Reservoir Animals and Their Roles in Transmission of Opisthorchis viverrini

Co-occurrence of leptospirosis and Opisthorchis viverrini infection in cats and their risk factors

Leptospirosis is a waterborne disease with a worldwide distribution. In Northeast Thailand, its prevalence overlaps with the endemicity of Opisthorchis viverrini, (OV). This study aimed to investigate the prevalence and risk factors of leptospirosis in cats and its association with opisthorchiasis in endemic area of Thailand. 115 cats were sampled for blood and feces. We tested Leptospira antibodies in blood using the Lepto-latex test. For fecal analysis, we applied the formalin-ether concentration technique (FECT) for OV and identified Leptospira spp. through PCR targeting the 16S rRNA and LipL32. Non-spatial analyses included Pearson's Chi-square, Fisher's exact test, and logistic regression, while spatial analyses involved Inverse Distance Weighted (IDW), spatial autocorrelation, and Geographically Weighted Logistic Regression (GWLR). Serological analysis revealed 15.65 % of cats positive for Leptospira spp., whereas 44.35 % of fecal samples positive for OV. PCR analysis identified 1 L. interrogans with the 16S rRNA, while the LipL32 identified 2 samples related to L. interrogans and 1 to L. borgpetersenii. The spatial autocorrelation indicated clustering of leptospirosis cases. Logistic regression revealed 2 significant risk factors; OV infection (OR 3.44, 95 % CI 1.10-10.73; p 0.03) and proximity to flooded areas (OR 3.47, 95 % CI 1.12-10.74; p 0.03). Furthermore, GWLR showed median coefficients of 0.59 (-1.62-5.15) for OV infection and 2.15 (1.30-6.47) for proximity to flooded areas. This study demonstrates a significant association between cat leptospirosis with OV infection and proximity to flooded areas. These highlight the importance of monitoring environmental and biological risk factors to mitigate leptospirosis in endemic regions.

Parasitic Helminth Infections and Intron Sequence Genotyping of Opisthorchis viverrini-like Eggs in Outdoor Domestic Cats and Dogs Across the Chi River Basin, Maha Sarakham Province, Thailand

This study investigates the prevalence of parasitic helminths in free-ranging domestic cats and dogs near the Chi River and natural reservoirs in Maha Sarakham Province, Thailand. Fecal samples from 39 cats and 148 dogs were analyzed using a modified formalin-ether concentration technique (FECT). The overall prevalence of helminth infections was 64.1% in cats and 51.4% in dogs. Common parasites were detected including soil-transmitted species like Ancylostoma sp. (hookworm), Toxocara spp., and Strongyloides sp., as well as foodborne helminths such as Taenia sp., Hymenolepis sp., Spirometra sp., and Opisthorchis sp. Multiple parasitic infections were commonly found in dogs (57.9%) and cats (46.2%). Our findings suggest that domestic cats and dogs act as important reservoirs for zoonotic helminths in the region. Notably, Opisthorchis viverrini-like eggs were found exclusively in cats, with a prevalence of 23.1%. The intron 5 of domain 1 of the taurocyamine kinase gene (TkD1Int5) was used for genotyping O. viverrini-like eggs. All O. viverrini-like egg samples with TkD1Int5 haplotypes (Ov116-Ov123) were uniquely found in cats. Genetic analysis revealed that TkD1Int5 haplotypes were similar to those previously reported for Opisthorchis viverrini in various species of cyprinid fish across opisthorchiasis-endemic regions in Thailand and Lao PDR. Three TkD1Int5 haplogroups (I-III) were classified, with O. viverrini-like eggs from cats distributed across all haplogroups. Notably, one haplotype (Ov118) was genetically distinct from the others and did not cluster into any haplogroup. These findings highlight the crucial role of cats as reservoir hosts and their potential contribution to the transmission of the zoonotic liver fluke O. viverrini, posing a notable public health concern.

