Performance of a dipstick dye immunoassay for rapid screening of Schistosoma japonicum infection in areas of low endemicity

Neglected tropical disease (NTD) diagnostics: current development and operations to advance control

Neglected tropical diseases (NTDs) have become important public health threats that require multi-faceted control interventions. As late treatment and management of NTDs contribute significantly to the associated burdens, early diagnosis becomes an important component for surveillance and planning effective interventions. This review identifies common NTDs and highlights the progress in the development of diagnostics for these NTDs. Leveraging existing technologies to improve NTD diagnosis and improving current operational approaches for deployment of developed diagnostics are crucial to achieving the 2030 NTD elimination target. Point-of-care NTD (POC-NTD) diagnostic tools are recommended preferred diagnostic options in resource-constrained areas for mapping risk zones and monitoring treatment efficacy. However, few are currently available commercially. Technical training of remote health care workers on the use of POC-NTD diagnostics, and training of health workers on the psychosocial consequences of these diagnostics are critical in harnessing POC-NTD diagnostic potential. While the COVID-19 pandemic has challenged the possibility of achieving NTD elimination in 2030 due to the disruption of healthcare services and dwindling financial support for NTDs, the possible contribution of NTDs in exacerbating COVID-19 pandemic should motivate NTD health system strengthening.

Current and upcoming point-of-care diagnostics for schistosomiasis

Point-of-care (POC) diagnostics are simple and effective portable tools that can be used for fast mapping of helminthic diseases and monitoring control programs. Most POC tests (POCTs) available for schistosomiasis diagnosis are lateral flow immunoassays (LFIAs). The emergence of simple and rapid DNA isolation methods, along with isothermal nucleic acid amplification strategies - for example, loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) - and recent clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostic methods facilitate the development of molecular-based POC diagnostics for schistosomiasis. Furthermore, smartphone-based techniques increase real-time connectivity and readout accuracy of POCTs. This review discusses the recent advances in immunological-, molecular-based POCTs and mobile phone microscopes for the diagnosis/screening of schistosomiasis.

A Miniature Biomedical Sensor for Rapid Detection of Schistosoma japonicum Antibodies

Schistosomiasis, typically characterized by chronic infection in endemic regions, has the potential to affect liver tissue and pose a serious threat to human health. Detecting and screening for this disease early on is crucial for its prevention and control. However, existing methods encounter challenges such as low sensitivity, time-consuming processes, and complex sample handling. To address these challenges, we report a soluble egg antigen (SEA)-based functionalized gridless and meander-type AlGaN/GaN high electron mobility transistors (HEMT) sensor for the highly sensitive detection of antibodies to Schistosoma japonicum. Immobilization of the self-assembled membrane on the gate surface was verified using a semiconductor parameter analyzer, scanning electron microscope (SEM), and atomic force microscopy (AFM). The developed biosensor demonstrates remarkable performance in detecting anti-SEA, exhibiting a linear concentration range of 10 ng/mL to 100 μg/mL and a sensitivity of 0.058 mA/log (ng/mL). It also exhibits similar excellent performance in serum systems. With advantages such as rapid detection, high sensitivity, miniaturization, and label-free operation, this biosensor can fulfill the requirements for blood defense.

The Efficiency of Commercial Immunodiagnostic Assays for the Field Detection of Schistosoma japonicum Human Infections: A Meta-Analysis

