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Objective:To explore the spatial and temporal distribution patterns of emerging snail-infested sites in different environmental types in Yunnan Province.Methods:The data of snail-infested sites in Yunnan Province from 1950 to 2014 (from Yunnan Institute for Endemic Diseases Control and Prevention), were collected and sorted out, a spatial and temporal database on the distribution of emerging snail-infested sites were established, and the changes in the spatial and temporal distribution of emerging snail-infested sites in different environments types (ditches, tangerines, paddy fields, dry land, beaches and other environments) were studied by using spatial autocorrelation analysis and scanning statistics analysis.Results:From 1950 to 2014, the annual number of emerging snail-infested sites in Yunnan Province reached a peak (1 730) in 1955 and then showed a fluctuating downward trend. From 1993 to 2014, the number of emerging snail-infested sites remained below 100, and increased to 160 and 131, respectively, in 2004 and 2013. The longest mean duration of 43.85 years was recorded for the beaches environment for emerging snail-infested sites, followed by the paddy fields environment with a mean duration of 37.01 years, and the shortest mean duration of 20.44 years for the tangerines environment. Spatial autocorrelation analysis showed that there was a positive spatial correlation between the duration of emerging snail-infested sites of different environmental types (global Moran's I ranged from 0.43 to 0.64, P < 0.05). Scanning statistics analysis showed that emerging snail-infested sites of different environmental types had spatial and temporal aggregation ( P < 0.001), with 3- 6 clusters of statistically significant aggregation detected respectively. Conclusion:The emerging snail-infested sites in different environments types in Yunnan Province have spatial and temporal aggregation, and it is necessary to strengthen monitoring and prevention and control of the aggregation areas of different environment types to prevent further spread of the snail.
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Objective To establish a snail control approach for spraying chemicals with drones against Oncomelania hupensis in complex snail habitats in hilly regions, and to evaluate its molluscicidal effect. Methods The protocol for evaluating the activity of spraying chemical molluscicides with drones against O. hupensis snails was formulated based on expert consultation and literature review. In August 2022, a pretest was conducted in a hillside field environment (12 000 m2) north of Dafengji Village, Dacang Township, Weishan County, Yunnan Province, which was assigned into four groups, of no less than 3 000 m2 in each group. In Group A, environmental cleaning was not conducted and 5% niclosamide ethanolamine salt granules were sprayed with drones at a dose of 40 g/m2, and in Group B, environmental cleaning was performed, followed by 5% niclosamide ethanolamine salt granules sprayed with drones at a dose of 40 g/m2, while in Group C, environmental cleaning was not conducted and 5% niclosamide ethanolamine salt granules were sprayed with knapsack sprayers at a dose of 40 g/m2, and in Group D, environmental cleaning was performed, followed by 5% niclosamide ethanolamine salt granules sprayed with knapsack sprayers at a dose of 40 g/m2. Then, each group was equally divided into six sections according to land area, with Section 1 for baseline surveys and sections 2 to 6 for snail surveys after chemical treatment. Snail surveys were conducted prior to chemical treatment and 1, 3, 5, 7 days post-treatment, and the mortality and corrected mortality of snails, density of living snails and costs of molluscicidal treatment were calculated in each group. Results The mortality and corrected mortality of snails were 69.49%, 69.09%, 53.57% and 83.48%, and 68.58%, 68.17%, 52.19% and 82.99% in groups A, B, C and D 14 days post-treatment, and the density of living snails reduced by 58.40%, 63.94%, 68.91% and 83.25% 14 days post-treatment relative to pre-treatment in four groups, respectively. The median concentrations of chemical molluscicides were 37.08, 35.42, 42.50 g/m2 and 56.25 g/m2 in groups A, B, C and D, and the gross costs of chemical treatment were 0.93, 1.50, 0.46 Yuan per m2 and 1.03 Yuan per m2 in groups A, B, C and D, respectively. Conclusions The molluscicidal effect of spraying 5% niclosamide ethanolamine salt granules with drones against O. hupensis snails is superior to manual chemical treatment without environmental cleaning, and chemical treatment with drones and manual chemical treatment show comparable molluscicidal effects following environmental cleaning in hilly regions. The cost of chemical treatment with drones is slightly higher than manual chemical treatment regardless of environmental cleaning. Spraying 5% niclosamide ethanolamine salt granules with drones is recommended in complex settings with difficulty in environmental cleaning to improve the molluscicidal activity and efficiency against O. hupensis snails.
