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.

The epidemiological status of schistosomiasis in P. R. China after the World Bank Loan Project, 2002-2017.

World Bank Loan Project (WBLP) for schistosomiasis control conducted from 1992 to 2001, resulted in significant reduction of schistosomiasis morbidity and mortality in People's Republic of China (P.R. China), with implementation of morbidity control. Thereafter, an integrated control strategy, which targeted blocking disease transmission from reservoir hosts to the environment, was initiated in order to conquer schistosomiasis rebound after WBLP completion. Data obtained from the national schistosomiasis control reporting systems was collected and analyzed. The number of confirmed cases and infected cattle decreased significantly from 2002 to 2017, while no infected snails were found by dissection for four consecutive years. However, lake and marshland regions and some parts areas of Yunnan Province require attention for rigorous schistosomiasis control efforts. There is need to strengthen precise interventions and sensitive surveillance to achieve schistosomiasis elimination in P.R. China.

Efficacy of China-made praziquantel for treatment of Schistosomiasis haematobium in Africa: A randomized controlled trial.

BACKGROUND: In the roadmap on the neglected tropical diseases (NTD) the World Health Organization (WHO) aims at attaining at least 75% coverage of preventive chemotherapy in pre-school and school-age children by 2020. A randomized controlled trial was used to compare the effectiveness of praziquantel in treating Schistosoma haematobium in Africa using two different sources for the drug, Merck Limited Partnership (KgaA), Germany and Nanjing Pharmaceutical Factory (NPF), China. METHODS: More than 6,000 participants testing positive for S. haematobium infection were enrolled from three villages (shehias) situated in the northern, middle and southern part of Pemba Island, Zanzibar. Applying criteria of inclusion and exclusion, resulted in a study population of 152 people (84 males, 68 females). A randomized controlled trial was conducted assigning participants to either praziquantel from NPF or Merck KGaA. After one month, the cure rate of S. haematobium and adverse events were compared to evaluate effectiveness. The ratio of male to female, the ratio of light/high infection intensity, and the average value of age were calculated between the two drug manufacturers. Chi-squared test and T-test were used for consistency analysis. RESULTS: Out of the total of 73 cases receiving praziquantel from NPF, the cure rate achieved was 97.3% (73/75), while the 74 cases receiving the drug from Merck KgaA reached a similar cure rate (96.1% or 74/77). There was no significant difference between the two outcomes (χ2 = 0.003, P = 0.956). Among the 75 patients treat, only one (a 16-years old female student), who had received the drug made in China had slight adverse reactions manifested as dizziness, headache and abdominal pain. CONCLUSION: The efficacy of China-made praziquantel does not differ significantly from praziquantel made by Merck KGaA in Germany. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03133832.

Field Testing Integrated Interventions for Schistosomiasis Elimination in the People's Republic of China: Outcomes of a Multifactorial Cluster-Randomized Controlled Trial.

Despite significant progress, China faces the challenge of re-emerging schistosomiasis transmission in currently controlled areas due, in part, to the presence of a range of animal reservoirs, notably water buffalo and cattle, which can harbor Schistosoma japonicum infections. Environmental, ecological and social-demographic changes in China, shown to affect the distribution of oncomelanid snails, can also impact future schistosomiasis transmission. In light of their importance in the S. japonicum, lifecycle, vaccination has been proposed as a means to reduce the excretion of egg from cattle and buffalo, thereby interrupting transmission from these reservoir hosts to snails. A DNA-based vaccine (SjCTPI) our team developed showed encouraging efficacy against S. japonicum in Chinese water buffaloes. Here we report the results of a double-blind cluster randomized trial aimed at determining the impact of a combination of the SjCTPI bovine vaccine (given as a prime-boost regimen), human mass chemotherapy and snail control on the transmission of S. japonicum in 12 selected administrative villages around the Dongting Lake in Hunan province. The trial confirmed human praziquantel treatment is an effective intervention at the population level. Further, mollusciciding had an indirect ~50% efficacy in reducing human infection rates. Serology showed that the SjCTPI vaccine produced an effective antibody response in vaccinated bovines, resulting in a negative correlation with bovine egg counts observed at all post-vaccination time points. Despite these encouraging outcomes, the effect of the vaccine in preventing human infection was inconclusive. This was likely due to activities undertaken by the China National Schistosomiasis Control Program, notably the treatment, sacrifice or removal of bovines from trial villages, over which we had no control; as a result, the trial design was compromised, reducing power and contaminating outcome measures. This highlights the difficulties in undertaking field trials of this nature and magnitude, particularly over a long period, and emphasizes the importance of mathematical modeling in predicting the potential impact of control intervention measures. A transmission blocking vaccine targeting bovines for the prevention of S. japonicum with the required protective efficacy would be invaluable in tandem with other preventive intervention measures if the goal of eliminating schistosomiasis from China is to become a reality.

