Transmission Control Of Schistosomiasis Research Articles

Progress of interruption of schistosomiasis transmission and prospects in Yunnan Province

Schistosomiasis was once hyper-endemic in Yunnan Province. Following concerted efforts for over 70 years, remarkable achievements have been made for schistosomiasis control in the province. In 2004, the Mid- and Long-term Plan for Schistosomiasis Prevention and Control in Yunnan Province was initiated in Yunnan Province, and the target for transmission control of schistosomiasis was achieved in the province in 2009. Following the subsequent implementation of the Outline for Key Projects in Integrated Schistosomiasis Control Program (2009-2015) and the 13th Five - year Plan for Schistosomiasis Control in Yunnan Province, no acute schistosomiasis had been identified in Yunnan Province for successive 12 years, and no local Schistosoma japonicum infections had been detected in humans, animals or Oncomelania hupensis snails for successive 6 years in the province by the end of 2020. The transmission of schistosomiasis was interrupted in Yunnan Province in 2020. This review summarizes the history of schistosomiasis, changes in schistosomiasis prevalence and progress of schistosomiasis control in Yunnan Province, and proposes the future priorities for schistosomiasis control in the province.

Distribution characteristics of emerging and reemerging Oncomelania hupensis in China from 2015 to 2021

To analyze the distribution characteristics of emerging and reemerging Oncomelania hupensis snails after the criteria for transmission control of schistosomiasis were achieved in China, so as to provide insights into assessment of schistosomiasis transmission risk and formulation of snail control strategies during the elimination phase. O. hupensis survey data in China from 2015 to 2021 were collected from the National Schistosomiasis Pevention and Control Information Management System, and the distribution characteristics of emerging and reemerging O. hupensis snails were descriptively analyzed. Emerging and reemerging O. hupensis snails were identified in China each year from 2015 to 2021, with relatively larger areas with emerging and reemerging O. hupensis snail habitats in 2016 and 2021, and relatively higher numbers of counties (districts) where emerging and reemerging O. hupensis snails were detected in 2016 and 2021. A total of 4 586.30 hm2 of emerging O. hupensis snail habitats were found in 10 schistosomiasis-endemic provinces of China (except Fujian and Yunnan Provinces) from 2015 to 2021, with 96.80% in Anhui, Hunan and Hubei provinces, where marshland and lake endemic foci were predominant. A total of 21 023.90 hm2 of reemerging O. hupensis snail habitats were found in 12 schistosomiasis-endemic provinces of China from 2015 to 2021, with 97.67% in six provinces of Hubei, Sichuan, Jiangxi, Jiangsu, Yunnan and Anhui, where marshland and lake and hilly endemic regions were predominant. Emerging snail habitats were found in 15.08% of all schistosomiasisendemic counties (districts) in China from 2015 to 2021, and 78.75% of all emerging snail habitats were identified in 11 schistosomiasis-endemic counties (districts), with the largest area of emerging snail habitats found in Lixian County, Hunan Province (645.00 hm2). Reemerging snail habitats were found in 47.67% of all schistosomiasis-endemic counties (districts) in China from 2015 to 2021, and 43.29% of all reemerging snail habitats were identified in 11 schistosomiasis-endemic counties (districts), with the largest area of reemerging snail habitats found in Weishan Li and Hui Autonomous County of Hunan Province (1 579.70 hm2). Emerging and reemerging O. hupensis snails were identified in China each year from 2015 to 2021, with much larger areas of reemerging snail habitats than emerging snail habitats, and larger numbers of schistosomiasis-endemic provinces and counties (districts) with reemerging snails were found that those of provinces and counties (districts) with emerging snails. Specific snail control interventions are required tailored to the causes of emerging and reemerging snail habitats. Both emergence and reemergence of O. hupensis snails should be paid attention to in marshland and lake endemic areas, and Guangxi Zhuang Autonomous Region, Shanghai Municipality and Zhejiang Province where schistosomiasis had been eliminated, and reemergence of O. hupensis snails should be given a high priority in hilly areas. In addition, monitoring of O. hupensis snails should be reinforced in snail-free areas after flooding.

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.

