[Construction of a forecast system for prediction of schistosomiasis risk in China based on the flood information].

OBJECTIVE: To create a model based on meteorological data to predict the regions at risk of schistosomiasis during the flood season, so as to provide insights into the surveillance and forecast of schistosomiasis. METHODS: An interactive schistosomiasis forecast system was created using the open-access R software. The schistosomiasis risk index was used as a basic parameter, and the species distribution model of Oncomelania hupensis snails was generated according to the cumulative rainfall and temperature to predict the probability of O. hupensis snail distribution, so as to identify the regions at risk of schistosomiasis transmission during the flood season. RESULTS: The framework of the web page was built using the Shiny package in the R program, and an interactive and visualization system was successfully created to predict the distribution of O. hupensis snails, containing O. hupensis snail surveillance site database, meteorological and environmental data. In this system, the snail distribution area may be displayed and the regions at risk of schistosomiasis transmission may be predicted using the species distribution model. This predictive system may rapidly generate the schistosomiasis transmission risk map, which is simple and easy to perform. In addition, the regions at risk of schistosomiasis transmission were predicted to be concentrated in the middle and lower reaches of the Yangtze River during the flood period. CONCLUSIONS: A schistosomiasis forecast system is successfully created, which is accurate and rapid to utilize meteorological data to predict the regions at risk of schistosomiasis transmission during the flood period.

[Performance of a recombinase - aided amplification assay for detection of Schistosoma japonicum infections in Oncomelania hupensis].

OBJECTIVE: To evaluate the efficiency of a recombinase-aided amplification (RAA) assay for the detection of Schistosoma japonicum infections in Oncomelania hupensis snails. METHODS: A group test was employed. Fifty Oncomelania snails were collected as a detection sample. The detection samples without infected snails were designated as negative specimens, while the detection samples that contained different numbers of infected snails were designated as positive specimens. A total of 10 negative specimens, 10 positive specimens containing 1 infected snail, 20 positive specimens containing 2 infected snails and 10 positive specimens containing 3 infected snails were assigned. Following random grouping, 40 specimens were subject to the florescent RAA assay using a blind method. The miradium shedding method served as a gold standard, and the sensitivity, specificity, Youden's index and coincidence rate of the florescent RAA assay were estimated. In addition, 20 samples consisted of 5 negative specimens and 15 positive specimens with 1, 2 and 3 infected snails respectively were grouped randomly. The same specimens were detected using the crushing method and fluorescent RAA assay with the blind method in a paired-design manner. Then, the test results were compared and analyzed. RESULTS: Florescent RAA assay detected 29 positives in the 30 specimens containing different numbers of infected snails, with a sensitivity of 96.67%, and 8 negatives in the 10 detection specimens without infected snails, with a specificity of 80.00%, showing a Youden's index of 0.77. The coincidence rate was 100% among 10 repeated assays for a detection specimen. In addition, there was no significant difference in the detection of infected snails between the florescent RAA assay and the crushing method (χ2 = 0, P > 0.05), and the actual coincidence rates of the florescent RAA assay and crushing method were 95.00% (19/20) and 90.00% (18/20) with the real results, respectively. CONCLUSION: Fluorescent RAA assay has a favorable efficiency for the detection of S. japonicum infections in Oncomelania snails, which shows a potential in screening of S. japonicum-infected Oncomelania snails.

[Endemic situation of schistosomiasis in national surveillance sites of Zhejiang Province from 2015 to 2019].

