A combination of the Kato-Katz methods and ELISA to improve the diagnosis of clonorchiasis in an endemic area, China

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.

High-throughput detection of parasites and ova in stool using the fully automatic digital feces analyzer, orienter model fa280

BACKGROUND

Intestinal parasitic infections can harm health by causing malnutrition, anemia, impaired growth and cognitive development, and alterations in microbiota composition and immune responses. Therefore, it is crucial to examine stool samples to diagnose parasitic infections. However, the traditional microscopic detection method is time-consuming, labor-intensive, and dependent on the expertise and training of microscopists. Hence, there is a need for a low-complexity, high-throughput, and cost-effective alternative to labor-intensive microscopic examinations.

METHODS

This study aimed to compare the performance of a fully automatic digital feces analyzer, Orienter Model FA280 (People's Republic of China) with that of the formalin-ethyl acetate concentration technique (FECT). We assessed and compared the agreement between the FA280 and the FECT for parasite detection and species identification in stool samples. The first part of the study analyzed 200 fresh stool samples for parasite detection using the FECT and FA280. With the FA280, the automatic feces analyzer performed the testing, and the digital microscope images were uploaded and automatically evaluated using an artificial intelligence (AI) program. Additionally, a skilled medical technologist conducted a user audit of the FA280 findings. The second set of samples comprised 800 preserved stool samples (preserved in 10% formalin). These samples were examined for parasites using the FECT and FA280 with a user audit.

RESULTS

For the first set of stool samples, there was no statistically significant difference in the pairwise agreements between the FECT and the FA280 with a user audit (exact binomial test, P = 1). However, there were statistically significant differences between the pairwise agreements for the FECT and the FA280 with the AI report (McNemar's test, P < 0.001). The agreement for the species identification of parasites between the FA280 with AI report and FECT showed fair agreement (overall agreement = 75.5%, kappa [κ] = 0.367, 95% CI 0.248-0.486). On the other hand, the user audit for the FA280 and FECT showed perfect agreement (overall agreement = 100%, κ = 1.00, 95% CI 1.00-1.00). For the second set of samples, the FECT detected significantly more positive samples for parasites than the FA280 with a user audit (McNemar's test, P < 0.001). The disparity in results may be attributed to the FECT using significantly larger stool samples than those used by the FA280. The larger sample size used by the FECT potentially contributed to the higher parasite detection rate. Regarding species identification, there was strong agreement between the FECT and the FA280 with a user audit for helminths (κ = 0.857, 95% CI 0.82-0.894). Similarly, there was perfect agreement for the species identification of protozoa between the FECT and the FA280 with user audit (κ = 1.00, 95% CI 1.00-1.00).

CONCLUSIONS

Although the FA280 has advantages in terms of simplicity, shorter performance time, and reduced contamination in the laboratory, there are some limitations to consider. These include a higher cost per sample testing and a lower sensitivity compared to the FECT. However, the FA280 enables rapid, convenient, and safe stool examination of parasitic infections.

Liver Flukes: Clonorchis and Opisthorchis

Clonorchis sinensis, Opisthorchis viverrini and O. felineus are liver flukes of human and animal pathogens occurring across much of Europe and Asia. Nevertheless, they are often underestimated compared to other, better known neglected diseases in spite of the fact that many millions of people are infected and hundreds of millions are at risk. This is possibly because of the chronic nature of the infection and disease and that it takes several decades prior to a life-threatening pathology to develop. Several studies in the past decade have provided more information on the molecular biology of the liver flukes which clearly lead to better understanding of parasite biology, systematics and population genetics. Clonorchiasis and opisthorchiasis are characterized by a chronic infection that induces hepatobiliary inflammation, especially periductal fibrosis, which can be detected by ultrasonography. These chronic inflammations eventually lead to cholangiocarcinoma (CCA), a usually fatal bile duct cancer that develops in some infected individuals. In Thailand alone, opisthorchiasis-associated CCA kills up to 20,000 people every year and is therefore of substantial public health importance. Its socioeconomic impacts on impoverished families and communities are considerable. To reduce hepatobiliary morbidity and CCA, the primary intervention measures focus on control and elimination of the liver fluke. Accurate diagnosis of liver fluke infections in both human and other mammalian, snail and fish intermediate hosts is important for achieving these goals. While the short-term goal of liver fluke control can be achieved by praziquantel chemotherapy, a comprehensive health education package targeting school children is believed to be more beneficial for a long-term goal/solution. It is recommended that transdisciplinary research or multisectoral control approach including one health and/or eco health intervention strategy should be applied to combat the liver flukes and hence contribute to reduction of CCA in endemic areas.

Spatio-temporal disparities of Clonorchis sinensis infection in animal hosts in China: a systematic review and meta-analysis

BACKGROUND

Clonorchis sinensis, one of the most important food-borne zoonotic trematodes, remains prevalent in China. Understanding its infection status in animals is crucial for controlling human clonorchiasis. Here we conducted a systematic review and meta-analysis to focus on the spatio-temporal disparities of C. sinensis infection in animals in China.