Although great strides have been achieved, schistosomiasis japonica remains a major public health concern in China. Immunodiagnostics have been widely accepted as the first choice in large-scale screening of Schistosoma japonicum human infections, and indirect hemagglutination test (IHA), enzyme-linked immunosorbent assay (ELISA), and dipstick dye immunoassay (DDIA) are currently the three most common immunological tests for the diagnosis of S. japonicum human infections in China. This meta-analysis aimed to comprehensively assess the performance of IHA, ELISA, and DDIA for the field diagnosis of S. japonicum human infections. A total of 37 eligible publications were enrolled in the final analysis, including 29 Chinese publications and 8 English publications. No significant heterogeneities were detected among the studies reporting ELISA (I2 = 88%, p < 0.05), IHA (I2 = 95%, p < 0.05), or DDIA (I2 = 84%, p < 0.05). DDIA showed the highest pooled sensitivity (90.8%, 95% CI: 84.6% to 94.7%) and IHA presented the highest pooled specificity for detection of S. japonicum human infections (71.6%, 95% CI: 65.9% to 76.7%). Summary receiver operating characteristic (SROC) curve analysis showed that IHA exhibited the highest area under the SROC curve (AUC) (0.88, 95% CI: 0.85 to 0.9), and ELISA presented the lowest AUC (0.85, 95% CI: 0.82 to 0.88). Deeks’ funnel plots indicated no publication bias. IHA presented the highest sensitivity in medium-endemicity regions and the highest specificity for diagnosis of S. japonicum human infections in low-endemicity regions, and ELISA showed the highest diagnostic sensitivity in high-endemicity regions and the highest specificity in medium-endemicity regions, while DDIA exhibited the highest diagnostic sensitivity in high-endemicity regions and the highest specificity in low-endemicity regions. IHA and DDIA presented a higher efficiency for the diagnosis of S. japonicum human infections in marshland and lake regions than in hilly and mountainous regions, while ELISA showed a comparable diagnostic sensitivity between in marshland and lake regions and hilly and mountainous regions (88.3% vs. 88.6%), and a higher specificity in marshland and lake regions than in hilly and mountainous regions (60% vs. 48%). Our meta-analysis demonstrates a comparable diagnostic accuracy of IHA, ELISA, and DDIA for S. japonicum human infections, and the diagnostic sensitivity and specificity of IHA, ELISA, and DDIA vary in types and infection prevalence of endemic regions. DDIA combined with IHA is recommended as a tool for screening chemotherapy targets and seroepidemiological surveys during the stage moving towards schistosomiasis elimination in China. Further studies to examine the effectiveness of combinations of two or three immunological tests for diagnosis of S. japonicum human infections are warranted.

Laboratory Evaluation of a Basic Recombinase Polymerase Amplification (RPA) Assay for Early Detection of Schistosoma japonicum

Early detection of Schistosoma japonicum (S. japonicum) within its intermediate and definitive hosts is crucial for case finding and disease surveillance, especially in low-endemic areas. Recombinase polymerase amplification (RPA) has many advantages over traditional methods of DNA-amplification, such as polymerase chain reaction (PCR), including high sensitivity and specificity whilst being deployable in resource-poor schistosomiasis-endemic areas. Here, we evaluated the performance of a basic RPA assay targeting the 28srDNA gene fragment of S. japonicum (Sj28srDNA) using schistosome-infected Oncomelania hupensis (O. hupensis) and mouse models, compared to the traditional pathological method and a PCR assay. Overall S. japonicum infection prevalence within O. hupensis hosts by microscopic dissection, PCR and RPA was 9.29% (13/140), 32.14% (45/140) and 51.43% (72/140), respectively, presenting significant differences statistically (χ2 = 58.31, p < 0.001). It was noteworthy that infection prevalence by PCR and RPA performed was 34.44% (31/90) and 53.33% (48/90) in snails within 6 weeks post-infection, while the dissection method detected all samples as negatives. In addition, the basic RPA assay presented positive results from the fourth week post-infection and third day post-infection when detecting fecal DNA and serum DNA, respectively, which were extracted from a pooled sample from mice infected with 20 S. japonicum cercariae. This study suggests that the RPA assay has high potential for early detection of S. japonicum infection within its intermediate and definitive hosts.

Contributions and achievements on schistosomiasis control and elimination in China by NIPD-CTDR

Being a zoonotic parasitic disease, schistosomiasis was widely spread in 12 provinces of Southern China in the 1950s, severly harming human health and hindering economic development. The National Institute of Parasitic Diseases at the Chinese Center for Diseases Control and Prevention, and Chinese Center for Tropical Diseases Research (NIPD-CTDR), as the only professional institution focussing on parasitic diseases at the national level, has played an important role in schistosomiasis control in the country. In this article, we look back at the changes of schistosomiasis endemicity and the contribution of NIPD-CTDR to the national schistosomiasis control programme. We review NIPD-CTDR's activities, including field investigations, design of control strategies and measures, development of diagnostics and drugs, surveillance-response of endemic situation, and monitoring & evaluation of the programme. The NIPD-CTDR has mastered the transmission status of schistosomiasis, mapped the snail distribution, and explored strategies and measures suitable for different types of endemic areas in China. With a good understanding of the life cycle of Schistosoma japonicum and transmission patterns of the disease, advanced research carried out in the NIPD-CTDR based on genomics and modern technology has made it possible to explore highly efficient and soft therapeutic drugs and molluscicides, making it possible to develop new diagnostic tools and produce vaccine candidates. In the field, epidemiological studies, updated strategies and targeted intervention measures developed by scientists from the NIPD-CTDR have contributed significantly to the national schistosomiasis control programme. This all adds up to a strong foundation for eliminating schistosomiasis in China in the near future, and recommendations have been put forward how to reach this goal.

