Schistosomiasis control in the People's Republic of China

The cultural policies of schistosomiasis control in China: a historical analysis

China has a history of using cultural policies to control infectious diseases, including schistosomiasis, which was once hyperendemic in the country. Since the founding of the People's Republic of China, significant achievements have been made in schistosomiasis control, with a decrease in the number of cases and infection rates. This study provides a historical analysis of cultural policies in schistosomiasis control in China. During the Mao era (1949-1976), socialist ideology shaped cultural policies that included mass mobilization campaigns, propaganda, and cultural education to promote health practices, and community participation and empowerment. During the Reform era (1978-2012), there was a shift towards market-oriented policies and individual responsibility, and cultural policies promoted behavioral change, but there were challenges in implementing them in a rapidly changing society. In the "New Era" of socialism (2012-now), cultural policies are focused on promoting comprehensive schistosomiasis control strategies, technological advancements and innovation, and international cooperation. The Chinese experience in schistosomiasis control provides valuable lessons for other countries facing similar challenges and underscores the importance of cultural policies in promoting health and well-being.

Establishing and Integrating a Female Genital Schistosomiasis Control Programme into the Existing Health Care System

Female genital schistosomiasis (FGS) is a complication of Schistosoma haematobium infection, and imposes a health burden whose magnitude is not fully explored. It is estimated that up to 56 million women in sub-Saharan Africa have FGS, and almost 20 million more cases will occur in the next decade unless infected girls are treated. Schistosomiasis is reported throughout the year in South Africa in areas known to be endemic, but there is no control programme. We analyze five actions for both a better understanding of the burden of FGS and reducing its prevalence in Africa, namely: (1) schistosomiasis prevention by establishing a formal control programme and increasing access to treatment, (2) introducing FGS screening, (3) providing knowledge to health care workers and communities, (4) vector control, and (5) water, sanitation, and hygiene. Schistosomiasis is focal in South Africa, with most localities moderately affected (prevalence between 10% and 50%), and some pockets that are high risk (more than 50% prevalence). However, in order to progress towards elimination, the five actions are yet to be implemented in addition to the current (and only) control strategy of case-by-case treatment. The main challenge that South Africa faces is a lack of access to WHO-accredited donated medication for mass drug administration. The establishment of a formal and funded programme would address these issues and begin the implementation of the recommended actions.

Contribution of NIPD-CTDR to the parasitic diseases control and elimination in China: Memory of the 70th anniversary for NIPD-CTDR

China has achieved a great success in control and elimination of key parasitic diseases. In 2007, the elimination of lymphatic filariasis was verified by WHO. The schistosomiasis incidence and snail-distributed areas have reduced to the lowest level in the history. The transmission and disease burden of echinococcosis have been contained largely, and the populations infected with soil-transmitted trematode and food-borne parasites have also shown a significantly declining trend. Because of rapid globalization and climate changes, however, many new challenges have arisen. In his paper, the 2020-2030 roadmaps towards the control and elimination of these key parasitic diseases are described. Moreover, China is actively implementing its global health strategy, and will be more and more engaged into global health affairs, in which a series of China-Africa health cooperation projects have been in planning with a wish of making a greater contribution to the SDGs.

Risk prediction of two types of potential snail habitats in Anhui Province of China: Model-based approaches

Elimination of the intermediate snail host of Schistosoma is the most effective way to control schistosomiasis and the most important first step is to accurately identify the snail habitats. Due to the substantial resources required for traditional, manual snail-searching in the field, and potential risk of miss-classification of potential snail habitats by remote sensing, more convenient and precise methods are urgently needed. Snail data (N = 15,000) from two types of snail habitats (lake/marshland and hilly areas) in Anhui Province, a typical endemic area for schistosomiasis, were collected together with 36 environmental variables covering the whole province. Twelve different models were built and evaluated with indices, such as area under the curve (AUC), Kappa, percent correctly classified (PCC), sensitivity and specificity. We found the presence-absence models performing better than those based on presence-only. However, those derived from machine-learning, especially the random forest (RF) approach were preferable with all indices above 0.90. Distance to nearest river was found to be the most important variable for the lake/marshlands, while the climatic variables were more important for the hilly endemic areas. The predicted high-risk areas for potential snail habitats of the lake/marshland type exist mainly along the Yangtze River, while those of the hilly type are dispersed in the areas south of the Yangtze River. We provide here the first comprehensive risk profile of potential snail habitats based on precise examinations revealing the true distribution and habitat type, thereby improving efficiency and accuracy of snail control including better allocation of limited health resources.

Village-based spatio-temporal cluster analysis of the schistosomiasis risk in the Poyang Lake Region, China

Background

The Poyang Lake Region, one of the major epidemic sites of schistosomiasis in China, remains a severe challenge. To improve our understanding of the current endemic status of schistosomiasis and to better control the transmission of the disease in the Poyang Lake Region, it is important to analyse the clustering pattern of schistosomiasis and detect the hotspots of transmission risk.

Results

Based on annual surveillance data, at the village level in this region from 2009 to 2014, spatial and temporal cluster analyses were conducted to assess the pattern of schistosomiasis infection risk among humans through purely spatial (Local Moran’s I, Kulldorff and Flexible scan statistic) and space-time scan statistics (Kulldorff). A dramatic decline was found in the infection rate during the study period, which was shown to be maintained at a low level. The number of spatial clusters declined over time and were concentrated in counties around Poyang Lake, including Yugan, Yongxiu, Nanchang, Xingzi, Xinjian, De’an as well as Pengze, situated along the Yangtze River and the most serious area found in this study. Space-time analysis revealed that the clustering time frame appeared between 2009 and 2011 and the most likely cluster with the widest range was particularly concentrated in Pengze County.