METHODS

Data on C. sinensis prevalence in snails, the second intermediate hosts, or animal reservoirs in China were extracted from electronic databases including PubMed, Embase, Web of Science, Chinese Wanfang database, CNKI, VIP, and China Biomedical Literature database. A random-effects meta-analysis model was utilized to estimate the pooled prevalence in each of the above animal hosts. Subgroup analysis and multivariable meta-regression were performed to explore potential sources of heterogeneity across studies and compare the temporal disparity of infection rates between high and low epidemic areas. Scatter plots were used to depict the biogeographical characteristics of regions reporting C. sinensis infection in animals.

RESULTS

The overall pooled prevalence of C. sinensis was 0.9% (95% CI: 0.6-1.2%) in snails, 14.2% (12.7-15.7%) in the second intermediate host, and 14.3% (11.4-17.6%) in animal reservoirs. Prevalence in low epidemic areas (with human prevalence < 1%) decreased from 0.6% (0.2-1.2%) before 1990 to 0.0% (0.0-3.6%) after 2010 in snails (P = 0.0499), from 20.3% (15.6-25.3%) to 8.8% (5.6-12.6%) in the second intermediate hosts (P = 0.0002), and from 18.3% (12.7-24.7%) to 4.7% (1.0-10.4%) in animal reservoirs. However, no similar decrease in prevalence was observed in high epidemic areas (with human prevalence ≥ 1.0%). C. sinensis infections were predominantly reported in areas with altitudes below 2346 m and annual cumulative precipitation above 345 mm and were mostly concentrated in eastern China.

CONCLUSIONS

There are spatio-temporal disparities in the animal infections of C. sinensis in different areas of China. Animal infections are primarily concentrated in regions with low altitude and high precipitation. The results suggest that implementing One Health-based comprehensive measures targeting both humans and animals, especially in high epidemic areas, is essential for successful eradication of C. sinensis in China.

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.

Serum metabolic profiling of rats infected with Clonorchis sinensis using LC-MS/MS method

Background

Clonorchiasis is an important foodborne parasitic disease. The omics-based-techniques could illuminate parasite biology and further make innovations in the research for parasitic diseases. However, knowledge about the serum metabolic profiles and related metabolic pathways in clonorchiasis is very limited.

Methods

A untargeted ultra-high performance liquid tandem chromatography quadrupole time of flight mass spectrometry (UHPLC-QTOF-MS) was used to profile the serum metabolites of rats at both 4 and 8 weeks post infection (wpi) with Clonorchis sinensis (C. sinensis). Additionally, multivariate statistical analysis methods were employed to identify differential metabolites. Next, serum amino acids and phosphatidylcholines (PCs) levels were determined by targeted metabolomics analysis.

Result

A total of 10530 and 6560 ions were identified in ESI+ and ESI- modes. The levels of phosphatidylcholines, glycerophosphocholine and choline were significantly changed, with the shift in lipid metabolism. Significant changes were also observed in amino acids (isoleucine, valine, leucine, threonine, glutamate and glutamine). Targeted analysis showed that BCAAs (isoleucine, valine, leucine) levels significantly increased at 4 wpi and decreased at 8 wpi; threonine was increased at 8 wpi, whereas glutamate and glutamine showed a decreasing trend at 8 wpi. Additionally, the level of 17 PCs were significantly changed in infected rats. Marked metabolic pathways were involved in clonorchiasis, including glycerophospholipid metabolism, alanine, aspartate and glutamate metabolism, histidine metabolism and pyrimidine metabolism.

Conclusion

These results show that C. sinensis infection can cause significant changes in the rat serum metabolism, especially in amino acids and lipids. The metabolic signature together with perturbations in metabolic pathways could provide more in depth understanding of clonorchiasis and further make potential therapeutic interventions.

Long Non-Coding RNA and mRNA Expression Analysis in Liver of Mice With Clonorchis sinensis Infection

Clonorchiasis is recognized as an important zoonotic parasitic disease worldwide. However, the roles of host long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) in the response to Clonorchis sinensis (C. sinensis) infection remain unknown. Here we compared the expression of lncRNAs and mRNAs in the liver tissue of mice infected with C. sinensis, in order to further understand the molecular mechanisms of clonorchiasis. A total of 388 lncRNAs and 1,172 mRNAs were found to be differentially expressed with absolute value of fold change (FC) ≥ 2.0 and p < 0.05 by microarray. Compared with controls, Gm6135 and 4930581F22Rik were the most over- and under-expressed lncRNAs; flavin-containing monooxygenase 3 (Fmo3) and deleted in malignant brain tumors 1 (Dmbt1) were the most over- and under-expressed mRNAs. Moreover, functional annotation showed that the significantly different mRNAs were related with “FOXO signaling pathway”, “Wnt signaling pathway”, and “AMPK signaling pathway”. Remarkably, lncRNA Gm8801 were significantly correlated with mRNA glycerol-3-phosphate acyltransferase mitochondrial (Gpam), insulin receptor substrate 2 (Irs2), and tumor necrosis factor receptor superfamily member 19 (Tnfrsf19) in ceRNA networks. These results showed that the expression profiles of lncRNAs and mRNAs in the liver changed after C. sinensis infection. Our results provided valuable insights into the lncRNAs and mRNAs involved in clonorchiasis pathogenesis, which may be useful for future control strategies.