The Current Distribution of Oncomelania hupensis Snails in the People’s Republic of China Based on a Nationwide Survey

Schistosomiasis is a helminth infection caused by the genus Schistosoma, which is still a threat in tropical and sub-tropical areas. In the China, schistosomiasis caused by Schistosoma japonicum is mainly endemic to the Yangtze River valley. The amphibious snail Oncomelania hupensis (O. hupensis) is the unique intermediate host of S. japonicum; hence, snail control is a crucial approach in the process of schistosomiasis transmission control and elimination. In 2016, a nationwide snail survey was conducted involving all snail habitats recorded since 1950 in all endemic counties of 12 provinces. A total of 53,254 existing snail habitats (ESHs) were identified, presenting three clusters in Sichuan Basin, Dongting Lake, and Poyang Lake. The overall habitat area was 5.24 billion m2, of which 3.58 billion m2 were inhabited by O. hupensis. The area inhabited by snails (AIS) in Dongting and Poyang Lakes accounted for 76.53% of the population in the country. Three typical landscape types (marshland and lakes, mountains and hills, and plain water networks) existed in endemic areas, and marshland and lakes had a predominant share (3.38 billion m2) of the AIS. Among the 12 endemic provinces, Hunan had a share of nearly 50% of AIS, whereas Guangdong had no ESH. Ditches, dryland, paddy fields, marshland, and ponds are common habitat types of the ESH. Although the AIS of the marshland type accounted for 87.22% of the population in the whole country, ditches were the most common type (35,025 or 65.77%) of habitat. Six categories of vegetation for ESHs were identified. A total of 39,139 habitats were covered with weeds, accounting for 55.26% of the coverage of the area. Multiple vegetation types of snail habitats appeared in the 11 provinces, but one or two of these were mainly dominant. Systematic sampling showed that the presence of living snails was 17.88% among the 13.5 million sampling frames. The occurrence varied significantly by landscape, environment, and vegetation type. The median density of living snails in habitats was 0.50 per frame (0.33 m × 0.33 m), and the highest density was 40.01 per frame. Furthermore, two main clusters with high snail densities and spatial correlations indicated by hotspot analysis were identified: one in Hunan and Hubei, the other in Sichuan. This national survey is the first full-scale census on the distribution of O. hupensis, which is significant, as transmission interruption and elimination are truly becoming the immediate goal of schistosomiasis control in China. The study discerns the detailed geographic distribution of O. hupensis with the hotspots of snail density in China. It is beneficial to understand the status of the snail population in order to finally formulate further national control planning.

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.

Elimination of Schistosomiasis Japonica in China: From the One Health Perspective.

Schistosomiasis japonica is caused by infection of Schistosoma japonicum (S. japonicum), which infected 12 million residents in the 1950s in China and was a heavy burden to public health and socioeconomic development (1). After more than seven decades of effort to control schistosomiasis, the prevalence of schistosomiasis has been reduced dramatically in China. Among the 450 endemic counties (including city and district-level jurisdictions), 74.89% (337/450), 21.87% (98/450), and 3.33% (15/450) have achieved the criteria of elimination, transmission interruption, and transmission control of schistosomiasis, respectively. As the overall endemic status of schistosomiasis remains at a low level, the strategies shifted from snail control to morbidity control and then to an integrated strategy that emphasized infection source control. However, being a vector-borne and zoonotic disease, schistosomiasis japonica is intricately linked to multiple factors including biological, natural, and socioeconomic risk factors. In order to eliminate schistosomiasis earlier and more thoroughly, the One Health approach should be adopted, which focuses on solving complex health problems from a macro-level perspective of interactions among human, animal, and environment, emphasizing multi-institution, interdisciplinary, and cross-regional collaboration and communication.

Reproductive alterations of Biomphalaria glabrata (Say, 1818) infected with Angiostrongylus cantonensis (Chen, 1935) and exposed to Euphorbia milii var. hislopii latex.

