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

Multi-epitope protein production and its application in the diagnosis of opisthorchiasis

BACKGROUND

Opisthorchiasis and cholangiocarcinoma (CCA) continue to be public health concerns in many Southeast Asian countries. Although the prevalence of opisthorchiasis is declining, reported cases tend to have a light-intensity infection. Therefore, early detection by using sensitive methods is necessary. Several sensitive methods have been developed to detect opisthorchiasis. The immunological detection of antigenic proteins has been proposed as a sensitive method for examining opisthorchiasis.

METHODS

The Opisthorchis viverrini antigenic proteins, including cathepsin B (OvCB), asparaginyl endopeptidase (OvAEP), and cathepsin F (OvCF), were used to construct multi-antigenic proteins. The protein sequences of OvCB, OvAEP, and OvCF, with a high probability of B cell epitopes, were selected using BepiPred 1.0 and the IEDB Analysis Resource. These protein fragments were combined to form OvCB_OvAEP_OvCF recombinant DNA, which was then used to produce a recombinant protein in Escherichia coli strain BL21(DE3). The potency of the recombinant protein as a diagnostic target for opisthorchiasis was assessed using immunoblotting and compared with that of the gold standard method, the modified formalin-ether concentration technique.

RESULTS

The recombinant OvCB_OvAEP_OvCF protein showed strong reactivity with total immunoglobulin G (IgG) antibodies against light-intensity O. viverrini infections in the endemic areas. Consequently, a high sensitivity (100%) for diagnosing opisthorchiasis was reported. However, cross-reactivity with sera from other helminth and protozoan infections (including taeniasis, strongyloidiasis, giardiasis, E. coli infection, enterobiasis, and mixed infection of Echinostome spp. and Taenia spp.) and no reactivity with sera from patients with non-parasitic infections led to a reduced specificity of 78.4%. In addition, the false negative rate (FNR), false positive rate (FPR), positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were 0%, 21.6%, 81.4%, 100%, and 88.9%, respectively.

CONCLUSIONS

The high sensitivity of the recombinant OvCB_OvAEP_OvCF protein in detecting opisthorchiasis demonstrates its potential as an opisthorchiasis screening target. Nonetheless, research on reducing cross-reactivity should be undertaken by detecting other antibodies in other sample types, such as saliva, urine, and feces.

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.

Accuracy of a new rapid diagnostic test for urinary antigen detection and assessment of drug treatment in opisthorchiasis

BACKGROUND

Screening for opisthorchiasis, a parasitic worm infection affecting many millions of people in Southeast Asia, has traditionally relied on faecal egg examination such as the formalin-ethyl acetate concentration technique (FECT) and Kato-Katz method. Although the urinary enzyme-linked immunosorbent assay (ELISA) has been used more recently, we developed a urinary antigen-based rapid diagnostic test (RDT) to simplify diagnosis and as a point-of-care testing (POCT) and field applications for surveillance and control of opisthorchiasis.

METHODS

A urinary Opisthorchis viverrini (OV)-RDT was developed using immunochromatographic methodology with a specific monoclonal antibody against OV. The diagnostic performance of the urinary OV-RDT was compared to that of quantitative faecal FECT and urinary antigen ELISA (n = 493). Cross-reactivities of urinary OV-RDT with other helminthiases coexisted with O. viverrini were determined (n = 96). A field trial in the application of urinary OV-RDT was compared with urinary antigen ELISA at baseline screening and assessment of drug treatment outcomes in opisthorchiasis (n = 1629). The McNemar chi-square, Kruskal-Wallis and Cohen's kappa coefficient (κ-value) tests were used for statistical analyses.

RESULTS

Urinary OV-RDT had sensitivity of 94.2% and specificity of 93.2%, compared to faecal FECT. Urinary OV-RDT had high diagnostic agreement (Kappa = 0.842-0.874, P < 0.001) and quantitative correlation with urinary antigen ELISA (Kruskal-Wallis tests = 316.2, P < 0.0001) and faecal FECT (Kruskal-Wallis tests = 362.3, P < 0.0001). The positive rates by OV-RDT, ELISA and FECT were 48.9%, 52.5% and 49.3%, respectively. Cross-reactions of urinary OV-RDT with other helminthiases were few (2%). Field trials of urinary OV-RDT yielded comparable prevalence of O. viverrini between urinary OV-RDT (53.2%) and urinary antigen ELISA (54.0%). OV screening showed high diagnostic agreement (kappa > 0.8, P < 0.0001) between urinary OV-RDT and urinary antigen ELISA. The cure rates of opisthorchiasis at 1 month post-praziquantel treatment determined by urinary OV-RDT (86.6%) and urinary antigen ELISA (80.5%) were similar (P > 0.05).