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.

Utility of an Automatic Vision-Based Examination System (AVE-562) for the Detection of Clonorchis sinensis Eggs in Stool

Stool examination is the gold standard for the detection of intestinal parasites. We assessed the performance of a newly developed AVE-562 analyzer (AVE Science & Technology Co., Hunan, China) for the vision-based detection of eggs of Clonorchis sinensis—the most common intestinal parasite in Korea—in stool samples. In total, 30 stool samples with a high or low egg count or without eggs (as negative control samples) (N=10 each) were prepared and analyzed. The performance of the AVE-562 analyzer was compared with that of the formalin-ether concentration (FEC) method. The overall correct identification rate of the AVE-562 analyzer based on FEC results was 66.6%. The sensitivity, specificity, positive predictive value, and negative predictive value of the AVE-562 analyzer for detecting C. sinensis eggs were 36.4%, 100.0%, 100.0%, and 73.1%, respectively. The average time required to run five tests simultaneously was 27 min using the AVE-562 analyzer and 58 min using the FEC method. Although the AVE-562 analyzer enables rapid and convenient stool examination, its sensitivity needs to be improved, particularly considering the prevalence of low-burden C. sinensis infection in Korea.

Clinical Characteristics of Clonorchis sinensis-Associated Cholangiocarcinoma: A Large-Scale, Single-Center Study

Background: Clonorchis sinensis (CS) infection is considered a group 1 carcinogen of cholangiocarcinoma (CCA). There were very few studies regarding clinical characteristics of CS-associated CCA (CACC). This study aimed to investigate clinical characteristics of patients with CCA with or without CS infection. Methods: A total of 367 patients diagnosed with CCA who underwent diagnostic tests for CS infection were enrolled. CS infection was defined as follows: at least one positive serum ELISA test, skin test, stool microscopy, or bile microscopy. Results: There were 95 (26%) patients with CS infections. The median follow-up duration was 14.9 months (range, 6.07-36.17). The following significant differences were noted among patients with CACC compared to non-CACC; diagnosis at younger age (median 62 years vs. 65 years, p = 0.018), higher male to female ratio (83.2 vs. 61.8%, p < 0.001), and residence in CS-endemic area (46.3 vs. 25.4%, p = 0.014). Univariate analysis of prognostic factors indicated that tumor location, curative resection, tumor stage, and laboratory tests including CA 19-9, CEA, and bilirubin were significantly associated with overall survival, but CS infection was not. In multivariate analysis, tumor location, CEA, curative resection and tumor stage were identified as independent prognostic factors. Among patients under age 64, CACC group had lower survival rate than non-CACC group (p = 0.022). Conclusions: CACC had the following significant characteristics compared to non-CACC; diagnosis at younger age, higher male to female ratio, higher prevalence in CS endemic areas and poorer overall survival in patients under age 64.

Risk Factors for Clonorchis sinensis Infection in Residents of Binyang, Guangxi: A Cross-Sectional and Logistic Analysis Study

Background: Clonorchiasis is a serious food-borne parasitic disease caused by Clonorchis sinensis infection. C. sinensis, a major fish-borne trematode, is a known causative agent of cholangiocarcinoma. The risk factors for C. sinensis infection include individual eating behaviors and environmental factors. In this study, we evaluated the C. sinensis infection rate and the associated risk factors among residents in Binyang County, Guangxi, China.

Methods: In 2016 and 2017, five villages from Binyang, Guangxi were selected by multistage cluster random sampling for a cross-sectional study. A modified Kato-Katz thick smear method was used to examine C. sinensis eggs in fecal samples in triplicate (three smears for each sample). Both uni-variate and multi-variate logistic regression analyses were carried out to identify the risk factors for C. sinensis infection.

Results: A total of 1,977 fecal samples were collected from villagers in the investigated areas. The overall infection rates of C. sinensis in Binyang County was 20.49% (405/1,977). The mean age of participants was 39.42 ± 23.48 (range: 3–89 years old), and the highest infection rate (33.72%) was seen in the age group of 40-49 years old, followed by those aged 50–59 (31.83%). Multi-variate logistic regression analysis showed that higher infection rates were significantly associated with males (aOR = 6.51, 95% CI = 4.67–9.08), Zhuang (aOR = 2.41, 95% CI = 1.62–3.59), ages (aOR = 33.51, 95% CI = 10.13–110.86), frequency of raw fresh fish consumption (aOR = 14.56, 95% CI = 9.80–21.63), and close contact with cats and dogs (aOR = 1.53, 95% CI = 1.02–2.30). Occupations and education levels showed no significant association with C. sinensis infection (P > 0.05).

Conclusions: High levels of C. sinensis infection were observed among residents in Binyang County, Guangxi. Intervention strategies should be strengthened among the investigated population at high risk, such as males, Zhuang and older individuals, especially those who frequently eat raw fresh fish. In addition, the individuals contacting with cats and/or dogs were observed to have significantly higher infection rate of C. sinensis than those having no contact with cats and dogs. The association between contacting with cats and/or dogs and C. sinensis infection needs to be explored and confirmed in the future study by more epidemiological investigations of human C. sinensis infection from different areas.