The natural phytochemical latex of Euphorbia milii var. hislopii is one of the most promising natural molluscicides for the control of Biomphalaria glabrata, and has been widely studied under laboratory conditions for selective control of schistosomiasis transmission. However, the effect of this product on B. glabrata infected by other helminths had not yet been investigated. The present study reports evaluation of the effect of E. milii var. hislopii latex on the survival and reproductive activity of B. glabrata infected by Angiostrongylus cantonensis. For this purpose, the following groups were formed: control (C), exposed (E), infected (I) and infected and exposed for different time intervals (1 day - I+E-1D, 7 days - I+E-7D, 14 days - I+E-14D, 21 days - I+E-21D and 28 days - I+E-28D). The experimental infection was performed with L1 larvae of A. cantonensis and exposure to 0.08 mg/L (LC50) of E. milii latex for a period of 24 hours. We analyzed the effects of E. milii latex on the survival of snails during four weeks, reproductive parameters and possible histophysiopathological changes in the gonad and albumen gland of the snails. Regarding survival, there was reduction of more than 50% in the groups exposed to latex (E and I + E) compared to the control group. As for the number of ovigerous masses, eggs, and average number of hatched snails, significant increases were observed in the I+E-1D group at the 4th week compared to the control group and the other weeks in the same group. Angiostrongylus cantonensis larvae were observed in the gonad and albumen gland from day 21 and 28 of infection in groups I and I+E, respectively, with granuloma-like formation. At these observation periods and in these groups, an increase in galactogen was observed in the albumen gland, which influenced egg laying, suggesting the existence of a fecundity compensation mechanism phenomenon. It was possible to conclude that both stressors - A. cantonensis infection and exposure to E. milii latex - directly influenced the survival and reproductive parameters of B. glabrata.

Genetic diversity and structure of Oncomelania hupensis hupensis in two eco-epidemiological settings as revealed by the mitochondrial COX1 gene sequences.

Oncomelania hupensis hupensis is the only intermediate host of Schistosoma japonicum, the causative agent of schistosomiasis in China and is therefore of significant medical and veterinary health importance. Although tremendous progress has been achieved, there remains an understudied area of approximately 2.06 billion m2 of potential snail habitats. This area could be further increased by annual flooding. Therefore, an understanding of population genetics of snails in these areas may be useful for future monitoring and control activities. We sampled snails from Hexian (HX), Zongyang (ZY) and Shitai (ST) in Anhui (schistosomiasis transmission control), and from Hengtang (HT), Taicang (TC), Dongsan (DS) and Xisan (XS) in Jiangsu (schistosomiasis transmission interrupted), downstream of Anhui. ST, DS and XS are classified as hilly and mountainous areas, and HX, ZY, TC and HT as lake and marshland areas. The mitochondrial cytochrome c oxidase subunit I gene were sequenced. Out of 115 snails analyzed, 29 haplotypes were identified. We observed 56 (8.72%) polymorphic sites consisting of 51 transitions, four transversions and one multiple mutational change. The overall haplotype and nucleotide diversity were 0.899 and 0.01569, respectively. Snail populations in Anhui had higher genetic diversity than in Jiangsu. 73.32% of total variation was distributed among sites and 26.68% within sites. Snails were significantly separated according to eco-epidemiological settings in both network and phylogenetic analyses. Our results could provide important guidance towards assessing coevolutionary interactions of snails with S. japonicum, as well as for future molluscan host monitoring and control activities.

Schistosomiasis control in the evolution of China's international discourse power

As a successful example of global public health, Chinese schistosomiasis control technology and experiences have been included in global public health governance. Chinese schistosomiasis control program progresses with China's international discourse power. During the period from the initial stage of the founding of the People's Republic of China to China's Reform and opening-up, the national schistosomiasis control program of China achieved great successes through mobilizing multi-sectorial resources under the policy of Independence and Self-reliance. Following China's Reform and opening-up, all advantageous opportunities were captured to solve problems pertaining to schistosomiasis control in the context of complex international situations. As a consequence, transmission control of schistosomiasis was achieved across China in 2015. Since the Eighteenth National Congress of the Communist Party of China, China has contributed the discourse system with distinct Chinese characteristics to the world, and has actively participated in health cooperation projects between China and other "Belt and Road" countries, which has contributed China's wisdom to global schistosomiasis control program and conveyed China's voice to the world.