OBJECTIVE: To analyze the endemic situation of schistosomiasis in national surveillance sites of Zhejiang Province, so as to provide the scientific evidence for formulating the new schistosomiasis surveillance program and consolidating schistosomiasis elimination achievements. METHODS: A total of 54 to 55 national surveillance sites and 6 risk monitoring sites were assigned in historical endemic regions of Zhejiang Province from 2015 to 2019, where the Schistosoma japonicum infections in humans, livestock, snails and wild feces were monitored. All data pertaining to the surveillance results were descriptively analyzed. RESULTS: There were 34 530 person-time local residents receiving serological screening for S. japonicum infections in national surveillance sites of Zhejiang Province from 2015 to 2019, and the seroprevalance of S. japonicum infections were 0.29% to 0.68%; however, no egg-positives were detected. During the period from 2015 to 2019, there were 62 086 person-time mobile populations receiving serological screening for S. japonicum infections in national surveillance sites of Zhejiang Province, and the seroprevalance of S. japonicum infections were 0.32% to 0.56%; additionally, there were 27 egg-positives identified, including 3 imported cases with schistosomiasis haematobia and one case with acute schistosomiasis japonica, indicating that the adjusted prevalence of Schistosoma infections were 0.01% to 0.07% among mobile populations. A total of 829 livestock were examined for S. japonicum infections, with no positives detected. There were 10.55 hm2 and 2.89 hm2 snail habitats found in national surveillance sites and risk monitoring sites of Zhejiang Province during the 5-year period, respectively; however, no S. japonicum infections were identified in snails. Moreover, a total of 305 wild feces were tested for S. japonicum infections, and no egg-positives were identified. CONCLUSIONS: The schistosomiasis elimination achievement have been consolidated in Zhejiang Province; however, the risk factors of re-emerging schistosomiasis have not been completely eliminated, such as residual snails and imported schistosomiasis cases. Further surveillance and control activities of snails and the source of S. japonicum infections should be reinforced.

[Effect of integrated schistosomiasis control measures on Oncomelania snails in river channels connecting the Yangtze River in Nanjing City].

OBJECTIVE: To evaluate the effectiveness of Oncomelania snails control following the implementation of integrated schistosomiasis control measures in river channels connecting the Yangtze River in endemic areas of Nanjing City. METHODS: The river channels connecting the Yangtze River with snails in Nanjing City were selected as the study pilots. The integrated schistosomiasis control measures implemented in the study pilots were investigated by means of retrospective analyses and field surveys from 1998 to 2019, and the effectiveness of snail control was evaluated. RESULTS: Integrated control measures with emphases on environmental improvements including water resource projects for schistosomiasis control were implemented in the study pilots during the period from 1998 to 2019, including river bank concretion with 84.51 km in length, marshland cutting and dredging with 50.41 km in length, building 2 sluices and 3 overflow dams, digging one floodway and snail control with chemical treatment that covered an area of 3 370.80 hm2. No Schistosoma japonicum infection had been detected in snails since the completion of the integrated control measures. In addition, snails had been eliminated in 6 river channels connecting the Yangtze River until 2019, with the snail habitats reducing from 214.33 hm2 to 52.22 hm2 in 10 river channels connecting the Yangtze River and the snail density reducing to below 0.1 snails/0.1 m2 in snail-breeding river channels connecting the Yangtze River. CONCLUSIONS: The integrated schistosomiasis control measures with emphases on environmental improvements may effectively control snail breeding and spread in rivers connecting the Yangtze River in endemic areas of schistosomiasis; however, the maintenance of the project and snail surveillance and control should be intensified following the completion of the integrated schistosomiasis control measures.

[Impact of "Elaphurus davidianus return home project" on the transmission of schistosomiasis in Poyang Lake areas].

