Effect of control strategies on prevalence, incidence and re-infection of clonorchiasis in endemic areas of China

Prevalence trend and burden of foodborne trematodiasis in China from 1990 to 2021 and its predictions until 2030: a comparative study with Japan and South Korea

Background

Foodborne trematodiasis (FBT) poses a significant public health challenge in East Asia, influenced by local dietary practices and environmental conditions. This study evaluates the prevalence trends and disease burden of FBT in China, Japan, and South Korea from 1990 to 2021, with future burden projections until 2030, to guide targeted prevention strategies and public health resource allocation.

Methods

The study utilized data from the Global Burden of Disease (GBD) 2021, including the absolute prevalence, age-standardized prevalence rate (ASPR), disability-adjusted life years (DALYs), and age-standardized DALY rate (ASDALR). Joinpoint regression analyzed the average annual percentage change (AAPC) and 95% confidence intervals (CI) to track FBT burden trends. A comparative analysis was conducted across different dimensions of the burden of FBT among China, Japan, and South Korea, including age, gender, and temporal trends. Additionally, the Bayesian age-period-cohort (BAPC) model projected future FBT burden trends.

Results

From 1990 to 2021, China showed significant reductions in ASPR (41.65%) and ASDALR (47.44%) of FBT. South Korea also noted a slight decrease, yet both had higher rates than the global average. Japan, conversely, saw a notable increase in FBT burden but with an overall lower burden compared to the global average. Males generally exhibited a higher disease burden than females. Future projections indicate a continued decline or stabilization in China and Japan, with a potential slight increase in South Korea by 2030.

Conclusion

The study reveals contrasting trends in FBT burden among the three East Asian countries, with significant declines in China, a slight decrease in South Korea despite higher-than-global rates, and an increasing but low burden in Japan. These insights are crucial for tailoring public health interventions and allocating resources effectively to combat FBT in the region.

Assessment of the application of the FA280-a fully automated fecal analyzer for diagnosing clonorchiasis: a mixed-method study

BACKGROUND

Clonorchiasis is an important foodborne parasitic disease in China caused by Clonorchis sinensis. Accurate and rapid diagnosis of this disease is vital for treatment and control. Traditional fecal examination methods, such as the Kato-Katz (KK) method, are labor-intensive, time-consuming, and have limited acceptance. The FA280, an advanced automated fecal analyzer, increases efficiency while significantly reducing labor load. This study aims to evaluate its performance, applicability, and scalability in clonorchiasis diagnosis to explore its potential application in the future.

METHODS

A mixed-methods study integrating both quantitative and qualitative approaches was conducted. The quantitative component consisted of a cross-sectional survey in Xinhui District, Guangdong, China, to evaluate the diagnostic performance of the FA280. The positive rate and agreement between the FA280 and the KK method were evaluated using McNemar's test. Additionally, Pearson's Chi-square test was used to analyze the consistency of positive results between the two methods across various eggs per gram (EPG) groups under different cut-off values. The qualitative component included semi-structured individual interviews with medical staff and institutional administrators to examine the FA280's applicability and potential for broader adoption, with thematic analysis of the data.

RESULTS

In the quantitative study of 1000 participants, both the FA280 and KK methods detected clonorchiasis with a positive rate of 10.0%, achieving 96.8% agreement and showing no significant difference (P > 0.999). The kappa value was 0.82 (95% confidence interval: 0.76-0.88), indicating a strong agreement between the methods. The agreement rate for positive results between the two methods was significantly higher in the high infection intensity group compared to the low infection intensity group (P < 0.05). The qualitative study, which involved interviews with three medical staff and two administrators revealed that the FA280 outperformed the KK method in testing procedures, detection results, and user acceptance. The benefits, challenges, and suggestions of FA280 promotion were also emphasized.

CONCLUSIONS

This study demonstrated the FA280's application value in clonorchiasis diagnosis by assessing its detection performance, applicability, and scalability. These findings contribute to the future prevention and control of the disease.

Risk factors for Clonorchis sinensis infections and control measures reinforced with focused interviews

Clonorchiosis, a disease that develops following the consumption of raw freshwater fish that harbors Clonorchis sinensis metacercariae, seriously threatens the health of residents in endemic areas. We aimed to assess the level of awareness of liver fluke infections among infected residents and restaurant workers in liver fluke infection-endemic areas. To identify and provide a more realistic description of C. sinensis infections, we conducted a focused interview and questionnaire survey of local residents in endemic areas in Korea. Most residents knew that freshwater fish are a source of C. sinensis infection. Nevertheless, the consumption of raw freshwater fish was the main risk factor for their infection with C. sinensis. The residents had little knowledge regarding their residential area being endemic to C. sinensis or about the symptoms and complications of C. sinensis infection. Although the participants had no experience with C. sinensis prevention or health education, they preferred on-site education during visits to village halls. The in-depth interviewees had a high level of knowledge about C. sinensis infection but were unaware that eating raw freshwater fish was its cause. Family and social gatherings encourage the habit of eating raw freshwater fish, which is a risk factor for repetitive infections. Based on these findings, to eliminate clonorchiosis, we propose strengthening the capacity of public health care personnel, giving C. sinensis prevention education, and screening educational videos during visits to village halls. Furthermore, intensive education is recommended for reinfected people and community opinion leaders, as well as reservoir host control.

Burden of Food-Borne Trematodiases in China: Trends from 1990 to 2021 and Projections to 2035

To assess the burden of food-borne trematodiases in China from 1990 to 2021 and project the burden through 2035, data were captured from the Global Burden of Disease Study (GBD) 2021 datasets. The estimated prevalent food-borne trematodiase cases were 33.32 million (95% uncertainty interval (UI): 29.25-38.35 million) in China in 2021, contributing to 768,297.4 disability-adjusted life years (DALYs) (95% UI: 383,882.8-1,367,826.1). The number of prevalent cases and DALYs declined by 9.02% and 18.11%, and a downward decline was seen in age-standardized prevalence and DALY rates (estimated annual percentage change: -0.96% and -1.21%, respectively). A higher prevalence and DALY rates were observed among males than females, and the middle-aged group bore the highest burden, while the older population showed the most rapid increase in prevalent cases and DALY numbers. Projected DALY counts and rates remain stable through 2035 using the Bayesian age-period-cohort (BAPC) model. These findings demonstrate a decline in the burden of food-borne trematodiases in China from 1990 to 2021; however, the prevalence remained high, which contributed considerably to disability and premature death. Continued control efforts and targeted interventions are essential to further reducing the burden of food-borne trematodiases in China.

The disease burden and its distribution characteristics of clonorchiasis in Guangdong Province, Southern China

BACKGROUND

Clonorchiasis has significant socioeconomic importance in endemic areas; however, studies investigating the disease burden in specific sub-regions are lacking. This study aims to address the gap by quantifying the current disease burden caused by clonorchiasis in Guangdong province and assessing its distribution characteristics.

METHODS

Comprehensive measures, including prevalence rates, disability-adjusted life years (DALYs), and direct medical costs, were used to assess the disease burden of clonorchiasis. To estimate the prevalence rate, the number of infections was divided by the examined population, based on the annual surveillance data on clonorchiasis cases during 2016-2021. The calculation of DALYs was based on the epidemiological parameters according to the definition issued by the World Health Organization. Cost data of clonorchiasis were utilized to quantify the direct medical costs. The distribution characteristics of disease burden were assessed through comparisons of groups of population defined by geographic area, time, and characteristics of people.

RESULTS

In 2021, clonorchiasis posed a significant disease burden in Guangdong Province. The prevalence rate was found to be 4.25% [95% CI (4.02%, 4.49%)], with an associated burden of DALYs of 406,802.29 [95% CI (329,275.33, 49,215,163.78)] person-years. The per-case direct medical costs of patients with clonorchiasis were estimated to be CNY 7907.2 (SD = 5154.4). Notably, while the prevalence rate and DALYs showed a steady decrease from 2016 to 2020, there was a rising trend in 2021. Spatial clustering of clonorchiasis cases and DALYs was also observed, particularly along the Pearl River and Han River. This suggests a concentration of the disease in these regions. Furthermore, significant differences in prevalence rates were found among various demographic groups, including sex, age, occupation, and education level. Additionally, patients with longer hospital stays were more likely to incur higher direct medical costs.