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Objective 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. Methods 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. Results 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). Conclusions 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.
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To evaluate the implementation of Survey of oncomelanid snails (WS/T 563—2017) in schistosomiasis-endemic foci, two schistosomiasis-endemic counties were selected from two provinces of Sichuan and Anhui. Professional staff working in province-, city-, county- and township-level disease control and prevention institutions, parasitic disease control institutions or medical institutions were recruited, and the understanding, use and implementation of Survey of oncomelanid snails (WS/T 563—2017) were investigated using questionnaires and interviews. The awareness, use, proportion of propagation and implementation and correct rate of answering questions pertaining to Survey of oncomelanid snails (WS/T 563—2017) were analyzed. A total of 270 questionnaires were allocated, and 269 were recovered, including 254 valid questionnaires. The overall awareness of Survey of oncomelanid snails (WS/T 563—2017) was 84.64% (215/254), and propagation and implementation of Survey of oncomelanid snails (WS/T 563—2017) was not performed in 23.28% (17/73) of the survey institutions following implementation of Survey of oncomelanid snails (WS/T 563—2017), with meeting training and allocation of propagation materials as the main type of propagation and implementation. Among 254 respondents, 77.16% (196/254) were familiar with the standard, 66.14% (168/254) understood the conditions for use of the standard during snail surveys, and 96.85% (246/254) had the approach for identifying snails. In addition, there were 41.73% (106/254), 50.78% (129/254) and 7.48% (19/254) of respondents that considered the operability of Survey of oncomelanid snails (WS/T 563—2017) was very good, good and general, respectively. The findings demonstrate that the issue and implementation of Survey of oncomelanid snails (WS/T 563—2017) has filled the gap for the standardization of snail control techniques, and which plays an importang guiding role in the national schistosomiasis control program.
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@#Abstract: Objective To establish a sensitive and specific nucleic acid detection method for Schistosoma japonicum based on loop-mediated isothermal amplification (LAMP) and clustered regularly interspaced short palindromic repeats (CRISPR) technology. Methods The LAMP primers, gRNA and ssDNA probe that target Schistosoma japonicum SjR2 genes were designed according to the principles of LAMP and CRISPR. The LAMP-CRISPR reaction system was established and optimized. The sensitivity and specificity of the method were evaluated against the ten-fold serial dilutions of plasmid containing SjR2 target sequences, as well as genomic DNA at different stages of Schistosoma japonicum and other parasites, including Fasciola hepatica, Schistosoma mansoni, Taenia saginata, Clonorchis sinensis, Ascaris lumbricoides, Necator americanus, Paragonimus westermani, and Echinococcus granulosus. Additionally, 15 schistosome-infected snail and 30 uninfected samples were tested by LAMP-CRISPR and LAMP methods, respectively, to evaluate the potential of this method for screening for infected snails. Results The developed LAMP-CRISPR method was able to specifically amplify and detect the SjR2 gene of S. japonicum. The optimal reaction temperature was 37 ℃, and the optimal reaction concentrations were both 40 nmol/L for gRNA and Cas12a protein. No cross-reaction was observed with genomic DNA from other parasites such as F. hepatica. The detection limit of the method was 10 copies/μL when testing 10-fold dilutions of recombinant plasmids as a template. Furthermore, the LAMP-CRISPR method was able to accurately detect genomic DNA from S. japonicum at various stages of development, including eggs, cercariae, schistosomula, juvenile worms, and adult worms. The results of testing 45 snail samples showed no significant difference between the LAMP-CRISPR and LAMP methods for detecting infected snails (χ2=0.05, P>0.05). The sensitivity and specificity of the LAMP-CRISPR method were 100.00% (15/15) and 96.67% (29/30), respectively, compared to the gold standard, while the sensitivity and specificity of the LAMP method were 100.00% (15/15) and 93.33% (28/30), respectively. Conclusions This established LAMP-CRISPR detection method presented good sensitivity, specificity and reliability, making it a promising tool for rapid detection and risk monitoring of S. japonicum.