Conclusions

This study detected areas at high risk for schistosomiasis both in space and time at the village level from 2009 to 2014 in Poyang Lake Region. The high-risk areas are now more concentrated and mainly distributed at the river inflows Poyang Lake and along Yangtze River in Pengze County. It was assumed that the water projects including reservoirs and a recently breached dyke in this area were partly to blame. This study points out that attempts to reduce the negative effects of water projects in China should focus on the Poyang Lake Region.

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.

Health access livelihood framework reveals potential barriers in the control of schistosomiasis in the Dongting Lake area of Hunan Province, China

Background

Access to health care is a major requirement in improving health and fostering socioeconomic development. In the People's Republic of China (P.R. China), considerable changes have occurred in the social, economic, and health systems with a shift from a centrally planned to a socialist market economy. This brought about great benefits and new challenges, particularly for vertical disease control programs, including schistosomiasis. We explored systemic barriers in access to equitable and effective control of schistosomiasis.

Methodology

Between August 2002 and February 2003, 66 interviews with staff from anti-schistosomiasis control stations and six focus group discussions with health personnel were conducted in the Dongting Lake area, Hunan Province. Additionally, 79 patients with advanced schistosomiasis japonica were interviewed. The health access livelihood framework was utilized to examine availability, accessibility, affordability, adequacy, and acceptability of schistosomiasis-related health care.

Principal Findings

We found sufficient availability of infrastructure and human resources at most control stations. Many patients with advanced schistosomiasis resided in non-endemic or moderately endemic areas, however, with poor accessibility to disease-specific knowledge and specialized health services. Moreover, none of the patients interviewed had any form of health insurance, resulting in high out-of-pocket expenditure or unaffordable care. Reports on the adequacy and acceptability of care were mixed.

Conclusions/Significance

There is a need to strengthen health awareness and schistosomiasis surveillance in post-transmission control settings, as well as to reduce diagnostic and treatment costs. Further studies are needed to gain a multi-layered, in-depth understanding of remaining barriers, so that the ultimate goal of schistosomiasis elimination in P.R. China can be reached.

China has made great strides toward reducing the burden of schistosomiasis, facilitated by sustained political commitment and a multi-faceted, integrated control strategy. The ultimate goal is disease elimination, which might be challenging due to high rates of re-infection, clusters of re-emergence, and growing health disparities. Market-oriented reforms and system-wide policies within the health care system offer new opportunities, but also entail challenges for the national schistosomiasis control program. Few studies have examined systemic barriers to equitable and effective schistosomiasis control in China. We explored the five core dimensions of access to health care, placing emphasis on schistosomiasis in the Dongting Lake area of Hunan Province. We collected and analyzed perspectives from staff working at local anti-schistosomiasis control stations and designated schistosomiasis hospitals, and from patients with advanced schistosomiasis. Our data suggest that a lack of affordability and high out-of-pocket expenditure posed a major barrier to the health care users, as did a lack of relevant health-information, and poorly accessible diagnostic and specialized surgical services. The lessons learned from this work are important in the design and development of disease control programs and entail key policy implications for schistosomiasis elimination.

A review of parasitic zoonoses in a changing Southeast Asia

Parasitic zoonoses are common and widely distributed in the Southeast Asian region. However, the interactions between parasites, hosts and vectors are influenced by environmental, socio-cultural and livestock production changes that impact on the distribution, prevalence and severity of disease. In this review we provide an update on new knowledge in the context of ongoing changes for the food-borne pig associated zoonoses Taenia solium and Trichinella spp., the food-borne trematodes Opisthorchis viverrini and Clonorchis sinensis, the water-borne trematodes Schistosoma spp., the vector-borne zoonotic protozoa Plasmodium knowlesi and Leishmania spp. and the soil-borne zoonotic hookworm Ancylostoma ceylanicum. These various changes need to be considered when assessing or developing regional control programs or devising new research initiatives in a changing SE Asia.

New insight into the antifibrotic effects of praziquantel on mice in infection with Schistosoma japonicum

BACKGROUND

Schistosomiasis is a parasitic disease infecting more than 200 million people in the world. Although chemotherapy targeting on killing schistosomes is one of the main strategies in the disease control, there are few effective ways of dealing with liver fibrosis caused by the parasite infection in the chronic and advanced stages of schistosomiasis. For this reason, new strategies and prospective drugs, which exert antifibrotic effects, are urgently required.

METHODS AND FINDINGS

The antifibrotic effects of praziquantel were assessed in the murine models of schistosomiasis japonica. Murine fibrosis models were established by cutaneous infection with 14 ± 2 Schistosoma japonicum cercariae. Then, the mice of both chronic (8 weeks post-infection) and advanced (15 weeks post-infection) schistosomiasis were treated by gavage of praziquantel (250 mg/kg, once daily for 3 days) to eliminate worms, and followed by praziquantel anti-fibrosis treatment (300 mg/kg, twice daily for 30 days). The fibrosis-related parameters assessed were areas of collagen deposition, content of hydroxyproline and mRNA expressions of Col1α1, Col3α1, α-SMA, TGF-β, MMP9, TIMP1, IL-4, IL-10, IL-13 and IFN-γ of liver. Spleen weight index, alanine aminotransferase activity and liver portal venous pressure were also measured. The results showed that anti-fibrosis treatment improved liver fibrosis, splenomegaly, hepatic function, as well as liver portal hypertension. In order to confirm the anti-fibrotic properties of praziquantel, we established a CCL(4)-induced model and revealed that CCL(4)-induced liver fibrosis was inhibited by PZQ treatment for 30 days. Furthermore, we analyzed the effects of praziquantel on mouse primary hepatic stellate cells (HSCs). It is indicated that mRNA expressions of Col1α1, Col3α1, α-SMA, TGF-β, MMP9 and TIMP1 of HSCs were all inhibited after praziquantel anti-parasite treatments.

CONCLUSIONS

The significant amelioration of hepatic fibrosis by praziquantel treatment validates it as a promising drug of anti-fibrosis and offers potential of a new chemotherapy for hepatic fibrosis resulting from schistosomiasis.

