Area Of Snail Habitats Research Articles

Progress of schistosomiasis control in People's Republic of China in 2023

To understand the progress of national schistosomiasis elimination program of China in 2023 and summarize the lessons and experiences, data on the endemic status of schistosomiasis and national schistosomiasis surveillance results in the People's Republic of China were collected and analyzed at a national level. By the end of 2023, Shanghai Municipality, Zhejiang Province, Fujian Province, Guangdong Province and Guangxi Zhuang Autonomous Region continued to consolidate the achievements of schistosomiasis elimination, and Sichuan and Jiangsu provinces maintained the criteria of transmission interruption, while Yunnan and Hubei provinces were identified to achieve the criteria of transmission interruption in 2020, and Anhui, Jiangxi and Hunan provinces achieved the criteria of transmission interruption in 2023. A total of 451 counties (cites, districts) were found to be endemic for schistosomiasis in China in 2023, including 26 250 endemic villages covering 73 034 500 residents at risk of infections. Among the 451 endemic counties (cities, districts), 78.49% (354/451) achieved the criteria of schistosomiasis elimination and 21.51% (97/451) achieved the criteria of transmission interruption, respectively. In 2023, a total of 4 216 643 individuals received immunological tests, with 47 794 sero-positives identified, and a total of 184 216 individuals received parasitological examinations, with 4 egg-positives detected. A total of 27 768 cases with advanced schistosomiasis were documented in China by the end of 2023. In 2023, 539 548 bovines were raised in schistosomiasis-endemic areas of China, and 125 440 bovines received immunological tests, with 124 sero-positives detected, while no egg-positives were identified among the 133 508 bovines receiving parasitological examinations. In 2023, snail survey was performed at an area of 641 339.53 hm2 and 184 819.77 hm2 snail habitats were identified, including 51.53 hm2 emerging snail habitats and 642.25 hm2 reemerging snail habitats. In 2023, there were 20 198 schistosomiasis patients receiving praziquantel chemotherapy, and 598 183 person-time individuals and 283 954 herdtime bovines were given expanded chemotherapy. In 2023, snail control with chemical treatment was performed in 116 347.95 hm2 snail habitats, and the actual area of chemical treatment was 65 690.89 hm2, while environmental improvements were performed in snail habitats covering an area of 1 334.62 hm2. The national schistosomiasis surveillance results showed that the mean prevalence of Schistosoma japonicum infections were both zero among humans and bovines in 2023, and no S. japonicum infection was detected in snails. These data demonstrated that transmission interruption of schistosomiasis had been achieved across all endemic provinces in China in 2023, and the endemic status of schistosomiasis tended to be stable, while advanced cases were predominant among all schistosomiasis cases. However, the areas of snail habitats remained high and cattle re-raising was very common in some regions. Intensified schistosomiasis surveillance and forecast and snail control in high-risk areas are needed.

Progress of schistosomiasis control in People's Republic of China in 2022

This report presented the endemic status of schistosomiasis and analyzed the data collected from the national schistosomiasis prevention and control system and national schistosomiasis surveillance program in the People's Republic of China in 2022. Among the 12 provinces (municipality and autonomous region) endemic for schistosomiasis, Shanghai Municipality, Zhejiang Province, Fujian Province, Guangdong Province and Guangxi Zhuang Autonomous Region continued to maintain the achievements of schistosomiasis elimination, and Sichuan and Jiangsu provinces maintained the criteria of transmission interruption, while Yunnan, Hubei, Anhui, Jiangxi and Hunan provinces maintained the criteria of transmission control by the end of 2022. A total of 452 counties (cites, districts) were found to be endemic for schistosomiasis in China in 2022, with 27 434 endemic villages covering 73 424 400 people at risk of infections. Among the 452 endemic counties (cities, districts), 75.89% (343/452), 23.45% (106/452) and 0.66% (3/452) achieved the criteria of elimination, transmission interruption and transmission control of schistosomiasis, respectively. In 2022, 4 317 356 individuals received serological tests for schistosomiasis, and 62 228 were sero-positive. A total of 208 646 individuals received stool examinations for schistosomiasis, with one positive and another two cases positive for urine microscopy, and these three 3 cases were imported schistosomiasis patients from Africa. There were 28 565 cases with advanced schistosomiasis documented in China by the end of 2022. Oncomelania hupensis snail survey was performed in 18 891 endemic villages in China in 2022 and O. hupensis snails were found in 6 917 villages (36.62% of all surveyed villages), with 8 villages identified with emerging snail habitats. Snail survey was performed at an area of 655 703.01 hm2 and 183 888.60 hm2 snail habitats were found, including 110.58 hm2 emerging snail habitats and 844.35 hm2 re-emerging snail habitats. There were 477 200 bovines raised in the schistosomiasis endemic areas of China in 2022, and 113 946 bovines received serological examinations for schistosomiasis, with 204 sero-positives detected. Among the 131 715 bovines received stool examinations, no positives were identified. In 2022, there were 19 726 schistosomiasis patients receiving praziquantel chemotherapy, and expanded chemotherapy was performed in 714 465 person-time for humans and 234 737 herd-time for bovines in China. In 2022, snail control with chemical treatment was performed at an area of 119 134.07 hm2, and the actual area of chemical treatment was 65 825.27 hm2, while environmental improvements were performed at an area of 1 163.96 hm2. Data from the national schistosomiasis surveillance program of China showed that the mean prevalence of Schistosoma japonicum infections was both zero in humans and bovines in 2022, and no S. japonicum infection was detected in O. hupensis snails. These data demonstrated that the endemic status of schistosomiasis continued to decline in China in 2022, with 3 confirmed schistosomiasis patients that had a foreign nationality and all imported from Africa, and the areas of snail habitats remained high. Further improvements in the construction of the schistosomaisis surveillance and forecast system, and reinforcement of O. hupensis survey and control are required to prevent the re-emerging schistosomiasis.