CONCLUSIONS

The urinary OV-RDT test has high potential as a new tool for screening and evaluating treatment outcomes in opisthorchiasis. The ease of sample collection and simplicity of urinary OV-RDT may facilitate mass screening, control and elimination of opisthorchiasis, thereby contributing to a reduction in the disease burden in Southeast Asia.

Opisthorchis viverrini-Current Understanding of the Neglected Hepatobiliary Parasite

Opisthorchiasis due to Opisthorchis viverrini infection continues to be a significant public healthcare concern in various subregions of Southeast Asia, particularly in Thailand, Laos, Cambodia, Myanmar, and Vietnam. The main mode of transmission is via consumption of raw or undercooked fish, which is deeply embedded in the culture and tradition of the people living near the Mekong River. After ingestion, the flukes migrate to the bile ducts, potentially causing many hepatobiliary complications, including cholangitis, cholecystitis, cholelithiasis, advanced periductal fibrosis and cholangiocarcinoma. Several mechanisms of opisthorchiasis-associated cholangiocarcinogenesis have been proposed and elucidated in the past decade, providing insight and potential drug targets to prevent the development of the sinister complication. The gold standard for diagnosing opisthorchiasis is still via stool microscopy, but the advent of novel serological, antigen, and molecular tests shows promise as more convenient, alternative diagnostic methods. The mainstay of treatment of opisthorchiasis is praziquantel, while treatment of opisthorchiasis-associated cholangiocarcinoma depends on its anatomic subtype and resectability. Thus far, the most successful fluke control programme is the Lawa model based in Thailand, which raised awareness, incorporated education, and frequent surveillance of intermediate hosts to reduce transmission of opisthorchiasis. Development of vaccines using tetraspanins shows promise and is currently ongoing.

A Socio-Ecological Framework for Examining Foodborne Parasitic Infection Risk

Human liver fluke infection through the consumption of raw freshwater fish is one of the foodborne parasitic infections of global concern. Despite decades of health campaign efforts, high prevalence of infection remains in different areas of the Lower Mekong Basin. This necessitates the consideration of the infection differences between places and the human-environment complexities of disease transmission. This paper used the socio-ecological model as a framework to unraveled the social science dimensions of liver fluke infection. We conducted questionnaire surveys in Northeast Thailand to gather participants' knowledge on liver fluke infection and reasons for raw fish consumption. We synthesized our findings with prior work to identify factors influencing liver fluke infection at four socio-ecological levels. At the individual level, gender and age differences in food consumption habits and personal hygiene of open defection presented the behavioral risks. At the interpersonal level, family tradition and social gathering affected the disease risk. At the community level, physical-social-economic environments of land use and modernization, community health infrastructure and health volunteer support accounted for the varying degree of infection. At the policy level, impacts of regional and national regulations on disease control, health system organization structure, and government development projects were of concerned. The findings provide insights into how infection risks are shaped by people's behavior, social connectedness, interactions with places, and the interplay of these multi-level socio-ecological influences. The framework therefore allows a more comprehensive understanding of liver fluke infection risks to inform a culturally sensitive and sustainable disease control program.

Production and Immunological Characterization of scFv Specific to Epitope of Opisthorchis viverrini Rhophilin-Associated Tail Protein 1-like (OvROPN1L)

(1) Background: Opisthorchis viverrini is a significant health problem in the Mekong subregion of Southeast Asia, causing aggressive cholangiocarcinoma. Current diagnostic procedures do not cover early diagnosis and low infection. Hence, an effective diagnostic tool is still required. Immunodiagnosis seems promising, but attempts to generate monoclonal antibodies have not yet been successful. This study aims to develop a single-chain variable antibody fragment (scFv) against Rhophilin-associated tail protein 1-like (ROPN1L), the sperm-specific antigen of adult O. viverrini, which has not been reported elsewhere. (2) Methods: The target epitope for phage screening was L3-Q13 of OvROPN1L, which showed the highest antigenicity to human opisthorchiasis analyzed in a previous study. This peptide was commercially synthesized and used for phage library screening. The isolated phage was produced in a bacterial expression system and tested for specificity in vitro and in silico. (3) Results: One of fourteen phages, named scFv anti-OvROPN1L-CL19, significantly bound to rOvROPN1L compared with non-infected hamster fecal extracts. This phage clone was successfully produced and purified using Ni-NTA chromatography. Indirect ELISA demonstrated that scFv anti-OvROPN1L-CL19 has a high reactivity with O. viverrini-infected hamster fecal extracts (12 wpi, n = 6) in comparison with non-infected hamster fecal extracts (0 wpi, n = 6), while the polyclonal rOvROPN1L antibodies did not show such a difference. Molecular modeling and docking confirmed our in vitro findings. (4) Conclusion: scFv anti-OvROPN1L-CL19 could be used as an effective material for developing O. viverrini-immunodiagnostic procedures in the future.