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ObjectiveTo analyze the monitoring data of schistosomiasis from 2004 to 2021 in Suzhou New District， Jiangsu Province， and to provide evidence for improving schistosomiasis elimination strategies. MethodsFollowing the Opinions on Prevention and Control of Schistosomiasis， Parasitic Diseases and Endemic Diseases in Suzhou and the Technical Plan for Prevention and Control of Schistosomiasis， Parasitic Diseases and Endemic Diseases in Suzhou， the monitoring of schistosomiasis in the population and snail habitats from 2004 to 2021 was conducted. The Mann-Kendall method and Joinpoint regression method were employed to analyze the trend of epidemic indicators （such as seropositive rate， prevalence of snail frames， etc.）. Time series analysis （exponential smoothing model） was conducted to predict snail occurrence. ResultsFrom 2004 to 2021， a total of 73 680 people were serologically tested for schistosomiasis， with a positive rate of 0.084%. The seropositivity rate showed statistically significant differences between different years （χ2=70.73， P<0.05）， but there was no significant trend over time. In addition， 3 053 fecal tests were conducted and no positive result was found. The snail habitats covered an area of 70.11 hm2 and showed a decreasing trend （Z=-1.97， P<0.05）. A total of 30 093 frames were surveyed， of which 19.038% contained snails. The difference in the prevalence of snail frames between different years was statistically significant （χ2=7 203.09， P<0.05）， with a decreasing trend in the prevalence of snail frames （Z=-2.05， P<0.05）. A total of 26 296 live snails were seized and density of live snails was 0.874 snails per frame， showing a decreasing trend in the density of live snails （Z=-2.35， P<0.05）. A total of 12 391 snails were dissected and no infected snail was found. The areas treated with molluscicides remained stable at 264.60 hm2. An area of 27.77 hm2 achieved the goal of snail eradication through environmental modification， with a decreasing trend （Z=-2.44， P<0.05）. It is estimated that the prevalence of snail frames and snail density will remain relatively stable from 2022 to 2026， but the snail habitat area will fluctuate significantly， showing an increasing trend. ConclusionNo indigenous cases of schistosomiasis and no infected snails are reported， indicating the successful consolidation of schistosomiasis prevention and control measures. However， the snail habitat area fluctuates greatly with an increasing trend， suggesting the need for long-term Oncomelania snail monitoring in local areas.
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Objective To evaluate the molluscicidal activity of surfactin against Oncomelania hupensis, so as to provide the experimental basis for use of Bacillus for killing O. hupensis. Methods O. hupensis snails were collected from schistosomiasisendemic foci of Wuhu City on September 2022, and Schistosoma japonicum-infected snails were removed. Then, 60 snails were immersed in surfactin at concentrations of 2, 1, 0.5, 0.25, 0.125 mg/mL and 0.062 5 mg/mL for 24, 48, 72 hours at 26 °C, while ultrapure water-treated snails served as controls. The median lethal concentration (LC50) of surfactin against O. hupensis snails was estimated. O. hupensis snails were immersed in surfactin at a concentration of 24 h LC50 and ultrapure water, and then stained with propidium iodide (PI). The PI uptake in haemocyte was observed in O. hupensis snails using fluorescence microscopy. Results The mortality of O. hupensis was 5.0% following immersion in surfactin at a concentration of 0.062 5 mg/mL for 24 h, and the mortality was 100.0% following immersion in surfactin at a concentration of 2 mg/mL for 72 h, while no snail mortality was observed in the control group. There were significant differences in the mortality of O. hupensis in each surfactin treatment groups at 24 (χ2 = 180.150, P < 0.05), 48 h (χ2 = 176.786, P < 0.05) and 72 h (χ2 = 216.487, P < 0.05), respectively. The average mortality rates of O. hupensis were 38.9% (140/360), 62.2% (224/360) and 83.3% (300/360) 24, 48 h and 72 h post-immersion in surfactin, respectively (χ2 = 150.264, P < 0.05), and the 24, 48 h and 72 h LC50 values of surfactin were 0.591, 0.191 mg/mL and 0.054 mg/mL against O. hupensis snails. Fluorescence microscopy showed more numbers of haemocytes with PI uptake in 0.5 mg/mL surfactintreated O. hupensis snails than in ultrapure water-treated snails for 24 h, and there was a significant difference in the proportion of PI uptake in haemocytes between surfactin-and ultrapure water-treated snails (χ2 = 6.690, P < 0.05). Conclusion Surfactin is active against O. hupensis snails, which may be associated with the alteration in the integrity of haemocyte membrane.