Trends in the prevalence of schistosomiasis in Anhui Province from 2004 to 2020 based on Joinpoint regression analysis

To investigate the changing trends in the prevalence of schistosomiasis in Anhui Province from 2004 to 2020, so as to provide the evidence for formulating the schistosomiasis elimination strategy in the province. The epidemiological data of schistosomiasis in Anhui Province from 2004 to 2020 were collected, and the trends in the endemic status of schistosomiasis were analyzed using a Joinpoint regression model. The trends in the prevalence of Schistosoma japonicum infections in humans, bovines and Oncomelania hupensis were measured in Anhui Province from 2004 to 2020 using average annual percent change (AAPC), and the correlations among the changing trends in the prevalence of S. japonicum infections in humans, bovines and O. hupensis snail status were evaluated using Pearson correlation analysis. The prevalence of S.japonicum human infections continued to decline in Anhui Province from 2004 to 2020, with an annual mean decline of 14.8% [AAPC = -14.8%, 95% confidential interval (CI): (-18.9%, -10.5%), P < 0.01]. The prevalence of S. japonicum infections continued to decline in bovines in Anhui Province from 2004 to 2015 [AAPC = -31.3%, 95%CI: (-35.1%, -27.2%), P < 0.01], and was 0 for 5 successive years from 2016 to 2020. During the period from 2004 to 2020, there was an annual mean decline of 0.7% in areas of snail habitats [AAPC = -0.7%, 95%CI: (-1.2%, 0.3%), P < 0.05] and an annual mean decline of 9.2% in the density of living snails [AAPC = -9.2%, 95%CI: (-18.3%, 1.0%), P = 0.08] in Anhui Province from 2004 to 2020, and an annual mean decline of 35.6% was found in the density of S. japonicum-infected snails [AAPC = -35.6%, 95%CI: (-49.2%, -18.3%), P < 0.01] from 2004 to 2012, with no infected snails detected in Anhui Province from 2013 to 2020. There were significant correlations in the prevalence of S. japonicum infections between humans and bovines (r = 0.959, P < 0.01), between the prevalence of S. japonicum human infections and the density of S. japonicum-infected snails (r = 0.823, P < 0.01) and between the prevalence of S. japonicum infections in bovines and the density of S. japonicum-infected snails (r = 0.902, P < 0.01). The prevalence of S. japonicum infections appeared a decline in humans, bovines and O. hupensis in Anhui Province from 2004 to 2020, and significant correlations were found among the changing trends in the prevalence of S. japonicum human infections, the prevalence of S. japonicum bovine infections and the density of S. japonicum-infected O. hupensis snails. Because of a minor decline in the area of snail habitats and widespread distribution of O. hupensis, however, there is still a risk of schistosomiasis transmission, and precision control for schistosomiasis remains to be reinforced in Anhui Province.

Progress of schistosomiasis control in People's Republic of China in 2021

This report presented the endemic status of schistosomiasis and analyzed the data collected from the national schistosomiasis prevention and control system and national schistosomiasis surveillance sites in the People's Republic of China at a national level in 2021. Among the 12 provinces (municipality and autonomous region) endemic for schistosomiasis in China, Shanghai Municipality, Zhejiang Province, Fujian Province, Guangdong Province and Guangxi Zhuang Autonomous Region continued to consolidate the achievements of schistosomiasis elimination, and Sichuan and Jiangsu provinces maintained the criteria of transmission interruption, while Yunnan, Hubei, Anhui, Jiangxi and Hunan provinces maintained the criteria of transmission control by the end of 2021. A total of 451 counties (cites, districts) were found to be endemic for schistosomiasis in China in 2021, with 27 571 endemic villages covering 73 250 600 people at risk of infections. Among the 451 endemic counties (cities, districts), 75.17% (339/451), 22.17% (100/451) and 2.66% (12/451) achieved the criteria of elimination, transmission interruption and transmission control of schistosomiasis, respectively. By the end of 2021, 29 037 cases with advanced schistosomiasis were documented in China. In 2021, 4 405 056 individuals received serological tests and 72 937 were sero-positive. A total of 220 629 individuals received stool examinations and 3 were positive. In 2021, snail survey was performed in 19 291 endemic villages in China and Oncomelania snails were found in 7 026 villages, accounting for 36.42% of all surveyed villages, with 12 villages identified with emerging snail habitats. Snail survey was performed at an area of 686 574.46 hm2 and 191 159.91 hm2 snail habitats were found, including 1 063.08 hm2 emerging snail habitats and 5 113.87 hm2 reemerging snail habitats. In 2021, 525 878 bovines were raised in the schistosomiasis endemic areas of China, and 115 437 received serological examinations, with 231 positives detected. Among the 128 719 bovines received stool examinations, no positives were identified. In 2021, there were 19 927 schistosomiasis patients receiving praziquantel chemotherapy, and 729 113 person-time individuals and 256 913 herd-time bovines were given expanded chemotherapy. In 2021, snail control with chemicals was performed in 117 372.74 hm2 snail habitats, and the actual area of chemical treatment was 65 640.50 hm2, while environmental improvements were performed in snail habitats covering an area of 1 244.25 hm2. Data from the national schistosomiasis surveillance sites of China showed that the mean prevalence of Schistosoma japonicum infections were both zero in humans and bovines in 2021, and no S. japonicum infection was detected in snails. The results demonstrate that the overall endemic status of schistosomiasis remained at a low level in China in 2021; however, the progress towards schistosomiasis elimination was slowed and the areas of snail habitats rebounded mildly. Strengthening researches on snail diffusion and control, and improving schistosomiasis surveillance and forecast are recommended to prevent reemerging schistosomiasis.