Enhancing collaboration between China and African countries for schistosomiasis control.

Schistosomiasis remains an important public health issue, with a large number of cases reported across sub-Saharan Africa, and parts of Asia and Latin America. China was once highly endemic, but has made substantial progress and is moving towards elimination of schistosomiasis. Meanwhile, despite long-term, repeated, school-based chemotherapy in many African countries, more than 90% of all schistosomiasis cases are concentrated in Africa, and hence, this continent constitutes the key challenge for schistosomiasis control. Opportunities and issues for international collaboration in the fight against schistosomiasis are outlined with a focus on China's experiences, including the role of public health authorities and intersectoral collaboration, use of new and effective snail control approaches and diagnostic tools adapted to the specific stage of control, as well as the strengthening of risk mapping and surveillance-response mechanisms. Training courses targeting African governmental officials and professionals, coupled with field visits of African scientists and control programme managers to China, and vice versa, are considered important for improved schistosomiasis control and elimination. The crucial question remains whether the Chinese experience can be translated and applied in African countries to improve the effectiveness of health interventions and scale-up.

[Effect of calcium cyanamid synthetic drug on Schistosoma japonicum egg morphology].

OBJECTIVE: To study the morphological change of Schistosoma japonicum eggs processed by calcium cyanamide synthetic drug, so as to provide the basis for further study of the mechanism that calcium cyanamide synthetic drug to schistosome eggs. METHODS: The calcium cyanamide synthetic drug was added to the cattle feces containing schistosome eggs and mixed up, and then the cattle feces was stacked as original shape on the marshland. Blank controls were set at the same time. The cattle feces samples were collected and.the schistosome eggs were observed under a microscope on the 1st, 2nd, 3rd, 7th day after the experiment. RESULTS: By the effect of calcium cyanamide synthetic drug, the color of eggs was deepening gradually, the miracidia were atrophied, and the shells of eggs were thickened. The embryonic membrane of miracidia was no longer completed 3 days later, and the miracidia were deformed severely 7 days later. The atrophy of miracidia was not obvious in the blank controls. CONCLUSION: The schistosome miracidia and embryonic membrane can be damaged by the calcium cyanamide synthetic drug, and worse damaged with time extending.

Schistosomiasis in a migrating population in the lake region of China and its potential impact on control operation.

Coverage of migrating people in schistosomiasis control program is a growing concern in China. Schistosomiasis caused by Schistosoma japonicum is still one of the major infectious diseases of public health importance in China though tremendous efforts have been made to control the transmission over the past decades. Along with the rapid social-economic development, migrant population has been remarkably increasing across the country. The infected migrants may introduce a new souse of infection to endemic areas or the areas where the transmission had been controlled or interrupted but the intermediate host Oncomelania snail is still present. Preliminary studies for surveillance on schistosomiasis prevalence in migrants were reported, but there is little basic information provided. We carried out an investigation on the prevalence in immigrants, emigrants and permanent residents in three villages of Hunan province located in the main endemic area of lake region, and analyzed the potential impact of migration on control practice. In the study villages, the migrant population accounts for 53.6% of the total. Schistosoma infection was detected by modified Kato-Katz method and miracidium hatching test. Questionnaire survey was conducted comprising knowledge of disease and its transmission, water contact, personal protective measures, and whether examined and treated after water contact. The survey indicated that the migrants and permanent residents had similar life style, and the majority of them experienced water contact in agricultural work or routine life activities. However, the infection rate in immigrants was significantly higher than that in permanent residents. It was also found that the migrants had significantly less knowledge about the disease than the permanent residents, and took no personal protective measures. This is due to that the control program could not cover the migrants when they were absent at the time the program being implemented. The present study suggested that the surveillance and intervention for migrants, immigrants in particular, should be included and strengthened in schistosomiasis control program and a feasible scheme be developed.