Long-term Persistence of Opisthorchis viverrini Antigen in Urine: A Prospective Study in Northeast Thailand

Antigen detected in urine for the diagnosis of opisthorchiasis has a low daily variation; however, the longer term variability in antigen concentrations is unknown. In this study, we prospectively monitored Opisthorchis viverrini antigen concentrations for 30 consecutive days and at subsequent monthly intervals in a cohort of opisthorchiasis-positive individuals. On the basis of the monoclonal antibody-based ELISA, the profiles of antigen-positive rate and antigen concentration exhibited no significant change over 30 days with a mean proportion positive of 87.1% (range 73.7%-100%), and the average antigen concentration was 29.7 ± 2.2 ng/mL (mean ± SE). The urine antigen concentration at baseline was similar to the subsequent measurements at 2, 4, 6, and 10 months in the follow-up study (P > 0.05). The consistency and low daily and long-term fluctuation of O. viverrini antigen in urine demonstrates the reliability of urine assay for diagnosis of opisthorchiasis.

Diagnosis of helminths depends on worm fecundity and the distribution of parasites within hosts

Helminth transmission and morbidity are dependent on the number of mature parasites within a host; however, observing adult worms is impossible for many natural infections. An outstanding challenge is therefore relating routine diagnostics, such as faecal egg counts, to the underlying worm burden. This relationship is complicated by density-dependent fecundity (egg output per worm reduces due to crowding at high burdens) and the skewed distribution of parasites (majority of helminths aggregated in a small fraction of hosts). We address these questions for the carcinogenic liver fluke Opisthorchis viverrini, which infects approximately 10 million people across Southeast Asia, by analysing five epidemiological surveys (n = 641) where adult flukes were recovered. Using a mechanistic model, we show that parasite fecundity varies between populations, with surveys from Thailand and Laos demonstrating distinct patterns of egg output and density-dependence. As the probability of observing faecal eggs increases with the number of mature parasites within a host, we quantify diagnostic sensitivity as a function of the worm burden and find that greater than 50% of cases are misdiagnosed as false negative in communities close to elimination. Finally, we demonstrate that the relationship between observed prevalence from routine diagnostics and true prevalence is nonlinear and strongly influenced by parasite aggregation.

Effects of day-to-day variation of Opisthorchis viverrini antigen in urine on the accuracy of diagnosing opisthorchiasis in Northeast Thailand

Antigen detection in urine using an enzyme-linked immunosorbent assay (ELISA) is more sensitive than fecal examination for diagnosis of opisthorchiasis and for assessment of the effects of drug treatment. It is not known whether day-to-day variation of urine composition, including levels of Opisthorchis viverrini antigen, influences the urine assay. We investigated this topic with the cooperation of participants from two localities in Northeast Thailand. Project participants were screened for parasite infections for three consecutive days using the quantitative formalin-ethyl acetate concentration technique (FECT) to detect O. viverrini eggs and the urine ELISA for detection of O. viverrini antigen. A subset of participants (n = 801) with matched fecal and urine samples were analyzed for comparison of inter-day prevalence estimates and the performance of the urine assay compared against FECT for diagnosis of opisthorchiasis. The daily prevalence measured by the urine assay ranged between 29.0%-30.2% while those by FECT ranged between 11.9%-20.2%. The cumulative three-day prevalence estimate determined by the urine antigen assay was 30.3%, which was significantly higher than that by FECT (20.2%, p < 0.05). A significant positive correlation was found between the concentration of antigen in urine and fecal egg counts (p < 0.001). Overall, the urine assay had better diagnostic performance for opisthorchiasis than fecal examination by FECT. The high sensitivity plus negligible daily variation of O. viverrini antigen in urine indicates the utility of the urine assay for diagnosis, as well as population screening, of opisthorchiasis.