Spatio-temporal distribution characteristics of Oncomelania hupensis in Anhui Province from 2011 to 2020

To analyze the spatial-temporal distribution characteristics of Oncomelania hupensis snails in Anhui Province from 2011 to 2020, to provide insights into precision control of O. hupensis snails in Anhui Province. O. hupensis snail distribution data were collected in Anhui Province from 2011 to 2020 and descriptively analyzed, including actual area of snail habitats, area of emerging snail habitats and area of Schistosoma japonicum-infected snails. The actual area of snail habitats and area of emerging snail habitats were subjected to spatial autocorrelation analysis, hotspot analysis, standard deviation ellipse analysis and space-time scanning analysis, and the clusters of snail distribution and settings at high risk of snail spread were identified in Anhui Province from 2011 to 2020. The actual area of snail habitats gradually decreased in Anhui Province from 2011 to 2020. The actual area of snail habitats were 26 238.85 hm2 in Anhui Province in 2020, which were mainly distributed in marshland and lake regions. There was a large fluctuation in the area of emerging snail habitats in Anhui Province during the period from 2011 to 2020, with the largest area seen in 2016 (1 287.65 hm2), and 1.96 hm2 emerging infected snail habitats were detected in Guichi District, Chizhou City in 2020. Spatial autocorrelation and hotspot analyses showed spatial clusters in the distribution of actual areas of snail habitats in Anhui Province from 2011 to 2020 (Z = 3.00 to 3.43, all P values < 0.01), and the hotspots were mainly concentrated in the marshland and lake regions and distributed along the south side of the Yangtze River, while the cold spots were mainly concentrated in the mountainous regions of southern Anhui Province. There were no overall spatial clusters in the distribution of areas of emerging snail habitats (Z = -2.20 to 1.71, all P values > 0.05), and a scattered distribution was found in local regions. Standard deviation ellipse analysis showed relatively stable distributions of the actual areas of snail habitats in Anhui Province from 2011 to 2020, which was consistent with the flow direction of the Yangtze River, and the focus of the distribution of areas of emerging snail habitats shifted from the lower reaches to upper reaches of Anhui section of the Yangtze River. Space-time scanning analysis identified two high-value clusters in the distribution of actual areas of snail habitats in lower and middle reaches of Anhui section of the Yangtze River from 2011 to 2020, and two high-value clusters in the distribution of areas of emerging snail habitats were identified in mountainous and hilly regions. There were spatial clusters in the distribution of O. hupensis snails in Anhui Province from 2011 to 2020, which appeared a tendency of aggregation towards the south side and upper reaches of the Yangtze River; however, the spread of O. hupensis snails could not be neglected in mountainous and hilly regions. Monitoring of emerging snail habitats should be reinforced in mountainous and hilly regions and along the Yangtze River basin.

Effects of urban construction on Oncomelania snails control in Wuhan City

To evaluate the effectiveness of urban construction projects on Oncomelania snails control in Wuhan City, so as to provide insights into the development of an integrated control strategy for urban schistosomiasis. The data pertaining to the endemic situation of schistosomiasis, schistosomiasis control data, the construction of the Yangtze River Bridge, marshland management and park constructions were collected from Wuhan City from 1990 to 2020. The changes of areas of snail habitats and high-risk settings were compared before and after implementation of these urban construction projects to evaluate the effectiveness of urban construction projects on Oncomelania snails control. The number of schistosomiasis cases decreased by 97.35%, and the number of cattle with schistosomiasis decreased by 100% in Wuhan City from 1990 to 2020, with a 41.99% reduction in areas of snail habitats, including 94.97% and 34.40% reductions in snail habitats inside and outside the embankment decreased. During the period from 1990 through 2020, a total of 10 Yangtze River bridges were built in Wuhan City, and areas of snail habitats around the bridges reduced from 11 699.05 hm2 before the bridge building to 8 726.14 hm2 after the building (a 25.41% reduction), while the areas of high-risk settings reduced from 411.69 hm2 before the bridge building to 276.78 hm2 after the building (a 32.77% reduction). Following treatment of three marshlands in Hankou, Hanyang and Wuchang, the areas of snail habitats reduced from 225.80 hm2 before the management to 199.47 hm2 after the management (a 11.66% reduction), and the areas of high-risk settings reduced from 23.14 hm2 before the treatment to 17.73 hm2 after the building (a 23.38% reduction). Following the building of 5 parks in snail-infested settings, the areas of snail habitats reduced from 319.61 hm2 before the construction to 280.80 hm2 after the construction (a 12.14% reduction), and the areas of high-risk settings reduced from 35.00 hm2 before the construction to 27.73 hm2 after the construction (a 20.77% reduction). Simultaneous implementation of urban construction projects and schistosomiasis control measures is effective to shrink snail-infested setting and high-risk settings and control the endemic situation of schistosomiasis in endemic foci in Wuhan City.