Three Gorges Dam and its impact on the potential transmission of schistosomiasis in regions along the Yangtze River

Large-scale hydroprojects have a propensity for incurring schistosomiasis epidemics by altering the environments of their vicinities. As the construction of the Three Gorges Dam, one of the world's largest hydroprojects to date, draws near its conclusion, an assessment of the dam's capacity in causing schistosomiasis becomes more urgent and pressing. This article reviews recent investigations into the possible effects of the dam on schistosomiasis in the Three Gorges region and areas along the Yangtze downstream from the dam. Data used in this article were extracted from peer-reviewed papers found in PubMed, Chinese Journal of Parasitology and Parasitic Diseases, and Chinese Journal of Schistosomiasis Control. Results indicate that the Three Gorges Dam is capable of inducing a wide variety of environmental and ecological changes both within the Three Gorges region and in downstream areas. These changes, however, carry ambivalent implications for the reproduction of Oncomelania snails and the spreading of schistosome infections. Furthermore, major changes in the demographics and agricultural practices of the Three Gorges and downstream Yangtze areas caused by the dam could also exert significant influence on the transmission of schistosomiasis in these regions. Major conclusions of this review include the need for further ecological simulations of the Three Gorges Dam and the need for deploying monitoring and intervention systems to provide successful prophylaxis of the Three Gorges Dam-associated schistosomiasis emergence.

Decision-model estimation of the age-specific disability weight for schistosomiasis japonica: a systematic review of the literature

Schistosomiasis is among the most prevalent parasitic infections worldwide. However, current Global Burden of Disease (GBD) disability-adjusted life year estimates indicate that its population-level impact is negligible. Recent studies suggest that GBD methodologies may significantly underestimate the burden of parasitic diseases, including schistosomiasis. Furthermore, strain-specific disability weights have not been established for schistosomiasis, and the magnitude of human disease burden due to Schistosoma japonicum remains controversial. We used a decision model to quantify an alternative disability weight estimate of the burden of human disease due to S. japonicum. We reviewed S. japonicum morbidity data, and constructed decision trees for all infected persons and two age-specific strata, <15 years (y) and ≥15 y. We conducted stochastic and probabilistic sensitivity analyses for each model. Infection with S. japonicum was associated with an average disability weight of 0.132, with age-specific disability weights of 0.098 (<15 y) and 0.186 (≥15 y). Re-estimated disability weights were seven to 46 times greater than current GBD measures; no simulations produced disability weight estimates lower than 0.009. Nutritional morbidities had the greatest contribution to the S. japonicum disability weight in the <15 y model, whereas major organ pathologies were the most critical variables in the older age group. GBD disability weights for schistosomiasis urgently need to be revised, and species-specific disability weights should be established. Even a marginal increase in current estimates would result in a substantial rise in the estimated global burden of schistosomiasis, and have considerable implications for public health prioritization and resource allocation for schistosomiasis research, monitoring, and control.

Schistosomiasis is a parasitic infection caused by a flatworm that disproportionately affects the world's poorest populations. Schistosomiasis is one of the most common infections worldwide, affecting over 207 million people in 76 countries. Current international estimates indicate that schistosomiasis has a minimal impact at the population level. This has contributed to its low prioritization in global health and subsequent resource allocation for disease control. However, recent studies indicate that these measures underestimate the extent of neglected tropical diseases, including schistosomiasis. Despite World Health Organization recommendations, the burden of schistosomiasis has not been re-examined in over a decade, and there are no established estimates for different types of schistosomiasis. The impact of symptoms associated with the Asian strain, Schistosoma japonicum, remains controversial. This study was conducted to provide an alternate measure of the burden of S. japonicum. We reviewed the literature and calculated a summary estimate for S. japonicum which was seven to 46 times greater than current measures for schistosomiasis. Findings suggest that current measures severely underestimate the extent of schistosomiasis, and urgently need to be revised. Further research is needed to examine the burden of schistosomiasis and other forgotten tropical diseases affecting the world's poorest people in endemic countries.

Large water management projects and schistosomiasis control, Dongting Lake region, China

Construction of the Three Gorges Dam across the Yangtze River will substantially change the ecology of the Dongting Lake in southern China. In addition, the Chinese Central and Hunan Provinces' governmental authorities have instigated a Return Land to Lake Program that will extend the Dongting Lake surface area from the current 2,681 km2 to 4,350 km2. The previous construction of embankments and the large silt deposits made by the Yangtze River and other connecting rivers have contributed to frequent disastrous flooding. As a consequence of the 2 water projects, > 2 million persons and their domestic animals are being resettled. This article provides an overview of the historical background of these 2 large water management projects, the associated population movement, and their impact on future transmission and control of schistosomiasis in the Dongting Lake area. The dam will likely substantially extend the range of the snail habitats and increase schistosome transmission and schistosomiasis cases.

Application of recombinant Sjc26GST for serodiagnosis of Schistosoma japonicum infection in water buffalo (Bos buffelus)

Schistosomiasis japonica is currently the most serious parasitic disease in mainland China and it is estimated that several million people are infected. Furthermore, it is also responsible for the deaths of many domestic animals. In order to establish an effective diagnostic method, the gene encoding Sjc26GST was cloned and expressed in Escherichia coli as a fusion protein with His-tag. The purified reSjc26GST was used as an antigen for an enzyme-linked immunosorbent assay (ELISA) and for immunoblotting detection of Schistosoma japonicum antibodies in water buffaloes. Our results showed that mean OD values of specific serum IgG antibodies from egg-positive buffaloes were 3.37-fold higher than what was found in egg-negative buffaloes from non-endemic areas. The data also showed the OD value of the endemic egg-negative group reached as high as 1.69 times as that found in non-endemic areas. The positivity rate of egg-positive buffaloes was 100%, but was 30.3% in the endemic egg-negative group. Infected bovine antisera also recognized reSjc26GST, a 27kDa protein as determined by Western blot. These results suggest that the recombinant GST expressed in E. coli should be an effective diagnostic reagent for detection of antibody against S. japonicum in buffaloes. Due to straightforward production, excellent sensitivity and high specificity, the reSjc26GST described in this study can be considered as a candidate protein for immunological diagnosis of bovine schistosomiasis. Developing reSjc26GST, with its potential diagnostic values, will be useful for diagnosis and surveillance of schistosomiasis in controlling the spread of this parasitic disease in domestic animals.