OBJECTIVE: To investigate the prevalence of Schistosoma japonicum infections in Elaphurus davidianus released to Poyang Lake areas and evaluate the impact of the project of "E. davidianus released to wild environments for natural reproduction and growth" "(E. davidianus return home project") on the transmission of schistosomiasis in Poyang Lake areas. METHODS: During the period from April 2018 to December 2019, the population distribution, inhabiting activity and natural reproduction of E. davidianus released to Poyang Lake areas were investigated by means of GPS and artificial observations. The S. japonicum infection was identified in animal feces in E. davidianus inhabitats using a hatching test, and snail distribution was surveyed in E. davidianus inhabiting grass islands using a systematic sampling method. RESULTS: A total of 51 E. davidianus were released to the Poyang Lake areas in 2018, which subsequently produced 5 E. davidianus habitats in Yinlong Lake, Longkou, Nanchi Lake, Lianzi Lake and Zhu Lake. E. davidianus was found to predominantly inhibit in grass islands, farmlands and forest lands in hilly regions around the Poyang Lake areas. The natural reproduction rate of E. davidianus was 25% in the habitats in 2019, and the mean density of snails was 0.009 to 0.039 snails/0.1 m2 in E. davidianus inhabitats; however, no S. japonicum infection was identified in snails. In addition, the mean densities of wild E. davidianus and bovine feces were 4.6 samples/hm2 and 2.1 samples/hm2, Conclusions The E. davidianus released to Poyang Lake areas may get infections with S. japonicum, and cause schistosomiasis transmission through fecal contamination in grass islands. The impact on and the prevalence of S. japonicum infection was 4.35% and 13.16% (P = 0.236), respectively; however, the intensities of S. japonicum infections were "+++" and "+", respectively. CONCLUSIONS: The E. davidianus released to Poyang Lake areas may get infections with S. japonicum, and cause schistosomiasis transmission through fecal contamination in grass islands. The impact on local schistosomiasis transmission and the response strategy requires to be investigated following the release of E. davidianus to lake regions, to ensure the achievement of the goal of schistosomiasis elimination and the successful implementation of the "E. davidianus return home project" in Poyang Lake areas.

[Survey of snail distribution in Four-lake Basin of Hubei Province].

OBJECTIVE: To investigate the distribution of Oncomelania snails in Four-Lake Basin of Hubei Province, so as to provide scientific evidence for the development of snail control interventions. METHODS: The snail distribution was surveyed by means of the retrospective study and cross-sectional survey in the Four-Lake Basin in Spring of 2016. The data pertaining to the endemic situation of schistosomiasis were collected and analyzed in the Four-Lake Basin from 2008 to 2018, and the associations of snail habitat areas with the prevalence of Schistosoma japonicum in humans and bovines were examined. RESULTS: There were 16 003 snail habitats in the 9 schistosomiasis-endemic counties (districts) in the Four-Lake Basin in 2016, covering an area of 246 million m2. The mean density of living snails was 0.622 5 snails/0.1 m2, which was relatively high in weed-type settings (0.688 0 snails/0.1 m2) and ditches (0.706 4 snails/0.1 m2). Type I (current snail habitats, 53.03%) and Ⅱ- Ⅳ (historical snail habitats, 46.97%) settings were predominant snail habitats. A big change was seen in snail habitats in dry farmland, marshland and paddy farmland, and environmental modification resulted in satisfactory snail control effectiveness. In addition, the area of snail habitats positively correlated with the changes in the prevalence of S. japonicum infections in humans (r = 0.842, P < 0.01) and livestock (r = 0.695, P < 0.01). CONCLUSIONS: The integrate strategy with an emphasis on the control of the source of S. japonicum infections results in remarkable snail control effectiveness in the Four-Lake Basin; however, there is a risk of re-emerging snail habitats.

[Flood disasters and schistosomiasis control].

Currently, the endemic situation of schistosomiasis has dropped to the lowest level in China; however, there are still factors affecting the transmission of schistosomiasis. Flood disasters may pose a great impact on the transmission of schistosomiasis and even affect the progress of schistosomiasis control and the consolidation of schistosomiasis control achievements. In 2020, major flood disasters occur across China. This paper analyzes the current status of schistosomiasis and the impact of flood disasters on the transmission of schistosomiasis in China, and systematically describes the assessment of and response to schistosomiasis transmission risk before flood disasters, the prevention of Schistosoma japonicum infections during flood disasters and the assessment of the endemic situation of schistosomiasis and surveillance of schistosomiasis after flood disasters. It is considered that schistosomiasis control is an important part of conventional schistosomiasis control activities and an important part of anti-flood and schistosomiasis-preventive activities in flood disaster-affected areas. It is recommended that emergence response interventions are implemented in a scientific and well-organized manner to avoid or reduce the risk of schistosomiasis transmission caused by flood disasters. In addition, the research on early surveillance and forecast approaches for schistosomiasis should be emphasized and reinforced to provide the scientific and precise tools for achieving the goal of the 13th Five-year Plan for Schistosomiasis Control and elimination of schistosomiasis in China.