CONCLUSIONS

The burden of clonorchiasis in Guangdong Province remains high, despite significant progress achieved through the implementation of the prevention and control programs. It is suggested that measures should be taken based on the distribution characteristics to maximize the effectiveness of prevention and control, with a primary focus on key populations and areas.

Effectiveness of health education in improving knowledge, attitude and practice related to foodborne zoonotic trematodes in Vietnam, with a particular focus on Clonorchis sinensis

OBJECTIVE

Foodborne zoonotic trematodes (FZT), which infect the liver, lungs and intestines of humans, are an emerging public health concern in tropical countries including Vietnam. In northern Vietnam, Clonorchis sinensis is recognised as the most important species of the FZT. Up to now, small-scale studies conducted in the country have indicated that health education could improve participants' knowledge and practices related to clonorchiasis, however strong evidence is still lacking. We conducted an intervention trial between 2020 and 2021 in four communes in Yen Bai and Thanh Hoa province, aiming to evaluate the impact of an extended educational package on knowledge, attitude and practices related to clonorchiasis, as well as on knowledge on the large liver fluke and minute intestinal flukes.

METHODS

To this end, baseline and post-intervention questionnaires were conducted. Generalised estimating equations models were run to analyse the impact of the intervention on knowledge, attitudes and practices over time in the intervention versus control group. Finally, 172 people in the intervention group and 162 in the control group were included for analysis.

RESULTS

Results demonstrated that the intervention significantly improved clonorchiasis knowledge, attitudes and practices, with higher odds for a correct knowledge response (odds ratio (OR) = 2.80, 95% confidence interval (CI) = 1.84-4.27, p-value < 0.001), increased average mean attitude score (mean = 0.363, 95%CI = 0.182-0.544, p-value < 0.001), and a reduced odds of consuming raw fish (OR = 0.15, 95%CI = 0.06-0.40, p = 0.002) in the intervention group compared to the control group post-intervention versus baseline. Additionally, participants in the intervention group exhibited enhanced basic knowledge of the large liver fluke and minute intestinal flukes post-intervention.

CONCLUSIONS

These findings demonstrate the potential of health education programs in preventing clonorchiasis in endemic areas, emphasising the importance of continued health education as a critical component of integrated control programs for clonorchiasis.

Clonorchiasis and opisthorchiasis: epidemiology, transmission, clinical features, morbidity, diagnosis, treatment, and control

Clonorchis sinensis, Opisthorchis viverrini, and Opisthorchis felineus are important liver flukes that cause a considerable public health burden in eastern Asia, southeastern Asia, and eastern Europe, respectively. The life cycles are complex, involving humans, animal reservoirs, and two kinds of intermediate hosts. An interplay of biological, cultural, ecological, economic, and social factors drives transmission. Chronic infections are associated with liver and biliary complications, most importantly cholangiocarcinoma. With regard to diagnosis, stool microscopy is widely used in epidemiologic surveys and for individual diagnosis. Immunologic techniques are employed for screening purposes, and molecular techniques facilitate species differentiation in reference laboratories. The mainstay of control is preventive chemotherapy with praziquantel, usually combined with behavioral change through information, education and communication, and environmental control. Tribendimidine, a drug registered in the People's Republic of China for soil-transmitted helminth infections, shows potential against both C. sinensis and O. viverrini and, hence, warrants further clinical development. Novel control approaches include fish vaccine and biological control. Considerable advances have been made using multi-omics which may trigger the development of new interventions. Pressing research needs include mapping the current distribution, disentangling the transmission, accurately estimating the disease burden, and developing new diagnostic and treatment tools, which would aid to optimize control and elimination measures.

From the discovery of helminths to the discovery of their carcinogenic potential

Cancer involves a major aberration in the normal behaviour of cells, making them divide continuously, which interferes with the normal physiology of the body. The link between helminths and their cancer-inducing potential has been proposed in the last century. The exact pathway is still not clear but chronic inflammation in response to the deposited eggs, immune response against soluble egg antigens, and co-infection with a third party (a bacteria, a virus, or infection leading to a change in microbiome) seems to be the reasons for cancer induction. This review looks into the historical outlook on helminths along with their epidemiology, morphology, and life cycle. It then focuses on providing correlations between helminth infection and molecular mechanism of carcinogenesis by elaborating upon epidemiological, clinical, and surgical studies. While the cancer-inducing potential has been convincingly established only for a few helminths and studies point out towards possible cancer-inducing ability of the rest of the helminths elucidated in this work, however, more insights into the immunobiology of helminths as well as infected patients are required to conclusively comment upon this ability of the latter.

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.

Children education for sustainable control of liver fluke infections

Significant disease burden is caused by infections with human liver flukes, including Clonorchis sinensis, Opisthorchis viverrini and O. felineus. Epidemiology is characterized by high burden in the male than the female, and in the elder than the younger. Chemotherapy is the mainstream for morbidity control, but it could not prevent re-infection. Meanwhile, behavioral change on the dietary habit of ingesting raw freshwater fish is challenging. In this opinion, we argue why it is important to educate children for sustainable control of liver fluke infections. Then, the design, development and key messages of an educational cartoon for preventing liver fluke infections is introduced. Technical focuses are emphasized based on a pilot using the education cartoon for preventing clonorchiasis in China. Finally, how to further develop and verify this education strategy is discussed.

Structure-based virtual screening and molecular dynamics of potential inhibitors targeting sodium-bile acid co-transporter of carcinogenic liver fluke Clonorchis sinensis

Background

Clonorchis sinensis requires bile acid transporters as this fluke inhabits bile juice-filled biliary ducts, which provide an extreme environment. Clonorchis sinensis sodium-bile acid co-transporter (CsSBAT) is indispensable for the fluke’s survival in the final host, as it circulates taurocholate and prevents bile toxicity in the fluke; hence, it is recognized as a useful drug target.

Methodology and principal findings

In the present study, using structure-based virtual screening approach, we presented inhibitor candidates targeting a bile acid-binding pocket of CsSBAT. CsSBAT models were built using tertiary structure modeling based on a bile acid transporter template (PDB ID: 3zuy and 4n7x) and were applied into AutoDock Vina for competitive docking simulation. First, potential compounds were identified from PubChem (holding more than 100,000 compounds) by applying three criteria: i) interacting more favorably with CsSBAT than with a human homolog, ii) intimate interaction to the inward- and outward-facing conformational states, iii) binding with CsSBAT preferably to natural bile acids. Second, two compounds were identified following the Lipinski’s rule of five. Third, other two compounds of molecular weight higher than 500 Da (Mr > 500 Da) were presumed to efficiently block the transporter via a feasible rational screening strategy. Of these candidates, compound 9806452 exhibited the least hepatotoxicity that may enhance drug-likeness properties.

Conclusions

It is proposed that compound 9806452 act as a potential inhibitor toward CsSBAT and further studies are warranted for drug development process against clonorchiasis.