One Health showcase from Asia: the Lawa model-a community-based approach to liver fluke control in Thailand

Liver fluke infection caused by Opisthorchis viverrini is a significant public health challenge in the Lower Mekong Basin, affecting over 10 million people and leading to cholangiocarcinoma, a fatal bile duct cancer. Traditional control efforts often fail due to complex socio-cultural and ecological factors. The Lawa model, implemented in the Lawa Lake region of Khon Kaen, Thailand, adopts a One Health framework to integrate human health interventions, environmental modifications, and animal reservoir management, addressing the transmission cycle comprehensively. This approach respects the cultural context of Isan communities and leverages evidence-based, community-driven strategies. Over 15 years, the model has achieved remarkable success, reducing human infection rates from 60 % to below 5 % and eliminating infections in intermediate hosts. Key lessons include the importance of systems thinking, transdisciplinary collaboration, and community engagement in achieving sustainable health outcomes, despite challenges like cultural dietary practices and environmental disruptions such as flooding.

Influence of knowledge, attitude and self-efficacy on Opisthorchis viverrini and cholangiocarcinoma prevention: A One Health approach in high-risk areas of Thailand

OBJECTIVE

Opisthorchis viverrini and cholangiocarcinoma have been recognised by the World Health Organisation as critical public health concerns, particularly in northeastern Thailand, where Opisthorchis viverrini is a significant cause of cholangiocarcinoma. This study examines the factors influencing Opisthorchis viverrini and cholangiocarcinoma prevention within the One Health framework in Kanthararom District, Sisaket Province, Thailand.

METHODS

A cross-sectional study was conducted among 327 residents aged 20 and above, utilising a structured questionnaire to assess knowledge, attitudes, perceived self-efficacy and prevention behaviours. Data were analysed using descriptive statistics, Pearson's product-moment correlation coefficient and multiple regression analysis to identify relationships and predictors within the dataset.

RESULTS

The results showed that 53.52% of participants had moderate knowledge and attitudes towards prevention, while perceived self-efficacy was generally high. Positive correlations were found between income, knowledge, attitudes, self-efficacy and prevention behaviours. Key predictors of Opisthorchis viverrini and cholangiocarcinoma prevention behaviours included attitudes towards human health (β = 0.212), perceived self-efficacy in human health (β = 0.211), attitudes towards animal health (β = 0.205) and knowledge about human health (β = 0.138), accounting for 24.40% of the variance in prevention behaviours. These predictors were statistically significant at 0.05 (F = 25.95; p <0.001).

CONCLUSION

The findings suggest that enhancing knowledge, attitudes and self-efficacy is crucial to improving Opisthorchis viverrini and cholangiocarcinoma prevention. This study underscores the need for integrated public health strategies incorporating human, animal and environmental health to reduce the prevalence of Opisthorchis viverrini and cholangiocarcinoma in high-risk regions.

Global, regional and national disease burden of food-borne trematodiases: projections to 2030 based on the Global Burden of Disease Study 2021

BACKGROUND

Food-borne trematodiases (FBTs), mainly encompassing clonorchiasis, fascioliasis, fasciolopsiasis, opisthorchiasis, and paragonimiasis, is a neglected public health problem, particularly in the WHO South-East Asia and the Western Pacific regions. This study evaluates the global, regional, and national disease burden of FBTs from 1990 to 2021 and projects trends to 2030, underscore the need for targeted prevention and control.

METHODS

Using the Global Burden of Disease 2021 database, the crude and the age-standardized prevalence rate (ASPR) and age-standardized prevalence disability-adjusted life years rate (ASDR) of FBTs at the global, regional and national level from 1990 to 2021 were described. The pivotal years of trend changes were identified using joinpoint regression analysis. The effects of age, period, cohort on FBTs prevalence and correlation with the sociodemographic index (SDI) was analyzed. Finally, the worldwide disability-adjusted life years (DALYs) for FBTs, projected up to 2030 using the Bayesian age-period-cohort model, were analyzed.