[Endemic situation of schistosomiasis in a national surveillance site of Yangzhong City from 2015 to 2018].

OBJECTIVE: To analyze the endemic situation of schistosomiasis in a national surveillance site of Yangzhong City, so as to provide the scientific evidence for adjusting the local schistosomiasis control strategy and consolidating the control achievements. METHODS: According to the National Schistosomiasis Surveillance Scheme (2014 version), the snail status, Schistosoma japonicum infections in humans and livestock and wild feces contamination were monitored in Zhinan Village, a national schistosomiasis surveillance site in Yangzhong City from 2015 to 2018. RESULTS: Theareasofsnailhabitatsreducedfrom 8.10 hm2 in 2015 to 2.72 hm2 in 2018, and the mean density of living snails decreased from 0.27 snails/0.1 m2 in 2015 to 0.07 snails/0.1 m2 in 2018 in Zhinan Village; however, no S. japonicum infections were identified in snails during the period from 2015 to 2018. Serological testing for S. japonicum infections was performed in 2 034 local populations and 858 mobile populations from 2015 to 2018, and the sero-prevalence of S. japonicum human infections was 0.59% to 1.98%, with no egg-positives detected. A total of 79 goats were detected for S. japonicum infections from 2015 to 2018, and no egg-positives were found. In addition, no other livestock was found in Zhinan Village from 2015 to 2018, and no wild feces were found in snail habitats. CONCLUSIONS: A great success has been achieved in schistosomiasis control in Yangzhong City; however, there are still snails breeding in the city. Monitoring of the risk factors pertaining to schistosomiasis transmission should be further intensified to consolidate the control achievements.

[Assessment of schistosomiasis transmission risk in Nanjian County of Yunnan Province in 2019].

OBJECTIVE: To assess the schistosomiasis transmission risk in Nanjing County, so as to provide the scientific evidence for the development of the schistosomiasis control strategy and consolidation of the control achievements. METHODS: On May 2019, the Deqiu Village in Deqiu Town and Baiyun Village in Nanjing Town of Yunnan Province, where schistosomiasis were historically relatively highly endemic, were selected to assess the risk of transmission of schistosomiasis by means of a retrospective review of the data pertaining to the historical endemic situation and schistosomiasis control, combined with a cross-sectional survey of snail and wild feces distribution. RESULTS: During the period between 2017 and 2018, the mean sero-prevalence rates of Schistosoma japonicum infections were 6.76% (202/2 990) and 2.86% (142/4 971) in humans and 0 (0/1 160) and 10.65% (31/291) in bovines in Deqiu and Baiyun villages of Nanjian County, respectively; however, no egg-positives were identified; in addition, there were 21.06 hm2 snail habitats found, but no S. japonicum infections were detected in snails. In 2019, there was 6.17 hm2 snail habitats detected, with 2.17% (245/11 298) occurrence of frames with snails and a 0.06 snails/0.1 m2 density of living snails; however, no positives for nucleic acid detection were seen in snails; among the 136 wild fecal samples captures from 23 settings, no S. japonicum infections were identified. CONCLUSIONS: The risk of schistosomiasis transmission remains at a low level in Nanjian County; however, the factors affecting the transmission of schistosomiasis have not been completed eliminated. The integrated schistosomiasis control strategy with an emphasis on the control of the source of S. japonicum infections requires to be reinforced to consolidate the control achievements.

[Comprehensive benefits of agroforestry snail control forests in Eryuan County, Yunnan Province].