Diagnostic performance of two specific schistosoma japonicum immunological tests for screening schistosoma haematobium in school children in Zambia

Dipstick Dye Immunoassay (DDIA) and Indirect Haemagglutination Assay (IHA), are two commercially available kits which have been widely used for screening Schistosoma japonicum in P.R. China. Whether they can be used for screening of Schistosoma haematobium are not clear. In order to evaluate the diagnostic efficiency of DDIA and IHA for screening Schistosoma haematobium, serum samples were collected from pupils in endemic areas in Zambia, Southern Africa, and tested by DDIA and IHA by single-blind manner. Meanwhile, the pupils were microscopically examined by infection with Schistosoma and soil-transmitted helminths, visually observed for parasite eggs. Of the enrolled 148 pupils, 61% tested positive for S. haematobium infection, while 31% and 36% of pupils were infected with hookworm and Ascaris respectively. Regarding the parasitological tests as reference standard, for the diagnosis of S. haematobium infection, IHA performed higher sensitivity (74%, 95% CI: 65%-83%) than that of DDIA (60%, 95%CI: 49%-70%). The sensitivities of IHA and DDIA are significant higher in 10-14 years old students than those of 7-9 years old group. The specificity of DDIA and IHA were 61% (95%CI: 49%-74%) and 72% (95%CI: 60%-84%), respectively. The co-infection with STHs decreased the specificity of DDIA but had no impact on that of IHA. Our study indicated that IHA has more potential as an alternative diagnostic tool for identifying schistosomiasis haematobium but need further improvement.

Serological approaches for the diagnosis of schistosomiasis - A review

Schistosomiasis is a common disease in endemic areas of Sub-Saharan Africa, South America and Asia. It is rare in Europe, mainly imported from endemic countries due to travelling or human migration. Available methods for the diagnosis of schistosomiasis comprise microscopic, molecular and serological approaches, with the latter detecting antigens or antibodies associated with Schistosoma spp. infection. The serological approach is a valuable screening tool in low-endemicity settings and for travel medicine, though the interpretation of any diagnostic results requires knowledge of test characteristics and a patient's history. Specific antibody detection by most currently used assays is only possible in a relatively late stage of infection and does not allow for the differentiation of acute from previous infections for therapeutic control or the discrimination between persisting infection and re-infection. Throughout the last decades, new target antigens have been identified, and assays with improved performance and suitability for use in the field have been developed. For numerous assays, large-scale studies are still required to reliably characterise assay characteristics alone and in association with other available methods for the diagnosis of schistosomiasis. Apart from S. mansoni, S. haematobium and S. japonicum, for which most available tests were developed, other species of Schistosoma that occur less frequently need to be taken into account. This narrative review describes and critically discusses the results of published studies on the evaluation of serological assays that detect antibodies against different Schistosoma species of humans. It provides insights into the diagnostic performance and an overview of available assays and their suitability for large-scale use or individual diagnosis, and thus sets the scene for serological diagnosis of schistosomiasis and the interpretation of results.

Evolution of the National Schistosomiasis Control Programmes in The People's Republic of China

Schistosomiasis japonica is caused by the parasitic trematode Schistosoma japonicum. It is endemic in The People's Republic of China and has significant impact on human health and socioeconomic development in certain regions. Over the last six decades, the national control programmes evolved in remarkable ways and brought schistosomiasis japonica largely under control. We describe the history and evolution of schistosomiasis control in The People's Republic of China, with an emphasis on shifts in control strategies that evolved with new insights into the biology of the parasite and its intermediate hosts, and the epidemiology of the disease in the country. We also highlight the achievements in controlling the disease in different socioecological settings, and identify persisting challenges to fully eliminate schistosomiasis japonica from the country. To reach the goal of schistosomiasis elimination, further integration of interventions, multisector collaboration, sensitive and effective surveillance are needed to strengthen.