High prevalence of opisthorchiasis in rural populations from Khammouane Province, central Lao PDR: serological screening using total IgG- and IgG4-based ELISA

BACKGROUND

Human opisthorchiasis, caused by Opisthorchis viverrini, is a public health problem in Southeast Asia and a major risk factor for cholangiocarcinoma. In Lao PDR, seroprevalence and the relationship between the number of O. viverrini eggs in infected people and specific antibody responses are still unknown. We evaluated and compared parasitological and serological screening methods in the community in an endemic area of opisthorchiasis in Lao PDR.

METHODS

Seroprevalence of O. viverrini-specific total IgG and IgG4 antibodies and their relationships with O. viverrini egg intensities were evaluated in Khammouane Province, central Lao PDR, using ELISA and a modified formalin ethyl-acetate concentration technique (FECT).

RESULTS

FECT stool examination revealed O. viverrini eggs in 70.3% (90/128) of individuals (95% CI 61.6 to 78.1%) while ELISA (based on total IgG and on IgG4 antibodies to O. viverrini) found 98.4% (95% CI 94.5 to 99.8%) and 89.8% (95% CI 83.3 to 94.5%) of sera, respectively. There was a positive and significant correlation between numbers of O. viverrini eggs per gram and levels of both IgG (R2=0.168, p<0.001) and IgG4 (R2=0.219, p<0.001) antibodies.

CONCLUSIONS

A high prevalence of human opisthorchiasis in Lao PDR was found using a new platform, serological screening in the community. This points to a need for sustainable control of this liver fluke infection.

Application of urine antigen assay to evaluate outcomes of praziquantel treatment and reinfection in opisthorchiasis in northeast Thailand

Background

A urine antigen assay was applied to evaluate chemotherapeutic outcomes and reinfection patterns of opisthorchiasis in Thailand.

Methods

We used a prospective study design by following opisthorchiasis subjects at baseline and post-treatment using a urine antigen assay and faecal examination by the formalin–ethyl acetate concentration technique (FECT).

Results

The antigen of Opisthorchis viverrini in urine diminished within 4 weeks after praziquantel treatment. Concurrent faecal examinations by FECT showed that faecal eggs were negative at 4 weeks after treatment. In a subsequent study, reinfection rates and intensity patterns of O. viverrini were evaluated at 48 weeks after praziquantel treatment. Within a group of subjects with curative treatment (n=137), 16.8% became reinfected according to FECT and 27.7% according to the urine antigen assay (p&lt;0.05). There were significant correlations in intensity of infection between pretreatment and at 48 weeks post-treatment in both faecal egg counts and antigen levels in urine.

Conclusions

The results suggested that in addition to screening, the urine antigen assay is an efficient tool for monitoring outcomes of drug treatment and reinfection in opisthorchiasis. Due to the ease of urine sample collection and handling, the urine assay becomes an alternative method to faecal examination for diagnosis and monitoring of opisthorchiasis.

A co-infection case report of Taenia saginata in a patient with subclinical clonorchiasis confirmed by the combination of diagnostic tools

Background

Clonorchiasis is the common parasitic infection in the general population of the Republic of Korea, however, taeniasis is scarcely reported recently. Here, we describe a case of co-infection with the cestode T. saginata in a patient with subclinical clonorchiasis diagnosed by a combination of diagnostic tools in Korea.

Case presentation

A 56-year-old man visited the hospital having passed proglottids in his stool for the past two months and brought a stool sample with segments to our hospital. He had no abdominal symptoms, such as nausea, vomiting, abdominal pain, diarrhea, or constipation. He used to consume raw beef and fish frequently. We could not find evidence of gravid proglottids which contain fully developed uteri filled with ova or branched uterine structures, within the submitted sample. To identify the tapeworm species, we carried out molecular analyses on the proglottids. The cox1 and ef1a sequences had a 100% match with those of T. saginata and differed from the sequences of the other Taenia species. Upon examination of stool samples fixed by formalin-ether concentration method, no Taenia species ova were observed in 10 slides. Instead, C. sinensis ova were observed, despite the level of IgG specific to C. sinensis being within the normal range. The patient was treated with praziquantel (25 mg/kg, three times a day) for 3 days, and subsequently C. sinensis ova were not found in his stool.

Conclusion

Our case indicates that a combination of morphological, serological, and molecular diagnostic tools should be used for the accurate diagnosis of subclinical parasitic infections.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3758-0) contains supplementary material, which is available to authorized users.