Performance of Mini Parasep® SF stool concentrator kit, Kato-Katz, and formalin-ethyl acetate concentration methods for diagnosis of opisthorchiasis in Northeast Thailand

BACKGROUND

Control and elimination of the liver fluke (Opisthorchis viverrini) is a primary preventive strategy against cholangiocarcinoma in Southeast Asia. A sensitive parasitological diagnostic method is required to facilitate a surveillance and control program. In this study, we evaluated the performance of Mini Parasep® SF stool concentrator kit (stool kit) compared with Kato-Katz (KK) and the quantitative formalin-ethyl acetate concentration technique (FECT) for detection of O. viverrini and co-endemic parasitic infections.

METHODS

A cross-sectional survey for parasitic infection in residents aged > 15 years in a community in Kalasin province, Northeast Thailand, was conducted in 2018. Fecal samples were collected and screened by KK method, and a subset of samples was further examined by the stool kit and FECT methods. The results were analyzed for prevalence of parasitic infections in addition to the diagnostic performance of the methods for qualitative and quantitative detection of helminthiases.

RESULTS

The initial survey of parasitic infection determined by the KK method (n = 567) showed the prevalence of O. viverrini was 32.63%, followed by Taenia 2.65%, echinostomes 1.76%, hookworms 1.41%, Trichuris trichiura 0.53% and Strongyloides stercoralis 0.53%. Within a subset of samples tested with multiple diagnostics (n = 150), the detection rates of O. viverrini by the stool kit, FECT and KK methods were 27.3%, 30.7% and 28.7%, respectively. The diagnostic sensitivity for opisthorchiasis was similar for FECT (75.5%), KK(66.0%) and the stool kit (67.3%). For other parasitic infections, FECT and stool kit methods performed better than KK, particularly in detecting minute intestinal flukes (MIF), S. stercoralis and coinfections. When measuring the intensity of O. viverrini infection (fecal egg counts), the stool kit results showed a significant positive correlation with KK and FECT (P < 0.05).

CONCLUSIONS

As the stool kit is simple to use and shows a comparable performance to FECT, it may serve as an alternative method of fecal examination for screening of helminthiasis including opisthorchiasis.

Application of Urine and Copro Antigen Assays after Primary Infection and Drug Treatment in an Experimental Opisthorchiasis Animal Model

Infection by Opisthorchis viverrini causes significant health problems, including cholangiocarcinoma (CCA); thus control and elimination of this trematode is an important strategy for the reduction of CCA. Currently, urine and copro antigen detection is more sensitive than parasitological examination of the feces for the diagnosis of opisthorchiasis. Given limitations in human studies, we used an animal model to quantify the parasite antigen profiles in urine and feces in O. viverrine-infected hamsters, and postdrug treatment. The positive detections of O. viverrini antigen began from week 1 in urine and week 2 in feces after infection until week 28 of the study. The recoveries of O. viverrini worms were detected starting from week 1 and eggs of O. viverrini were detected in feces from week 3 after infection and remained detectable throughout the study period. There was a significant positive correlation of urine and copro antigen levels with the number of fecal egg counts (P < 0.01) and worm recovery (P < 0.01). In the drug-treatment experiment, treatment of infected hamsters with praziquantel significantly reduced worm burden, fecal egg output, and antigen in urine and feces compared with the untreated controls (P < 0.001). At 4 weeks posttreatment, the egg and worm reduction rates were 100% and 95.5%, respectively. The positive antigen detections in urine and feces corresponded with partial worm clearance from praziquantel treatment. This study demonstrated a direct link of urine and copro antigen tests with worms infecting the liver thereby reaffirming the reliability of urine and copro antigen assay in opisthorchiasis diagnosis.

Novel and emerging targets for cholangiocarcinoma progression: therapeutic implications

INTRODUCTION

Cholangiocarcinoma (CCA) is a heterogeneous group of aggressive biliary malignancies. While surgery and liver transplantation are the only potentially curative modalities for early-stage disease, limited options are available for most patients with incurable-stage disease. Survival outcomes remain dismal. Recent molecular profiling efforts have led to improved understanding of the genomic landscape of CCA and to the identification of subgroups with distinct diagnostic, prognostic, and therapeutic implications.

AREAS COVERED

: We provide an updated review and future perspectives on features of cholangiocarcinogenesis that can be translated into therapeutic biomarkers and targets. We highlight the critical studies that have established current systemic chemotherapy and targeted therapeutics, while elaborating on novel targeted and immunotherapeutic approaches in development. Relevant literature and clinical studies were identified by searching PubMed and www.ClinicalTrials.gov.