Advances in the Diagnosis of Human Schistosomiasis

Schistosomiasis is a major neglected tropical disease that afflicts more than 240 million people, including many children and young adults, in the tropics and subtropics. The disease is characterized by chronic infections with significant residual morbidity and is of considerable public health importance, with substantial socioeconomic impacts on impoverished communities. Morbidity reduction and eventual elimination through integrated intervention measures are the focuses of current schistosomiasis control programs. Precise diagnosis of schistosome infections, in both mammalian and snail intermediate hosts, will play a pivotal role in achieving these goals. Nevertheless, despite extensive efforts over several decades, the search for sensitive and specific diagnostics for schistosomiasis is ongoing. Here we review the area, paying attention to earlier approaches but emphasizing recent developments in the search for new diagnostics for schistosomiasis with practical applications in the research laboratory, the clinic, and the field. Careful and rigorous validation of these assays and their cost-effectiveness will be needed, however, prior to their adoption in support of policy decisions for national public health programs aimed at the control and elimination of schistosomiasis.

Tools for diagnosis, monitoring and screening of Schistosoma infections utilizing lateral-flow based assays and upconverting phosphor labels

The potential of various quantitative lateral flow (LF) based assays utilizing up-converting phosphor (UCP) reporters for the diagnosis of schistosomiasis is reviewed including recent developments. Active infections are demonstrated by screening for the presence of regurgitated worm antigens (genus specific polysaccharides), whereas anti-Schistosoma antibodies may indicate ongoing as well as past infections. The circulating anodic antigen (CAA) in serum or urine (and potentially also saliva) is identified as the marker that may allow detection of single-worm infections. Quantitation of antigen levels is a reliable method to study effects of drug administration, worm burden and anti-fecundity mechanisms. Moreover, the ratio of CAA and circulating cathodic antigen (CCA) is postulated to facilitate identification of either Schistosoma mansoni or Schistosoma haematobium infections. The UCP-LF assays allow simultaneous detection of multiple targets on a single strip, a valuable feature for antibody detection assays. Although antibody detection in endemic regions is not a useful tool to diagnose active infections, it gains potential when the ratio of different classes of antibody specific for the parasite/disease can be determined. The UCP-LF antibody assay format allows this type of multiplexing, including testing a linear array of up to 20 different targets. Multiple test spots would allow detection of specific antibodies, e.g. against different Schistosoma species or other pathogens as soil-transmitted helminths. Concluding, the different UCP-LF based assays for diagnosis of schistosomiasis provide a collection of tests with relatively low complexity and high sensitivity, covering the full range of diagnostics needed in control programmes for mapping, screening and monitoring.

Vaccines and diagnostics for zoonotic schistosomiasis japonica

Schistosomiasis is one of the most prevalent, insidious and serious of the tropical parasitic diseases. Although the effective anthelmintic drug, praziquantel, is widely available and cheap, it does not protect against re-infection, drug-resistant schistosome may evolve and mass drug administration programmes based around praziquantel are probably unsustainable long term. Whereas protective anti-schistosome vaccines are not yet available, the zoonotic nature of Schistosoma japonicum provides a novel approach for developing a transmission-blocking veterinary vaccine in domestic animals, especially bovines, which are major reservoir hosts, being responsible for up to 90% of environmental egg contamination in China and the Philippines. However, a greater knowledge of schistosome immunology is required to understand the processes associated with anti-schistosome protective immunity and to reinforce the rationale for vaccine development against schistosomiasis japonica. Importantly as well, improved diagnostic tests, with high specificity and sensitivity, which are simple, rapid and able to diagnose light S. japonicum infections, are required to determine the extent of transmission interruption and the complete elimination of schistosomiasis following control efforts. This article discusses aspects of the host immune response in schistosomiasis, the current status of vaccine development against S. japonicum and reviews approaches for diagnosing and detecting schistosome infections in mammalian hosts.

Diagnostics for the control and elimination of neglected tropical diseases

Practical diagnostic tools of sufficient sensitivity to detect levels of infection that can lead to transmission have been identified as a critical component of successful disease elimination programmes. In this review we describe the diagnostic tests currently available for six neglected tropical diseases that have been targeted for elimination; assess their performance in the light of the requirements for surveillance, certification of elimination and post-elimination surveillance; consider the unmet need for diagnostic tests for these diseases; and review recent technical developments that could meet these needs.