Large water management projects and schistosomiasis control, Dongting Lake region, China

Construction of the Three Gorges Dam across the Yangtze River will substantially change the ecology of the Dongting Lake in southern China. In addition, the Chinese Central and Hunan Provinces' governmental authorities have instigated a Return Land to Lake Program that will extend the Dongting Lake surface area from the current 2,681 km2 to 4,350 km2. The previous construction of embankments and the large silt deposits made by the Yangtze River and other connecting rivers have contributed to frequent disastrous flooding. As a consequence of the 2 water projects, > 2 million persons and their domestic animals are being resettled. This article provides an overview of the historical background of these 2 large water management projects, the associated population movement, and their impact on future transmission and control of schistosomiasis in the Dongting Lake area. The dam will likely substantially extend the range of the snail habitats and increase schistosome transmission and schistosomiasis cases.

Applications and outcomes of periodic epidemiological surveys for schistosomiasis and related economic evaluation in the People's Republic of China

The great success in schistosomiasis control in China is attributable to a range of factors. Periodic epidemiological surveys (PES) used for monitoring and adapting control interventions over time are an integral feature of the national schistosomiasis control programme. PES have enabled the dynamic trends of schistosomiasis epidemics to be closely pursued and have assisted in analysing subtle changes in endemicity. The results can be summarised mathematically allowing the variation in efficacy of control measures to be readily determined and enabling control strategies to be adjusted and updated. PES have been used in both cross-sectional and longitudinal pilot studies selected by appropriate sampling methods. In the early 1990s, when the World Bank Loan Project for schistosomiasis control commenced, economic evaluations were initiated in parallel. Cost-effectiveness analysis became a necessary tool to identify the most financially feasible yet effective options among a range of alternative control strategies. There was, however, a lack of standardised approaches rendering study comparisons across sites difficult. The global burden of disease study established the disability adjusted life year (DALY) as a measure of population health, combining in a single indicator years lost from premature death and years of life lived with disability. However, a recent meta-analysis reveals that the burden of schistosomiasis is underestimated, and hence, needs to be revised. It is envisaged that after the revision of DALYs lost due to schistosomiasis japonica, they will become an essential measure in future schistosomiasis control assessments in China and in other schistosome-endemic areas of the world.

Evaluation of the 1992-1999 World Bank Schistosomiasis Control Project in China

The 1992-1999 World Bank Schistosomiasis Control Project in China contributed significantly to the disease control with its specific strategy and approach. An evaluation was made in this paper based on project control and surveillance data collected from all project provinces systematically year by year. Several indicators were computed, comparison was made using the 1989 survey data as the baseline, and correlation analysis was carried out on prevalence in humans, prevalence in cattle and buffaloes and infection rate of snails. From 1992 to 1998, the overall prevalence in human population, prevalence in children aged 7-14 and prevalence in cattle and buffaloes decreased by 5.74, 59.55 and 62.30%, respectively. Snail areas increased by 14.85% throughout the project period, while snail infection rate and density of infected snails decreased by 68.75 and 44.95%. Hubei province was among all eight provinces the most impressive in schistosomiasis control during the project. Results show that coverage of chemotherapy was among other factors the most directly-related to the prevalence in humans. The drug for chemotherapy-praziquantel was effective for new cases rather than reinfection. As to the overall achievement, most of the objectives set for the project had been achieved, especially the decrease in prevalence, in both human population and cattle and buffaloes. However, the achievement of snail control was not so ideal, which calls for rectification for a more applicable and practical strategy of snail control in China.

Expressed sequence tag (EST) analysis of a Schistosoma japonicum cercariae cDNA library

Expressed sequence tags (ESTs) constitute a rapid and informative strategy for studying gene-expression profiles of specific stages of schistosomes. To date, only approximately equal 2000 ESTs of Schistosoma japonicum have been deposited in databases. This is insufficient to understand the biology and development of this species. In this report, a cDNA library constructed from S. japonicum cercariae RNA was used to generate ESTs. Cercariae are the larval forms of Schistosoma responsible for infection of the vertebrate host and one of the main objectives of this research was to discover and characterize new and unique genes from this stage. The expression products of those stage-specific genes can potentially be useful as new drugs or vaccine targets applicable for controlling Asian schistosomiasis. In our study, 101 cDNA clones were sequenced either from 5' or 3' end of the cDNAs. Some 42 ESTs (42%) matched known genes, while 59 ESTs did not match with any known genes. Among the 42 former ESTs, 29 (informative ESTs) matched to functional genes and 13 matched with ribosomal proteins or RNA genes. Among the latter 59 ESTs, 21 matched with published ESTs of S. japonicum or S. mansoni, two matched with human ESTs and the other 18 did not match with any published sequences. The informative ESTs could be grouped into nine categories: regulatory and signaling proteins (24.1%), transcription and translation machinery proteins (13.8%), RNA binding proteins (6.9%), structural and cytoskeletal proteins (6.9%), DNA binding proteins (3.4%), DNA scaffold proteins (3.4%), transporter proteins (3.4%) and others (31%). Some functional genes relevant to the physiology of cercariae are discussed.