[Space-time clustering analysis of acute schistosome infections in marshland and lake areas in five provinces].

OBJECTIVE: To analyze the time and space aggregation of acute schistosome infections in marshland and lake areas in five provinces (Jiangsu, Anhui, Jiangxi, Hubei and Hunan province) from 2005 to 2012, so as to provide the evidence for establishing control strategies and taking effective control measures. METHODS: The data of patients with acute schistosome infection in marshland and lake areas in five provinces from 2005 to 2012 were collected and analyzed with the concentration ratio and circular distribution methods for the epidemic season features and time aggregation of the infection, and with the spatial autocorrelation analysis for the space aggregation of the infected cases. RESULTS: According to the concentration ratio, the occurrence of acute schistosome infection had strong seasonality, and the concentration ratio was 0.758; according to the circular distribution method, the peak day of acute schistosome infections was 10th, August. The spatial analysis suggested that the infected cases highly gathered around Poyang Lake, Dongting Lake and Yangtze River Basin in 23 counties of the five provinces, and the result of spatial autocorrelation analysis showed that the spatial autocorrelation index I was 0.16 (P = 0.01). CONCLUSION: The occurrence of acute schistosome infections in lake regions of the 5 provinces shows strong seasonality and space aggregation, therefore we can bring the control mark forward, and take targeted prevention and control measures in high aggregation areas of acute schistosomiasis.

[Investigation on schistosomiasis japonica infection and preventive knowledge of immigration population in Jinshan District, Shanghai].

OBJECTIVE: To investigate the schistosomiasis japonica infection and preventive knowledge of immigration population in Jinshan District, Shanghai so as to provide the evidence for improving the control work. METHODS: The immigration population from schistosomiasis endemic provinces and local people were screened by serum IHA screening for schistosome infection, and the positives were further examined by Kato-Katz technique and the miracidium hatching method. The schistosomiasis preventive knowledge and behaviors were investigated by questionnaires. RESULTS: A total of 579 were investigated with 348 immigration people and 231 local people, and among them, the male accounted for 72.0% and female accounted for 28.0%. In the immigration population, the main age group was 20-29 (56.0%), and 56.6% of the immigration had an education level at senior middle school or higher. The most proportion of immigration was from Anhui Province (36.2%). There were 4 IHA positive persons (1.15%) in the immigration, and 1 was positive in the stool test, and the schistosome infection rate was 0.29%. There were no positives in the local people. The schistosomiasis preventive knowledge of the immigration was generally poor, and some people' s behaviors of see doctor and medication were incorrect. CONCLUSION: There are schistosome infected persons among the immigration population from schistosomiasis endemic provinces, and their schistosomiasis prevention knowledge was poor, thus there is a schistosomiasis transmission risk.

Surveillance-response systems: the key to elimination of tropical diseases.

Tropical diseases remain a major cause of morbidity and mortality in developing countries. Although combined health efforts brought about significant improvements over the past 20 years, communities in resource-constrained settings lack the means of strengthening their environment in directions that would provide less favourable conditions for pathogens. Still, the impact of infectious diseases is declining worldwide along with progress made regarding responses to basic health problems and improving health services delivery to the most vulnerable populations. The London Declaration on Neglected Tropical Diseases (NTDs), initiated by the World Health Organization's NTD roadmap, set out the path towards control and eventual elimination of several tropical diseases by 2020, providing an impetus for local and regional disease elimination programmes. Tropical diseases are often patchy and erratic, and there are differing priorities in resources-limited and endemic countries at various levels of their public health systems. In order to identify and prioritize strategic research on elimination of tropical diseases, the 'First Forum on Surveillance-Response System Leading to Tropical Diseases Elimination' was convened in Shanghai in June 2012. Current strategies and the NTD roadmap were reviewed, followed by discussions on how to identify and critically examine prevailing challenges and opportunities, including inter-sectoral collaboration and approaches for elimination of several infectious, tropical diseases. A priority research agenda within a 'One Health-One World' frame of global health was developed, including (i) the establishment of a platform for resource-sharing and effective surveillance-response systems for Asia Pacific and Africa with an initial focus on elimination of lymphatic filariasis, malaria and schistosomiasis; (ii) development of new strategies, tools and approaches, such as improved diagnostics and antimalarial therapies; (iii) rigorous validation of surveillance-response systems; and (iv) designing pilot studies to transfer Chinese experiences of successful surveillance-response systems to endemic countries with limited resources.