Lateral flow test using Echinococcus granulosus native antigen B and comparison of IgG and IgG4 dipsticks for detection of human cystic echinococcosis

Cystic echinococcosis (CE) caused by infection with Echinococcus granulosus is of major concern for humans in many parts of the world. Antigen B was prepared from E. granulosus hydatid fluid, and Western blots confirmed eight batches showing a band corresponding to the 8-/12-kDa subunit with positive serum and no low-molecular mass band (< 15 kDa) with negative serum. The batches were pooled and used to prepare lateral flow immunoglobulin G4 (IgG4) and IgG dipsticks. Diagnostic sensitivity was determined using serum samples from 21 hydatidosis patients, and diagnostic specificity was established using sera from 17 individuals infected with other parasites and 15 healthy people. IgG4 dipstick had a diagnostic sensitivity of 95% (20 of 21) and a specificity of 100% (32 of 32). The IgG dipstick had a sensitivity of 100% (21 of 21) and a specificity of 87.5% (28 of 32). Thus, both IgG and IgG4 dipsticks had high sensitivities, but IgG4 had greater specificity for the diagnosis of human CE.

Field comparison of circulating antibody assays versus circulating antigen assays for the detection of schistosomiasis japonica in endemic areas of China

BACKGROUND

Schistosomiasis remains a serious public health problem in affected countries, and routine, highly sensitive and cost-effective diagnostic methods are lacking. We evaluated two immunodiagnostic techniques for the detection of Schistosoma japonicum infections: circulating antibody and circulating antigen assays.

METHODS

A total of 1864 individuals (between 6 and 72 years old) residing in five administrative villages in Hubei province were screened by serum examination with an indirect hemagglutination assay (IHA). The positive individuals (titer ≥20 in IHA) were reconfirmed by stool examination with the Kato-Katz method (three slides from a single stool specimen). Samples of good serum quality and a volume above 0.5 ml were selected for further testing with two immunodiagnostic antibody (DDIA and ELISA) and two antigen (ELISA) assays.

RESULTS

The average antibody positive rate in the five villages was 12.7%, while the average parasitological prevalence was 1.50%; 25 of the 28 egg-positive samples were also circulating antigen-positive. Significant differences were observed between the prevalence according to the Kato-Katz method and all three immunodiagnostic antibody assays (P-value <0.0001). Similar differences were observed between the Kato-Katz method and the two immunodiagnostic antigen assays (P-value <0.0001) and between the antigen and antibody assays (P-value <0.0001).

CONCLUSION

Both circulating antibody and circulating antigen assays had acceptable performance characteristics. Immunodiagnostic techniques to detect circulating antigens have potential to be deployed for schistosomiasis japonica screening in the endemic areas.

Transmission risks of schistosomiasis japonica: extraction from back-propagation artificial neural network and logistic regression model

BACKGROUND

The transmission of schistosomiasis japonica in a local setting is still poorly understood in the lake regions of the People's Republic of China (P. R. China), and its transmission patterns are closely related to human, social and economic factors.

METHODOLOGY/PRINCIPAL FINDINGS

We aimed to apply the integrated approach of artificial neural network (ANN) and logistic regression model in assessment of transmission risks of Schistosoma japonicum with epidemiological data collected from 2339 villagers from 1247 households in six villages of Jiangling County, P.R. China. By using the back-propagation (BP) of the ANN model, 16 factors out of 27 factors were screened, and the top five factors ranked by the absolute value of mean impact value (MIV) were mainly related to human behavior, i.e. integration of water contact history and infection history, family with past infection, history of water contact, infection history, and infection times. The top five factors screened by the logistic regression model were mainly related to the social economics, i.e. village level, economic conditions of family, age group, education level, and infection times. The risk of human infection with S. japonicum is higher in the population who are at age 15 or younger, or with lower education, or with the higher infection rate of the village, or with poor family, and in the population with more than one time to be infected.

CONCLUSION/SIGNIFICANCE

Both BP artificial neural network and logistic regression model established in a small scale suggested that individual behavior and socioeconomic status are the most important risk factors in the transmission of schistosomiasis japonica. It was reviewed that the young population (≤15) in higher-risk areas was the main target to be intervened for the disease transmission control.