Susceptibility of Schistosoma japonicum to praziquantel in China

To look for possible evidence of the development of resistance in Schistosoma japonicum to praziquantel, we conducted a field study in China. During the non-transmission period of schistosomiasis a random sample of 2860 individuals from six villages in three provinces of China were examined using a parasitological stool examination. Of the 372 stool-positive subjects, 363 subjects were treated with a single oral dose of 40 mg/kg of praziquantel. Six to Seven weeks after treatment, of 334 subjects examined using the same stool examination, stool-negative results were found in 319 patients which represents a 95.5% parasitologic cure rate. Fifteen subjects still excreting eggs were treated a second time with the same dose of praziquantel. All stool samples, including those from participants re-treated with praziquantel, were re-examined 12 weeks after the first treatment and no stool-positive subjects were found. The results indicate that there was no evidence for reduced susceptibility of S. japonicum to praziquantel despite its extensive use in the main endemic areas of China for more than 10 years. The in vitro responses to praziquantel of cercariae, miracidia and eggs of S. japonicum compared with S. mansoni demonstrate that the cercariae, miracidia and eggs of S. japonicum are more sensitive to praziquantel than those of S. mansoni. More sensitive worms would be less likely to develop resistance and this could explain why no evidence for resistance was found in S. japonicum in China.

Schistosomiasis in the People's Republic of China: prospects and challenges for the 21st century

Schistosomiasis japonica is a serious communicable disease and a major disease risk for more than 30 million people living in the tropical and subtropical zones of China. Infection remains a major public health concern despite 45 years of intensive control efforts. It is estimated that 865,000 people and 100,250 bovines are today infected in the provinces where the disease is endemic, and its transmission continues. Unlike the other schistosome species known to infect humans, the oriental schistosome, Schistosoma japonicum, is a true zoonotic organism, with a range of mammalian reservoirs, making control efforts extremely difficult. Clinical features of schistosomiasis range from fever, headache, and lethargy to severe fibro-obstructive pathology leading to portal hypertension, ascites, and hepatosplenomegaly, which can cause premature death. Infected children are stunted and have cognitive defects impairing memory and learning ability. Current control programs are heavily based on community chemotherapy with a single dose of the drug praziquantel, but vaccines (for use in bovines and humans) in combination with other control strategies are needed to make elimination of the disease possible. In this article, we provide an overview of the biology, epidemiology, clinical features, and prospects for control of oriental schistosomiasis in the People's Republic of China.

Pathology and course of natural Schistosoma japonicum infection in pigs: results of a field study in Hubei province, China

In order to obtain information on the natural course of porcine infection with Schistosoma japonicum, pigs were exposed to the cercariae of this parasite in a highly endemic region of China. Five, 5-month-old pigs previously infected with S. japonicum (group A) and 10, schistosome-naïve piglets (group B) were allowed on a pasture infested with Oncomelania snails for one transmission period (approximately 5.5 months). All the piglets rapidly acquired infection, and both groups remained infected throughout the study period. Group B showed fever, diarrhoea and anorexia in the early egg-excretion phase, and marked growth reduction. In both groups, post-mortem examination revealed live schistosomes and lesions associated with dead worms in the intestinal and mesenteric vasculature, and egg-related pathology in the large intestine and liver. Major findings were exudative lesions connected with egg excretion in the intestine, and granulomatous obstruction of portal veins in the liver. Signs of granuloma modulation were found in the liver, but not in the intestine. In conclusion, the study showed that field exposure of pigs to S. japonicum for one transmission period resulted in clinical disease and growth retardation in the youngest pigs, and significant pathology in both groups. Self cure, prominent in experimental porcine infections produced with single, high-dose inocula, was not induced in either group.

Drug resistance in human helminths: current situation and lessons from livestock

In this review the available reports on drug resistance in human helminths, particularly hookworms and schistosomes, are critically analyzed. The experiences with helminths of livestock are then reviewed, in particular the factors contributing to the development of anthelmintic resistance, the mechanisms and genetics of resistance to various anthelmintic classes, and the methods available for detection. These experiences appear to be worryingly similar and relevant to the potential development of drug resistance in human helminths. Recommendations to reduce its risks are suggested.

Drug resistance in human helminths: current situation and lessons from livestock

In this review the available reports on drug resistance in human helminths, particularly hookworms and schistosomes, are critically analyzed. The experiences with helminths of livestock are then reviewed, in particular the factors contributing to the development of anthelmintic resistance, the mechanisms and genetics of resistance to various anthelmintic classes, and the methods available for detection. These experiences appear to be worryingly similar and relevant to the potential development of drug resistance in human helminths. Recommendations to reduce its risks are suggested.

Is there immunity to Schistosoma japonicum?

The Oriental schistosome, Schistosoma japonicum, unlike the other two major schistosomes that infect humans (S. mansoni and S. haematobium), is a zoonotic species. The transmission dynamics and the potential effects of host-related regulatory factors, including immunity, are likely to be distinct for this parasite. Here, Allen Ross and collaborators from Australia, China and the Philippines discuss recently published and established epidemiological and laboratory data bearing on anti-infection immunity to Asian schistosomiasis, and contrast these findings with the emerging picture of development of anti-infection immunity against the African schistosomes. Implications for vaccines and other control strategies for schistosomiasis japonica are also discussed.

The prophylactic effects of artemether against Schistosoma japonicum infections

The fight against schistosomiasis in China has been very effective in reducing the number of infections across the country. However, the drug of choice, praziquantel, has no prophylactic effect, which reduces its efficacy in high transmission areas. This situation has prompted efforts to find prophylactic compounds, the most promising of which is the drug artemether. In this article, Xiao Shuhua, Mark Booth and Marcel Tanner review the results of laboratory tests and field trials of artemether against schistosomiasis in China.