RESULTS

In 2021, 44,466,329 FBTs cases [95% uncertainty interval (UI): 40,017,217, 50,034,921], and 998,028 DALYs [95% UI: 569,766, 1,638,112] were estimated across 17 countries. The Western Pacific region exhibited the highest ASPR and ASDR, with the values of 1649.26 (95% UI: 1461.95, 1881.64) and 36.54 (95% UI: 19.77, 64.16), respectively. From 1990 to 2021, Lao PDR, Thailand, and the Philippines showed the most substantial declines in FBTs, while Kazakhstan had the largest average annual percentage change in DALYs (- 6.60, 95% UI: - 7.10, - 6.10). High-middle and middle SDI countries exhibited higher burden, with ASDR values of 28.03 (95% UI: 15.41, 48.73) and 16.63 (95% UI: 9.32, 27.68), respectively. The disease burden was greater among males, peaking in the 50-59 age group. The projected ASDR in 2030 is 13.10 for males and 8.40 for females.

CONCLUSIONS

FBTs remain a public health threat, with the global ASDR projected to remain stable, showing only a slight decrease by 2030. Low-income countries face ambiguous mortality rates and underestimated disease burdens, highlighting the need for improved surveillance. To achieve the 2030 NTD goal, comprehensive surveillance and integrated strategies derived using a One Health approach should be prioritized to control FBTs effectively.

Prevalence of opisthorchiid and other endoparasitic infections among cats and dogs in Novosibirsk oblast (Western Siberia, Russia)

To determine the current reservoir status and prevalence of Opisthorchis felineus infection in opisthorchiosis-endemic areas, feces samples were collected from 103 cats and 101 dogs admitted to shelters or discount sterilization centers from various districts of Novosibirsk city and from villages and towns along the Ob River (Novosibirsk Oblast). The feces samples were evaluated using two methods simultaneously: the formalin-ether sedimentation assay and a modified flotation assay. The prevalence of opisthorchiid infection was higher among cats (12.6%; 95% confidence interval 6.9-20.6%) than among dogs (4.0%; 95% confidence interval 1.1-9.8%). Overall prevalence of endoparasites among cats was 42.7% (five helminthic and four protozoan species) and among dogs 51.5% (eight helminthic and five protozoan species). Among the parasites found in the dogs, the prevalence of Sarcocystis sp. was the highest (16.8%), and in cats, the highest prevalence was shown by Giardia sp. and Toxocara cati (14.6% for each species). These results confirm the considerable contribution of stray cats and dogs to the maintenance of opisthorchiid eggs in the environment; these data should be taken into account for the development of effective control and education programs.

Integrated One-Health approach for prevention and control of Opisthorchis viverrini infection in rural Thailand: a 3-year study

Opisthorchis viverrini infection is a pressing health issue in rural Southeast Asia and is associated with the risk of cholangiocarcinoma. Despite control efforts, high infection rates persist, including evidence of reinfection post-treatment. This study aimed to address this public health concern through an integrated One-Health approach in endemic areas in rural Thailand over a 3-year period. The study included data from 3600 participants from Udon Thani Province, Thailand, during the years 2020 to 2022 and involved integrated epidemiological data collection and risk factor analysis to understand the impact of various interventions on disease transmission in the community. The efficacy of interventions was assessed by monitoring the incidence of O. viverrini reinfection in 2021 and 2022. In 2020, 218 cases of O. viverrini infection (6.0%) were identified. Significant risk factors included proximity to water bodies and consumption of raw fish. Variables contributing to infection risk among participants (P < 0.001) were education level, engagement in traditional ceremonies, poor sanitation, absence of ducks in nearby water bodies, self-medication for parasitic conditions, and multiple infections within a household. Dogs, cats, and cyprinoid fish showed prevalence rates of 5.4%, 6.3%, and 11.5%, respectively. Geographic analysis revealed clusters of infected households around water bodies. Interventions, including in-depth interviews, focus-group discussions, health education, anthelminthic treatment, and biological control using local free-range ducks, were implemented, resulting in no human reinfections in the second year and a minimal 0.3% prevalence rate in the third year. This study offers valuable insights into the dynamic changes in infection prevalence, making a significant contribution to effective disease control and community health promotion. This integrated One-Health approach proved to be an effective strategy for the prevention and control of opisthorchiasis.