Comparing the performance of urine and copro-antigen detection in evaluating Opisthorchis viverrini infection in communities with different transmission levels in Northeast Thailand

To combat and eventually eliminate the transmission of the liver fluke Opisthorchis viverrini, an accurate and practical diagnostic test is required. A recently established urine antigen detection test using monoclonal antibody-based enzyme-linked-immunosorbent assay (mAb-ELISA) has shown promise due to its high diagnostic accuracy and the use of urine in place of fecal samples. To further test the utility of this urine assay, we performed a cross sectional study of 1,043 people in 3 opisthorchiasis endemic communities in northeast Thailand by applying urine antigen detection together with copro-antigen detection methods. The quantitative formalin-ethyl acetate concentration technique (FECT) was concurrently performed as a reference method. The prevalence of O. viverrini determined by urine antigen detection correlated well with that by copro-antigen detection and both methods showed 10-15% higher prevalence than FECT. Within the fecal negative cases by FECT, 29% and 43% were positive by urine and copro-antigen detection, respectively. The prevalence and intensity profiles determined by antigen detection and FECT showed similar patterns of increasing trends of infection with age. The concentration of antigen measured in urine showed a positive relationship with the concentration of copro-antigen, both of which were positively correlated with fecal egg counts. The data observed in this study indicate that urine antigen detection had high diagnostic accuracy and was in concordance with copro-antigen detection. Due to the ease and noninvasiveness of sample collection, the urine assay has high potential for clinical diagnosis as well as population screening in the program for the control and elimination of opisthorchiasis.

Liver Flukes: Clonorchis and Opisthorchis

Clonorchis sinensis, Opisthorchis viverrini, and O. felineus are liver flukes of human and animal pathogens occurring across much of Europe and Asia. Nevertheless, they are often underestimated compared to other, better known neglected diseases in spite of the fact that many millions of people are infected and hundreds of millions are at risk. This is possibly because of the chronic nature of the infection and disease and that it takes several decades prior to a life-threatening pathology to develop. Several studies in the past decade have provided more information on the molecular biology of the liver flukes which clearly lead to better understanding of parasite biology, systematics, and population genetics. Clonorchiasis and opisthorchiasis are characterized by a chronic infection that induces hepatobiliary inflammation, especially periductal fibrosis, which can be detected by ultrasonography. These chronic inflammations eventually lead to cholangiocarcinoma (CCA), a usually fatal bile duct cancer that develops in some infected individuals. In Thailand alone, opisthorchiasis-associated CCA kills up to 20,000 people every year and is therefore of substantial public health importance. Its socioeconomic impacts on impoverished families and communities are considerable. To reduce hepatobiliary morbidity and CCA, the primary intervention measures focus on control and elimination of the liver fluke. Accurate diagnosis of liver fluke infections in both human and other mammalian, snail and fish intermediate hosts, are important for achieving these goals. While the short-term goal of liver fluke control can be achieved by praziquantel chemotherapy, a comprehensive health education package targeting school children is believed to be more beneficial for a long-term goal/solution. It is recommended that a transdisciplinary research or multisectoral control approach including one health and/or eco health intervention strategy should be applied to combat the liver flukes, and hence contribute to reduction of cholangiocarcinoma in endemic areas.

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.

Testing for soil-transmitted helminth transmission elimination: Analysing the impact of the sensitivity of different diagnostic tools

In recent years, an increased focus has been placed upon the possibility of the elimination of soil-transmitted helminth (STH) transmission using various interventions including mass drug administration. The primary diagnostic tool recommended by the WHO is the detection of STH eggs in stool using the Kato-Katz (KK) method. However, detecting infected individuals using this method becomes increasingly difficult as the intensity of infection decreases. Newer techniques, such as qPCR, have been shown to have greater sensitivity than KK, especially at low prevalence. However, the impact of using qPCR on elimination thresholds is yet to be investigated. In this paper, we aim to quantify how the sensitivity of these two diagnostic tools affects the optimal prevalence threshold at which to declare the interruption of transmission with a defined level of confidence. A stochastic, individual-based STH transmission model was used in this study to simulate the transmission dynamics of Ascaris and hookworm. Data from a Kenyan deworming study were used to parameterize the diagnostic model which was based on egg detection probabilities. The positive and negative predictive values (PPV and NPV) were calculated to assess the quality of any given threshold, with the optimal threshold value taken to be that at which both were maximised. The threshold prevalence of infection values for declaring elimination of Ascaris transmission were 6% and 12% for KK and qPCR respectively. For hookworm, these threshold values are lower at 0.5% and 2% respectively. Diagnostic tests with greater sensitivity are becoming increasingly important as we approach the elimination of STH transmission in some regions of the world. For declaring the elimination of transmission, using qPCR to diagnose STH infection results in the definition of a higher prevalence, than when KK is used.

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.

Dysregulation of hepatic microRNA expression profiles with Clonorchis sinensis infection

Background

Clonorchiasis remains an important zoonotic parasitic disease worldwide. The molecular mechanisms of host-parasite interaction are not fully understood. Non-coding microRNAs (miRNAs) are considered to be key regulators in parasitic diseases. The regulation of miRNAs and host micro-environment may be involved in clonorchiasis, and require further investigation.

Methods

MiRNA microarray technology and bioinformatic analysis were used to investigate the regulatory mechanisms of host miRNA and to compare miRNA expression profiles in the liver tissues of control and Clonorchis sinensis (C. sinensis)-infected rats.

Results

A total of eight miRNAs were downregulated and two were upregulated, which showed differentially altered expression profiles in the liver tissue of C. sinensis-infected rats. Further analysis of the differentially expressed miRNAs revealed that many important signal pathways were triggered after infection with C. sinensis, which were related to clonorchiasis pathogenesis, such as cell apoptosis and inflammation, as well as genes involved in signal transduction mechanisms, such as pathways in cancer and the Wnt and Mitogen-activated protein kinases (MAPK) signaling pathways.