Cloning and molecular characterization of calpain, a calcium-activated neutral proteinase, from different strains of Schistosoma japonicum

cDNA coding for calpain of Schistosoma japonicum were cloned and sequenced, and serological basis of host responses to calpain were analyzed. cDNA of calpain from S. japonicum of two different isolates, Yamanashi strain (Sj-J) and Hunan strain (Sj-C), were 2, 468 bp and 2, 465 bp in length, including the same number (2, 274) of open reading frame. Nucleotide sequence and amino acid sequence between the two calpains are 99.1% and 98.8% identity, respectively. Sj-J and Sj-C calpains were considered to be translated as a preproenzyme, and a 746-amino acid mature enzyme contains eight motifs without a signal peptide at the N-terminal based on the deduced amino acid sequences. mRNA for calpain were detectable in different developmental stages, however, sera obtained from mice immunized with recombinant calpain showed enhanced binding to cercarial antigen. Human sera from S. japonicum-infected individuals recognized the large subunit of schistosomal calpain, and light-infected sera showed stronger reactivities to the recombinant calpain than moderate/high infection cases. When we tested synthetic peptides, there were four common human B cell epitopes in schistosomal calpain, all of which are shared with S. mansoni. Together with these results, calpain of S. japonicum seems to be not only a vaccine candidate, but also a target antigen for immunodiagnosis of human schistosomiasis.

The search for a vaccine against schistosomiasis--a difficult path but an achievable goal

The search for an effective vaccine against schistosomiasis, a parasitic disease currently affecting over 200 million people, remains a desirable but as yet challenging and elusive goal. Progress in the area has been relatively slow but research demonstrating the ability of humans to acquire natural immunity to schistosome infection, together with the successful use in animals of attenuated vaccines, supplemented with encouraging results obtained with defined antigens, suggests that development of a vaccine is achievable. Noteworthy also are recent immune correlate findings which shed light on the complex, putatively protective immune responses in humans, which have improved the prospects of success. With the first human clinical trial having been completed with a schistosome vaccine candidate, this review examines current progress aimed at achieving the objective of a safe and effective vaccine for widespread use against schistosomiasis. The review emphasises work undertaken in the author's laboratory and those of his chief collaborators in the search for a vaccine against schistosomiasis japonica, a disease of major public health significance in The People's Republic of China and The Philippines. Schistosomiasis vaccines should not be considered as the panacea for schistosomiasis control as, when available, it is generally envisaged that they would be used as one component of an integrated strategy complementing currently available and effective tools such as chemotherapy, improvements to sanitation, piped water supply, effective sewage draining and health education.

Measuring exposure to S. japonicum in China. II. Activity diaries, pathways to infection and immunological correlates

In this study we examine the pathways to schistosomiasis exposure and infection among residents residing on two islands (large, Qingshan; small, Niangashan) in the Dongting Lake region (Hunan province) of China. An exposure model, based on activity diaries, was used to quantify an individual's square-metre-minute (sq.m.min) daily water contact. Subjects living on the small island had a significantly higher (P=0.0002) degree of exposure (mean+/-S.D., 13.2+/-11.0 sq.m.min) than individuals dwelling on the large island (mean+/-S.D., 5.5+/-7.1 sq.m.min). Participants identified as stool egg positive (mean+/-S.D., 8.3+/-10.4 sq.m.min) had higher exposures than for those never treated (mean+/-S.D., 2.2+/-3.4 sq.m.min) for schistosomiasis, and these high exposures rose steadily to peak at 35-49 years of age and decline after age 50. This exposure pattern differs markedly from those reported for African or South American schistosomiasis. The majority of human water contact occurs on the lake. Egg-positive subjects reported significantly higher (P < 0.05) episodes of water contact on the lake versus their egg-negative counterparts, who reported significantly higher (P < 0.01) exposure at the aquaculture ponds. The results of path analysis revealed that sex, age, island of residence and whether a fisherman or not were the most highly significant independent predictors of lake exposure. This accounted for approximately 40% (R2=0.39) of the total lake exposure. Exposure to lake water was a strong predictor (P=0.0006) of past infection and a modest predictor (P=0.05) of current infection.

Measuring exposure to S. japonicum in China. I. Activity diaries to assess water contact and comparison to other measures

We introduce a new method, activity diaries, in order to evaluate human water contact among fishing communities in an area moderately endemic for Schistosoma japonicum in the Dongting Lake region of Southern China. Two hundred and forty-nine subjects (76% male) were followed prospectively over a 9-month-period in order to verify exposure and reinfection. Exposure was determined crudely with questionnaires, direct 12-h water observations, and more precisely with activity diaries and an adjusted exposure model which took into account the time of day, the duration of contact and the percent body surface area in contact with water. Cohort subjects filled in activity diaries for an average of 85 days as compared with 2 days for the direct water observations. The typical unadjusted mean daily water contact (duration) based on the activity diaries was 53 min with 62% of this time spent in fishing. In contrast, the direct water observations revealed an average daily duration of 149 min with 53% of the time spent in fishing. Human water contact patterns (min/day) by site, activity and body part exposed were examined with the activity diaries. Individuals in the 36-49-year-old age range had the highest degree of water contact. Most of this daily contact occurred by males on the hands (mean+/-S.D.; 83.53+/-67.80 min/day) while fishing (mean+/-S.D.; 87.84+/-8.88 min/day) on the lake (mean+/-S.D.; 85.98+/-69.90 min/day). There was a strong positive log correlation (r=0.95) between the crude and adjusted (based on our derived exposure model) diary outcomes for the entire study sample, however, at higher exposure levels this relationship was differentially weaker (r=0.70). Results from this study suggest that current methods used in evaluating schistosomiasis exposure in China may overestimate and bias measures of the risk of infection. Activity diaries adjusted for the time of day, duration and the percent body surface area exposed are cost-effective and practical instruments to accurately quantify human exposure in the vast lake regions of Southern China where most of the endemic schistosomiasis japonica occurs.