Association between Opisthorchis viverrini infection in cats and humans: Non-spatial and spatial analyses

Cats are recognized as significant reservoir hosts for human opisthorchiasis, particularly in areas with a high prevalence of infection. Despite this, the precise role of cats in the transmission of Opisthorchis viverrini between humans and felines remains unclear. This study investigates the association between these two hosts through both spatial and non-spatial analyses in the endemic Thanya sub-district of Thailand. A total of 105 owned cats were randomly sampled from 15 villages within the sub-district for stool examination. A questionnaire was administered to 66 cat owners to explore the human-pet relationship. Household locations were collected using GPS devices. Non-spatial analyses revealed a positive association between the two hosts (P= 0.011; OR 7, 95% CI: 1.6-30.9), highlighting two independent significant risk factors: cat owners consuming raw fish (P = 0.028; OR = 4.52, 95% CI: 1.25-19.45) and feeding cats raw fish (P = 0.011; OR = 16.41, 95% CI: 2.78-317.04) according to multivariate analysis. Spatial analysis provided further support to the non-spatial findings (p = 0.0123; OR = 3.45, 95% CI = 0.88-13.61). Multiple autologistic regression confirmed two significant risk factors: cat owners consuming raw fish (p = 0.054; OR = 3.37, 95% CI: 0.98-11.59) and feeding cats raw fish (p = 0.014; OR = 7.43, 95% CI: 1.49-37.05). Risk mapping identified the western part of the study site as a hotspot for O. viverrini infection. Hyper-endemic focusing revealed a union of human and cat buffers at 0.46 km², with an overlapping area of 0.22 km² (47.83%). This study underscores the impact of owners' behaviors, specifically consuming and feeding raw fish to cats, on the increased probability of infection in cats. It emphasizes the need for effective opisthorchiasis control through health education targeting cat owners in endemic areas.

Modeling the persistence of Opisthorchis viverrini worm burden after mass-drug administration and education campaigns with systematic adherence

Opisthorchis viverrini is a parasitic liver fluke contracted by consumption of raw fish, which affects over 10 million people in Southeast Asia despite sustained control efforts. Chronic infections are a risk factor for the often fatal bile duct cancer, cholangiocarcinoma. Previous modeling predicted rapid elimination of O. viverrini following yearly mass drug administration (MDA) campaigns. However, field data collected in affected populations shows persistence of infection, including heavy worm burden, after many years of repeated interventions. A plausible explanation for this observation is systematic adherence of individuals in health campaigns, such as MDA and education, with some individuals consistently missing treatment. We developed an agent-based model of O. viverrini which allows us to introduce various heterogeneities including systematic adherence to MDA and education campaigns at the individual level. We validate the agent-based model by comparing it to a previously published population-based model. We estimate the degree of systematic adherence to MDA and education campaigns indirectly, using epidemiological data collected in Lao PDR before and after 5 years of repeated MDA, education and sanitation improvement campaigns. We predict the impact of interventions deployed singly and in combination, with and without the estimated systematic adherence. We show how systematic adherence can substantially increase the time required to achieve reductions in worm burden. However, we predict that yearly MDA campaigns alone can result in a strong reduction of moderate and heavy worm burden, even under systematic adherence. We predict latrines and education campaigns to be particularly important for the reduction in overall prevalence, and therefore, ultimately, elimination. Our findings show how systematic adherence can explain the observed persistence of worm burden; while emphasizing the benefit of interventions for the entire population, even under systematic adherence. At the same time, the results highlight the substantial opportunity to further reduce worm burden if patterns of systematic adherence can be overcome.