Cost-effectiveness evaluation of different control strategies for Clonorchis sinensis infection in a high endemic area of China: A modelling study

Clonorchiasis is an important food-borne parasitic disease caused by Clonorchis sinensis infection. The evaluation of long-term cost-effectiveness of control strategies is important for disease control and prevention. The present study aimed to assess the cost-effectiveness of the three recommended strategies (i.e., WHO, Chinese and Guangdong strategies) and different combinations of commonly used measures (i.e., preventive chemotherapy, information, education, and communication (IEC) and environmental improvement) on clonorchiasis. The study area, Fusha town in Guangdong Province, was a typical high endemic area in China. The analysis was based on a multi-group transmission model of C. sinensis infection. We set the intervention duration for 10 years and post-intervention period for 50 years. The corresponding costs and DALYs were estimated. Strategies with incremental cost-effectiveness ratios (ICERs) less than 1/5 of the willingness-to-pay threshold were identified as highly cost-effective strategies. The optimal control strategy was obtained using the next best comparator method. The ICERs of Guangdong strategy were $172 (95% CI: $143-$230) US for praziquantel and $106 (95% CI: $85-$143) US for albendazole, suggesting the highest cost-effectiveness among the three recommended strategies. For praziquantel, 470 sets of control strategies were identified as highly cost-effective strategies for achieving infection control (prevalence<5%). The optimal strategy consisted of chemotherapy targeted on at-risk population, IEC and environmental improvement, with coverages all being 100%, and with the ICER of $202 (95% CI: $168-$271) US. The results for transmission control (prevalence<1%) and albendazole were obtained with the same procedures. The findings may help to develop control policies for C. sinensis infection in high endemic areas. Moreover, the method adopted is applicable for assessment of optimal strategies in other endemic areas.

Clonorchiasis, a food-borne trematodiases, affects millions of people in Asia. Highly cost-effective control strategies are critical for its control. Previous studies considering the economic evaluation of control strategies were rare, mostly based on interventions in practical, and not capable of evaluating long-term cost-effectiveness of strategies with possible combinations of control measures or under various coverages. Based on a dynamic, multi-group transmission model, we simulated different control strategies in a high clonorchiasis endemic area, and evaluated their cost-effectiveness. Among the three recommended strategies (i.e., WHO, Chinese and Guangdong strategies), the Guangdong strategy was the most cost-effective. For praziquantel, 470 sets of control strategies were identified as highly cost-effective strategies for achieving infection control (prevalence<5%) among the strategies of possible combinations of the three common measures (i.e., preventive chemotherapy, information, education, and communication (IEC) and environmental modification). The optimal strategy consisted of chemotherapy targeted on at-risk population, IEC and environmental improvement, with coverages all being 100%. The results for transmission control (prevalence<1%) and albendazole were obtained with the same procedures. The numerical results may help to develop control strategies for C. sinensis infection in high endemic areas. The methodology is applicable for other different endemic areas.

Molecular Mechanisms of Clonorchis sinensis-Host Interactions and Implications for Vaccine Development

Infections caused by Clonorchis sinensis remain a significant public health challenge for both humans and animals, causing pyogenic cholangitis, cholelithiasis, cholecystitis, biliary fibrosis, and even cholangiocarcinoma. However, the strategies used by the parasite and the immunological mechanisms used by the host have not yet been fully understood. With the advances in technologies and the accumulated knowledge of host-parasite interactions, many vaccine candidates against liver flukes have been investigated using different strategies. In this review, we explore and analyze in-depth the immunological mechanisms involved in the pathogenicity of C. sinensis. We highlight the different mechanisms by which the parasite interacts with its host to induce immune responses. All together, these data will allow us to have a better understanding of molecular mechansism of host-parasite interactions, which may shed lights on the development of an effective vaccine against C. sinensis.

Cost yield of different treatment strategies against Clonorchis sinensis infection

BACKGROUND

Clonorchiasis is attributed to the ingestion of raw freshwater fish harboring Clonorchis sinensis. Morbidity control is targeted through the administration of antihelminthics. This study modelled the cost yield indicated by effectiveness and utility of different treatment strategies against clonorchiasis.

METHODS

About 1000 participants were enrolled from each of 14 counties selected from four provincial-level administrative divisions namely Guangxi, Guangdong, Heilongjiang and Jilin in 2017. Fecal examination was adopted to detect C. sinensis infection, while behavior of ingesting raw freshwater fish was enquired. Counties were grouped into four categories based on prevalence, namely low prevalence group (< 1%), moderate prevalence group (1-9.9%), high prevalence group (10-19.9%) and very high prevalence group (≥ 20%), while population were divided into three subgroups, namely children aged below 14 years old, adult female and adult male both aged over 14 years old. The average of cost effectiveness indicated by the cost to treat single infected cases with C. sinensis and of cost utility indicated by the cost to avoid per disability-adjusted life years (DALYs) caused by C. sinensis infection was calculated. Comparisons were performed between three treatment schedules, namely individual treatment, massive and selective chemotherapy, in which different endemic levels and populations were considered.

RESULTS

In selective chemotherapy strategy, the cost to treat single infected case in very high prevalence group was USD 10.6 in adult male, USD 11.6 in adult female, and USD 13.2 in children. The cost increased followed the decrease of endemic level. In massive chemotherapy strategy, the cost per infected case in very high prevalence group was USD 14.0 in adult male, USD 17.1 in adult female, USD 45.8 in children, which were also increased when the endemic level decreased. In individual treatment strategy, the cost was USD 12.2 in adult male, USD 15.0 in adult female and USD 41.5 in children in very high prevalence group; USD 19.2 in adult male, USD 34.0 in adult female, and USD 90.1 in children in high prevalence group; USD 30.4 in adult male, USD 50.5 in adult female and over USD 100 in children in moderate prevalence group; and over USD 400 in any population in low prevalence group. As to cost utility, the differences by treatment strategies, populations and endemic levels were similar to those in cost effectiveness.

CONCLUSIONS

Both cost effectiveness and cost utility indicators are highly impacted by the prevalence and population, as well as the treatment schedules. Adults especially men in the areas with a prevalence over 10% should be prioritized, in which selective chemotherapy was best and massive chemotherapy was also cost effective. In moderate endemic areas, the yield is not ideal, but selective chemotherapy for adult male may also be adopted. In low endemic areas, all strategies were high costly and new strategies need to be developed.

Clonorchis sinensis re-infection rate and the determinants: a prospective cohort study in Hengxian County, Guangxi, China

BACKGROUND

To understand Clonorchis sinensis re-infection and the determinants in endemic areas is important in establishment of control measures.

METHODS

A prospective cohort study was implemented in Hengxian County, Guangxi, China. Individuals with C. sinensis infection were completely treated, and those cured were enrolled as study subjects and followed up for 3, 6 and 12 months. The re-infection frequency and incidence were calculated, and a multivariable Cox proportional hazard model was constructed to capture re-infection determinants.

RESULTS

Among 635 enrolled subjects, 436 (68.7%) completed follow-up. Of these, 177 (40.6%) were re-infected; 133 (75.1%) were re-infected once, 41 (23.2%) twice and 3 (1.7%) three times. The incidence of re-infection was 64.0 per 100 person-years. Males (aHR: 1.67, 95% CI: 1.14-2.44), those with underlying diseases (aHR: 1.41, 95% CI: 1.02-1.95), and those with moderate- and heavy-intensity infections (aHR: 1.45, 95% CI: 1.14-1.85) had increasing re-infection probabilities.

CONCLUSIONS

C. sinensis re-infection is high in endemic areas. Males and high-intensity infection are important determinants of re-infection. Repeated chemotherapy is necessary to control re-infection and its associated morbidities, especially in high-risk individuals. In addition, behavioural education is advised to decrease overall re-infection in endemic areas.

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.

Prevalence of Clonorchis sinensis infection in fish in South-East Asia: A systematic review and meta-analysis

Clonorchis sinensis, an important fish-borne zoonotic trematode, is widely distributed in South-East Asia, especially in China. Infections from human and animal reservoir hosts occur due to the consumption of raw or undercooked fish with C. sinensis metacercariae. This study aimed to evaluate the prevalence of C. sinensis metacercariae in fish in South-East Asia via systematic review and meta-analysis. We searched PubMed, ScienceDirect, China National Knowledge Infrastructure, Wanfang and Chongqing VIP databases for studies published between 1976 and 2020 that are related to the prevalence of C. sinensis metacercariae in fish. Studies were screened with keywords based on inclusion and exclusion criteria. Seventy-one eligible articles were identified, covering three countries: China, Korea and Vietnam. The pooled prevalence of C. sinensis metacercariae in fish from South-East Asia was 30.5%, with 35.1% in China, 29.7% in Korea and 8.4% in Vietnam. In subgroup analyses of climate, season, water source and publication date, the highest prevalence was identified in the Dwb climate type (43.3%), summer (70.2%), river (34.5%) and pre-2001 publications (38.9%), respectively. In comparison, the lowest prevalence was found in the Dfa climate type (14.5%), winter (19.5%), lake (8.0%) and post-2001 publications (23.8%). Meta-regression results indicated that country (p = .009), the published time (p = .035) and water source subgroups (p = .003) may be the source of heterogeneity. Overall, our study indicates that a high prevalence of C. sinensis infections occurs in fish in China, Korea and Vietnam, illuminating a significant public health concern in these countries.