Snail Control Strategies for Reduction of Schistosomiasis Transmission

As intermediate hosts, molluscs play a major role in the transmission of schistosomes; they are the sites of an intense multiplication of parasites. Thus, snail control strategies are considered a priority for the reduction of schistosomiasis transmission. Here, Vinca Lardans and Colette Dissous review the efficacy of environmental management and the use of molluscicides and biological agents to control snail populations. They then describe the development of diagnostic tests, based on the detection of parasite antigens or specific parasite DNA sequences in snail tissues, to detect the early infection of snails. Finally, they discuss progress in studying the molecular basis of susceptibility and resistance phenotypes, and the possible application of the genetic manipulation of molluscs.

Five year impact of chemotherapy on morbidity attributable to Schistosoma japonicum infection in the Dongting Lake region

OBJECTIVE

To determine changes in the last 5 years of the fraction of acute and chronic symptoms attributable to schistosomiasis japonica in fishing communities with moderate endemicity in the Dongting Lake region of China.

METHOD

Complete medical histories, physical examinations, and stool samples were obtained from 1909 individuals (53% male) ranging in age from 4 to 81 years. Age, sex, occupation, frequency of water contact, number of times treated for schistosomiasis, and last year of treatment were tested as potential effect modifiers and confounders.

RESULTS

Overall, there were very few infected cases and very little variation in any prevalence ratio with infection intensity, sex, age, year of last treatment, number of times treated or frequency of water contact. The attributable fraction of liver enlargement in one village was estimated at 0.114 (11.4%), although this was not significantly > 0(95% CI; -0.008-0.237).

CONCLUSION

The chemotherapy-based schistosomiasis control programme in this locality has succeeded in reducing attributable morbidity to undetectable levels, but many uncertainties remain about sustaining control efforts in the future. Both old and new control strategies will have to be examined if the health and well-being of these people are to be maintained into the next millennium, given that periodic chemotherapy will not be accepted indefinitely.

Immunolocalization of schistosome proteins

This review discusses some of the recent advances in the characterization of potential vaccine molecules against Schistosoma japonicum, utilizing microscopy and immunocytochemistry methods. Microscopy has demonstrated the stage-specific expression of the muscle protein paramyosin onto the parasite surface, an important consideration as a vaccine target. Other potential vaccine component proteins examined include glutathione S-transferase (GST) and fatty acid binding protein (FABP); although not associated with the adult parasite surface, their localization to internal structures such as lipid droplets and regions of the female reproductive system have provided valuable insights into the biology of the parasite. Localization of the transport protein SGTP (schistosome glucose transporter protein) has demonstrated that the protein is more prevalent in the juvenile stages of the parasite development. This further highlights the diversity of the parasite life cycle. Using both light microscopy and transmission electron microscopy, the localization of a number of schistosome proteins has demonstrated the functions and significance of these proteins within the parasite. Molecular localization studies are crucial in understanding how and when a vaccine may work against the organism and may provide insights into which can be used in the design of future vaccines.

Faecal egg aggregation in humans infected with Schistosoma japonicum in China

In this study we examine the variation in Schistosoma japonicum egg counts caused by differences in worm loads between individuals and the variability of egg counts within individuals with a given worm load. Six villages were selected from an area moderately endemic for Asian schistosomiasis in the Dongting Lake region (Hunan province), China. From a total population of 3451 individuals (53.8% male; x = 31 years), 163 subjects were identified as consistently stool egg-positive based on three successive positive Kato-Katz (KK) smears (41.67 mg/smear) obtained from one stool specimen. The distribution of eggs among individuals was found to be strongly aggregated (k = 0.27), but the distribution within the three smears was found to be only slightly aggregated (k = 2.59), indicating only minor clustering of eggs in stools. The relatively slight clustering of eggs within stool specimens suggests that a single KK smear may be quite adequate for detecting individuals moderately to heavily infected (> 100 eggs/g stool (epg)), as needed for a strategy of morbidity control. However, for estimating the true prevalence of infection in a community, or for obtaining an accurate estimate of egg excretion for research studies, multiple KK smears are warranted.

Financing changes of schistosomiasis control programmes in China 1980-1995: a case study in Songzi county

To assess the financing changes of schistosomiasis control programmes in China and estimate the impact of these changes on patients' treatment-seeking behaviour and control of schistosomiasis, a survey was conducted in five schistosomiasis-endemic areas of the lake regions, Hubei province, in 1996. This paper reports financing changes and their impact on the incidence and prevalence of schistosomiasis from one of the five areas as a case study. By examining the surveillance and financial data from 1980 to 1995, and through focus group discussions we found that the schistosomiasis control programmes in People's Republic of China have gone through dramatic financing changes from 1980 to 1995, when the transitions of China's social, economic, and political systems happened. The proportions of funding to schistosomiasis control programmes from high level governmental agencies, county budgets, and services revenue changed from 60%, 23%, and 17%, respectively, in 1980-1987 to 0.7%, 22.3%, and 72% in 1995. The percentages of expenditure of schistosomiasis control activities, salaries and bonuses, and other activities unrelated to schistosomiasis control, were 53.5%, 14.4, and 17.2% in 1980. These percentages changed to 7.7%, 33.3%, and 53.3%, respectively, in 1995. The preponderant role of the state in organizing, financing, and delivery of the services was replaced with the new system which is more influenced by the market economy. The incidence and the prevalence of schistosomiasis in the study area have increased year by year from 1980 to 1990, although there has been a tendency to decrease after 1991 but not to the low pre1980 levels. The collapse of the community-based medical system in rural areas and the dramatic financing changes of schistosomiasis control programmes have created major difficulties for schistosomiasis control in China.