Establishment of an indicator system for schistosomiasis transmission risk assessment after transmission interruption in Hubei Province based on the Delphi method

To establish an indicator system for assessment of schistosomiasis transmission risk after transmission interruption in Hubei Province, so as to provide insights into the precise control of schistosomiasis. The indicator system was preliminarily established based on data collection, literature review, expert interviews. Two rounds of expert consultation were performed. The indicator system was screened based on the importance, operability, sensitivity and comprehensive score of the indicators, and the weights of each indicator were calculated. The credibility of the Delphi method was evaluated by calculating the active coefficient of the experts, degree of expert authority and coordination levels of experts' opinions. An indicator system for assessment of schistosomiasis transmission risk was preliminarily established, including 3 primary indicators, 12 secondary indicators and 44 tertiary indicators. A Delphi consultation was performed among 17 experts participating in schistosomiasis control, management and research. Following two rounds of consultation, a risk assessment indicator system was finally constructed, including 3 primary indicators, 10 secondary indicators and 35 tertiary indicators. Among the primary indicators, the variable with the highest normalized weight was the current status of schistosomiasis (0.420 2), followed by social factors (0.397 3) and natural environments (0.182 5). Among the secondary indicators, those with high combined weights included risk monitoring (0.142 3), current snail status (0.140 1), and current prevalence of human and livestock infections (0.137 8). Among the tertiary indicators, those with high combined weights included the positive rate of wild feces (0.049 8), the prevalence of snail infections (0.047 4), and the area of snail habitats submerged by floods (0.046 8). During the two-round consultation, the active coefficients of the experts were 85.00% and 100.00%, the degree of expert authority was both 0.75 and greater, and the coordination levels of experts' opinions were 0.405 to 0.521 and 0.592 to 0.695 (all P values < 0.05). An indicator system for assessment of schistosomiasis transmission risk is successfully established after transmission interruption in Hubei Province based on the Delphi method, which provides insights into the identification of the schistosomiasis transmission risk and the targets for schistosomiasis control in Hubei Province.

Survey of Oncomelania hupensis in national schistosomiasis surveillance sites of Guangxi Zhuang Autonomous Region from 2015 to 2019

To investigate the distribution characteristics of Oncomelania hupensis in Guangxi Zhuang Autonomous Region, so as to provide insights into the assessment of the risk of schistosomiasis transmission and the scientific formulation of the schistosomiasis surveillance strategy. From 2015 to 2019, a total of 19 national schistosomiasis surveillance sites were assigned in Guangxi Zhuang Autonomous Region, including 4 fixed sites and 15 mobile sites. Snail survey was performed by means of systematic sampling in combination with environmental sampling, and the infection of Schistosoma japonicum was detected by the crushing method combined with loop-mediated isothermal amplification (LAMP) assay. From 2015 to 2019, snail habitats were detected at areas of 17 040 to 39 527 m2, including 6 214 m2 emerging snail habitats and 16 563 m2 re-emerging snail habitats. The overall mean density of living snails was 0.019 2 snails/0.1 m2 and the occurrence of frames with snails was 1.11% in the national schistosomiasis surveillance sites; however, no S. japonicum infection was identified in snails. The area of snail habitats increased by 121.46% in the national surveillance sites in 2019 as compared to that in 2015; however, 50.34% (Z = -0.422, P > 0.05) and 42.85% (χ2 = 130.41, P < 0.01) reductions were seen in the overall means density of living snails and the occurrence of frames with snails. All snail habitats were distributed in the 4 fixed surveillance sites, and were mainly found in ditches, paddy fields and dry lands, with weeds as the primary vegetation type. There are still risk factors leading to re-emergent transmission of schistosomiasis in Guangxi Zhuang Autonomous Region, such as local snail spread, and the monitoring of schistosomiasis remains to be reinforced to further consolidate the achievements of schistosomiasis elimination in the region.

Endemic situation of schistosomiasis in national surveillance sites of Hubei Province from 2015 to 2019

