Katz method. Consenting people shedding Opisthorchis-like eggs with their stools were treated with praziquantel and MgSO4 and adult worms were collected from stools for morphological and molecular identifications. Risk factors were studied with a structured questionnaire and the association with infection was evaluated by univariate and multivariate Firth's logistic regression analysis. The apparent prevalence in the investigated population determined by stool examination was 11.4% (CI: 8-16%). Infection with O. viverrini was confirmed in all 11 individuals consenting to receive praziquantel treatment and subsequent worm recovery from stools. The mean number of worms recovered after treatment/purgation was 14.5 (range 2-44). Male gender and the consumption of dishes prepared from raw small wild-caught freshwater fish (Carassius auratus) were found to be significant risk factors associated with opisthorchiasis in the area. These findings confirm the presence of O. viverrini infection in Central Vietnam related to the consumption of raw fish dishes. Awareness campaigns and control programs should be implemented in the region to combat this potentially fatal fluke infection.