EXPERT OPINION

: While therapies targeting the various molecular subgroups of CCA are rapidly emerging and changing treatment paradigms, their success has been limited by the genetic heterogeneity of CCA and the plasticity of the targets. Novel strategies aiming to combine immunotherapy, chemotherapy, and molecularly-targeted therapeutics will be required to offer durable clinical benefit and maximize survival.

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

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

Plasma checkpoint protein 1 (Chk1) as a potential diagnostic biomarker for opisthorchiasis and cholangiocarcinoma

BACKGROUND

Patients infected with a parasite often develop opisthorchiasis viverrini, which often progresses into cholangiocarcinoma (CCA) due to the asymptomatic nature of the infection. Currently, there are no effective diagnostic methods for opisthorchiasis or cholangiocarcinoma.

OBJECTIVE

The aim of this study was to identify the host-responsive protein that can be developed as a diagnostic biomarker of opisthorchiasis and cholangiocarcinoma.

METHODS

Plasma samples were collected from non-OVCCA, OV, and CCA subjects, and the proteomes were investigated by LC-MS/MS. Venn diagrams and protein network prediction by STITCH were used to identify the potential biomarkers. The level of candidate protein, the plasma checkpoint protein 1 (Chk1), was measured by indirect enzyme-linked immunosorbent assay (ELISA).

RESULTS

Chk1 was present in the center of the protein network analysis in both the OV and CCA groups. In addition, the plasma Chk1 levels were significantly increased in both groups (P< 0.05). The sensitivity of the opisthorchiasis viverrini and cholangiocarcinoma was 59.38% and 65.62%, respectively, while the specificity of both was 85.71%.

CONCLUSION

Chk1 was identified by differential plasma proteomes and was increased in O. viverrini-infected and cholangiocarcinoma-derived plasma samples. Higher levels of plasma Chk1 levels may serve as a potential diagnostic biomarker for opisthorchiasis and cholangiocarcinoma.

Monoclonal Antibodies Targeting an Opisthorchis viverrini Extracellular Vesicle Tetraspanin Protect Hamsters against Challenge Infection

Opisthorchis viverrini causes severe pathology in the bile ducts of infected human hosts, and chronic infection can culminate in bile duct cancer. The prevention of infection by vaccination would decrease opisthorchiasis-induced morbidity and mortality. The tetraspanin protein, Ov-TSP-2, is located on the membrane of secreted extracellular vesicles (EVs), and is a candidate antigen for inclusion in a subunit vaccine. To address the role of anti-Ov-TSP-2 antibodies in protection, we assessed the protective capacity of anti-Ov-TSP-2 monoclonal antibodies (mAbs) against opisthorchiasis. Two anti-TSP-2 IgM mAbs, 1D6 and 3F5, and an isotype control were passively transferred to hamsters, followed by parasite challenge one day later. Hamsters that received 3F5 had 74.5% fewer adult flukes and 67.4% fewer eggs per gram of feces compared to hamsters that received the control IgM. Both 1D6 and 3F5 (but not the control IgM) blocked the uptake of fluke EVs by human bile duct epithelial cells in vitro. This is the first report of passive immunization against human liver fluke infection, and the findings portend the feasibility of antibody-directed therapies for liver fluke infection, bolstering the selection of TSPs as components of a subunit vaccine for opisthorchiasis and fluke infections generally.

Analysis of Daily Variation for 3 and for 30 Days of Parasite-Specific IgG in Urine for Diagnosis of Strongyloidiasis by Enzyme-Linked Immunosorbent Assay

Recent work has found urine analysis to be as sensitive as serology for diagnosis of strongyloidiasis. Here, we examined the daily variation of Strongyloides-specific IgG in urine by qualitative and quantitative ELISA and its effects on diagnostic accuracy and reliability. In the first part of the study, matched urine and fecal samples were collected from project participants in northeast Thailand for three consecutive days. Urine samples were analyzed for Strongyloides-specific IgG by ELISA using Strongyloides ratti as the antigen source. Performance of urine ELISA was compared with parasitological diagnosis by agar plate culture technique (APCT) and formalin-ethyl acetate concentration technique (FECT). In the second part of the study, urine IgG levels were compared daily for thirty consecutive days. The prevalence of Strongyloides infection, as measured by urine ELISA for three consecutive days, was significantly higher than that found using parasitological methods (63.1% vs. 22%). There was slight daily variation in prevalence estimates according to urine ELISA while there were significant variations according to parasitological examination methods over three consecutive days. For the 3-day experiment, urine ELISA had 83-86% diagnostic sensitivity when compared with the fecal examination method or with a composite standard (combined results from fecal examination methods (APCT or FECT) and/or urine ELISA). The levels of parasite-specific IgG in urine were stable throughout both the 3-day and the 30-day studies. In conclusion, diagnosis of strongyloidiasis by urine ELISA is more sensitive than by fecal methods, with minimal daily variation for qualitative and quantitative diagnosis. Urine ELISA has potential for clinical diagnosis and population screening of strongyloidiasis.