A multi-component integrated approach for the elimination of schistosomiasis in the People's Republic of China: design and baseline results of a 4-year cluster-randomised intervention trial.

Despite major successes in its control over the past 50years, schistosomiasis japonica continues to be a public health problem in the People's Republic of China (P.R. China). Historically, the major endemic foci occur in the lakes and marshlands along the Yangtze River, areas where transmission interruption has proven difficult. The current endemic situation may alter due to the closure of the Three Gorges Dam. Considerable environmental and ecological changes are anticipated that may result in new habitats for the oncomelanid intermediate snail host of Schistosoma japonicum (Sj), thereby increasing the risk of transmission. The current national control program for P.R. China involves a multi-component integrated strategy but, despite targeting multiple transmission pathways, certain challenges remain. As the Chinese government pushes towards elimination, there is a requirement for additional tools, such as vaccination, for long-term prevention. Whereas the zoonotic nature of schistosomiasis japonica adds to the complexity of control, it provides a unique opportunity to develop a transmission blocking vaccine targeting bovines to assist in the prevention of human infection and disease. Mathematical modelling has shown that control options targeting the various transmission pathways of schistosomiasis japonica and incorporating bovine vaccination, mass human chemotherapy and mollusciciding could lead to its elimination from P.R. China. Here we present the study design and baseline results of a four-year cluster randomised intervention trial we are undertaking around the schistosomiasis-endemic Dongting Lake in Hunan Province aimed at determining the impact on schistosome transmission of the multi-component integrated control strategy, including bovine vaccination using a heterologous "prime-boost" delivery platform based on the previously tested SjCTPI vaccine.

Comparison of the miracidium hatching test and modified Kato-Katz method for detecting Schistosoma japonicum in low prevalence areas of China.

The diagnosis of Schistosoma japonicum (Sj) infection in low prevalence areas of the People's Republic of China is challenging due to the sensitivity of the detection methods, leading to an underestimation of the disease burden. We compared the sensitivities of the miracidium hatching test (MHT) with the modified Kato-Katz method (KK) and the combination of the two methods (KK-MHT) to detect Sj infection in low prevalence areas of China. The stool samples of 3,853 residents from 8 villages with a light to moderate prevalence (0-23%) of Sj infection were examined by KK, MHT and KK-MHT. The findings were inconsistent. The KK-MHT conbination gave more positives than either the KK or MHT alone. Using the KK-MHT, we determined the missed rates with the KK (mR(K)) and MHT (mR(H)) to be 30.1% and 10.2%, respectively. At light prevalence sites (infection rate < 10%) the mR(K) was 60.6%, significantly higher than the mR(K) of 22.3% found at moderate prevalence sites (10-23%). However, the mR(H) at the light and moderate prevalence sites were 11.54% and 9.90%, respectively (p > 0.05). The combination KK-MHT had the best sensitivity in low Sj prevalence areas in China and the KK method alone was the least sensitive. Using KK alone as a screening method will result in an underestimation of Sj infection disease burden.

Reduction patterns of acute schistosomiasis in the People's Republic of China.

BACKGROUND: Despite significant, steady progress in schistosomiasis control in the People's Republic of China over the past 50 years, available data suggest that the disease has re-emerged with several outbreaks of acute infections in the early new century. In response, a new integrated strategy was introduced. METHODS: This retrospective study was conducted between Jan 2005 and Dec 2012, to explore the effectiveness of a new integrated control strategy that was implemented by the national control program since 2004. RESULTS: A total of 1,047 acute cases were recorded between 2005 and 2012, with an annual reduction in prevalence of 97.7%. The proportion of imported cases of schistosomiasis was higher in 2011 and 2012. Nine clusters of acute infections were detected by spatio-temporal analysis between June and November, indicating that the high risk areas located in the lake and marshland regions. CONCLUSION: This study shows that the new integrated strategy has played a key role in reducing the morbidity of schistosomiasis in the People's Republic of China.

[Schistosomiasis control effect of measures of replacing cattle with machine for cultivation and forbidding depasturage of livestock on marshlands in marshland and lake regions].