Conclusions

The present study revealed that the miRNA expression profiles of the host were changed by C. sinensis infection. This dysregulation in miRNA expression may contribute to the etiology and pathophysiology of clonorchiasis. These results also provide new insights into the regulatory mechanisms of miRNAs in clonorchiasis, which may present potential targets for future C. sinensis control strategies.

Investigation of the use of serology and ultrasonography to detect hepatic cystic echinococcosis in Heilongjiang, China, using a Bayesian framework

BACKGROUND

Cystic echinococcosis (CE) is a public health problem in China. However, the prevalence and incidence of CE in Heilongjiang province is still poorly understood. Because there is no perfect gold standard, evaluation of ultrasound (US) and serological methods have been limited. This study evaluated the use of these two diagnostic methods for the diagnosis of CE in suspected cases.

METHODS

A total of 522 suspected hepatic CE patients, as well as their demographic and clinical features were collected and detected by immunoglobulin (IgG)-ELISA and US. The marginal posterior densities of sensitivity and specificity for both tests, and the prevalence of hepatic CE amongst participants, were estimated from the product of the likelihood function of observed and latent data by a Bayesian framework.

RESULTS

Most of the patients were from rural areas. The most common symptom was upper abdominal pain. The antibody-positive proportion determined by IgG-ELISA was 24.33% (127/522), significantly higher than with US examination (17.24%, 90/522). Bayesian analysis indicated that the estimated prevalence of CE amongst suspected cases was 17.70% (95% credible interval: 14.23-21.54%). The sensitivity and specificity of the ELISA test were 92.63% and 90.37%, and that of US were 93.05% and 98.44%, respectively. Among US-confirmed hepatic CE cases, the male to female ratio was 0.46 and the peak age group was 40-49 years.

CONCLUSIONS

The results of the current study demonstrate that CE is present in Heilongjiang province. They also suggest that, whilst ultrasonography appears to be the detection modality of choice, serology may have a use for detection of infection in individuals suspected to be infected. This may have applications for surveillance within the province.

Molecular characterization of S. japonicum exosome-like vesicles reveals their regulatory roles in parasite-host interactions

Secreted extracellular vesicles play an important role in pathogen-host interactions. Increased knowledge of schistosome extracellular vesicles could provide insights into schistosome-host interactions and enable the development of novel intervention strategies to inhibit parasitic processes and lessen disease transmission. Here, we describe biochemical characterization of Schistosoma japonicum exosome-like vesicles (S. japonicum EVs). A total of 403 proteins were identified in S. japonicum EVs, and bioinformatics analyses indicated that these proteins were mainly involved in binding, catalytic activity, and translation regulatory activity. Next, we characterized the population of small RNAs associated with S. japonicum EVs. Further studies demonstrated that mammalian cells could internalize S. japonicum EVs and transfer their cargo miRNAs to recipient cells. Additionally, we found that a specific miRNA, likely originating from a final host, ocu-miR-191–5p, is also associated with S. japonicum EVs. Overall, our findings demonstrate that S. japonicum EVs could be implicated in the pathogenesis of schistosomiasis via a mechanism involving the transfer of their cargo miRNAs to hosts. Our findings provide novel insights into the mechanisms of schistosome-host interactions.

Evaluation of recombinant multi-epitope proteins for diagnosis of goat schistosomiasis by enzyme-linked immunosorbent assay

Background

Schistosomiasis is a huge threat to human and animal health. Apart from bovines, goats play an important role in the transmission of schistosomiasis in some endemic areas of China. An accessible, quality-assured goat schistosomiasis diagnostic technique is needed. Recently, our laboratory identified two recombinant diagnostic antigens, SjPGM and SjRAD23 via an immuno-proteomic method. The application of these two recombinant antigens to develop a higher sensitivity and specificity technique for the sheep schistosomiasis diagnosis is urgently needed.

Methods

Epitopes of SjPGM and SjRAD23 were predicted and three polypeptides, two from SjRAD23 and one from SjPGM, were selected. Recombinant plasmids containing two to three DNA sequences encoding predicted polypeptides or large hydrophilic region of Sj23 (LHD-Sj23) were constructed and expressed. Eight recombinant schistosome antigens including four multi-epitope proteins and four recombinant single-molecule antigens as well as SEA, were assessed by ELISA in 91 sera from schistosome-infected goats, 44 sera from non-infected goats, 37 sera from Orientobilharzia-infected goats, and 12 from Haemonchus contortus-infected goats.

Results

ELISA tests showed that three multi-epitope proteins had higher sensitivity than the four single-molecule antigens (rSjRAD23, rSjPGM, rBSjRAD23-1, rBSj23) and the multi-epitope protein rBSjPGM-BSjRAD23-1-BSj23 had the highest sensitivity (97.8 %, 89/91) and maintained good specificity (100 %, 44/44) as well as low cross-reactivity with haemonchosis (8.33 %, 3/12) and orientobilharziasis (13.51 %, 5/37) in the diagnosis of goat schistosomiasis. In contrast, when SEA was applied as a diagnosis antigen, it had 100 % (91/91) sensitivity, 75 % (33/44) specificity, 25 and 83.78 % cross-reactivity with haemonchosis (3/12) and orientobilharziasis (31/37), respectively.