Diagnosis of schistosomiasis japonica in Chinese schoolchildren by administration of a questionnaire

This paper describes a rapid, simple, cost-effective questionnaire for screening school-aged children at risk for Asian schistosomiasis in China. Five hundred and thirty-two children, aged 8-14 years, were selected from 3 schools in an area moderately endemic for Schistosoma japonicum in Hunan province. The questionnaire, comprising 15 multiple-choice questions, was administered by teachers in order to collect both ethnographic and epidemiological data relevant to current S. japonicum infections. This was followed by Kato-Katz thick smear stool examinations, miracidium hatching tests, and soluble egg antigen-enzyme linked immunosorbent assays in order to validate the efficacy of the questionnaire approach. The results from a combination of all 3 procedures indicated that the overall schistosomiasis prevalence in the 3 schools was 29.9% (138/472). Six risk factors (episodes of diarrhoea, frequency of water contact, school grade attained, weakness, past history of S. japonicum infection(s), and whether a subject had been previously treated for schistosomiasis) in the questionnaire were determined by logistic regression to be highly statistically significant predictors of individual current infection. The sensitivity (93.7%), specificity (91.9%) and low cost (c. US$ 0.6/true positive case) associated with the 6 variables model make the questionnaire approach a very useful diagnostic tool for screening marshland and lake communities at high risk for schistosomiasis in China before selective treatment with praziquantel or diagnostic follow-up. An even simpler 3 variables 'yes/no' model was derived from the questionnaire and found to be nearly as good at predicting individual infection (sensitivity 86.2% and specificity exceeding 97.6%) and extremely simple to use. If validated in other ecological settings in China the questionnaire, modified or as presented here, could be adopted by the national schistosomiasis control programme.

The Role of Microscopy in the Investigation of Paramyosin as a Vaccine Candidate against Schistosoma japonicum

There has been growing interest in paramyosin as a vaccine component to combat schistosomiasis. Immunological and molecular techniques have been used in the past to investigate the effectiveness of a paramyosin vaccine as an anti-schistosomal treatment. However, recent localization studies at ultrastructural and morphological levels have highlighted a number of questions concerning the role of paramyosin within schistosome parasites. Debates about how a non-surface protein such as paramyosin might provide protection against schistosome infections have recently been addressed by microscopy results. Immunolocalization studies have indicated multiple functions of paramyosin within the parasite and provided insights into how a vaccine may target the parasite, as discussed here by Geoffrey Gobert.

Control of schistosomiasis — A global picture

The control of schistosomiasis has been a challenging task for most endemic countries. Thus, despite the concerted efforts to date, schistosomiasis remains a major public health concern, second only to malaria in the tropics and subtropics. In this review, Lorenzo Savioli and colleagues highlight changes in schistosomiasis prevalence and distribution over the past decades, discuss the success and limitations of the various control strategies, and present possible control initiatives for the future.

An evaluation of Schistosoma japonicum infections in three villages in the Dongting lake region of China. I. Prevalence, intensity and morbidity before the implementation of adequate control strategies

We examined three Chinese villages (one farming village and two fishing villages) in an area highly endemic for schistosomiasis japonica in order to study the prevalence, intensity of infection and the associated morbidities before the implementation of adequate control strategies. Socio-economic status, medical histories including the frequency and type of water contact, physical examinations, parasitological examinations and questionnaires relevant to the knowledge of schistosomiasis were performed on a random sample of 1542 individuals (45% female; 55% male). The prevalence of Schistosoma japonicum was 9.4% in the farming village and 16.5 and 26.2% in the fishing villages. Eighty-three percent of the infected population had light infections (8-100 eggs per gram stool (epg)) and only 6% had heavy infections (> 400 epg). Both the prevalence and intensity of infection varied significantly (P < 0.01) with the frequency of water contact. All the morbidity indicators (weakness, inability to work, diarrhoea, hepatomegaly and splenomegaly) were significantly higher (P < 0.01) among those infected with S. japonicum. Knowledge of schistosomiasis, in general, was unsatisfactory in all three villages; 12.4% of the population was infected when their knowledge of schistosomiasis was good, whereas 26.6% of the population was infected when their knowledge was poor. Further, it appears that schistosomiasis control based on selective chemotherapy (praziquantel) of randomly selected stool-positive individuals was ineffective in significantly reducing the prevalence of S. japonicum and its associated clinical manifestations in the villages under study.

An examination of current control strategies for Asian schistosomiasis in the Dongting lake region of China. II. A five year follow-up survey on Qingshan island

In 1995-1996 we conducted an epidemiological survey in two communities (1656 individuals) on Qingshan island, Hunan province P.R. China, in order to determine the efficacy of current control strategies since their upgrading in 1991. In 1996, the overall prevalence for Schistosoma japonicum, Ascaris lumbricoides, Ancylostoma duodenale, and Trichuris trichiura had decreased moderately since 1991. The age-specific prevalence for S. japonicum for each of the representative age groups decreased slightly, but there was a significant reduction in these prevalences for the 5-9 (P < 0.01), 55-59 (P < 0.05) and the over 60 (P < 0.01) age groups. The 1996 intensities of infection for schistosomiasis were higher for all the age categories except for those aged 0-4 and 25-29 years of age. When the study population was further classified according to the percent uninfected, lightly infected (8-100 eggs/g (epg)), moderately infected (101-400 epg) and heavily infected (> 400 epg) for S. japonicum, there were fewer (5.6%) people infected in 1996 but the proportions of moderately (21.3 vs. 15.5%) and heavily (7.6 vs. 2.3%) infected individuals were higher than those observed in 1991. The reported cases of weakness and hepatomegaly (MSL > or = 3) were significantly lower (P < 0.01) in 1996 for both uninfected and infected (all intensities) individuals. General episodes of diarrhoea were also significantly lower in 1996 for those lightly (P < 0.05) and heavily (P < 0.01) infected. Likewise, the occurrence of splenomegaly (Hackett's > or = 2) was significantly lower among uninfected (P < 0.01) and heavily infected (P < 0.05) patients. In summary, although significant progress has been made in controlling schistosomiasis and other helminth infections in this highly endemic focus for schistosomiasis, there is still room for improvement. Chemotherapy for bovines and humans, mollusciding for Oncomelania control and health education should be initiated and upgraded if the health and well being of these island communities is to further improve.