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Objective To identify the spatial distribution pattern of Oncomelania hupensis spread in Hubei Province, so as to provide insights into precision O. hupensis snail control in the province. Methods Data pertaining to emerging and reemerging snails were collected from Hubei Province from 2020 to 2022 to build a spatial database of O. hupensis snail spread. The spatial clustering of O. hupensis snail spread was identified using global and local spatial autocorrelation analyses, and the hot spots of snail spread were identified using kernel density estimation. In addition, the correlation between environments with snail spread and the distance from the Yangtze River was evaluated using nearest-neighbor analysis and Spearman correlation analysis. Results O. hupensis snail spread mainly occurred along the Yangtze River and Jianghan Plain in Hubei Province from 2020 to 2022, with a total spread area of 4 320.63 hm2, including 1 230.77 hm2 emerging snail habitats and 3 089.87 hm2 reemerging snail habitats. Global spatial autocorrelation analysis showed spatial autocorrelation in the O. hupensis snail spread in Hubei Province in 2020 and 2021, appearing a spatial clustering pattern (Moran’s I = 0.003 593 and 0.060 973, both P values < 0.05), and the mean density of spread snails showed spatial aggregation in Hubei Province in 2020 (Moran’s I = 0.512 856, P < 0.05). Local spatial autocorrelation analysis showed that the high-high clustering areas of spread snails were mainly distributed in 50 settings of 10 counties (districts) in Hubei Province from 2020 to 2022, and the high-high clustering areas of the mean density of spread snails were predominantly found in 219 snail habitats in four counties of Jiangling, Honghu, Yangxin and Gong’an. Kernel density estimation showed that there were high-, secondary high- and medium-density hot spots in snail spread areas in Hubei Province from 2020 to 2022, which were distributed in Jingzhou District, Wuxue District, Honghu County and Huangzhou District, respectively. There were high- and medium-density hot spots in the mean density of spread snails, which were located in Jiangling County, Honghu County and Yangxin County, respectively. In addition, the snail spread areas negatively correlated with the distance from the Yangtze River (r = −0.108 9, P < 0.05). Conclusions There was spatial clustering of O. hupensis snail spread in Hubei Province from 2020 to 2022. The monitoring and control of O. hupensis snails require to be reinforced in the clustering areas, notably in inner embankments to prevent reemerging schistosomiasis.
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Objective To investigate ecological isolation between Oncomelania hupensis snail populations in hilly regions and marshland and lake regions in Yuanjiang valley, Changde City, Hunan Province, and to unravel its underlying mechanisms. Methods Taoyuan County, Shimen County, Linli County and Lixian County in Changde City were selected as snail sampling sites in hilly regions, and Lixian County, Jinshi City, West Lake Administration District, Hanshou County and Dingcheng District were selected as snail sampling sites in marshland and lake areas. Cytochrome C oxidase 1 (cox 1) gene was amplified in snail samples and sequenced. The genetic sequences of O. hupensis snails were aligned using the software MEGA 11, and the haplotypes of O. hupensis snails were determined using the software DNASP 5.10.01. The phylogenetic tree was generated using Bayesian inference with the software MrBayes 3.2, and analysis of molecular variance (AMOVA) was performed to analyze the source of genetic divergence and estimate the genetic divergence index (FST) among snail populations with the software Arlequin 3.5.2.2. The genetic barrier among 11 O. hupensis snail populations was estimated using the Monmonier algorithm of adegenet toolkit in R package. The settings with “land in winter and water in summer” in the Yuanjian River section were divided into two categories according to the upstream and downstream, and the areas with “land in winter and water in summer” in the upstream and downstream were transformed into raster data, and then loaded into the software Fragstats 4 for analysis of landscape indicators. The trends in changes of digital elevation were extracted from the Yuanjiang River section based on the digital elevation model, and made three-dimensional visualization using the R package. Results The mitochondrial cox 1 gene were amplified in 165 O. hupensis snais from 11 sampling sites and sequenced, and a total of 152 valid gene sequences were obtained, with 46 haplotypes or 9 populations determined. No haplotype was shared in snails between Taoyuan County and Dingcheng District and Hanshou County along the downstream of the Yuanjiang River. The total area of settings with “land in winter and water in summer” was 617.66 hm2 in the upsteram of the Yuanjiang River, which consisted of 473 patches, with each patch measuring 1.31 hm2, the largest area index of 0.735 2, the landscape division index of 0.999 9, and the landscape shape index of 45.293 7. The total area of settings with “land in winter and water in summer” was 9 956.92 hm2 in the downstream of the Yuanjiang River, which consisted of 771 patches, with each patch measuring 12.91 hm2, the largest area index of 97.839 9, the landscape division index of 0.042 7, and the landscape shape index of 7.249 6. The area of settings with “land in winter and water in summer” was much larger in the downstream than that in the upstream of the Yuanjiang River, and the stronger landscape connectivity and non-remarkable alteration of riverbed elevation provided suitable habitats for snail breeding. Conclusion The hydrological and environmental characteristics of the upstream of the Yuanjiang River restrain the breeding and spread of O. hupensis, resulting in ecological isolation between Oncomelania hupensis in Taoyuan County and those in the downstream of Yuanjiang River.