Conclusions

The application of recombinant multi-epitope proteins may increase the sensitivity of diagnosis technique and retain high specificity of single-molecule antigens for schistosomiasis, and the recombinant antigen rBSjPGM-BSjRAD23-1-BSj23 has the potential to be used as a diagnosis antigen for goat schistosomiasis.

Advances in the Diagnosis of Human Opisthorchiasis: Development of Opisthorchis viverrini Antigen Detection in Urine

BACKGROUND

Many strategies to control opisthorchiasis have been employed in Thailand, but not in the other neighbouring countries. Specific control methods include mass drug administration (MDA) and health education to reduce raw fish consumption. These control efforts have greatly shifted the epidemiology of Opisthorchis viverrini (OV) infection over the last decade from presenting as densely concentrated "heavy" infections in single villages to widespread "light" OV infections distributed over wide geographical areas. Currently, the "gold standard" detection method for OV infection is formalin ethyl-acetate concentration technique (FECT), which has limited diagnostic sensitivity and diagnostic specificity for light OV infections, with OV eggs often confused with eggs of minute intestinal flukes (MIFs) in feces. In this study, we developed and evaluated the diagnostic performance of a monoclonal antibody-based enzyme-linked immunosorbent assay for the measurement of OV excretory-secretory (ES) antigens in urine (urine OV-ES assay) for the diagnosis of opisthorchiasis compared to the gold standard detection FECT method.

METHODOLOGY

We tested several methods for pre-treating urine samples prior to testing the diagnostic performance of the urine OV-ES assay. Using trichloroacetic acid (TCA) pre-treated urine, we compared detection and quantification of OV infection using the urine OV-ES assay versus FECT in OV-endemic areas in Northeastern Thailand. Receiver operating characteristic (ROC) curves were used to determine the diagnostic sensitivity and specificity of the urine OV-ES assay using TCA pre-treated urine, and to establish diagnostic positivity thresholds. The Positive Predictive Value as well as the likelihood of obtaining a positive test result (LR+) or a negative test result (LR-) were calculated for the established diagnostic positivity threshold. Diagnostic risks (Odds Ratios) were estimated using logistic regression.

RESULTS

When urine samples were pre-treated with TCA prior to use in the urine OV-ES assay, the analytical sensitivity was significantly improved. Using TCA pre-treatment of urine, the urine OV-ES assay had a limit of detection (LoD) of 39 ng/ml compared to the LoD of 52 ng/mL reported for coprological antigen detection methods. Similarly, the urine OV-ES assay correlated significantly with intensity of OV infection as measured by FECT. The urine OV-ES assay was also able to detect 28 individuals as positive from the 63 (44.4%) individuals previously determined to be negative using FECT. The likelihood of a positive diagnosis of OV infection by urine OV-ES assay increased significantly with the intensity of OV infection as determined by FECT. With reference to FECT, the sensitivity and specificity of the urine OV-ES assay was 81% and 70%, respectively.

CONCLUSION

The detection of OV-infection by the urine OV-ES assay showed much greater diagnostic sensitivity and diagnostic specificity than the current "gold standard" FECT method for the detection and quantification of OV infection. Due to its ease-of-use, and noninvasive sample collection (urine), the urine OV-ES assay offers the potential to revolutionize the diagnosis of liver fluke infection and provide an effective tool for control and elimination of these tumorigenic parasites.

Detection of active schistosome infection by cell-free circulating DNA of Schistosoma japonicum in highly endemic areas in Sorsogon Province, the Philippines

The current status of schistosomiasis in highly endemic areas is difficult to determine by ovum detection because of the superficially low parasite load after mass drug administration, whereas the parasite transmission rates are still high. Cell-free parasite DNA is fragments of parasite-derived DNA existing in the host's body fluids. We conducted population-based studies to test the presence of cell-free schistosome DNA in endemic areas of Sorsogon Province, the Philippines. Schistosome DNA in the serum and urine of Kato-Katz (KK)-positive subjects was detected by PCR (100% sensitivity). Schistosome DNA was also detected from KK-negative subjects (9/22 serum and 10/41 urine samples). Schistosome DNA was found to be network echogenic pattern (NW)-positive (serum 53.3%, urine 42.9%) or NW-negative (serum 25.5%, urine 20.8%) and enzyme-linked immunosorbent assay (ELISA)-positive (serum 47.1%, urine 40%) or ELISA-negative (serum 33.3%, urine 13.3%). These results indicate that cell-free schistosome DNA is a promising diagnostic marker for active schistosome infection in the case of light infection.