To analyze the changing tendency in the endemic situation of schistosomiasis in the national surveillance sites of Hubei Province, so as to provide the scientific evidence for facilitating the progress towards the elimination of schistosomiasis in the province. According to the National Schistosomiasis Surveillance Scheme (2014 version), a total of 65 national schistosomiasis surveillance sites were assigned in Hubei Province, and the Schistosoma japonicum infections in humans, domestic animals, snails and wild feces were monitored in these national surveillance sites from 2015 to 2019. All data pertaining to the surveillance results were descriptively analyzed. There were 151 159 person-time local residents and 70 928 person-time mobile populations screened for S. japonicum infections in the 65 national surveillance sites of Hubei Province from 2015 to 2019, and the seroprevalance of S. japonicum infections reduced from 3.45% (1 077/31 197) in 2015 to 1.57% (431/27 371) in 2019 among local residents and from 1.06% (98/9 249) in 2015 to 0.81% (116/14 318) in 2019 among mobile populations. During the period from 2015 through 2019, there were 22 egg-positive local residents and 2 egg-positive mobile populations identified in 2015, with 0.07% and 0.02% prevalence rates of S. japonicum infections, respectively. During the 5-year period, a total of 7 025 herd-time domestic animals examined for S. japonicum infections, with no infections detected, and a total of 2 035 wild feces were tested, with no egg-positives identified in the 65 national surveillance sites of Hubei Province. Snail survey was conducted covering 28 767.35 hm2 during the 5-year period, and the area of snail habitats ranged from 1 609.82 to 2 119.81 hm2. The mean density of living snails and occurrence of frames with snails reduced from 0.360 5 snails/0.1 m2 and 11.26% in 2015 to 0.175 9 snails/0.1 m2 and 8.43% in 2019, respectively, and no S. japonicum infection was found in snails during the 5-year period. In addition, no snails were found in the potential schistosomiasis transmission foci in the two national surveillance sites in the Three Gorges Dam. The overall endemic situation of schistosomiasis appears a tendency towards a decline in Hubei Province during the period from 2015 through 2019; however, the schistosomiasis transmission risk remains. Improving the surveillance system of schistosomiasis and increasing the sensitivity and performance of the surveillance system are required to provide insights into the implementation of precision control strategy and interventions in Hubei Province.

Assessment of schistosomiasis transmission risk along the Yangtze River basin after the flood disaster in 2020

To evaluate the impact of the flood disaster on schistosomiasis transmission along the Yangtze River basin in 2020, so as to provide insights into schistosomiasis prevention and control in flood-affected areas. The data pertaining to the endemic situation of schistosomiasis were collected from 5 provinces of Hunan, Hubei, Jiangxi, Anhui and Jiangsu from 2013 to 2019, including Schistosoma japonicum infections in humans and livestock and snail distribution, and the warning water levels and actual water status were collected in water regions locating in these 5 provinces. The cumulative numbers of S. japonicum egg-positive individuals and bovines during the period from 2013 to 2019, the area of snail habitats in 2019 and the water level on July 12, 2020 were estimated at a county level and employed as parameters for classification of schistosomiasis transmission risk. Then, the cumulative value of each risk index was calculated to assess the risk of schistosomiasis transmission risk. After the flood disaster along the Yangtze River basin in 2020, there were 10, 5 and 9 counties (districts) at high risk of schistosomiasis transmission in 5 provinces of Hunan, Hubei, Jiangxi, Anhui and Jiangsu based on number of egg-positive individuals, number of egg-positive bovines and snail distribution, respectively. Based on comprehensive risk indices, there were 10 (8 in Dongting Lake regions of Hunan Province and 2 in Poyang Lake regions of Jiangxi Province) and 15 counties (districts) (4 in Hubei Province, 7 in Hunan Province and 4 in Jiangxi Province) identified at grades 5 and 4 risk of schistosomiasis transmission. Dongting Lake regions and Poyang Lake regions are the most severely flood-affected schistosomiasis-endemic foci of China in 2020, and the flood disaster may facilitate the transmission of schistosomiasis in affected areas. Therefore, schistosomiasis control requires to be intensified after the flood disaster to prevent the rebound of the disease.

Effect of integrated schistosomiasis control measures in Hunan Province from 2004 to 2019

To examine the effect of the integrated schistosomiasis control measures in Hunan Province from 2004 to 2019, so as to provide insights into the development of the schistosomiasis elimination strategy. The integrated schistosomiasis control measures implemented by the health, agriculture, water resources, forestry, land and resources sectors were retrospectively collected in Hunan Province from 2004 to 2019, and the completion of each measure, cost of control measures, Schistosoma japonicum infections in humans and bovines, and snail status were analyzed each year. An index system for assessing the integrated schistosomiasis control effect was constructed using the Delphi method to calculate the integrated schistosomiasis control effect index. In addition, a cost-effect analysis was performed in terms of the decline in the prevalence of S. japonicum infections in humans and bovines, areas with snails in inner embankments, and areas with infected snails. A total of 7 110 926 500 Yuan were invested into the integrated schistosomiasis control program of Hunan Province from 2004 to 2019. During the 16-year period, a total of 277 437.12 hm2 snail habitats received molluscicidal treatments, 6 927 230 person-times given expanded chemotherapy, 2 116 247 bovine-times given expanded chemotherapy, 954 850 harmless toilets built, 290 359 bovines fenced, 136 666 bovines eliminated, 141 905 machines used to replace bovines, 39 048.63 hm2 water lands improved as dry lands, 724.12 km irrigation regions improved, 3 994 300 populations covered with safe water, 191 102.89 hm2 forests planted and 38 535.27 hm2 lands leveled. The prevalence of S. japonicum infections was 4.29% in humans and 4.48% in bovines in Hunan Province in 2004, with 2 449.37 hm2 snail habitats in inner embankments and 3 423.74 hm2 infected snail areas. In 2019, the prevalence of S. japonicum infections reduced to 0 in both humans and bovines, and areas of snail habitats reduced to 540.92 hm2 (77.92% reductions), while the areas with infected snails reduced to 0. The overall integrated schistosomiasis control effect index appeared a tendency towards a rise over years since 2004, and the integrated schistosomiasis control effect index was 97.35 in 2019; the annual mean costs for a 1% reduction in the prevalence of S. japonicum infections in 100 populations and 100 bovines were 70.11 Yuan and 4 204.78 Yuan, and the annual mean costs for a 1% reduction in the snail areas in inner embankments and infected snail areas were 2 010.20 Yuan and 1 298.09 Yuan, respectively. The integrated control measures achieve remarkable effectiveness for schistosomiasis control in Hunan Province, with a remarkable decline in the prevalence of S. japonicum infections in humans and bovines and great shrinking of snail areas in inner embankments and infected snail areas. Adequate fund investment is required to improve the integrated schistosomiasis control measures and consolidate the control achievements.