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Objective To optimize the culture and fermentation conditions of the Penicillium aurantiocandidum Z12 strain, a fungal strain with molluscicidal actions against Oncomelania hupensis, so as to provide the basis for the research and development of molluscicidal active substances from the P. aurantiocandidum Z12 strain and its fermentation broth and large-scale fermentation. Methods The carbon source, nitrogen source and mineral salts were identified in the optimal culture medium for the P. aurantiocandidum Z12 strain with a single-factor experiment to determine the best fermentation condition for the P. aurantiocandidum Z12 strain. Factors that significantly affected the growth of the P. aurantiocandidum Z12 strain were identified using the Plackett-Burman design, and the best range of each factor was determined using the steepest climb test. Response surface analyses of temperature, pH value, seeding amount and liquid-filling quantity were performed using the Box-Behnken design to create a regression model for fermentation of the P. aurantiocandidum Z12 strain to identify the optimal culture medium. Results Single-factor experiment preliminarily identified the best culture medium and conditions for the P. aurantiocandidum Z12 strain as follows: sucrose as the carbon source at approximately 20 g/L, tryptone as the nitrogen source at approximately 5 g/L, K2HPO4 as the mineral salt at approximately 5 g/L, initial pH at approximately 8, temperature at approximately 28 °C, seeding amount at approximately 6%, and liquid-filling quantity at approximately 50 mL/100 mL. Plackett-Burman design showed that factors that significantly affected the growth of the P. aurantiocandidum Z12 strain included temperature (t = −5.28, P < 0.05), seeding amount (t = 5.22, P < 0.05), pH (t = −4.30, P < 0.05) and liquid-filling quantity (t = −4.39, P < 0.05). Steepest climb test showed the highest mycelial growth at pH of 7.5, seeding amount of 8%, and liquid-filling quantity of 40 mL/100 mL, and this condition was selected as the central point of response surface analysis for the subsequent optimization of fermentation conditions. Response surface analyses using the Box-Behnken design showed that the optimal conditions for fermentation of the P. aurantiocandidum Z12 strain included sucrose at 15 g/L, tryptone at 5 g/L, K2HPO4 at 5 g/L, temperature at 28.2 °C, pH at 7.5, seeding amount at 10%, and liquid-filling quantity at 35.8 mL/100.0 mL, resulting in 0.132 g yield of the P. aurantiocandidum Z12 strain. Conclusion The optimal culture condition for the P. aurantiocandidum Z12 strain has been identified, and the optimized culture medium and fermentation condition may effectively improve the fermentation yield of the P. aurantiocandidum Z12 strain.
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Objective@#To compare the effectiveness before and after the adjustment of schistosomiasis control strategies in Nanjing City, so as to provide the evidence for improving schistosomiasis control interventions.@*Methods@#The prevalence of Schistosomasis japonicum infections in humans, livestock, Oncomelania hupensis and sentinel mice was collected in Nanjing City from 1993 to 2018, and the prevalence of S. japonicum infections in humans, livestock, sentinel mice and O. hupensis, and the areas of snail habitats, areas of infected snail habitats and snail control areas were compared before (1993-2004) and after (2005-2018) the adjustment of schistosomiasis control strategies to evaluate the effectiveness.@*Results@#The prevalence of S. japonicum infections in humans, livestock, O. hupensis and sentinel mice was 0.77% and 0.02% (χ2=6 430.634, P<0.001), 0.46% and 0.01% (χ2=344.401, P<0.001), 0.19% and 0.11% (χ2=239.685, P<0.001), and 34.35% and 1.56% (χ2=1 856.286, P<0.001) in Nanjing City before and after the adjustment of schistosomiasis control strategies, respectively. The median areas (interquartile range) of snail habitats, infected snail habitats and snail control were 4 175.37 (1 301.65) and 2 366.44 (885.27) hm2 (Z=-3.755, P<0.001), 870.49 (1 001.75) and 0 (158.89) hm2 (Z=-3.654, P<0.001) and 1 383.23 (793.57) and 5 031.94 (629.11) hm2 (Z=-4.320, P<0.001) in Nanjing City before and after the adjustment of schistosomiasis control strategies, respectively.@*Conclusions@#After the adjustment of schistosomiasis control strategies, remarkable effects on schistosomiasis control has achieved in Nanjing City, where the transmission of schistosomiasis was interrupted. Nevertheless, the strategy requires to be continued and improved to move towards elimination of schistosomiasis in Nanjing City.