Detection of Clonorchis sinensis circulating antigen in sera from Chinese patients by immunomagnetic bead ELISA based on IgY

BACKGROUND

Clonorchiasis, caused by Clonorchis sinensis, is widely distributed in Southeast Asia including China. Clonorchiasis is included in control programs of neglected tropical diseases by World Health Organization (WHO) because it is one of the major health problems in most endemic areas. Diagnosis of clonorchiasis plays a key role in the control programs. However, so far, there is no satisfactory method for clonorchiasis because of low sensitivity, poor practicality and high false positivity of available diagnostic tools.

METHODOLOGY/PRINCIPAL FINDINGS

We developed an immunomagnetic bead enzyme-linked immunosorbent assay (ELISA) based on IgY (egg yolk immunoglobulin) against cysteine proteinase of C. sinensis for detection of circulating antigen in serum samples of patients infected with C. sinensis. The polyclonal IgY, coated with magnetic beads, was used as a capture antibody and a monoclonal IgG labeled with horseradish peroxidase as a detection antibody in the IgY-based immunomagnetic bead ELISA system (IgY-IMB-ELISA). The results showed that the sensitivity of IgY-IMB-ELISA was 93.3% (14 of 15) in cases of heavy infection (5000 to 9999 eggs per gram feces, i.e, EPG 5000-9999), 86.7% (13 of 15) in cases of moderate infection (EPG 1000-4999) and 75.0% (9 of 12) in cases of light infection (EPG <1000) of clonorchiasis. Together 36 of total 42 (85.7%) serum samples of human clonorchiasis gave a positive reaction. There was a significant correlation between ELISA optical density and egg counts (EPG) with a correlation coefficient of 0.83 in total 42 patients. There were no positive results in patients with trichinosis (n = 10) or cysticercosis (n = 10). Cross-reactivity was 6.7% (2 of 30) with schistosomiasis japonica and 10.0% (3 of 30) with paragonimiasis, respectively. No positive reaction was found in 20 healthy persons.

CONCLUSIONS

Our findings suggest that IgY-IMB-ELISA appears to be a sensitive and specific assay for detection of circulating antigen in human clonorchiasis.

Microscopic identification of possible Clonorchis/Opisthorchis infection in two Ghanaian women with undiagnosed abdominal discomfort: two case reports

INTRODUCTION

The impact of foodborne trematode infections is gaining recognition worldwide. Clonorchiasis and opisthorchiasis are some of the most neglected tropical foodborne diseases that pose a significant threat to human health. Persistent or chronic infection of Clonorchis/Opisthorchis often leads to hepatobiliary diseases including cholangitis, cholelithiasis, cholecystitis, pancreatitis, hepatic fibrosis, cholangiocarcinoma and liver cancer. Two cases of Clonorchis/Opisthorchis infection in humans in the Central Region of Ghana are reported.

CASE PRESENTATION

Eggs suspected to be from Clonorchis sinensis or Opisthorchis species were detected in the stools of a 29-year-old Ghanaian woman and an 18-year-old Ghanaian woman in two clinics in the Central Region of Ghana. The diagnosis was based on clinical symptoms as well as detection of the eggs of the trematode in the faeces of the patients using light microscopy after staining with Giemsa or Ziehl-Neelsen stains.

CONCLUSIONS

To the best of our knowledge these are the first documented cases of Clonorchis sinensis or Opisthorchis species infection in Ghana. The detection of this infection in these patients in Ghana should be of concern to clinicians because the infection can be easily misdiagnosed since the accompanying clinical symptoms are malaria-like. Consideration should therefore be given to Clonorchis sinensis and Opisthorchis species when diagnosing patients presenting with malaria-like symptoms.

Improved performance and quantitative detection of copro-antigens by a monoclonal antibody based ELISA to diagnose human opisthorchiasis

Copro-antigen detection has been advocated as a promising method for diagnosis of opisthorchiasis, particularly in people that harbored light infection or have had recent drug treatment. This study aimed to improve performance of a monoclonal antibody-based enzyme-linked immunosorbent assay (Mab-ELISA) for detection of Opisthorchis viverrini copro-antigen and assess the correlation between copro-antigen and intensity of infection. Four different treatment methods of 71 samples from the Lawa endemic area, Khon Kaen province were assessed for copro-antigen detection, namely (1) phosphate buffer saline (PBS), (2) heating (70°C 30min), (3) alkaline (pH 9.6 in carbonate buffer), and (4) trichloroacetic acid (TCA) treatment. Comparison of these protocols showed that the TCA method gave the best performance in discriminating O. viverrini positive and negative samples with high sensitivity (97.9%) and moderate specificity (54.2%) compared with other methods. Application of TCA-based Mab-ELISA method for antigen detection in fecal samples obtained from an endemic area of opisthorchiasis revealed that 86 of 141 samples (61.0%) were positive compared with 68 (48.2%) by PBS-based protocol, while the formalin ethyl-acetate concentration technique (FECT) yielded a positive proportion of 71.6%. Among 40 egg-negative samples confirmed by a gold standard parasitological method (FECT) from the same endemic area, 19 (47.5%) were positive by the TCA-based while only 6 (15%) were positive by PBS-based Mab-ELISA protocol. In addition, levels of antigen detection significantly correlated with intensity of infection (egg per gram feces). The results show that the improved Mab-ELISA method has high sensitivity and also quantifiable diagnosis of opisthorchiasis.

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.