Schistosomiasis in areas of low endemicity: a new era in diagnosis

Parasitological detection of Schistosoma is the cornerstone of schistosomiasis diagnosis in areas of transmission worldwide. However, a steep decrease of sensitivity in low-endemicity areas (LEAs) compromises estimation of schistosomiasis. Despite the restricted utilization of molecular and immunodiagnostic techniques, recent improvements and advances have been contributing to change this scenario, especially in LEAs. Nonetheless, the main issue in a new era of diagnosis overcomes technical advances per se and relates to the loss of 'gold standards' in schistosomiasis diagnosis in LEAs. Here, we review and discuss the current role of molecular and immunodiagnostic methods in schistosomiasis management.

Frontiers of parasitology research in the People's Republic of China: infection, diagnosis, protection and surveillance

Control and eventual elimination of human parasitic diseases in the People's Republic of China (P.R. China) requires novel approaches, particularly in the areas of diagnostics, mathematical modelling, monitoring, evaluation, surveillance and public health response. A comprehensive effort, involving the collaboration of 188 scientists (>85% from P.R. China) from 48 different institutions and universities (80% from P.R. China), covers this collection of 29 articles published in Parasites & Vectors. The research mainly stems from a research project entitled “Surveillance and diagnostic tools for major parasitic diseases in P.R. China” (grant no. 2008ZX10004-011) and highlights the frontiers of research in parasitology. The majority of articles in this thematic series deals with the most important parasitic diseases in P.R. China, emphasizing Schistosoma japonicum, Plasmodium vivax and Clonorchis sinensis plus some parasites of emerging importance such as Angiostrongylus cantonensis. Significant achievements have been made through the collaborative research programme in the following three fields: (i) development of strategies for the national control programme; (ii) updating the surveillance data of parasitic infections both in human and animals; and (iii) improvement of existing, and development of novel, diagnostic tools to detect parasitic infections. The progress is considerable and warrants broad validation efforts. Combined with the development of improved tools for diagnosis and surveillance, integrated and multi-pronged control strategies should now pave the way for elimination of parasitic diseases in P.R. China. Experiences and lessons learned can stimulate control and elimination efforts of parasitic diseases in other parts of the world.

Magnetic affinity enzyme-linked immunoassay for diagnosis of Schistosomiasis japonicum in persons with low-intensity infection

Most schistosome-endemic areas in China are characterized by low-intensity infections that are independent of prevalence. To establish an effective diagnostic method, we developed a magnetic affinity enzyme-linked immunoassay based on soluble egg antigens (SEA-MEIA) for diagnosing schistosomiasis in persons with low-intensity infection with Schistosoma japonicum by comparing it with a conventional enzyme-linked immunosorbent assay (ELISA). Our results showed that the SEA-MEIA had a higher sensitivity and greater precision in the diagnosis of low-intensity S. japonicum infections than the ELISA. In addition, when we used Pearson's correlation in associating SEA-MEIA with ELISA, a significant correlation existed between the two assays (r = 0.845, P < 0.001). Our data indicated that SEA-MEIA, with a higher sensitivity and greater ease of performance, would be valuable for diagnosis of schistosomiasis japonicum in persons with low-intensity infections.

Effect of an integrated control strategy for schistosomiasis japonica in the lower reaches of the Yangtze River, China: an evaluation from 2005 to 2008

Background

Schistosomiasis japonica remains a major public health concern in China. There are many interventions implemented to control the transmission of the disease. The purpose of the present study was to investigate the effects of an integrated control strategy for schistosomiasis control.

Methods

An integrated control strategy for schistosomiasis japonica with emphasis on removing cattle from snail-infested grasslands, providing farmers with mechanized farm equipment, improving sanitation by supplying tap water and building lavatories and latrines and providing boats with fecal-matter containers was implemented in 107 villages of the lower reaches of the Yangtze River, Jiangsu Province, China, during a 32-month period from May 2005 to 2008, and the effectiveness was investigated.

Results

Following the effects of the comprehensive control, the snail habitat, infected snail habitat, snail infection rate, and S. japonicum prevalence in both humans and livestock all appeared a declining trend year by year, with reductions of 47.88%, 94.29%, 92.55%, 96.94%, and 100% compared with those before the comprehensive control. In addition, all of the 17 counties achieved the infection control in 2007, and 7 reached the criteria of transmission control in 2008. The confirmed snail habitats reduced from 107 to 20, and the acute infections have also been controlled for 2 successive years since 2007.