Endemic situation of schistosomiasis in national surveillance sites of Anhui Province from 2015 to 2018

To analyze the endemic situation of schistosomiasis in national surveillance sites of Anhui Province from 2015 to 2018, so as to provide scientific evidence for schistosomiasis control and prevention in Anhui Province. According to the National Schistosomiasis Surveillance Programme (2014 version), a total of 51 national schistosomiasis surveillance sites were assigned in Anhui Province in 2015, and Schistosoma japonicum infections in humans and livestock and snail distribution were monitored from 2015 to 2018. A total of 89 638 local residents and 42 609 mobile populations received serological screening of schistosomiasis in 51 national surveillance sites of Anhui Province from 2015 to 2018, and the sero-prevalence of S. japonicum infections was 1.41% to 3.69% in local residents and 0.84% to 2.13% in mobile populations, respectively. There were 5 egg-positive local residents and 1 egg-positive mobile populations detected in 2015, with occupations of farmers and fishermen. There were 6 405 livestock detected for S. japonicum infections, and no egg-positives were identified. Among an area of 12 661 hm2 surveyed in the national schistosomiasis surveillance sites of Anhui Province from 2015 to 2018, the areas of snail habitats were 2 461.27 to 2 628.96 hm2, andthemeandensityoflivingsnailswas 0.3757 to 0.4330 snails/0.1 m2, with no S. japonicum infections identified in snails. The endemic situation of schistosomiasis is at a low level in Anhui Province; however, the risk of schistosomiasis transmission remains in local regions of the province. The construction of the surveillance-responsesystemshouldbereinforcedtoconsolidatetheachievementsofschistosomiasis control in Anhui Province.

Endemic situation of schistosomiasis in surveillance sites of Tianmen City from 2015 to 2018

To monitor the change patterns of the endemic situation of schistosomiasis in Tianmen City from 2015 to 2018, so as to provide the evidence for formulating the schistosomiasis control strategy in the city. A total of 8 schistosomiasis surveillance sites were assigned in Tianmen City from 2015 to 2018, and the endemic situation of schistosomiasis and the related epidemiological factors were monitored. During the period from 2015 to 2018, a total of 15 983 local person-times and 3 629 mobile populations were detected for schistosomiasis using an indirect hemagglutination test (IHA) in Tianmen City, and the sero-prevalence was 0.88% to 1.44% and 0.96% to 2.39%, respectively; however, no egg-positives were identified. A total of 1 245 herd-times were detected, and no egg-positives were found in bovines. In addition, the areas of snail habitats were 116.69 to 117.23 hm2 and the mean densities of living snails were 0.07 to 0.17 snails/0.1 m2 during the study period; however, no infections were identified in snails. The endemic situation of schistosomiasis appears low in Tianmen City; however, the factors related to schistosomiasis transmission remain in the city. The integrated strategy with emphasis on the control of infectious sources should be still intensified to consolidate the schistosomiasis control achievements.

Endemic situation of schistosomiasis in Wuhu City from 2009 to 2018

To analyze the endemic situation of schistosomiasis in Wuhu City from 2009 to 2018, so as to provide evidence for adjusting and developing the control strategy. The data regarding the endemic situation were retrospectively collected and analyzed in Wuhu City from 2009 to 2018. The prevalence of human Schistosoma japonicum infections reduced from 0.450% in 2009 to 0.035% in 2018 in Wuhu City, and a reduction rate of 92.22% (χ2 = 1 6128.307, P < 0.01), and the prevalence of S. japonicum infections decreased from 0.483% in 2009 to 0 in 2018 (χ2 = 27.570, P < 0.01) in livestock. The area of snail habitats increased from 1 501.07 hm2 in 2009 to 4 408.62 hm2 in 2018, with an increase of 193.70%. No infected snails were found in Wuhu City since 2012, and no egg positives were detected in humans and livestock since 2016. Currently, the endemic situation of schistosomiasis is at a low level in Wuhu City; however, there are still factors affecting schistosomiasis transmission. In the future, the integrated strategy with emphasis on the control of infectious source and the surveillance-response system should be intensified to consolidate the achievements of schistosomiasis control.