High endemicity of Clonorchis sinensis infection in Binyang County, southern China

High-intensity clonorchiasis infection is associated with serious outcomes, including cancer. Understanding the infection intensity of Clonorchis sinensis and its risk factors in local endemic regions could facilitate effective control measures. In a county located in a highly endemic area in Guangxi Province, P. R. China, local residents were randomly enrolled in the study; helminth egg examinations were performed with the Kato-Katz method, and the intensity of infection was identified as mild, moderate or heavy. Knowledge, attitudes, and high-risk behaviours were investigated among those infected with Clonorchis sinensis. A total of 2521 local residents participated in this study, and the Clonorchis sinensis-positive proportion was 28.9% (728 persons). Among the infected persons, the percentages of mild, moderate and heavy infections were 66.2%, 28.4% and 5.4%, respectively. Males experienced a higher proportion of moderate and heavy infections (37.5%) than females (18.1%) (p<0.05). The highest infection proportion among the different levels of infection intensity was identified among persons aged 30-59 years (15.7% for moderate and heavy infections). Among the 509 persons who reported eating raw fish, 302 persons (59.3%) had eaten raw fresh fish for more than 10 years, and 131 (25.7%) persons ate raw fish ≥12 times a year. Multivariate logistic regression revealed that eating raw fish 12-50 times in the last year (adjusted odds ratio [aOR] = 1.74, 95%CI: 1.09-2.80) and eating raw fish >50 times in the last year (aOR = 2.89, 95%CI: 1.20-7.50) were risk factors for high-intensity infections (moderate and heavy). The overall infection proportion was high in the study area, with a large group of residents experiencing high-intensity infections. High frequency of raw fish consumption was associated with high-intensity infections. Intervention strategies targeting people with a high frequency of raw fish consumption should be implemented to reduce the probability of severe consequences.

Effectiveness of health education in improving knowledge, practice and belief related to clonorchiasis in children

Clonorchiasis is caused by the ingestion of raw freshwater fish containing Clonorchis sinensis larvae. Health education is crucial in sustainable control of clonorchiasis but extremely challenging when dealing with adults. To investigate if education in children would be a beneficial long-term approach, a cluster-controlled trial was implemented in two primary schools between 2017 and 2019 in Binyang county, Guangxi, China. A baseline survey was conducted in both schools, and then comprehensive education activities were implemented in the interventional one. Six and 12 months later, all pupils were subjected to a survey to assess the potential change of knowledge, practice and belief related to clonorchiasis. Finally, 247 pupils in interventional school and 151 ones in control were eligible for analysis. In the interventional school, the percentage of pupils with knowledge on transmission route, early symptoms, complications and carcinogenicity increased from 15.0% to 78.5% (p < 0.001), from 6.5% to 36.8% (p < 0.001), from 4.0% to 93.9% (p < 0.001) and from 4.5% to 49.4% (p < 0.001) after 12 months. In this school, 16 pupils (6.5%) had eaten raw freshwater fish during the year immediately before the baseline survey, a number that decreased to 3 (1.2%) (p = 0.002) 12 months later. The percentage of students had the belief on the ability not to eat raw freshwater fish in the future was 70.9% at the baseline and 97.2% 12 months later (p < 0.001). Although knowledge related to clonorchiasis also increased in the control school, the absolute percentage of changes was lower; in particular, practice and belief had not changed.

Rapid screening of Clonorchis sinensis infection: Performance of a method based on raw-freshwater fish-eating practice

Clonorchis sinensis infection is caused by ingestion of raw freshwater fish containing the infective larvae of Clonorchis sinensis. It is highly endemic in East Asia, especially in China. Selective chemotherapy of people who report habitual eating of raw freshwater fish is a control measure. As the performance of this screening technique has not yet been fully evaluated in China, a cross-sectional study was conducted, covering 17 counties in four major clonorchiasis-endemic provinces. About 1 000 participants were enrolled from each county. Fecal samples were collected and examined for helminth eggs and each person enrolled was asked about their practice with respect to eating raw freshwater fish. In total, 16 230 participants from 16 counties were finally included. The overall prevalence of C. sinensis infection was 10.8%, ranging from 0 to 53.7% in the 16 counties, while the percentage of inhabitants eating raw freshwater fish was 26.5%, ranging from 0 to 79.1%. The overall sensitivity and specificity of screening for C. sinensis infection in this approach was 82.3% and 80.3%, respectively, yielding a Youden's index of 0.6. The overall positive and negative likelihood ratios were 4.2 and 0.2, respectively, while the overall positive and negative predictive values were 33.5% and 97.4%, respectively. Furthermore, the sensitivity was higher with regard to high-intensity infections compared to light infections.

Familial assimilation in transmission of raw-freshwater fish-eating practice leading to clonorchiasis

Clonorchiasis is caused by raw-freshwater fish-eating practice and causes high burden in Asia. Transmission mechanism of this behavior hasn't been illuminated, which hinders the adoption of sustainable control activities. A cross-sectional survey was implemented in students from four endemic provinces in China. Data with 23,222 students aged 9-18 and their parents were eligible. Familial clustering of raw-eating practice, impact of parents' practice on children, interaction of spouses' practice was analyzed. Raw-eating practice met β-binomial distribution (χ2 = 0.8, p>0.05). Clustering coefficient increased by students' age (R2 = 0.82, p<0.001) and was higher in those families with boys compared to girls (t = 4.1, p<0.01). The proportion of students with raw-eating practice increased yearly by 8.9% in girls and 10.5% in boys. Compared to those without parents' raw-eating practice, adjusted odds ratio of students' raw-eating practice was 10.5 (95% confidential intervals (95% CI): 9.4-11.7) in those with fathers' practice, 33.6 (95% CI: 26.3-42.9) in those with mothers' practice and 47.1 (95% CI: 42.0-52.8) in those with both parents' practice. There existed interaction between spouses' practice (χ2 = 6713.1, p<0.001) and the impact from husband on his wife was higher than that from wife on her husband. Familial assimilation characterizes the transmission of raw-freshwater fish-eating practice, consisted of vertical intergenerational assimilation from parents to their children and horizontal martial assimilation between spouses. A sustainable strategy against clonorchiasis should interrupt the transmission of raw-freshwater fish-eating practice. Additionally, further studies are expected to explore more information, e.g. the frequency in raw-eating practice and type of raw freshwater fish, infection status of C. sinensis in participants, as well as direct collection of parents' eating information from themselves.