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Objective To screen the targets of traditional Chinese medicine-derived potential plant molluscicides based on network pharmacology and explore the mechanisms of molluscicidal actions. Methods The traditional Chinese medicines with molluscicidal actions were screened based on retrospective literature reviews, and their molluscicidal efficiency was summarized. The active ingredients and potential targets of traditional Chinese medicines were captured from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform, Unified Protein Database and literature mining using network pharmacology. The drug-active ingredient-target network was created using the software Cytoscape 3.7.2, and the key targets were subjected to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis using the Metascape software. Results A total of 27 types of snail control drugs derived from traditional Chinese medicines were screened from publications and classified into 14 categories. Network pharmacology identified 190 active ingredients, and the active ingredients with a high degree in the drug-active ingredient-target network included quercetin, linoleyl acetate, luteolin, beta-carotene, (24S)-ethylcholesta-5,22,25-trans-3beta-ol, fumarine and arctiin, with 181 corresponding potential targets screened. KEGG pathway enrichment analysis revealed that these targets were mainly located in 16 pathways, including the neuroactive ligand-receptor interactions, regulation of adipocyte lipolysis and adrenergic signal in myocardial cells. Conclusions This study preliminarily demonstrates the multi-ingredient, multi-target and multi-pathway mechanisms of action of 27 molluscicides. The screened key ingredient may provide the basis for isolation, purification and pharmacological studies of molluscicides, and the screened key targets and key pathways may facilitate the illustration of mechanisms of actions of traditional Chinese medicine-derived molluscicides and development of novel green molluscicides.
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Objective To evaluate the molluscicidal effect of 25% wettable powder of pyriclobenzuron sulphate (WPPS) against Oncomelania snails in hilly schistosomiasis-endemic regions and test its toxicity to fish. Methods In October 2020, a snail-infested setting which had been cleared was selected in Nanjian County, Yunnan Province and divided into several blocks, and the natural snail mortality was estimated. 25% WPPS was prepared into solutions at concentrations of 1 and 2 g/L, and 25% wettable powder of niclosamide ethanolamine salt (WPNES) was prepared into solutions at a concentration of 2 g/L. The different concentrations of drugs were sprayed evenly, and the same amount of water was used as blank control. Snails were surveyed using the systematic sampling method 1, 3 and 7 days post-treatment, and snail survival was observed. A fish pond was selected in Nanjian County, and 2 kg 25% WPPS was evenly sprayed on the water surface to allow the effective concentration of 20 g/L. Fish mortality was estimated 8, 24, 48 and 72 h post-treatment. Results One-day treatment with 1 and 2 g/L WPPS and 2 g/L WPNES resulted in 97.99%, 97.99% and 94.11% adjusted snail mortality rates (χ2 = 3.509 and 3.509, both P values > 0.05), and the adjusted snail mortality was all 100% 3 d post-treatment with 1 and 2 g/L WPPS and 2 g/L WPNES, while 7-day treatment with 1 and 2 g/L WPPS and 2 g/L WPNES resulted in 91.75%, 86.57% and 57.76% adjusted snail mortality rates (χ2 = 14.893 and 42.284, both P values < 0.05). Treatment with 2 g/L WPPS for 72 h resulted in a 0.67% cumulative mortality rate of fish. Conclusion 25% WPPS is effective for snail control and highly safe for fish, which is feasible for use in hilly schistosomiasis-endemic regions.