Administrative village-based spatial distribution specificity of Oncomelania hupensis and its relationship with water systems in Hubei Province

To investigate the spatial distribution of Oncomelania hupensis snail habitats at the administrative village scale in schistosomiasis-endemic areas of Hubei Province, so as to provide scientific bases for precise control of O. hupensis snails in the province. Data regarding snail distribution at the village level in Hubei Province in 2017 were collected to create a spatial analysis database of snail distribution in Hubei Province. The spatial aggregations of O. hupensis distribution were analyzed using Moran's I index and Local Moran's I index. In addition, the distances from schistosomiasis-endemic villages to the Yangtze River were captured using the software ArcGIS 13.0, and their correlations with area of snail habitats were examined with the Spearman correlation method. O. hupensis snails were mainly distributed in 5 450 endemic villages from 63 counties of 13 cities in Hubei Province in 2017. The global spatial autocorrelation analysis showed spatial aggregations in the areas of historically accumulated snail habitats, current areas of snail habitats, areas of snail habitats outside the embankment and snail habitats inside the embankment (all Z Scores > 0, all P values < 0.05), and no spatial aggregation was seen in the areas of snail habitats in hilly areas (Z Score > 0, P > 0.05). There were four types of spatial distribution of historically accumulated areas of snail habitats, areas of current snail habitats, areas of snail habitats outside the embankment and snail habitats inside the embankment, including the high-high type (H-H type), high-low type (H-L type), low-high type (L-H type) and random distribution type, and a high percentage of the H-H type was found. There were 340, 125 and 110 endemic villages with the H-H type of areas of historically accumulated snail habitats, current areas of snail habitats and areas of snail habitats outside the embankment, and these villages were mainly concentrated in Wuhan and Jingzhou cities, with almost consistent spatial aggregation locations. There were 319 endemic villages with the H-H type of distribution of snail habitats inside the embankment, which were mainly distributed in Jingzhou, Xiaogan and Huangshi cities. In addition, the areas of historically accumulated snail habitats, current areas of snail habitats and areas of snail habitats outside the embankment negatively correlated with the distance from the endemic villages to the Yangtze River (r = -0.094, P < 0.01; r = -0.225, P < 0.01; r = -0.177, P < 0.01). The clustering areas of snail habitats along the Yangtze River Basin, notably the villages near the Yangtze River are key regions for snail monitoring and control in Hubei Province.

Application and effect of integrated control model of schistosomiasis interruption in mountainous and hilly endemic regions

To explore the integrated schistosomiasis control model in mountainous and hilly endemic regions, so as to provide insights into the development of the schistosomiasis elimination strategy. Five hilly and mountainous areas endemic for schistosomiasis were selected as the integrated control demonstration areas in Sichuan Province from 2011 to 2015. According to the epidemic characteristics, economic levels and overall development planning of the demonstration areas, the goals, strategies and measures were developed, and the effectiveness of schistosomiasis control was evaluated following implementation of the integrated control. The support system of the integrated schistosomiasis control model was built in the integrated control demonstration areas in Sichuan Province from 2011 to 2015, and five ecological, industrialized and sustainable development models of integrated schistosomiasis control were developed, including integration of balancing rural and urban development, systematic ecological improvement, intensified ecological agriculture, scientific management and health education of schistosomiasis control and ecological ethnic circular economy. Since the implementation of the integrated schistosomiasis control model, the snail habitats were completely changed. Until 2015, 92.0% of all historical areas with snails were managed, the coverage of safe drinking water was 100.0%, and more than 95.0% of the livestock were fenced. The coverage of sanitary toilets increased by 93.0%, 96.8%, 78.8%, 87.1% and 82.0% from 2011 to 2015, respectively, and the farmers'mean yearly income increased by 32.7% in the demonstration areas. From 2011 to 2015, the seroprevalence of human Schistosoma japonicum infections reduced from 3.1% in 2011 to 1.6% in 2015 in the demonstration areas, and no egg-positives were identified. In addition, the number of fenced bovines reduced year by year, and no egg-positives were detected. The areas of snail habitats were 398.7, 108.2 hm2 and 52.9 hm2 in the demonstration areas from 2011 to 2013, with no infected snails found, and no snails were detected since 2014. The awareness of schistosomiasis control knowledge and percentage of correct behavior formation increased year by year among residents in the demonstration areas from 2011 to 2015. The five integrated schistosomiasis control models meet the needs of the current schistosomiasis control activities in mountainous and hilly endemic areas of Sichuan Province, and achieve the goals of controlling the sources of S. japonicum infections, economic development, social progress and improving the ecological environment, which provides new insights into schistosomiasis elimination in the country.

Risk assessment of schistosomiasis transmission in Chuxiong City of Yunnan Province

To evaluate the potential risk of schistosomiasis transmission so as to provide the evidence for formulating the control strategy. Two villages were selected as the investigated sites in Chuxiong City and the risk of schistosomiasis transmission was evaluated by reviewing the data of schistosomiasis epidemic situation and prevention and control work, and carrying out the field survey for Oncomelania hupensis snail status, wild faeces, and schistosome infection of the population from 2015 to 2017. There was 1.49 hm2 area of snail habitats, with an average density of 0.54 snails/0.1 m2. The occurrence rate of frames with snails was 5.41%. No schistosome-infected snails were found. The positive rate of schistosomiasis serological tests of the residents was 3.36%, but the stool examination positive cases were not found. A total of 58 wild faeces samples were collected but no schistosome infested cases were found. The risk levels of schistosomiasis transmission in both villages were Grade III. Although Chuxiong City has been in a low risk state of schistosomiasis transmission, the density of snails is still high, and there is a risk of infection source importation. In the future, the infection source control and snail control should be strengthened.