Assessment of control strategies against Clonorchis sinensis infection based on a multi-group dynamic transmission model

Clonorchiasis is one of the most important food-borne trematodiases affecting millions of people. Strategies were recommended by different organizations and control programmes were implemented but mostly in short-time periods. It's important to assess the long-term benefits and sustainability of possible control strategies on morbidity control of the disease. We developed a multi-group transmission model to describe the dynamics of C. sinensis transmission among different groups of people with different raw-fish-consumption behaviors, based on which, a full model with interventions was proposed and three common control measures (i.e., preventive chemotherapy, information, education, and communication (IEC) and environmental modification) and their possible combinations were considered. Under a typical setting of C. sinensis transmission, we simulated interventions according to different strategies and with a series of values of intervention parameters. We found that combinations of measures were much beneficial than those singly applied; higher coverages of measures had better effects; and strategies targeted on whole population performed better than that on at-risk population with raw-fish-consumption behaviors. The strategy recommended by the government of Guangdong Province, China shows good and sustainable effects, under which, the infection control (with human prevalence <5%) could be achieved within 7.84 years (95% CI: 5.78-12.16 years) in our study setting (with original observed prevalence 33.67%). Several sustainable strategies were provided, which could lead to infection control within 10 years. This study makes the effort to quantitatively assess the long-term effects of possible control strategies against C. sinensis infection under a typical transmission setting, with application of a multi-group dynamic transmission model. The proposed model is easily facilitated with other transmission settings and the simulation outputs provide useful information to support the decision-making of control strategies on clonorchiasis.

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.

From awareness to action: NIPD's engagement in the control of food-borne clonorchiasis

Clonorchiasis is caused by ingestion of raw freshwater fish containing infective larvae of Clonorchis sinensis. China harbours the largest number of people with C. sinensis infection. During the past three decades, the National Institute of Parasitic Diseases, affiliated to the Chinese Center for Disease Control and Prevention (NIPD) conducted many studies to facilitate the control on clonorchiasis. Three national surveys have shown the updated epidemiology of clonorchiasis in China. Recently, a national surveillance system has also been established, which will enable the production of high-resolution map. The evaluation of the disease burden has enhanced the awareness on clonorchiasis. Diverse diagnosis techniques including rapid screening by questionnaire, serological tests, faecal examination and a molecular method have been developed or evaluated. The NIPD also participated in the early evaluation of praziquantel against clonorchiasis, which enhanced its application in China. Also, the NIPD has verified the efficacy of tribendimidine against clonorchiasis. A new sustainable strategy is also being explored. However, more research is expected to further facilitate control of clonorchiasis in China, as well as international cooperation in fighting human liver fluke infections in Asia.

Differential Change in the Prevalence of the Ascaris, Trichuris and Clonorchis infection Among Past East Asian Populations

As we learn more about parasites in ancient civilizations, data becomes available that can be used to see how infection may change over time. The aim of this study is to assess how common certain intestinal parasites were in China and Korea in the past 2000 years, and make comparisons with prevalence data from the 20th century. This allows us to go on to investigate how and why changes in parasite prevalence may have occurred at different times. Here we show that Chinese liver fluke (Clonorchis sinensis) dropped markedly in prevalence in both Korea and China earlier than did roundworm (Ascaris lumbricoides) and whipworm (Trichuris trichiura). We use historical evidence to determine why this was the case, exploring the role of developing sanitation infrastructure, changing use of human feces as crop fertilizer, development of chemical fertilizers, snail control programs, changing dietary preferences, and governmental public health campaigns during the 20th century.

Acute shock caused by Clonorchis sinensis infection: a case report

Background

Clonorchiasis, caused by Clonorchis sinensis (C. sinensis) infection, is a serious food-borne zoonotic disease that is often asymptomatic or shows only mild symptoms, which leads to delayed treatment and chronic clonorchiasis and results in various complications, such as cholelithiasis, cholangitis, cholecystitis and cholangiocarcinoma. However, acute shock caused by C. sinensis infection has not been reported. Here, for the first time, we describe a fatal case of acute shock caused by C. sinensis infection.

Case presentation

A patient with a history of eating raw or undercooked freshwater fish was hospitalized with acute shock caused by severe abdominal pain. Physical examination suggested acute abdomen with severe abdominal pain and rigidity. Computed tomography (CT) detection indicated acute cholecystitis and cholelithiasis. After cholecystectomy, several liver flukes were found in the drainage tube. Furthermore, morphological analysis and polymerase chain reaction (PCR) identified the pathogen as C. sinensis. The liver gradually restored normal function after anthelmintic therapy with praziquantel.

Conclusions

In this fatal case, C. sinensis infection was the cause of acute shock, which is rarely found in the clinic environment. This report aims to increase awareness of the hazards and complications related to clonorchiasis. The PCR diagnosis method used in this report might be helpful in reducing the misdiagnosis of clonorchiasis and unnecessary cholecystectomy.

Neglected tropical diseases in the People's Republic of China: progress towards elimination

Since the founding of the People's Republic of China in 1949, considerable progress has been made in the control and elimination of the country's initial set of 11 neglected tropical diseases. Indeed, elimination as a public health problem has been declared for lymphatic filariasis in 2007 and for trachoma in 2015. The remaining numbers of people affected by soil-transmitted helminth infection, clonorchiasis, taeniasis, and echinococcosis in 2015 were 29.1 million, 6.0 million, 366 200, and 166 100, respectively. In 2017, after more than 60 years of uninterrupted, multifaceted schistosomiasis control, has seen the number of cases dwindling from more than 10 million to 37 600. Meanwhile, about 6000 dengue cases are reported, while the incidence of leishmaniasis, leprosy, and rabies are down at 600 or fewer per year. Sustained social and economic development, going hand-in-hand with improvement of water, sanitation, and hygiene provide the foundation for continued progress, while rigorous surveillance and specific public health responses will consolidate achievements and shape the elimination agenda. Targets for poverty elimination and strategic plans and intervention packages post-2020 are important opportunities for further control and elimination, when remaining challenges call for sustainable efforts.

Improving diagnostic performance of the Kato-Katz method for Clonorchis sinensis infection through multiple samples

BACKGROUND

Clonorchiasis is caused by eating of raw or undercooked freshwater fish containing the larvae of Clonorchis sinensis; the Kato-Katz method is widely applied in diagnosis. The improvement of repeated Kato-Katz smears from multiple stool samples has been well illuminated in many helminths other than C. sinensis.

METHODS

A cross-sectional investigation was implemented to capture the epidemiology and risk factors of clonorchiasis among middle school students in Qiyang county, China. Students with complete data of six Kato-Katz thick smears from two stool samples were included in this analysis. Data on the habits of eating raw freshwater fish were also collected and compared.

RESULTS

Altogether, 397 students had complete information of six smears, out of which 394 reported the information on eating habits. According to the 'gold' standard by six smears, 77 students (19.4%) were detected with C. sinensis. However, only 45 (11.3%) were detected using a single smear, with an underestimation of 41.6% compared to the 'gold' standard. However, the geometric mean of eggs per gram of feces in detected cases was 126.4 in a single smear, overestimated by 105.2% compared to 61.6 by the 'gold' standard. The linear relationship between prevalence and infection intensity of detected cases based on different smears was significantly negative. The habits of eating raw freshwater fish in the false negative cases was similar to those in the detected cases, but these two groups had significantly higher levels for habits of eating raw freshwater fish than negative individuals.

CONCLUSIONS

In low endemicity situations, underestimation of C. sinensis infection could not be avoided based on a limited number of Kato-Katz smears. Thus, repeated smears from at least two stool samples should be considered when an individual eats raw freshwater fish, drug efficacy is evaluated or elimination of C. sinensis is verified. Additionally, when logistics are insufficient for multiple samples to be taken for diagnosis for survey and surveillance in the areas or populations of low endemicity, prevalence accuracy needs to be corrected.

Molecular Identification and Phylogenetic Analysis of Nuclear rDNA Sequences of Clonorchis sinensis Isolates From Human Fecal Samples in Heilongjiang Province, China

Studying the genetic diversity of parasite is important for understanding their biogeography and molecular epidemiology, as well as for establishing disease prevention and control strategies. Clonorchis sinensis is an important foodborne parasite worldwide. However, despite its epidemiological significance, the genetic diversity of C. sinensis has not been well studied from human in northeastern China. In this study, a total of 342 fecal specimens were collected from residents living in five villages in Heilongjiang Province and analyzed for the presence of C. sinensis by PCR amplification and sequencing of the internal transcribed spacer 1 (ITS1) and ITS2 regions of nuclear ribosomal DNA. 21.64% (74/342) of fecal samples were found to be positive for C. sinensis by PCR. The sequences of the ITS1 region in 34 of the 74 samples (45.95%) matched that of MK179278, Genetic polymorphisms were observed at six nucleotide sites. The ITS2 gene sequence of 37 of the 74 samples (50%) matched that of MK179281. In conclusion, a low degree of genetic diversity between C. sinensis isolates from China and different geographical regions was found at ITS loci. Despite this conservation, sequencing of the rDNA region has provided important data that will be useful for future studies addressing the molecular evolution, biology, medical implications and ecology of C. sinensis.