OBJECTIVE: To evaluate the schistosomiasis control effect of the measures of replacing cattle with machine for cultivation and forbidding depasturage of livestock on marshlands in marshland and lake regions. METHODS: The retrospective review and field survey were implemented in the Jiangling and Gongan counties of Hubei Province where were implemented with the measure of replacing cattle with machine for cultivation, and Yuanjiang and Huarong counties of Hunan Province where were implemented with the measure of forbidding the depasturage of livestock on marshlands. The schistosome infection status of human, cattle, and Oncomelania hupensis snails, and schistosome-infested field excreta were surveyed from 2007 to 2013. The effects of the interventions were compared before and after their implementations. RESULTS: The 6 villages of Hubei Province were implemented with the measure of replacing cattle with machine for cultivation, and 7 villages of Hunan Province were implemented with the measure of forbidding the depasturage of livestock on marshlands. From 2007 to 2013, the schistosome infection rates of residents declined from 3.95% to 0.70% (χ2 = 128.376, P < 0.05), with the descend range of 82.53%. The descend ranges of the measures of replacing cattle with machine for cultivation and forbidding the depasturage of livestock on marshlands were 83.081% and 81.62% respectively, and there was no significant difference between the two measures (χ2 = 0.132, P > 0.05). The infection rate of cattle decreased from 3.66% in 2007 to 0.65% in 2013, and the descend range was 82.24% (χ2 = 13.692, P < 0.05). The field excreta was surveyed in the snail breeding place in 2013. The investigated area was 157.435 hm2, and 625 samples of field feces of cattle were collected with the density of field excreta of 3.97/hm2, and the positive rate was 1.12% (7/625). The schistosome infection rate of snails and the density of infected snails decreased successively from 2007, and no infected snails were detected from 2011 to 2013. CONCLUSIONS: The schistosomiasis endemic situation are decreased significantly after the interventions of replacing cattle with machine for cultivation and forbidding the depasturage of livestock on marshlands. Therefore, schistosomiasis control effect of these measures is notable in the marshland and lake regions.

Impact and cost-effectiveness of a comprehensive Schistosomiasis japonica control program in the Poyang Lake region of China.

Schistosomiasis japonica remains a significant public-health problem in China. This study evaluated cost-effectiveness of a comprehensive schistosomiasis control program (2003-2006). The comprehensive control program was implemented in Zhangjia and Jianwu (cases); while standard interventions continued in Koutou and Xiajia (controls). Incurred costs were documented and the schistosomiasis comprehensive impact index (SCI) and cost-effectiveness ratio (Comprehensive Control Program Cost/SCI) were applied. In 2003, prevalence of Schistosoma japonicum infection was 11.3% (Zhangjia), 6.7% (Jianwu), 6.5% (Koutou), and 8.0% (Xiajia). In 2006, the comprehensive control program in Zhangjia and Jianwu reduced infection to 1.6% and 0.6%, respectively; while Koutou and Xiajia had a schistosomiasis prevalence of 3.2% and 13.0%, respectively. The year-by-year SCIs in Zhangjia were 0.28, 105.25, and 47.58, with an overall increase in cost-effectiveness ratio of 374.9%-544.8%. The SCIs in Jianwu were 16.21, 52.95, and 149.58, with increase in cost-effectiveness of 226.7%-1,149.4%. Investment in Koutou and Xiajia remained static (US$10,000 unit cost). The comprehensive control program implemented in the two case villages reduced median prevalence of schistosomiasis 8.5-fold. Further, the cost effectiveness ratio demonstrated that the comprehensive control program was 170% (Zhangjia) and 922.7% (Jianwu) more cost-effective. This work clearly shows the improvements in both cost and disease prevention effectiveness that a comprehensive control program-approach has on schistosomiasis infection prevalence.

[Establishment and application of rapid assessment system of environment with high transmission risk of schistosomiasis in marshland and lake regions. I. Establishment of an index system with Delphi method].