Influence of the Three Gorges Dam on schistosomiasis control in the middle and lower reaches of the Yangtze River

Abstract This paper summarizes the factors affecting schistosomiasis transmission in the middle and lower reaches of the Yangtze River before and after the completion of the Three Gorges Dam and analyzes schistosomiasis prevalence trends to provide a basis for the application of the Three Gorges project methodologies in other areas. The Three Gorges Dam has demonstrated a positive effect on schistosomiasis control. Hubei, Hunan, Jiangxi, Anhui, and Jiangsu in the middle and lower reaches of the Yangtze River are currently regions with a high prevalence of schistosomiasis. These five provinces contained 97.62% of known snail areas and 93.66% of calculated schistosomiasis cases with 90.07% of counties (cities, districts) not yet meeting the criteria for schistosomiasis transmission interruption by the end of 2016. After the Three Gorges Dam was built, the prevalence of schistosomiasis in the middle and lower reaches of the Yangtze River decreased. By the end of 2016, the estimated number of cases decreased by 92.75% and the snail habitat areas decreased by 6.56% compared to 2004. No acute schistosomiasis cases have occurred for two consecutive years since 2015.

Investigation of Oncomelania hupensis snails in Anhui Province in 2016

To investigate the status of Oncomelania hupensis snails in Anhui Province in 2016, so as to provide the evidence for formulating the 13th Five-Year Plans for Schistosomiasis Control. In 2016, a snail survey was conducted in Anhui Province according to the National Programme of the Oncomelania Snail Survey, covering all snail habitats or historical snail habitats and suspected environments of snail breeding, and the results of the survey were analyzed. In 2016, 22 848 environments were surveyed, and no schistosome-infected snails were found. There were 17 927 historical snail habitats in whole province, among which, the environments without changes, changed partly and changed completely accounted for 71.2%, 19.3% and 9.5%, respectively. The area of historical snail habitats was 1.410 billion m2. There were 4 830 environments with snail habitats covering an area of 0.265 billion m2 in 38 counties of 7 cities, including newly emerging area of 1 287.65 hm2 and reemerging area of 1 375.32 hm2. The density of living snails was 0.392 0 snails/0.1 m2, and the rate of frame with living snails was 12.93%. The type of marshland and lake regions, and the type of hilly and mountainous regions accounted for 22.4% and 77.6% of number of snail habitats, and accounted for 86.7% and 13.3% of areas of snail habitats, respectively. Among the different types of vegetation in snail habitats, grass was superior owe to accounting for 82.2% of the number of snail habitats, 57.3% of the area with snail habitats, and the highest density of living snails (0.413 9 snails/0.1 m2). Among the different types of environments in snail habitats, the ditch was superior owe to accounting for 56.8% of the number of snail habitats, the highest density of living snails (0.570 3 snails/0.1m2) and the highest rate of frame with living snails (18.57%), and the beach was superior owe to accounting for 87.8% of the area with snail habitats. In Anhui Province, the first year of snails and schistosome-infected snails being found was 1950 and 1952, respectively, and the latest year of schistosome-infected snails being found was 2012. The map showed that the most environments with snail habitats were distributed along the Yangtze River in Anhui Province. For the first time, the investigation has built the database and map of snail spatial distribution, which truly reflect the historic and current status of snail distribution in Anhui Province and can provide the evidence for formulating the 13th Five-Year Plans for Schistosomiasis Control and improving the schistosomiasis prevention and control work in the future.

Long-term effectiveness of the integrated schistosomiasis control strategy with emphasis on infectious source control in China: a 10-year evaluation from 2005 to 2014.

Schistosomiasis is a neglected tropical parasitic disease of great public health significance worldwide. Currently, mass drug administration with praziquantel remains the major strategy for global schistosomiasis control programs. Since 2005, an integrated strategy with emphasis on infectious source control was implemented for the control of schistosomiasis japonica, a major public health concern in China, and pilot studies have demonstrated that such a strategy is effective to reduce the prevalence of Schistosoma japonicum infection in both humans and bovines. However, there is little knowledge on the long-term effectiveness of this integrated strategy for controlling schistosomiasis japonica. The aim of this study was to evaluate the long-term effectiveness of the integrated strategy for schistosomiasis control following the 10-year implementation, based on the data from the national schistosomiasis control program released by the Ministry of Health, People's Republic of China. In 2014, there were 5 counties in which the transmission of schistosomiasis japonica had not been interrupted, which reduced by 95.2% as compared to that in 2005 (105 counties). The number of schistosomiasis patients and acute cases reduced by 85.5 and 99.7% in 2014 (115,614 cases and 2 cases) as compared to that in 2005 (798,762 cases and 564 cases), and the number of bovines and S. japonicum-infected bovines reduced by 47.9 and 98% in 2014 (919,579 bovines and 666 infected bovines) as compared to that in 2005 (1,764,472 bovines and 33,736 infected bovines), respectively. During the 10-year implementation of the integrated strategy, however, there was a minor fluctuation in the area of Oncomelania hupensis snail habitats, and there was only a 5.6% reduction in the area of snail habitats in 2014 relative to in 2005. The results of the current study demonstrate that the 10-year implementation of the integrated strategy with emphasis on infectious source has greatly reduced schistosomiasis-related morbidity in humans and bovines. It is concluded that the new integrated strategy has remarkable long-term effectiveness on the transmission of schistosomiasis japonica in China, which facilitates the shift of the national schistosomiasis control program from transmission control to transmission interruption and elimination. However, such a strategy seems to have little effect on the shrinking of areas of snail habitats.