Roaming behavior of the owned domestic cats (Felis catus) with possible roles in the transmission of Opisthorchis viverrini in the endemic area in Khon Kaen, Thailand

In the endemic area of the liver fluke (Opisthorchis viverrini) infection, effective control of opisthorchiasis using One Health approaches requires transmission interruption in all hosts in the parasite life cycle. Owned domestic cats (Felis catus) are considered an important species among mammalian reservoirs. Similar to humans, household cats become infected by eating raw, contaminated fish and spread the O. viverrini eggs to the environment by defecation. In rural areas, cat owners usually feed their cats with human food or food waste, especially fish dishes. There is a high risk for cats to become infected and deposit eggs in the peri-household environment. The lack of research on domestic cats led us to study their roaming behavior, roaming range, habitat preference and risk of disease transmission. GPS loggers were harnessed to 28 domestic cats in 7 villages around Lawa Lake, the endemic area of human opisthorchiasis. All cats were examined for the O. viverrini infection status using modified formalin-ether concentration technique (MFECT) before application of the GPS device used to observe and record their roaming distance and range area. Then, composition analysis for habitat selection was performed using the location data. Additionally, cat owners were interviewed using participatory epidemiologic methods for their perceptions and knowledge about the reservoir hosts of this trematode. Our study suggested that the prevalence of O. viverrini in cats in this area has not declined appreciably in comparison with our previous study four years ago, although the treatment and control has been applied intensively in humans. The longest distance that individual cats roamed ranged from 51 to 363 meters (mean±SD = 154.48±90.71). The cats traveled tracks around their home. There was no significant difference in the average distance that cats ranged between O. viverrini infected group (154.13±72.80 meters) and the non-infected group (154.67±101.39 meters) was found. Compositional analysis suggested that the domestic cats preferred urban habitats where food and safety were probably more available. It appears that the main transmission route for infection of cats was contaminated fish fed to cats or fish that remained in their houses. Therefore, owners should refrain from feeding their cats potentially contaminated foods, food scraps and raw fish remains and prevent their cats from accessing them. Moreover, the participatory epidemiology results suggest that awareness of villagers is not enough for the effective and sustainable control of the disease.

Cancerogenic parasites in veterinary medicine: a narrative literature review

Parasite infection is one of the many environmental factors that can significantly contribute to carcinogenesis and is already known to be associated with a variety of malignancies in both human and veterinary medicine. However, the actual number of cancerogenic parasites and their relationship to tumor development is far from being fully understood, especially in veterinary medicine. Thus, the aim of this review is to investigate parasite-related cancers in domestic and wild animals and their burden in veterinary oncology. Spontaneous neoplasia with ascertained or putative parasite etiology in domestic and wild animals will be reviewed, and the multifarious mechanisms of protozoan and metazoan cancer induction will be discussed.

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.

Does Opisthorchis viverrini circulate between humans and domestic cats in an endemic area in Thailand?

The liver fluke Opisthorchis viverrini is a foodborne trematode that, in chronic infection, is a leading cause of bile-duct cancer – cholangiocarcinoma. Cats and dogs are acknowledged as reservoir hosts of this parasite. However, this assumption is based on morphological similarity of flukes recovered from these hosts, without any molecular genetic evidence. The aim of this study was to obtain molecular data from O. viverrini eggs present in feces of humans and cats in the same locality in Thanya sub-district, Kalasin, Thailand. The mitochondrial cytochrome c oxidase subunit 1 (cox1) gene was used as the marker for a population-genetic study. A DNA fragment of the cox1 gene was amplified from stool samples and subjected to nucleotide sequencing. Phylogenetic and haplotype network analyses were performed. The cox1 sequences of O. viverrini eggs from humans and cats largely formed separate clades on the phylogenetic trees, with an Fst value of 0.64 (P < 0.05), indicating largely distinct populations in the 2 species. However, 5 samples from cats were placed in the human cluster and 1 sample from a human was placed in the cat cluster. This suggests that host specificity of ‘human’ and ‘cat’ clades is not absolute. These results indicate that there are 2 populations of O. viverrini, one circulates primarily in humans and the other in cats. However, cross-transmission can occur between these 2 hosts. Taken altogether, the population-genetic evidence from this study partially supports the assumption that the cat can act as a reservoir host of O. viverrini.