OBJECTIVE: To investigate the efficiency of various agroforestry systems for snail control in plateau hilly schistosomiasis-endemic areas of Yunnan Province, so as to provide insights into the construction of agroforestry schistosomiasis control projects in plateau hilly regions. METHODS: The pilot areas of snail control forests with various agroforestry systems were built in snail-breeding farmlands in Eryuan County, Yunnan Province in 2010, and the economic benefits and snail control effect were investigated in 2018. In addition, a fuzzy comprehensive evaluation model was created to screen the agroforestry system with high comprehensive benefits. RESULTS: A total of 14 types of pilot areas of snail control forests with various agroforestry systems were built. Economic benefit analysis showed that the"walnut + garlic"pattern had the best economic benefit, with annual economic benefits of 270 000 Yuan/hm2, followed by the"walnut + chili"pattern (annual economic benefits of 120 000 Yuan/hm2) and the "walnut + vegetables"pattern (annual economic benefits of 105 000 Yuan/hm2). No snails were detected in 8 types of the agroforestry systems, including the"walnut + chili"pattern, the"walnut + tobacco"pattern and the"walnut + garlic"pattern; however, there were snail found with various densities in other types of systems. Fuzzy comprehensive evaluation showed that the"walnut + garlic"pattern had the best comprehensive control effect, followed by the"walnut + chili"pattern and the"walnut + tobacco" pattern, while the pure grassland pattern showed no effect on snail control. CONCLUSIONS: The agroforestry system is a preferential approach of forestry schistosomiasis control in plateau hilly schistosomiasis-endemic areas, which not only achieves snail control effects, but also promotes economic development and ecological construction in poor hilly areas.

[Molecular identification of Tricula spp. and the parasitized trematode cercariae in schistosomiasis-endemic areas of Yunnan Province].

OBJECTIVE: To characterize a species of the genus Tricula and parasitized trematodes in schistosomiasis-endemic areas of Yunnan Province using a molecular analysis, so as to understand their taxonomic positions. METHODS: Tricula spp. and Oncomelania snails were collected from Xiangyun County, Yunnan Province, and cercaria parasitizing snails were observed using crushing followed by microscopy. Cercaria parasitizing Tricula snails at various morphologies were sampled using a shedding method. Genomic DNA was extracted from snail soft tissues and cercariae, and the 16S rRNA, COI, 28S rDNA genes in snails and the ND1 and 28S rDNA genes in cercariae were amplified using a PCR assay and sequenced. The species of Tricula snails and their parasitized trematodes was characterized using sequence alignment and phylogenetic analysis. RESULTS: Among 382 Tricula snails detected, there were three types of trematode cercariae found, including the non-forked (20.94%, 80/382), double-forked (3.40%, 13/382) and swallow shapes (7.07%, 27/382). Sequence and phylogenetic analyses showed that the 16S rRNA, COI and 28S rDNA gene sequences of this species of Tricula had high homology to those in Delavaya dianchiensis, and were clustered in a branch. Sequencing analysis of the ND1 and 28S rDNA genes revealed that the non-forked cercariae belonged to the family Pleu- rogenidae, the swallow-shaped cercariae belonged to the family Opecoelidae, and the double-forked cercariae belonged to another species of the genus Schistosoma that was different from S. sinensium and S. ovuncatum. CONCLUSIONS: The species and taxonomy of Triculla spp. and their parasitized trematodes are preliminarily determined in schistosomiasis-endemic areas of Yunnan Province; however, further studies are required to investigate the more definite taxonomy and pathogenicity.

[Survival analysis of laboratory - bred smooth - shelled Oncomelania snails in Yunnan Province].