Public health interventions for preventing re-infection of Opisthorchis viverrini: application of the self-efficacy theory and group process in high-prevalent areas of Thailand

OBJECTIVE

To study the effectiveness of public health interventions in preventing Opisthorchis viverrini (OV) re-infection in high-prevalence areas of Thailand.

METHODS

68 people from Sisaket, the province with the second-highest prevalence in Thailand, who tested positive for OV eggs in faeces and took praziquantel before the start of the study, participated. 34 participants were allocated to the experimental group, which received a 12-week public health intervention based on the self-efficacy theory and group process between July and October 2018. The control group received the usual services. Data were collected using a questionnaire with a reliability of 0.84. Faecal examinations using the formalin-ether concentration technique were conducted before and after the experiment. The re-infection rate was analysed after the experimental 12 weeks and after one year. Descriptive and inferential statistics, including paired t-test and independent t-test, were employed for data analysis.

RESULTS

After the experiment, the mean scores of knowledge, perceived self-efficacy, self-efficacy expectation and OV prevention behaviour of the experimental group were significantly higher than before the experiment and also higher than scores of the control group (P < 0.05).

CONCLUSION

The public health intervention is useful. It educated the experimental group about OV, perceived self-efficacy and self-efficacy expectation in changing behaviour to prevent OV re-infection. As a result, no re-infections were observed after the 12-week intervention nor at the one-year follow-up. Public health benefits will be evident if the results are extended to other high-prevalence areas.

Foodborne zoonotic parasites of the family Opisthorchiidae

Several foodborne zoonotic trematodes of the family Opisthorchiidae have been reported to infect people, specifically two genera, Clonorchis and Opisthorchis. Three species Clonorchis sinensis, Opisthorchis felineus and Opisthorchis viverrini are the most extensivley studied of the Opisthorchiidae. At least 680 million people worldwide are at risk of infection of these liver flukes through the consumption of raw or partially cooked freshwater cyprinid fish. An estimated 45 million people in Europe and Asia are currently infected with these liver flukes. Of these, the 35 million are infected with C. sinensis mainly in China, 10 million with O. viverrini in Southeast Asia, and 1.2 million with O. felineus in Eastern Europe and Russia. These liver flukes have been proven to be causative agents of bile duct cancer or cholangiocarcinoma (CCA). A multidisciplinary program should be implemented involving comprehensive research on molecular genetics, diagnosis, treatment, prevention, as well as educational and control programs should progressively be introduced and applied in endemic regions of O. viverrini, O. felineus and C. sinensis throughout their ranges, hence, opisthorchiasis and clonorchiasis free communities can be realised globally.

Production and characterization of monoclonal antibodies against highly immunogenic Opisthorchis viverrini proteins and development of coproantigen detection

Opisthorchis viverrini and other foodborne trematode infections are major health concerns in the Greater Mekong Subregion. Currently, the gold-standard diagnostic method for opisthorchiasis is conventional stool examination for the presence of parasite eggs. This method lacks sensitivity and needs an experienced technician. We therefore produced monoclonal antibodies to highly immunogenic O. viverrini proteins aiming at detecting specific antigens in the feces. In this study, BALB/C mice were immunized using semi-purified somatic antigens and spleen cells were fused with a Sp2/0 myeloma cell line. Four hybridomas (1A2, 1E12, 2C7 and 8D6) were selected and cloned due to their strong reaction against O. viverrini somatic protein, resulting in three IgM clones and one IgG2 clone. Immunohistochemistry showed that 1A2, 1E12, 2C7 and 8D6 stained the parenchyma cells, gut, tegument and muscles, respectively. Western-blot analysis revealed that only antibody 1A2 could detect coproantigen (approx. 73 kDa protein) in feces of hamsters infected with O. viverrini. The 1A2 monoclonal antibody may be of value in the diagnosis of opisthorchiasis by coproantigen detection.

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.