The burden of opisthorchiasis and leptospirosis in Thailand: A nationwide syndemic analysis

Opisthorchiasis, caused by the foodborne trematode parasite Opisthorchis viverrini, is co-endemic with leptospirosis in the Greater Mekong Subregion. Socio-economic determinants, occupational risk factors, and reservoir hosts interact with the diseases in the threat to human health, but the situation has not been explored. We, therefore, studied the interaction between the diseases and their associated risks using a syndemic approach with nationwide data for Thailand. Methods included Bayesian mapping, principal component analysis (PCA), and nested correlation analysis to analyze the data for 2009 and 2014. Bayesian mapping demonstrates that opisthorchiasis acts in a synergistic manner to massively alter the risk of leptospirosis at the provincial level, particularly in areas of opisthorchiasis endemicity in Northeast Thailand. Socio-economic and occupational factors significantly influence the disease syndemic with moderate effect sizes of -0.4 and 0.5, respectively (P<0.001). These effects are most remarkable in the northeastern region, which has not only the highest poverty level but also the highest proportion of occupational risk (P<0.001). Cats and dogs play crucial roles in maintaining the syndemic (r-value 7 and 6 with P<0.001). The study shows that opisthorchiasis and leptospirosis become syndemic, especially in North-East, Thailand. Socio-economic and occupational variables are positively syndemic as they are representative of neglected tropical diseases. The role of reservoir hosts underlines the value of an interdisciplinary approach, such as One Health for Sustainability Disease Control.

Current status of human liver fluke infections in the Greater Mekong Subregion

The Greater Mekong Subregion (GMS) is a trans-national region of the Mekong River basin in Southeast Asia comprising Cambodia, the People's Republic of China (specifically Yunnan Province and Guangxi Zhuang Autonomous Region), Lao People's Democratic Republic (Lao PDR), Myanmar, Thailand, and Vietnam home to more than 340 million people or almost 4.5% of the global population. Human liver fluke infections caused by Opisthorchis viverrini and Clonorchis sinensis have been major public health problems in this region for decades. Opisthorchiasis caused by O. viverrini is prevalent in Thailand, Lao PDR, Cambodia and central-southern Vietnam with more than 12 million people infected. Clonorchiasis caused by C. sinensis is endemic in northern Vietnam and Guangxi with estimated 3.5 -5 million infected. The infections can cause several liver and biliary diseases such as cholangitis, periductal fibrosis, gallstones, and cholangiocarcinoma (CCA), a fatal bile duct cancer. Key determinants of the geographical distribution differences of the two liver fluke species are snail species and geographic barriers. Main risk behaviour of the infections is the culture of eating raw fish "the raw attitude" of people in the GMS, especially the Tai/Dai/Thai/Laos ethnic groups, the major population in the GMS. Over the past 20 years, there is a big change in prevalence of the infections. Opisthorchiasis has long been endemic, particularly in northern and northeastern Thailand and Lao PDR with over 8-10 million cases estimated. However, after several rounds of national campaign against opisthorchiasis using integrated control approach in Thailand over the past three decades, the prevalence of O. viverrini infection has reduced from over 15% in 1996 to 2.2% in 2019. High prevalence of O. viverrini infection continues in Lao PDR and central Vietnam. Emerging high prevalence, up to a maximum of 47.5%, has been noted in Cambodia during the past 10 years possibly due to more studies being conducted rather than increasing prevalence. O. viverrini infection has now also been reported in Lower Myanmar in recent years. Clonorchiasis has been known in northern Vietnam and southern China for a long time. Several surveys have reported infections in Guangxi in the last 10 years, and until now liver fluke infected cases have not been reported in Yunnan. Overall, nowadays, there is a shift in high risk areas for GMS liver fluke infection from northeastern Thailand to Lao PDR, Cambodia, Vietnam, Myanmar, and Guangxi P.R. China. Urgent systematic disease mapping and integrated liver fluke control using One Health approaches should be implemented nationwide in GMS countries.