OBJECTIVE: To establish an index system for rapid assessment of environment with high transmission risk of schistosomiasis in marshland and lake regions. METHODS: The alternative indices were established preliminarily by the documentary method, and then the Delphi method was used two rounds to select the indices and establish the index system. The degree of familiar and authority of the experts as well as the weights of all indices were assessed. RESULTS: A total of 3 primary indices namely morbidity in domestic animals, morbidity in humans and Oncomelania snail status were established, among which the weight of morbidity in domestic animals (0.68) was the highest. Totally 16 secondary indices were established, among which the combinative weights of the positive rate of wild feces (0.09), the infection rate of livestock (0.09), the infection rate of humans (0.07), the number of cases with acute schistosomiasis (0.07), the area with infected snails (0.07), and the density of infected snails (0.07) were the highest. The coefficients of familiar degree and authority degree of the experts of the primary indices were 0.79-0.85 and 0.88-0.91, and those of the secondary indices were 0.68-0.86 and 0.77-0.91, respectively. CONCLUSIONS: The index system for rapid assessment of environment with high transmission risk of schistosomiasis in marshland and lake regions is established preliminarily. Using this system, we can assess the key endemic indices of humans, domestic animals and snails to understand the endemic situation in the investigated sites.

[Parasitological characteristics, epidemiological and clinical features, and current control approaches for three major kinds of human schistosomiasis].

Schistosomiasis is a tropical disease, which could do serious damage to the people's health, and it hinders the development of the social economy but may be neglected. After a positive control, some countries and regions have blocked the spread of schistosomiasis. However, in the past few years, with the development of social economy, due to the global movement of people, schistosomiasis not only poses a threat to control areas, but also may cause new endemic areas. This article reviews the parasitological characteristics, clinical manifestations, epidemiological situation, and control approaches of three major kinds of human schistosomiasis, schistosomiasis japonica, schistosomiasis haematobia, and schistosomiasis mansoni.

[The impact of water level changes on the Oncomelania snail habitats in Poyang Lake regions before and after the impoundment of Three Gorges reservoir].

OBJECTIVE: To explore the impact of the impoundment of Three Gorges reservoir on Oncomelania snail habitats of Poyang Lake. METHODS: Four counties with schistosomiasis endemic around the Poyang Lake, naming as Xingzi, Duchang, Jinxian and Xinjian, were selected as study areas. The average daily water level of four major hydrological stations near the above 4 counties from 1997 to 2008 were collected, as well as the elevation of 215 marshlands with snails in those 4 counties, the data of schistosomiasis endemic situation and snail survey of 4 counties in the year before the impoundment of Three Gorges reservoir (2002) and the 6th year after the impoundment of Three Gorges reservoir (2008). The fluctuations of water levels of Poyang Lake, flooding day of marshland with snails as well as the changes of the indicators in snail survey and prevention and control measures before and after the impoundment of Three Gorges reservoir were compared. RESULTS: Before the impoundment of Three Gorges reservoir, the fluctuations of average water level of the four hydrological stations around Poyang Lake was 6.91-12.93 m; which reduced to 5.72 - 10.75 m after the impoundment. The D-value of the fluctuations of average water level was (1.06 ± 0.47) m. The date of the annual maximum water level delayed by an average of 12 d; while the date of annual minimum water level arrived an average of 12 d earlier than the impoundment of Three Gorges reservoir. The average flooding days of marshland with snails were separately (100.04 ± 42.06) d before the impoundment and (64.13 ± 22.30) d after the impoundment. The difference was statistically significant (t = 3.70, P < 0.05). The density of snails in the 4 counties around Poyang Lake was 0.8437/0.1 m(2) after the impoundment; declining by 31.04% from the snail density (1.2234/0.1 m(2)) before the impoundment. The density of infectious snails was 0.0014/0.1 m(2) after the impoundment; dropping by 67.34% from it (0.0042/0.1 m(2)) before the impoundment; the infection rate of snails was separately 0.34% after the impoundment and 0.16% before the impoundment. The difference was statistically significant (χ(2) = 53.25, P < 0.05). The coverage rate of chemotherapy increased from 4.45% (35 558/798 200) in 2002 to 9.80% (79 457/810 400) in 2008; the difference was statistically significant (χ(2) = 17 336.63, P < 0.05). The coverage rate of snail killing increased from 1.35% (389.04/28 824.66) in 2002 to 7.49% (2260.90/30 166.22) in 2008; the difference was also statistically significant (χ(2) = 28 824.66, P < 0.05). CONCLUSION: The impact of the impoundment of Three Gorges reservoir shortened the flooding days of marshland with snails and helped the prevention and control of schistosomiasis in Poyang Lake regions as the environment went against the breeding of the snails.