Endemic status of schistosomiasis in People's Republic of China in 2020

This report presented the endemic status of schistosomiasis in the People's Republic of China at a national level in 2020, and analyzed the data collected from the national schistosomiasis prevention and control system and national schistosomiasis surveillance sites. 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 2020. A total of 450 counties (cites, districts) were found to be endemic for schistosomiasis in China, with 28 376 endemic villages covering 71 370 400 people at risk of infections. Among the 450 endemic counties (cities, districts), 74.89% (337/450), 21.87% (98/450) and 3.33% (15/450) achieved the criteria of elimination, transmission interruption and transmission control of schistosomiasis, respectively. By the end of 2020, 29 517 cases with advanced schistosomiasis were documented in China. In 2020, 11 117 655 individuals received inquiry examinations and 1 798 580 were positive; 5 263 082 individuals received serological tests and 83 179 were sero-positive. A total of 273 712 individuals received stool examinations and 3 were positive, including one case of acute schistosomiasis. In 2020, snail survey was performed in 19 733 endemic villages in China and Oncomelania snails were found in 7 309 villages, accounting for 37.04% of all surveyed villages, with 15 villages identified with emerging snail habitats. Snail survey covered an area of 736 984.13 hm2 and 206 125.22 hm2 snail habitats were found, including 1 174.67 hm2 emerging snail habitats and 1.96 hm2 habitats with infected snails. In 2020, 544 424 bovines were raised in the schistosomiasis-endemic areas of China, and 147 887 received serological examinations, with 326 positives detected, while 130 673 bovines received stool examinations, with no positives identified. In 2020, there were 19 214 patients with schistosomiasis receiving praziquantel chemotherapy, and 964 103 person-time individuals and 266 280 herd-time bovines were given expanded chemotherapy. In 2020, molluscicide treatment was performed in 136 141.92 hm2 snail habitats, and the actual area of chemical treatment was 71 980.22 hm2, while environmental improvements were performed in snail habitats covering an area of 1 464.03 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 2020, and no S. japonicum infection was detected in snails. The results demonstrate that the overall endemic status of schistosomiasis remains at a low level in China and the goal of the National Thirteenth Five-Year Plan for Schistosomiasis Control was achieved as scheduled; however, the endemic situation of schistosomiasis rebounded in local areas. Precision schistosomiasis control and intensified monitoring of the endemic situation and transmission risk of schistosomiasis are required to be performed to facilitate the progress towards elimination of schistosomiasis steadily.

Assessing the effects of diagnostic sensitivity on schistosomiasis dynamics

Schistosomiasis is a parasite infection that affects millions of people around the world. It is endemic in 13 different states in Brazil and responsible for increasing morbidity in the population. One of its main characteristics is a heterogeneous distribution of worm burden in the human population, which makes the diagnosis difficult. We aimed to investigate how the sensitivity of the diagnostic method may contribute to successful control interventions against infections in a population. In order to do that, we present an ordinary differential equations model that considers three levels of worm burden in the human population, a snail population, and a miracidium reservoir. Through a steady-state analysis and its local stability, we show how this worm-burden heterogeneity can be responsible for the persistence of infection, especially due to reinfection in the highest level of worm burden. The analysis highlights sensitive diagnosis, besides treatment and sanitary improvements, as a key factor for schistosomiasis transmission control.

An assessment of the molluscicidal potential of Cucurbita maxima seed extracts on Biomphalaria pfeifferi and Bulinus globosus snails

Reports of snails’ resistance to niclosamide appeared recently and finding new molluscicides becomes necessary. We investigated the molluscicidal effects of Cucurbita maxima seed extracts on Biomphalaria pfeifferi, and Bulinus globosus snails under laboratory conditions. For B. pfeifferi, we tested seed extracts on juvenile and adult snails while only adult B. globosus were available for testing. Snails were exposed to water and crude ethanol extracts for 72 h and significant concentration-dependent mortality rates were observed. The number of B. pfeifferi juveniles collected was not enough for a comprehensive investigation against both solvents. We, therefore, tested them against water extracts only. A lethal concentration of 0.02 mg/mL killed 50% of the snails (LC50) for both water and ethanol extracts on adult B. pfeifferi snails. Our results suggest that pumpkin seed extracts have a significant molluscicidal effect on B. pfeifferi and B. globosus snails. The LC50 values for all the extracts in B. pfeifferi and B. globosus snails are within the threshold set for potential molluscicides by the World Health Organisation. We propose that C.maxima seed extracts be considered as potential molluscicidal agents in Schistosomiasis transmission control.