Opisthorchis viverrini antigens up-regulates the expression of CD80 and MHC class II in JAWSII mouse dendritic cells and promotes IL-10 and TGF-β secretions

Dendritic cells (DCs) are antigen-presenting cells (APC) involved in the initiation of immune responses. Maturation of DCs is characterized by the high expression of major histocompatibility complex (MHC) class II and co-stimulatory clusters of differentiation (CD) 40, CD80, and CD86 molecules. Matured DCs are required for T cell differentiation and proliferation. However, the response of DCs to Opisthorchis viverrini antigens has not yet been understood. Therefore, this study sought to determine the expression of surface molecules of JAWSII mouse DCs stimulated by crude somatic (CS) and excretory-secretory (ES) antigens of O. viverrini. ES antigen significantly induced only mRNA expression of CD80 and MHC class II in JAWSII mouse DCs, while CS antigen promoted up-regulation of both mRNA and protein levels of CD80 and MHC class II, indicating relative maturation of JAWII mouse DCs. Moreover, the secreted cytokines from the co-cultures of O. viverrini antigens stimulated JAWSII DC with naïve CD4⁺ T cells was determined. Significantly increased levels of immunosuppressive cytokines interleukin (IL)-10 and transforming growth factor beta (TGF-β) were found. The up-regulation of these cytokines may indicate the response of regulatory T cells (Treg) to CS antigen-stimulated JAWSII DC. These findings may lead to a better understanding of the role that DCs play in O. viverrini infection.

Investigation of possible alternate animal reservoir hosts of Opisthorchis viverrini

Chronic opisthorchiasis caused by Opisthorchis viverrini (O. viverrini) adversely affects human health and is associated with a fatal bile duct cancer (cholangiocarcinoma). Although cats and dogs are known animal reservoir hosts of opisthorchiasis, there is limited information about whether other fish-eating animals are fluke reservoirs. Wetlands along Chi River of Thailand have abundant intermediate host snails and fish for O. viverrini and diverse other animal species. This led to our investigation into whether other fish-eating animals can also become infected and be alternate reservoir hosts for human opisthorchiasis. Our preliminary study focused on the O. viverrini infection status of crab-eating or long-tailed macaques roaming in Kosumpi National Forest Park in Chi River Basin, Kosumpisai District of Mahasarakam Province, and rodents, small residential mammals and fish-eating birds living in Lawa wetland complex of Khon Kaen Province. Fecal samples of each animal were collected and modified formalin ether concentration technique was applied to identify infections. Additionally, participatory epidemiology was used to retrieve information from local communities on opisthorchiasis transmission in these animals. No O. viverrini infection was found in any fecal samples suggesting that monkeys, rodents, small residential mammals and birds in these two wetlands probably do not serve as alternate reservoir hosts of O. viverrini.

Towards Evidence-based Control of Opisthorchis viverrini

Transmission of the carcinogenic liver fluke Opisthorchis viverrini is ongoing across Southeast Asia. Endemic countries within the region are in different stages of achieving control. However, evidence on which interventions are the most effective for reducing parasite transmission, and the resulting liver cancer, is currently lacking. Quantitative modelling can be used to evaluate different control measures against O. viverrini and assist the design of clinical trials. In this article we evaluate the epidemiological parameters that underpin models of O. viverrini and the data necessary for their estimation, with the aim of developing evidence-based strategies for parasite control at a national or regional level.