OBJECTIVE: To investigate the survival period of Yunnan Province-derived smooth-shelled Oncomelania snails bred in laboratory. METHODS: Oncomelania snails were sampled from Heqing and Yongsheng counties where schistosomiasis is endemic, and uninfected adult snails were collected and bred in laboratory. The survival period of snails sampled from these two counties was compared. RESULTS: The 1-, 2-, 3- and 4-year survival rates of laboratory-bred smooth-shelled snails sampled from Yunnan Province were 72.36%, 29.11%, 13.08% and 0.21%, respectively, and were 74.66%, 38.91%, 19.46% and 0.45% for snails derived from Heqing County, and 70.36%, 20.55%, 7.51% and 0 for snails sampled from Yongsheng County, respectively. The mean and median survival period of Yunnan Province-derived adult snails was 20.90 and 20.67 months, and there were significant differences between the snails sampled from Heqing and Yongsheng counties in terms of the mean (22.94 vs. 19.13 months, P < 0.05) and median survival period (21.63 vs. 19.81 months, P < 0.05). CONCLUSIONS: The mean survival period of Yunnan Province-derived smooth-shelled adult snails is approximately 20 months in laboratory, and the survival varies in geographical areas.

[Spatio-temporal distribution of Oncomelania hupensis snails along the Danyang section of the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal].

OBJECTIVE: To explore the spatio-temporal characteristics of Oncomelania hupensis snails along the Danyang section of the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal, so as to provide scientific evidence for the dynamic assessment of the risk of snail spread in this region. METHODS: O. hupensis snail status was collected in the plain regions with waterway networks in the study area from 2012 to 2017. The spatio-temporal variations of snail distribution were investigated along the Danyang section of the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal using buffer zone analysis, spatial autocorrelation, hotspot analysis and standard deviational ellipse with the geographical information system (GIS) tools. RESULTS: The number of snail habitats showed a tendency towards a rise in the study area from 2012 to 2017, and snail habitats were predominantly distributed in the 1 000 m long buffer zone of the Danyang-Jintan-Liyang Canal, notably along the Jiuqu River at the junction between the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal. The distribution of snail habitats appeared spatial autocorrelations in 2014, 2016 and 2017, and the hotspot areas were mainly identified at the junction between the Danyang-Jintan-Liyang Canal and the Beijing-Hangzhou Grand Canal. In addition, the overall distribution of snail habitats was located in the northeastern-southwestern part of the study aera, and gradually shifted to the southern and northern parts with the time. CONCLUSIONS: The spatial distribution of O. hupensis snails is complex along the Danyang section of the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal, and there is a risk of snail spread from the upper reaches to the lower reaches, where snail control needs to be intensified.

[Effectiveness of snail control by immersion of molluscicides through tide diversion in marshlands: a field evaluation].

OBJECTIVE: To compare the effectiveness of snail control between immersion of molluscicides through tide diversion and mollusciciding by spraying in marshland areas. METHODS: Immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion and spraying 26% suspension concentrate of metaldehyde and niclosamide alone were employed for snail control in two neighboring snail-breeding marshlands, and snails were surveyed before and after mollusciciding. The mortality of snails and the density of living snails were estimated. RESULTS: The density of living snails reduced by 72.19% and 100.00% 1 and 2 years after immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion, and 5.93% and 18.15% 1 and 2 years after spraying 26% suspension concentrate of metaldehyde and niclosamide alone. CONCLUSIONS: Immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion is significantly superior to spraying 26% suspension concentrate of metaldehyde and niclosamide along for snail control, and implementation of immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion for more than 2 successive years may achieve a higher snail control efficiency.

[Surveillance of schistosomiasis 34 years after transmission interruption in Songjiang District, Shanghai City].

OBJECTIVE: To analyze the surveillance data after schistosomiasis transmission interruption from 1985 to 2018, so as to provide scientific basis for the future prevention and control of schistosomiasis. METHODS: The data pertaining to snail survey, surveillance of schistosomiasis in humans and livestock, and health education were collected and analyzed in Songjiang District after schistosomiasis transmission interruption from 1985 to 2018. RESULTS: From 1985 to 2018, there were 8 townships, 68 villages and 1 462 settings with snails in Songjiang District, covering an area of 96.399 hm2. There were 4 townships and 59 villages with snails newly identified in previously schistosomiasis non-endemic areas, with emerging snail habitats of 60.161 hm2. A total of 26 148 snails were captured, and no infections were detected. The snail habitats were mainly distributed in the river course, ditches and farmlands, which accounted for 45.28%, 33.17% and 21.55% of total snail habitats, respectively. A total of 245 955 humans were subjected to the serological test, with a positive rate of 0.03%, and 37 humans were subjected to the parasitological test, with 3 positives detected. These three egg-positives were all imported chronic cases with schistosomiasis. A total of 9 109 livestock were detected using the serological test, and no infection was found. Most of the awareness rate of schistosomiasis control knowledge and the rate of correct behavior formation were over 80% in residents and students. CONCLUSIONS: The achievements of schistosomiasis control are consolidated in Songjiang District; however, there are still risk factors of schistosomiasis transmission, including residual snails, snail diffusion and importation of external source of infection. The future surveillance of schistosomiasis should focus on snails and sources of infection.