Endemic status of schistosomiasis in People's Republic of China in 2019

This report presented the endemic status of schistosomiasis in the People's Republic of China at a national level in 2019, and analyzed the data collected from the national schistosomiasis prevention and control system and 455 national schistosomiasis surveillance sites. Among the 12 provinces (municipality and autonomous region) endemic for schistosomiasis in China, Shanghai, Zhejiang, Fujian, Guangdong and Guangxi continued to consolidate the achievements of schistosomiasis elimination, Sichuan Province achieved transmission interruption, Jiangsu newly achieved the standard of transmission interruption and 5 provinces of Yunnan, Hubei, Anhui, Jiangxi and Hunan maintained transmission control by the end of 2019. There were 450 endemic counties (cities, districts) endemic for schistosomiasis, including 28 500 endemic villages covering 70 667 800 people at risk of infections. Among the 450 endemic counties (citis, districts), 66.89% (301/450), 28.44% (128/450) and 4.67% (21/450) kept the criteria of elimination, transmission interruption and transmission control of schistosomiasis, respectively. By the end of 2019, a total of 30 170 advanced schistosomiasis cases were documented in China. In 2019, a total of 12 090 712 individuals received inquiry examinations and 1 740 764 were positive; 5 158 369 individuals received serological tests and 89 753 were seropositive. A total of 327 475 individuals received stool examinations and 5 were positive, including one case of acute schistosomiasis. In 2019, snail survey was performed in 19 726 endemic villages in China and Oncomelania snails were found in 7 322 villages, accounting for 37.12% of all surveyed villages, with 6 villages with emerging snail habitats. Snail survey covered an area of 585 286.24 hm2 and 174 270.42 hm2 snail habitats were found, including emerging snail habitats of 64.20 hm2; however, no infected snails were identified. In 2019, a total of 605 965 bovines were raised in the schistosomiasis endemic areas of China, and 183 313 received serological examinations, with 1 176 positives detected, while 134 978 bovines received stool examinations, with 7 positives identified. In 2019, there were 28 557 patients with schistosomiasis receiving praziquantel chemotherapy, and expanded chemotherapy was given to 1 008 083 person-times; there were 7 bovines with schistosomiasis receiving praziquantel chemotherapy, and 296 053 herd-times expanded chemotherapy was given to bovines. In 2019, snail habitats at an area of 128 754.26 hm2 were given chemical treatment, and the actual area of chemical treatment was 69 605.55 hm2, while environmental improvements were performed in snail habitats covering an area of 2 847.00 hm2. Data from the 455 national schistosomiasis surveillance sites of China showed that the mean Schistosoma japonicum infection rates were both zero in humans and bovines in 2019, and no infected snails were found. The results demonstrate that the overall endemic situation of schistosomiasis remains at a lower infection level in China; however, there is still a risk of schistosomiasis transmission. To achieve the target set in the National Thirteenth Five-Year Plan for Schistosomiasis Control and consolidate the achievements of schistosomiasis control, precision control on schistosomiasis still needs to be reinforced in China.

Progress of schistosomiasis control in Dongting Lake regions

As an ancient parasitic disease, schistosomiasis has been endemic in Dongting Lake areas for more than 2 100 years. In the early 20th century, the first human case of schistosomiasis in China was reported in Dongting Lake areas, which was paid extensive attention. After the founding of the People's Republic of China, large-scale schistosomiasis control activities were launched promptly in Dongting Lake areas, and great successes have been achieved following the three stages of control efforts, including the snail control-based stage, synchronous chemotherapy for humans and livestock-based control stage and infectious source control-based control stage. In 2015, transmission control of schistosomiasis was achieved in Hunan Province. This paper comprehensively describes the discovery and control of schistosomiasis, analyzes the challenges for the current schistosomiasis control programs and proposes the emphasis for future control activities in Dongting Lake areas, so as to provide insights into the schistosomiasis control program in this area.

Obtaining elevation of Oncomelania Hupensis habitat based on Google Earth and it\u2019s accuracy evaluation: an example from the Poyang lake region, China