Performance evaluation of existing immunoassays for Clonorchis sinensis infection in China

BACKGROUND

Clonorchiasis ranks among the most important food-borne parasitic diseases in China. However, due to low compliance to traditional fecal examination techniques in the general population and medical personnel, immunodiagnosis is expected. This study evaluated, in parallel, the performance of four immunodiagnostic kits detecting clonorchiasis in China.

RESULTS

A bank with 475 sera was established in this study. Except for the low performance of the kit detecting IgM, the other three kits detecting IgG showed sensitivities ranging from 81.51% (194/238) to 99.16% (236/238). Higher sensitivity was presented in heavy infection intensity [89.47% (68/76) to 100% (76/76)]. Among the four kits, the overall specificity varied from 73.42% (174/237) to 87.34% (207/237). It was observed that the specificity was lower in the sera of the participants living in clonorchiasis-endemic areas but without any parasite infection [67.5% (81/120) to 90% (108/120)], as compared to those from the non-endemic area [94% (47/50) to 98% (49/50)]. The cross-reaction rate varied from 14.93% (10/67) to 31.34% (21/67). Youden's index was -0.022, 0.689, 0.726, and 0.802 for kits T1, T2, T3 and T4, respectively. Repeatability was high in all four kits.

CONCLUSIONS

Three immunodiagnosis kits targeting IgG antibody had high performance on detecting chronic Clonorchis sinensis infection, but that detecting IgM antibody had not. The kits detecting IgG antibody also showed high sensitivity in heavy infection intensity. Research on immunological diagnosis of clonorchiasis is expected to be strengthened to improve the sensitivity in light infection and specificity.

Clonorchis sinensis and Clonorchiasis: The Relevance of Exploring Genetic Variation

Parasitic trematodes (flukes) cause substantial mortality and morbidity in humans. The Chinese liver fluke, Clonorchis sinensis, is one of the most destructive parasitic worms in humans in China, Vietnam, Korea and the Russian Far East. Although C. sinensis infection can be controlled relatively well using anthelmintics, the worm is carcinogenic, inducing cholangiocarcinoma and causing major suffering in ~15 million people in Asia. This chapter provides an account of C. sinensis and clonorchiasis research-covering aspects of biology, epidemiology, pathogenesis and immunity, diagnosis, treatment and control, genetics and genomics. It also describes progress in the area of molecular biology (genetics, genomics, transcriptomics and proteomics) and highlights challenges associated with comparative genomics and population genetics. It then reviews recent advances in the sequencing and characterisation of the mitochondrial and nuclear genomes for a Korean isolate of C. sinensis and summarises salient comparative genomic work and the implications thereof. The chapter concludes by considering how advances in genomic and informatics will enable research on the genetics of C. sinensis and related parasites, as well as the discovery of new fluke-specific intervention targets.

Hepatic iron overload is associated with hepatocyte apoptosis during Clonorchis sinensis infection

Background

Hepatic iron overload has been implicated in many liver diseases; however, whether it is involved in clonorchiasis remains unknown. The purpose of this study is to investigate whether Clonorchis sinensis (C. sinensis) infection causes hepatic iron overload, analyze the relationship between the iron overload and associated cell apoptosis, so as to determine the role of excess iron plays in C. sinensis-induced liver injury.

Methods

The Perls’ Prussian staining and atomic absorption spectrometry methods were used to investigate the iron overload in hepatic sections of wistar rats and patients infected with C. sinensis. The hepatic apoptosis was detected by transferase uridyl nick end labeling (TUNEL) methods. Spearman analysis was used for determining the correlation of the histological hepatic iron index and the apoptotic index.

Results

Blue iron particles were deposited mainly in the hepatocytes, Kupffer cells and endothelial cells, around the liver portal and central vein area of both patients and rats. The total iron score was found to be higher in the infected groups than the respective control from 8 weeks. The hepatic iron concentration was also significantly higher in treatment groups than in control rats from 8 weeks. The hepatocyte apoptosis was found to be significantly higher in the portal area of the liver tissue and around the central vein. However, spearman’s rank correlation coefficient revealed that there was a mildly negative correlation between the iron index and hepatocyte apoptosis.

Conclusions

This present study confirmed that hepatic iron overload was found during C. sinensis infection. This suggests that iron overload may be associated with hepatocyte apoptosis and involved in liver injury during C. sinensis infection. Further studies are needed to investigate the molecular mechanism involved here.

Molecular and Structural Characterization of the Tegumental 20.6-kDa Protein in Clonorchis sinensis as a Potential Druggable Target

The tegument, representing the membrane-bound outer surface of platyhelminth parasites, plays an important role for the regulation of the host immune response and parasite survival. A comprehensive understanding of tegumental proteins can provide drug candidates for use against helminth-associated diseases, such as clonorchiasis caused by the liver fluke Clonorchis sinensis. However, little is known regarding the physicochemical properties of C. sinensis teguments. In this study, a novel 20.6-kDa tegumental protein of the C. sinensis adult worm (CsTegu20.6) was identified and characterized by molecular and in silico methods. The complete coding sequence of 525 bp was derived from cDNA clones and encodes a protein of 175 amino acids. Homology search using BLASTX showed CsTegu20.6 identity ranging from 29% to 39% with previously-known tegumental proteins in C. sinensis. Domain analysis indicated the presence of a calcium-binding EF-hand domain containing a basic helix-loop-helix structure and a dynein light chain domain exhibiting a ferredoxin fold. We used a modified method to obtain the accurate tertiary structure of the CsTegu20.6 protein because of the unavailability of appropriate templates. The CsTegu20.6 protein sequence was split into two domains based on the disordered region, and then, the structure of each domain was modeled using I-TASSER. A final full-length structure was obtained by combining two structures and refining the whole structure. A refined CsTegu20.6 structure was used to identify a potential CsTegu20.6 inhibitor based on protein structure-compound interaction analysis. The recombinant proteins were expressed in Escherichia coli and purified by nickel-nitrilotriacetic acid affinity chromatography. In C. sinensis, CsTegu20.6 mRNAs were abundant in adult and metacercariae, but not in the egg. Immunohistochemistry revealed that CsTegu20.6 localized to the surface of the tegument in the adult fluke. Collectively, our results contribute to a better understanding of the structural and functional characteristics of CsTegu20.6 and homologs of flukes. One compound is proposed as a putative inhibitor of CsTegu20.6 to facilitate further studies for anthelmintics.

Risk mapping of clonorchiasis in the People's Republic of China: A systematic review and Bayesian geostatistical analysis

BACKGROUND

Clonorchiasis, one of the most important food-borne trematodiases, affects more than 12 million people in the People's Republic of China (P.R. China). Spatially explicit risk estimates of Clonorchis sinensis infection are needed in order to target control interventions.

METHODOLOGY

Georeferenced survey data pertaining to infection prevalence of C. sinensis in P.R. China from 2000 onwards were obtained via a systematic review in PubMed, ISI Web of Science, Chinese National Knowledge Internet, and Wanfang Data from January 1, 2000 until January 10, 2016, with no restriction of language or study design. Additional disease data were provided by the National Institute of Parasitic Diseases, Chinese Center for Diseases Control and Prevention in Shanghai. Environmental and socioeconomic proxies were extracted from remote-sensing and other data sources. Bayesian variable selection was carried out to identify the most important predictors of C. sinensis risk. Geostatistical models were applied to quantify the association between infection risk and the predictors of the disease, and to predict the risk of infection across P.R. China at high spatial resolution (over a grid with grid cell size of 5×5 km).