Surveillance of clonorchiasis in China in 2016

Clonorchiasis is an important food-borne parasitic disease in China, and infection with C. sinensis can cause hepatobiliary diseases. Comprehensive and systematic prevention and control of clonorchiasis requires the establishment of an effective surveillance. A total of 301 surveillance points were set up in 30 provinces across China in 2016, and 1000 people were selected by cluster sampling at each surveillance point annually for C. sinensis infection screening using Kato-Katz thick smear method. C. sinensis infection was detected in 6226 people following screening of 305081 people at the 301 surveillance points in 2016. Infection rate was 2.04%; with C. sinensis infection detected in 70 counties spread across 15 provinces, 89.37% of the infected people were distributed in Jilin, Heilongjiang, Guangdong and Guangxi provinces. Highest infection rate was observed in Da'an city, Jilin Province (49%). The national infection rate in male and female was 2.70% and 1.40% respectively. Infection rate between male and female was significantly different (P <0.01). Disease prevalence increases with age in both male and female, reaches peak in age group 40-49. Result obtained indicate that major C. sinensis endemic areas are distributed in the north and south of China, and areas with high prevalence are distributed along the river system at county level. Result, also, shows that middle-aged men are at high-risk of infection. These results suggest that surveillance activities should be sustained nationwide and highlight the need for an integrated approach to control C. sinensis transmission in regions with high disease prevalence in China.

Zoonotic transmission of intestinal helminths in southeast Asia: Implications for control and elimination

Intestinal helminths are extremely widespread and highly prevalent infections of humans, particularly in rural and poor urban areas of low and middle-income countries. These parasites have chronic and often insidious effects on human health and child development including abdominal problems, anaemia, stunting and wasting. Certain animals play a fundamental role in the transmission of many intestinal helminths to humans. However, the contribution of zoonotic transmission to the overall burden of human intestinal helminth infection and the relative importance of different animal reservoirs remains incomplete. Moreover, control programmes and transmission models for intestinal helminths often do not consider the role of zoonotic reservoirs of infection. Such reservoirs will become increasingly important as control is scaled up and there is a move towards interruption and even elimination of parasite transmission. With a focus on southeast Asia, and the Philippines in particular, this review summarises the major zoonotic intestinal helminths, risk factors for infection and highlights knowledge gaps related to their epidemiology and transmission. Various methodologies are discussed, including parasite genomics, mathematical modelling and socio-economic analysis, that could be employed to improve understanding of intestinal helminth spread, reservoir attribution and the burden associated with infection, as well as assess effectiveness of interventions. For sustainable control and ultimately elimination of intestinal helminths, there is a need to move beyond scheduled mass deworming and to consider animal and environmental reservoirs. A One Health approach to control of intestinal helminths is proposed, integrating interventions targeting humans, animals and the environment, including improved access to water, hygiene and sanitation. This will require coordination and collaboration across different sectors to achieve best health outcomes for all.

Integrative EcoHealth/One Health Approach for Sustainable Liver Fluke Control: The Lawa Model

The Lawa model is a successful integrative and sustainable means of controlling opisthorchiasis in Thailand. The model integrates the EcoHealth and One Health holistic approaches with systems thinking to target the interruption of Opisthorchis viverrini transmission. Using the six principles of EcoHealth and emphasizing the three domains of One Health (human-animal-ecosystem), the program targets each step of the parasite life cycle, thus maximizing the chances of interrupting the life cycle of the parasite. The main drivers of success are the village health volunteers and health-promoting hospitals, together with the support of the government and academia. The success of the model has led to continuous expansion, adoption nationally and internationally and application to the control of other neglected tropical diseases as well as noncommunicable diseases.