Schistosomiasis japonicum is a major zoonosis that seriously harms human health and affects social and economic development in China. The control of Oncomelania Hupensis, the only intermediate host of schistosome japonicum, is one of the integrated measures for schistosomiasis control in China. Acquiring updated elevation data of snail habitat environment, as well as it’s spatial analysis, play an important role for the risk evaluation and precise control of schistosomiasis transmission and prevalence. Currently, the elevation database of snail habitat environment in schistosomiasis epidemic areas has not been available in the world, which affects the development of research and application work regarding to snail control. Google Earth(GE) can provide massive information related to topography, geomorphology and ground objects of a region due to its indisputable advantages such as wide use, free charge and rapidly updating. In this paper, taking the Poyang lake region as a example, we extracted elevation data of snail-inhabited environment of the lake from GE and established a elevation correction regression model(CRM) for acquiring accurate geospatial elevations, so as to provide a decision-making reference for snail control and risk evaluation of schistosomiasis in China. We developed a GE Application Programming Interface(API) program to extract elevation data from GE, which was compared with the actual elevation data obtained from topographic map of the Poyang Lake bottom. Then, a correction regression model was established and evaluated by 3 index, Mean Absolute Error(MAE), Root Mean Squared Error(RMSE) and Index of Agreement(IOA) for the accuracy of the model. The elevation values extracted from GE in 15086 sample grid points of the lake ranged from 8.5 m to 24.8 m. After the sample points were divided randomly to three groups, the mean elevations of three groups were 13.49 m, 13.52 m and 13.65 m, respectively, with standard deviation ranged from 2.04–2.06. The mean elevation among three groups has no statistic difference (F = 1.536, P = 0.215). A elevation correction regression model was established as y = 6.228 + 0.485×. the evaluation results for the accuracy of the model showed that the MAE and RMSE before correction was 1.28 m and 3.95 m respectively, higher than that after correction, which were 0.74 and 1.30 m correspondingly. The IOA before correction (−0.40)was lower than that after correction(0.34). Google Earth can directly or indirectly get access to massive information related to topography, geomorphology and ground objects due to its indisputable advantages. However, it still needs to be converted into more reliable and accurate data by combining with pre-processing tools. This study used self-developed API program to extract elevation data from GE through precisely locating and improved the accuracy of elevation by using a correction regression model, which can provide reliable data sources for all kinds of spatial data researches and applications.

Gene drives for schistosomiasis transmission control.

Schistosomiasis is one of the most important and widespread neglected tropical diseases (NTD), with over 200 million people infected in more than 70 countries; the disease has nearly 800 million people at risk in endemic areas. Although mass drug administration is a cost-effective approach to reduce occurrence, extent, and severity of the disease, it does not provide protection to subsequent reinfection. Interventions that target the parasites’ intermediate snail hosts are a crucial part of the integrated strategy required to move toward disease elimination. The recent revolution in gene drive technology naturally leads to questions about whether gene drives could be used to efficiently spread schistosome resistance traits in a population of snails and whether gene drives have the potential to contribute to reduced disease transmission in the long run. Responsible implementation of gene drives will require solutions to complex challenges spanning multiple disciplines, from biology to policy. This Review Article presents collected perspectives from practitioners of global health, genome engineering, epidemiology, and snail/schistosome biology and outlines strategies for responsible gene drive technology development, impact measurements of gene drives for schistosomiasis control, and gene drive governance. Success in this arena is a function of many factors, including gene-editing specificity and efficiency, the level of resistance conferred by the gene drive, how fast gene drives may spread in a metapopulation over a complex landscape, ecological sustainability, social equity, and, ultimately, the reduction of infection prevalence in humans. With combined efforts from across the broad global health community, gene drives for schistosomiasis control could fortify our defenses against this devastating disease in the future.

Effectiveness of infectious source control after transmission control of schistosomiasis in Eryuan County of Yunnan Province

To assess the effectiveness of infectious source control at various stages of transmission control of schistosomiasis in Eryuan County of Yunnan Province, so as to provide insights into the further monitoring and management of infectious sources of schistosomiasis. Wenbi Village, a plateau subtype region and Qiandian Village, a mountain subtype region in Eryuan County were selected as the study areas. The species, schistosome infection and transmission capability of infectious sources were investigated in Wenbi and Qiandian villages in 2011 and 2018 and were compared. Schistosome infections were detected in human, bovine, horse, dog and mouse in Qiandian Village in 2011, with positive rates of 1.19%, 0.91%, 1.25%, 3.13% and 0.95%, respectively, and human, bovine and dog were found to have schistosome infections, with positive rates of 0.76%, 1.66% and 9.30%, respectively. However, no infections were identified in human, bovine, horse, pig, dog, sheep or mouse in these two villages in 2018. A total of 731 wild feces were collected in both villages in 2011. In Qiandian Village, horse, bovine and dog feces accounted for 34.40%, 29.80% and 20.20% of all fecal samples, and dog and horse feces were found to have schistosome infections (11.94% and 6.90% positive rates, respectively). In Wenbi Village, dog, bovine and human feces accounted for 44.59%, 39.83% and 14.29% of all fecal samples, and dog, human and bovine feces were found to have schistosome infections (16.95%, 9.52% and 2.33% positive rates, respectively). In 2018, a total of 204 wild feces were collected in both villages, and no schistosome infections were identified. Sheep, dog and bovine feces accounted for 36.27%, 33.33% and 27.45% of all fecal samples in Qiandian Village, and dog, bovine and human feces accounted for 72.55%, 11.76% and 10.78% of all fecal samples in Wenbi Village. A remarkable achievement has been obtained in the control of infectious sources of schistosomiasis in Eryuan County, and the role of human and bovine as the major infectious sources of schistosomiasis has been effectively controlled. In the future, the integrated strategy with emphasis on the control of infectious sources should be intensified, and the management of reservoir hosts including dog and mouse should be strengthened.