Conclusions

The integrated control strategy for schistosomiasis japonica is effective to control the transmission of S. japonicum.

A diagnostic challenge for Schistosomiasis japonica in China: consequences on praziquantel-based morbidity control

Worldwide schistosomiasis continues to be a serious public health problem. Over the past five decades, China has made remarkable progress in reducing Schistosoma japonicum infections in humans to a relatively low level. Endemic regions are currently circumscribed in certain core areas where re-infection and repeated chemotherapy are frequent. At present, selective chemotherapy with praziquantel is one of the main strategies in China's National Schistosomiasis Control Program, and thus diagnosis of infected individuals is a key step for such control. In this paper we review the current status of our knowledge about diagnostic tools for schistosomiasis japonica. A simple, affordable, sensitive, and specific assay for field diagnosis of schistosomiasis japonica is not yet available, and this poses great barriers towards full control of schistosomiasis. Hence, a search for a diagnostic approach, which delivers these characteristics, is essential and should be given high priority.

Monitoring specific antibody responses against the hydrophilic domain of the 23 kDa membrane protein of Schistosoma japonicum for early detection of infection in sentinel mice

Background

Schistosomiasis remains an important public health problem throughout tropical and subtropical countries. Humans are infected through contact with water contaminated with schistosome cercariae. Therefore, issuing early warnings on the risk of infection is an important preventive measure against schistosomiasis. Sentinel mice are used to monitor water body infestations, and identifying appropriate antibody responses to schistosome antigens for early detection of infection would help to improve the efficiency of this system. In this study we explored the potential of detecting antibodies to the hydrophilic domain (HD) of the 23-kDa membrane protein (Sj23HD) and soluble egg antigen (SEA) of Schistosome japonicum for early detection of schistosome infection in sentinel mice.

Results

Development of IgM and IgG antibody levels against Sj23HD and SEA in S. japonicum infected mice was evaluated over the course of 42 days post-infection by enzyme-linked immunosorbent assay (ELISA) and immunoblotting. The Sj23HD and SEA specific IgM and IgG levels in mice all increased gradually over the course of infection, but IgM and IgG antibodies against Sj23HD presented earlier than those against SEA. Furthermore, the rates of positive antibody responses against Sj23HD were higher than those against SEA in the early stage of schistosome infection, suggesting that the likelihood of detecting early infection using anti-Sj23HD responses would be higher than that with anti-SEA responses. The use of immunoblotting could further improve the early detection of schistosome infection due to its greater sensitivity and specificity compared to ELISA. Additionally, the levels of Sj23HD and SEA specific antibodies positively correlated with the load of cercariae challenge and the duration of schistosome infection.

Conclusions

This study demonstrated that antibody responses to the Sj23HD antigen could be monitored for early detection of schistosome infection in mice, especially by immunoblotting which demonstrated greater sensitivity and specificity than ELISA for detection Sj23HD antibodies.

Detection of the circulating antigen 14-3-3 protein of Schistosoma japonicum by time-resolved fluoroimmunoassay in rabbits

Background

Schistosomiasis remains a major public health concern that afflicts millions of people worldwide. Low levels of Schistosoma infection require more sensitive diagnostic methods. In this study, a time-resolved fluoroimmunoassay (TRFIA) was developed for detecting the signal transduction protein 14-3-3, a circulating antigen of Schistosoma japonicum.

Results

The detection limit of 14-3-3-TRFIA was 0.78 ng/ml, with a linear measurement range from 0.78 to 800 ng/ml. The average intra-assay and inter-assay variability of this TRFIA was 8.9% and 12.2% respectively, and the mean recovery rate ranged from 92.1% to 115.5%. Within the first 21 days post-infection in rabbits, the positive rates of the 14-3-3-TRFIA were distinctly higher compared to ELISA. All these findings illustrate that 14-3-3-TRFIA has a higher detection efficacy and is a good early diagnostic method for active Schistosoma infection.

Conclusions

A sandwich TRFIA for detecting the circulating antigen 14-3-3 of S. japonicum has been developed, and has demonstrated to be a good potential diagnostic method for schistosomiasis.