[Construction and application of the surveillance system for schistosomiasis transmission risk in Sichuan Province].

OBJECTIVE: To build a schistosomiasis transmission risk surveillance system in Sichuan Province, so as to provide technical support for facilitating the progress towards schistosomiasis elimination in the province. METHODS: The surveillance sites for schistosomiasis transmission risk were assigned in 63 endemic counties (districts) of 11 cities (prefectures) in Sichuan Province. During the period from 2015 through 2018, wild feces contamination, the sources of Schistosoma japonicum infections (fever patients, livestock and wild animals), water infectivity in key settings, snail distribution in key settings, and snail breeding risk (snail importation and spread, floating debris carrying snails and snail breeding in ecological wetlands) were monitored in the surveillance sites. RESULTS: From 2015 to 2018, a total of 1 636 wild faces were detected in Sichuan Province, and 3 faces were positive for S. japonicum, with a 0.18% positive rate; among 3 995 livestock and 59 wild mice monitored, no S. japonicum infection was detected. A total of 49 414 fever patients were monitored in 2018, and 493 were seropositive for S. japonicum infection; then, 445 seropositives were subjected to stool examinations, and no egg-positives were found. From 2010 to 2018, a total of 93 sentinel sites were assigned, and 3 994 sentinel mice were placed for monitoring the water infectivity, with one S. japonicum-infected mouse detected. Between 2015 and 2018, a total of 4 156 key settings were investigated covering an area of 1 998.46 hm2, and 668 settings were detected with snails (16.07%), covering an area of 193.26 hm2; 497 suspected settings with a likelihood of snail importation with plant introduction were monitored from 2017 to 2018, and 65 settings with snails were found with 2 673 snails captured; 593 sites were assigned to collect the floating debris from 2017 to 2018, and 9 191.39 kg floating debris were collected with 186 snails captured; 4 wetlands were monitored for the risk of schistosomiasis transmission from 2013 to 2015, and snail breeding was found in 2 wetlands. No S. japonicum infection was identified in snails captured from all surveillance sites. CONCLUSIONS: A sensitive and effective schistosomiasis transmission risk surveillance system has been successfully established in Sichuan Province. There is still a risk of schistosomiasis transmission risk in local areas of Sichuan Province. Therefore, the integrated schistosomiasis control measures with emphasis on the control of the source of S. japonicum infections should be further intensified, and snail monitoring and control and monitoring and control of schistosomiasis in wetlands should be also intensified.

[Investigation on current distribution of Oncomelania snails in schistosomiasis-endemic areas of Sichuan Province].