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Objective To investigate the morphological variation of Oncomelania hupensis shells in Yunnan Province, so as to provide insights into the understanding of O. hupensis genetic evolution and control. Methods According to the O. hupensis density, geographical location, altitude, water system and environmental type, 12 administrative villages were sampled from 10 schistosomiasis-endemic counties (districts) in 3 prefectures (cities) of Yunnan Province as snail collection sites. From December 2021 to January 2022, about 200 snails were collected from each collection site, among which thirty adult snails (6 to 7 spirals) were randomly selected from each site, and the 11 morphological indexes of snail shells were measured and subjected to cluster analysis and principal component analysis. Results Of O. hupensis snails from 12 localities of Yunnan Province, the longest shell (7.33 mm) was detected in snails from Yongle Village, Eryuan County, with the shortest (4.68 mm) in Dongyuan Village, Gucheng District, and the largest angle of apex (59.47°) was measured in snails from Caizhuang Village, Midu County, with the smallest (41.40°) in Qiandian Village, Eryuan County. The mean coefficient of variation was 9.075% among O. hupensis snails from 12 localities of Yunnan Province, with the largest coefficient of variation seen in the thickness of the labra brim (29.809%). Among O. hupensis snails from 12 localities of Yunnan Province, the mean Euclidean distance was 2.26, with the shortest Euclidean distance seen between O. hupensis snails from Qiandian Village of Eryuan County and Wuxing Village of Dali City (0.26), and the largest found between O. hupensis snails from Caizhuang Village of Midu County and Cangling Village of Chuxiong County (8.17). Cluster analysis and principal component analysis classified O. hupensis snails from 12 localities of Yunnan Province into three categories, including the O. hupensis snail samples from Caizhuang Village of Midu County, O. hupensis snail samples from Cangling Village of Chuxiong County, and O. hupensis snail samples from Qiandian Village of Eryuan County, Wuxing Village of Dali City, Yangwu Village of Yongsheng County, Xiaoqiao Village of Xiangyun County, Yongle Village of Eryuan County, Xiaocen Village of Dali City, Anding Village of Nanjian County, Dongyuan Village of Gucheng District, Lianyi Village of Heqing County, and Dianzhong Village of Weishan County. The variations in these three categories of snail samples were mainly measured in the principal component 2 related to the angle of apex and the thickness of the labra brim. Conclusions The variations in the Euclidean distance and morphological features of shells of O. hupensis from 12 localities of Yunnan Province gradually rise with the decrease in the latitude of the collection sites. The angle of apex is an indicator for the growth of O. hupensis whorl.
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Oncomelania hupensis is the only intermediate host of Schistosoma japonicum, and O. hupensis control is an important measure for schistosomiasis control. With the progress of national schistosomiasis control program, the prevalence of schistosomiasis is low in China; however, there are still multiple challenges for O. hupensis breeding and schistosomiasis transmission risk. Considering the target of the national schistosomiasis elimination program and environmental protection in the new era, the introduction of precision identification, precision interventions and precision assessment into O. hupensis control may facilitate the progress towards elimination of schistosomiasis in China.
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@#Abstract: Objective To analyze the impact of the flood disaster on the distribution of Oncomelania snails in 2020 in Wuhu City, to provide scientific basis for formulating the "14th Five-Year Plan" for schistosomiasis control and precise prevention and control measures in Wuhu City. Methods Systematic sampling combined with environmental spot check was used to investigate the distribution of snails in the historical snail's environment, existing snail's environment and suspected snail's environment in Wuhu City. The collected snails were crushed and examined by microscope to understand the death and life of snails and the infection of Schistosoma japonicum, and the density of live snails and other indicators were counted. Results The historical area of snails was 14 475.24 hm2 in Wuhu City, and the existing area of snails was 4 588.72 hm2, including 4 210.32 hm2 for lake type and 378.40 hm2 for hill type snails. The average occurrence rate of live snails was 14.59%, and the average density of live snails was 0.50 snails/0.1 m2 in Wuhu City. There were 2 745 snail breeding environments, of which 491 were lake type and 2 254 are hill type, accounting for 17.89% and 82.11% respectively. The existing snail area was mainly distributed in the beaches and ditches, accounting for 92.51% and 6.29% of the existing snail area respectively. Some snails were distributed in ponds, paddy fields and other environments. Among all the historical snail habitats, the majority were class Ⅱ and class Ⅲ environments (which still have the basic conditions for snail breeding at present), with a total of 1 739 sites (blocks), accounting for 63.35% of the total environment. No schistosomiasis infected snails have been found, and the newly discovered and recovered snails cover an area of 268.21 hm2 in Wuhu City. Conclusions The distribution of snails is extensive in Wuhu City, and snails are mostly distributed in beaches, which are vulnerable to the impact of flood disasters. The spread of Oncomelania snails is found in 30 marshlands in 3 counties in this survey. It is necessary to continue to strengthen snail monitoring after disasters, and take class Ⅱ and class Ⅲ environments as key areas for snail monitoring, so as to find, identify and evaluate the risk of schistosomiasis transmission as soon as possible, to avoid or reduce the impact of flood disasters on the process of schistosomiasis control, and promote the process of schistosomiasis elimination.