PRINCIPAL FINDINGS

We obtained clonorchiasis survey data at 633 unique locations in P.R. China. We observed that the risk of C. sinensis infection increased over time, particularly from 2005 onwards. We estimate that around 14.8 million (95% Bayesian credible interval 13.8-15.8 million) people in P.R. China were infected with C. sinensis in 2010. Highly endemic areas (≥ 20%) were concentrated in southern and northeastern parts of the country. The provinces with the highest risk of infection and the largest number of infected people were Guangdong, Guangxi, and Heilongjiang.

CONCLUSIONS/SIGNIFICANCE

Our results provide spatially relevant information for guiding clonorchiasis control interventions in P.R. China. The trend toward higher risk of C. sinensis infection in the recent past urges the Chinese government to pay more attention to the public health importance of clonorchiasis and to target interventions to high-risk areas.

Current status and perspectives of Clonorchis sinensis and clonorchiasis: epidemiology, pathogenesis, omics, prevention and control

Clonorchiasis, caused by Clonorchis sinensis (C. sinensis), is an important food-borne parasitic disease and one of the most common zoonoses. Currently, it is estimated that more than 200 million people are at risk of C. sinensis infection, and over 15 million are infected worldwide. C. sinensis infection is closely related to cholangiocarcinoma (CCA), fibrosis and other human hepatobiliary diseases; thus, clonorchiasis is a serious public health problem in endemic areas. This article reviews the current knowledge regarding the epidemiology, disease burden and treatment of clonorchiasis as well as summarizes the techniques for detecting C. sinensis infection in humans and intermediate hosts and vaccine development against clonorchiasis. Newer data regarding the pathogenesis of clonorchiasis and the genome, transcriptome and secretome of C. sinensis are collected, thus providing perspectives for future studies. These advances in research will aid the development of innovative strategies for the prevention and control of clonorchiasis.

Painless Jaundice Caused by Clonorchis sinensis Infection: A Case Report

A man with only yellowing of the skin and eye sclera was diagnosed with clonorchiasis, which rarely manifested jaundice as the initial symptom. However, because of a lack of evidence for a diagnostic gold standard, the time until definitive diagnosis was more than a week. The diagnostic process relied on inquiring about the patient's history, including the place of residence, dietary habits, and symptoms, as well as on serological findings, an imaging examination, and pathological findings. MRCP and CT results showed mild dilatation of intrahepatic ducts and increased periductal echogenicity. The eggs were ultimately found in stool by water sedimentation method after the negative report through direct smear. DNA sequencing of PCR production of the eggs demonstrated 98-100% homology with ITS2 of Clonorchis sinensis. After anti-parasite medical treatment, the patient's symptoms were gradually relieved. Throughout the diagnostic procedure, besides routine examinations, the sedimentation method or concentration method could be used as a sensitive way for both light and heavy C. sinensis infection in the definite diagnosis.

Clonorchiasis

On Aug 21, 1875, James McConnell published in The Lancet his findings from a post-mortem examination of a 20-year-old Chinese man--undertaken at the Medical College Hospital in Calcutta, India--in whom he found Clonorchis sinensis in the bile ducts. Now, exactly 140 years later, we have a sound understanding of the lifecycle of this liver fluke, including key clinical, diagnostic, and epidemiological features. Developments in the so-called -omics sciences have not only advanced our knowledge of the biology and pathology of the parasite, but also led to the discovery of new diagnostic, drug, and vaccine targets. C sinensis infection is primarily related to liver and biliary disorders, especially cholangiocarcinoma. Clonorchiasis mainly occurs in east Asia, as a result of the region's social-ecological systems and deeply rooted cultural habit of consuming raw freshwater fish. The Kato-Katz technique, applied on fresh stool samples, is the most widely used diagnostic approach. Praziquantel is the treatment of choice and has been considered for preventive chemotherapy. Tribendimidine showed good safety and therapeutic profiles in phase 2 trials and warrants further investigation. Still today, the precise distribution, the exact number of infected people, subtle morbidities and pathogenesis, and the global burden of clonorchiasis are unknown. Integrated control strategies, consisting of preventive chemotherapy; information, education, and communication; environmental management; and capacity building through intersectoral collaboration should be advocated.

Rare cause of jaundice in a post liver transplant patient

A hepatitis B virus carrier suffering from acute flare of chronic hepatitis B infection underwent deceased-donor liver transplantation. He was put on the immunosuppressive agent tacrolimus. On routine follow-up, he was found to have abnormal liver function. Computed tomography scan of the abdomen did not show any dilatation of the biliary system. Liver biopsy showed scattered microabscesses, and a microgranuloma was detected. Endoscopic retrograde cholangiography was performed and a biliary anastomotic stricture (BAS) was noted. In addition, the Chinese liver fluke, Clonorchis sinensis, was discovered. Balloon dilatation and stenting were performed. The patient was given a course of praziquantel. His liver function improved and normalized. We present the case of a liver transplant recipient with cholangitis caused by C. sinensis infestation and infection and biliary obstruction resulting from BAS.

High reinfection rate after preventive chemotherapy for fishborne zoonotic trematodes in Vietnam

Background

The World Health Organization aims for complete morbidity control of fishborne zoonotic trematodes (FZT) in endemic areas by 2020. The main intervention tool for achieving this goal is regular use of preventive chemotherapy by offering praziquantel to those at risk in endemic areas. The purpose of this study was to investigate the effectiveness of preventive chemotherapy to control FZT in an endemic area in Northern Vietnam.

Methodology and principle findings

We followed a cohort of 396 people who fulfilled the criteria for receiving preventive chemotherapy. Stool samples were examined by Kato-Katz technique for the presence of trematode eggs before, and two, 16, 29 and 60 weeks after preventive chemotherapy. The prevalence of trematode eggs in stool was 40.2% before, 2.3% two weeks after and increased to a cumulative prevalence of 29.8% sixty weeks after preventive chemotherapy.

Conclusions

The effectiveness of preventive chemotherapy as a main component in control of FZT is not well documented in most endemic areas. We found a high reinfection rate within the first year after preventive chemotherapy. Since these trematodes are zoonoses, preventive chemotherapy may not have sufficient impact alone on the transmission to have a lasting effect on the prevalence. Animal reservoirs and farm management practices must be targeted to achieve sustainable control of fishborne zoonotic trematode infections, hence control programs should consider a One Health approach.

Fishborne zoonotic trematodes (FZT) are small parasitic flatworms (flukes) living either in the intrahepatic bile ducts or in the intestines of humans and many species of animals and birds. Transmission occurs by eating infected raw freshwater fish. FZT are especially common in Southeast and East Asia. WHO suggests using preventive chemotherapy in the control of these parasites by providing an effective drug, praziquantel, once a year to either all inhabitants in the endemic areas or selectively to those who are at special risk because they eat raw fish. Preventive chemotherapy has been used for some years in Northern Vietnam, but the effectiveness has not been thoroughly examined. We followed a group of 396 people who had eaten raw fish and examined the stool for the presence of trematode eggs before preventive chemotherapy and two, 16, 29 and 60 weeks after. The proportions of egg positive persons were 40.2% before, 2.3% two weeks after and increased to 29.8% sixty weeks after preventive chemotherapy. We found a high rate of reinfection. Contribution from animals to the transmission implies that preventive chemotherapy of humans alone will most likely be insufficient to control the FZT infections.

Control of clonorchiasis in Korea: effectiveness of health education for community leaders and individuals in an endemic area

OBJECTIVES

To develop effective intervention programmes to control Clonorchis sinensis infection, three interventions were evaluated in a clonorchiasis-endemic area of Korea.