Effect of integrated schistosomiasis control in Honghu City from 2008 to 2018

To evaluate the effect of integrated schistosomiasis control measures in Honghu City during the period from 2008 through 2018. The data pertaining to schistosomiasis control measures and the endemic situation of schistosomiasis in Honghu City were collected from 2008 to 2018, and the effect of integrated schistosomiasis control measures implemented was evaluated. The resources from agriculture, water resources, forestry, land, education and communication sectors were integrated to implement the integrated schistosomiasis control strategy with the focus on the control of source of Schistosoma japonicum infection in Honghu City from 2008 to 2018. The prevalence of S. japonicum infection reduced from 3.03% in 2008 to 0 in 2018 in humans in the city, and no acute infection was detected since 2009. In addition, the prevalence of S. japonicum infection in cattle reduced from 2.85% in 2008 to 0 in 2018, and no snail infection was found since 2012. Transmission control of schistosomiasis was achieved in the city in 2013, and transmission interruption was achieved in 2018. The integrated schistosomiasis control measures achieve remarkable effects in Honghu City; however, there is still a risk of schistosomiasis transmission.

Potential Biological Control of Schistosomiasis by Fishes in the Lower Senegal River Basin.

.More than 200 million people in sub-Saharan Africa are infected with schistosome parasites. Transmission of schistosomiasis occurs when people come into contact with larval schistosomes emitted from freshwater snails in the aquatic environment. Thus, controlling snails through augmenting or restoring their natural enemies, such as native predators and competitors, could offer sustainable control for this human disease. Fishes may reduce schistosomiasis transmission directly, by preying on snails or parasites, or indirectly, by competing with snails for food or by reducing availability of macrophyte habitat (i.e., aquatic plants) where snails feed and reproduce. To identify fishes that might serve as native biological control agents for schistosomiasis in the lower Senegal River basin—one of the highest transmission areas for human schistosomiasis globally—we surveyed the freshwater fish that inhabit shallow, nearshore habitats and conducted multivariate analyses with quantitative diet data for each of the fish species encountered. Ten of the 16 fish species we encountered exhibited diets that may result in direct (predation) and/or indirect (food competition and habitat removal) control of snails. Fish abundance was low, suggesting limited effects on schistosomiasis transmission by the contemporary fish community in the lower Senegal River basin in the wild. Here, we highlight some native species—such as tilapia, West African lungfish, and freshwater prawns—that could be aquacultured for local-scale biological control of schistosomiasis transmission.

Progress and challenges of schistosomiasis elimination in China

Schistosomiasis is an old and geographically widespread parasitic disease that severely damages human health and affects socioeconomic development in China. The implementation of the integrated strategy with emphasis on controlling the source of Schistosoma japonicum infection and the National Mid- and Long-Term Plan for Schistosomiasis Prevention and Control (2004-2015) in China greatly facilitated the progress towards the elimination of schistosomiasis in China. Since transmission control of schistosomiasis was achieved in 2015, the goal of the national schistosomiasis control program has moved to transmission interruption and elimination in China. Because of the impacts of natural and social factors, and the new situation, new task and new demands following the continuous decline in the endemic situation of schistosomiasis, several challenges exist to achieve the goal of schistosomiasis elimination nationwide. This paper analyzed the current endemic status of schistosomiasis, progress and challenges of schistosomiasis elimination, and proposed some suggestions for the national chistosomiasis elimination program in China.