OBJECTIVE: To understand the current distribution of Oncomelania snails in Sichuan Province, so as to provide scientific evidence for formulating the schistosomiasis elimination strategy and implementing the precision schistosomiasis control measures in the province. METHODS: According to the National Scheme on Oncomelania hupensis Snails in China and the Scheme on Oncomelania hupensis Snails in Sichuan Province, snail surveys were performed in current snail habitats, historical snail habitats and suspected snail habitats using systematic sampling in Sichuan Province from 2016 to 2017, and the survey results were analyzed. RESULTS: From 2016 to 2017, a total of 88 346 settings were surveyed in schistosomiasis-endemic areas of Sichuan Province, and 19 314 settings were detected with snails, covering an area of 4 829.25 hm2, with no Schistosoma japonicum infection identified in snails. A total of 3 017 915 frames were investigated in Sichuan Province, and 1 041 417 frames were found to have living snails, with totally 1 791 115 living snails captured. The mean density of living snails was 0.59 snails/0.1 m2, and the mean percentage of frames with living snails was 34.51% in Sichuan Province. The current snail habitats were mainly distributed in 1 704 villages, 377 townships, 54 counties (districts) of 9 cities (prefectures) across the schistosomiasis-endemic areas of Sichuan Province. Snail habitats were mainly found in ditches (70.22%), and weeds were the predominant vegetation in snail habitats (66.45%). Snails were firstly discovered in Sichuan Province in 1913, and S. japonicum-infected snails were firstly identified in 1956, with the latest identification of S. japonicum-infected snails in 2008. CONCLUSIONS: There are many settings suitable for snail breeding in Sichuan Province, and snail monitoring and control should be intensified in the future.

[Surveillance of epidemic factors of schistosomiasis in wetlands in Sichuan Province].

OBJECTIVE: To investigate the epidemic factors of schistosomiasis in wetlands in Sichuan Province, so as to provide scientific evidence for the prevention and control of schistosomiasis in wetlands. METHODS: The artificial and natural wetlands were selected from Sichuan Province, and the relevant data regarding wetlands were collected. Routine snail survey, investigation on human morbidity due to schistosomiasis, snail diffusion experiments, questionnaire survey, determination of water infectivity and retrospective survey were conducted. RESULTS: In Sichuan Province, the mean densities of living snails were 0.003 snails/0.1 m2 and 2.033 snails/0.1 m2 in the upper and lower reaches of the Meiwan Reservoir wetlands, 0.08 snails/0.1 m2 in the Jinyan Lake of Guanghan City, 0.21 snails/0.1 m2 in Muhe River of Guanghan City, and 0.02 snails/0.1 m2 prior to the construction of Qiong-hai wetland park in Xichang City in 2015. Artificial simulation experiments showed that the largest distance of snail diffusion in water was 2 000 m. There were 8.80% (41/466) of subjects that lived neighboring wetlands, worked in wetlands and visited wet-lands having infested water contact behaviors. A total of 690 sentinel mice were assigned, and no Schistosoma japonicum infection was detected in the 677 mice dissected. Retrospective survey showed that the construction of the Meiwan Reservoir caused the spread of schistosomiasis in Dailing County, and snails were found in the ditches entering the Jinyan Lake and in Jinyan Lake areas 5 years following the construction of the Jinyan Lake in Guanghan City, with S. japonicum -infected snails detected in the ditches entering the Jinyan Lake. CONCLUSIONS: O. hupensis snails are found in some wetlands in Sichuan Province. Protection of wetlands and snail control with environmental improvements are recommended for the prevention of snail importation in natural wetlands, while in artificial wetlands, thorough snail control is recommended during the construction of the wetlands because of the likelihood of snail importation via water systems. In addition, both natural and artificial wetlands require long-term systematic surveillance of schistosomiasis.

[Impact of earthquake disaster on schistosomiasis transmission and emergency prevention and control in Sichuan Province].

Earthquake is a serious natural disaster. The earthquake that occurs in schistosomiasis-endemic areas not only causes direct human and economic losses, but also induces secondary disasters that greatly threaten public health safety in affected areas. This paper analyzed the impact of the 2008 Wenchuan Earthquake and 2013 Lushan Earthquake on schistosomiasis transmission in Sichuan Province, and proposed emergency measures and assessment activitiesresponding to schistosomiasis following earthquake disasters. The experiences from schistosomiasis control after two earthquake disasters in Sichuan Province may provide insights into the emergency control in other regions or after other natural disasters.

[Risk assessment of schistosomiasis transmission in Chuxiong City of Yunnan Province].

OBJECTIVE: To evaluate the potential risk of schistosomiasis transmission so as to provide the evidence for formulating the control strategy. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.