METHODS

Four thousand two hundred and sixty-seven voluntary participants in Sancheong county were tested at baseline and two follow-up surveys after 1 and 3 years. Faecal samples were examined for C. sinensis eggs using the Kato-Katz method. Participants were divided into three intervention groups by areas and year recruited: national prevention programme only (mass health campaign and praziquantel treatment) for Group A; health education for community leaders added for Group B; and individual health education added for Group C.

RESULTS

The prevalence of C. sinensis infection fell substantially in all three intervention groups between baseline and 3-year follow-up: from 31.1% to 14.9% in Group A, from 29.6% to 6.8% in Group B and from 21.9% to 8.6% in Group C. The control effectiveness was highest in Group B with 76.8%. The new infection rate was 16.3%, 12.8% and 7.6% in Group A, B and C, respectively. The reinfection rate was lower in Group B (3.8%) than Group C (12.2%).

CONCLUSIONS

To control C. sinensis infection in endemic areas of Korea, health education for community leaders or individuals on prevention of C. sinensis infection should be added to national control programmes.

Trends in prevalence of clonorchiasis among patients in Heilongjiang province, Northeast China (2009-2012): implications for monitoring and control

Background

Clonorchiasis is an important zoonotic parasitic disease worldwide. Past estimates showed the prevalence increased based on studies undertaken ten years or more ago. However, control strategies, changing ecology and migration may have resulted to changes in the prevalence of clonorchiasis. The purpose of the present study was to analysis the prevalence and epidemiological characterisation of clonorchiasis in Heilongjiang Province, Northeast China.

Methodology/Principal Findings

A total of 4951 clinically suspected outpatients were examined from January 2009 to December 2012. Overall prevalence of clonorchiasis was 25.93% (1284/4951) by the combination strategy of the Kato-Katz technique (KK) and enzyme-linked immunosorbent assay (ELISA), with a significant increase from 22.53% in 2009 to 34.25% in 2012. Apart from Daxinganling city, clonorchiasis was reported throughout Heilongjiang Province and mainly along the Songhua River and Nen River basin, with an increased annual prevalence. The annual prevalence in men increased significantly in 2012 and was higher than that in women over 4 years. A similar pattern was seen for the annual infection rate in rural and urban areas. Farm labourers accounted for the majority of cases (65.93%), with a higher prevalence than in other occupations. Consumption of freshwater fish was considered the strongest risk factor of clonorchiasis. The infection rates in the 40–49 and 50–59 years age groups showed a significant increasing trend in 2012. Cases of re-infection were common.

Conclusions/Significance

The present study revealed that clonorchiasis remained widespread and prevalent in Heilongjiang Province. An integrated control programme is urgently needed to reduce the public health impact of clonorchiasis in this endemic area.

Accuracy of the Kato-Katz method and formalin-ether concentration technique for the diagnosis of Clonorchis sinensis, and implication for assessing drug efficacy

Background

Clonorchiasis is a chronic neglected disease caused by a liver fluke, Clonorchis sinensis. Chemotherapy is the mainstay of control and treatment efficacy is usually determined by microscopic examination of fecal samples. We assessed the diagnostic accuracy of the Kato-Katz method and the formalin-ether concentration technique (FECT) for C. sinensis diagnosis, and studied the effect of diagnostic approach on drug efficacy evaluation.

Methods

Overall, 74 individuals aged ≥18 years with a parasitological confirmed C. sinensis infection at baseline were re-examined 3 weeks after treatment. Before and after treatment, two stool samples were obtained from each participant and each sample was subjected to triplicate Kato-Katz thick smears and a single FECT examination.

Results

Thirty-eight individuals were still positive for C. sinensis according to our diagnostic ‘gold’ standard (six Kato-Katz thick smears plus two FECT). Two FECT had a significantly lower sensitivity than six Kato-Katz thick smears (44.7% versus 92.1%; p <0.001). Examination of single Kato-Katz and single FECT considerably overestimated cure rates.

Conclusions

In settings where molecular diagnostic assays are absent, multiple Kato-Katz thick smears should be examined for an accurate diagnosis of C. sinensis infection and for assessing drug efficacy against this liver fluke infection.

Prevalence and Risk Factors of Clonorchiasis among the Populations Served by Primary Healthcare Posts along Five Major Rivers in South Korea

Objectives:

Clonorchiasis is an infectious disease caused by the Chinese liver fluke Clonorchis sinensis. In this study, we investigated the prevalence and risk factors of clonorchiasis among the populations served by primary healthcare posts along five major rivers in South Korea.

Methods:

Forty primary healthcare posts that are located less than 5 km from one of the five rivers were selected from 26 counties. For the purpose of the survey, community health practitioners selected the nearest villages from the riversides in their own catchment area. From January to May 2009, a total of 2788 stool samples were collected and examined using the formalin–ether sedimentation technique. Village inhabitants were also interviewed by means of questionnaires in order to obtain information on potential risk factors.

Results:

The prevalence rates of clonorchiasis at various river basins were as follows: Seomjin River, 21.3%; Nakdong River, 13.5%; Geum River, 9.2%; Han River, 7.6%; and Yeongsan River, 4.9%. The total number of people infected with C. sinensis was 329 (11.3%). By gender, 14.3% of males and 7.6% of females were infected. In case of both males and females, the prevalence rate was highest in those in their 40s. Consumption of raw freshwater fish was confirmed as a risk factor based on a logistic regression analysis.

Conclusion:

The present findings suggest that clonorchiasis is still highly prevalent among the inhabitants of riverside areas in southern Korea, and, accordingly, it is necessary to implement a systematic control program in the endemic areas.

Epidemiological profile of Clonorchis sinensis infection in one community, Guangdong, People's Republic of China

BACKGROUND

Clonorchiasis caused by ingesting improperly prepared fish ranks among the most important but still neglected food-borne parasitic diseases, especially in the People's Republic of China (P.R. China). To promote the implementation of interventions efficiently, the demonstration of an epidemiological profile of Clonorchis sinensis infection is essential in hyper-epidemic areas.

METHODS

In one community with higher levels of economic development in Guangdong province, P.R. China, villagers were motivated to provide stool samples for examining helminth eggs. Then, those infected with C. sinensis completed the structured questionnaire including demographical characteristics, knowledge and behavior.

RESULTS

A total of 293 villagers infected with C. sinensis participated in questionnaire investigation. Among them, 94.54% were adult and 93.17% were indigenous. The geometric mean of C. sinensis eggs per gram of feces in the children, adult females and adult males was 58, 291 and 443, respectively. The divergence between knowledge and behavior in the adults, especially the adult males, was shown. Out of 228 persons eating raw fish, 160 did it more frequently at restaurants, the proportion of which varied in different populations, showing 25.00%, 54.88% and 80.28% in the children, adult females and adult males, respectively.

CONCLUSIONS

Different interventions need to be adopted in different populations. Chemotherapy should be prioritized in the adults, especially the adult males. In addition, health education targeting the children, is essential and may play a crucial role in controlling clonorchiasis in the long term. In order to successfully control clonorchiasis, intervention in the restaurant should not be overlooked in some endemic areas.

Microscopic examination of gallbladder stones improves rate of detection of Clonorchis sinensis infection

To improve the rate of detection of Clonorchis sinensis infection, we compared different specimens from patients with cholecystolithiasis. Feces, gallbladder bile, and gallbladder stones collected from 179 consecutive patients with cholecystolithiasis underwent microscopic examination, and according to the results, 30 egg-positive and 30 egg-negative fecal, gallbladder bile, and gallbladder stone specimens, respectively, underwent real-time fluorescent PCR. The detection rates of eggs in feces, bile, and gallbladder stones were 30.7%, 44.7%, and 69.8%, respectively, and the differences were statistically significant (P<0.01). The PCR results confirmed that the eggs in the specimens were C. sinensis eggs. Eggs in the feces were "fresh" and in the gallbladder stones were "old." Microscopic examination of gallbladder stones may improve the detection rates of C. sinensis infection, which is important for developing individualized treatments to prevent the recurrence of gallbladder stones and to prevent the occurrence of severe liver damage and cholangiocarcinoma.