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Objective 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. Methods 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. Results 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). Conclusion 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.
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Objective To investigate the effectiveness and cost of 50% and 80% wettable powder of niclosamide ethanolamine salt (NESWP) and 26% metaldehyde and niclosamide suspension concentrate (MNSC) in hilly schistosomiasis-endemic regions, so as to provide insights into the selection of chemical molluscicides in hilly regions. Methods In September 2020, a wasteland in Guanshanqiao Village, Yanrui Township, Yushan County of Jiangxi Province was selected as the experimental region, which was sectioned into five blocks and defined as four experimental groups (A1, A2, B, C) and a blank control group (D). 80% NESWP were given at doses of 1 g/m2 and 1.5 g/m2 in groups A1 and A2 using the spraying method, 50% NESWP was given at a dose of 2 g/m2 in Group B using the spraying method, and 26% MNSC was at a dose of 4 g/m2 in Group C using the spraying method, while no chemical treatment was given in Group D. Snail survey was performed using a systematic sampling method before chemical treatment and 1, 3, 7 d and 15 d post-treatment to examine the molluscicidal effect, and all molluscicidal costs were estimated to calculate the cost of chemical treatment per 1 m2 and the cost of the reduction in the mean density of living snails per 1%. Results The highest mortality of snails was 78.95% and the lowest density of living snails was 0.2388 snails/0.1 m2 in the experimental groups within 7 d of chemical treatment, and the highest mortality of snails was 94.74% and the lowest density of living snails was 0.058 0 snails/0.1 m2 7 d post-treatment. There were no significant differences in the snail mortality among the A1, A2, B and C groups 1 (χ2 = 2.250, P > 0.05), 3 (χ2 = 1.779, P > 0.05) or 15 d post-treatment (χ2 = 2.286, P > 0.05), while a significant difference was detected in the snail mortality among the four groups 7 d post-treatment (χ2 = 7.990, P = 0.046). In addition, there were no significant differences in the snail mortality between A1 and A2 groups 1 (χ2 = 0.724, P > 0.05), 3 (χ2 = 0.584, P > 0.05), 7 (χ2 = 0.400, P > 0.05) or 15 d post-treatment (χ2 = 0.251, P > 0.05). The costs of chemical treatment per 1 m2 were 0.58, 0.60, 0.64 Yuan and 0.73 Yuan in groups A1, A2, B and C, and the costs of the mean density of living snail per 1% reduction were 19.29, 20.44, 21.68 Yuan and 23.53 Yuan in groups A1, A2, B and C, respectively. Conclusion 80% NESWP shows a high molluscicidal efficacy and low cost in hilly schistosomiasis-endemic regions.
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Objective To evaluate the impact of water pollutants, water levels and meteorological factors on the Oncomelania hupensis density in Eastern Dongting Lake regions, so as to provide insights into schistosomiasis control. Methods O. hupensis snails were surveyed using a systematic sampling method in snail-infested marshlands in Eastern Dongting Lake regions from 2007 to 2014, and data pertaining to water pollutants, water levels and meteorological factors were collected. The duration of submergence and the date of the start of submergence were calculated. The snail density and its influencing factors were descriptively analyzed, and a linear mixed model was generated to examine the impacts of variables on the snail density. In addition, smooth curves were fitted to investigate the relationship between snail density and variables. Results The snail density appeared a fluctuation in Eastern Dongting Lake regions during the period from 2007 to 2014, with the highest density on October, 2010 (52.79 snails/0.1 m2) and the lowest density on January 2009 (2.15 snails/0.1 m2). Linear mixed-model analysis showed that permanganate index, total phosphorus and the date of the start of submergence affected the snail density (t = 6.386, −2.920 and −3.892, all P values < 0.01). Smooth curve analysis revealed that the associations of the snail density with the permanganate index and total phosphorus appeared an approximately quadratic curve. After the end of April, the earlier date of the start of submergence resulted in a higher snail density. Conclusion Permenganate index, total phosphorus and the date of the start of submergence affect the O. hupensis snail density in Eastern Dongting Lake regions.
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Objective To establish a deep learning-based visual model for intelligent recognition of Oncomelania hupensis, the intermediate host of Schistosoma japonicum, and evaluate the effects of different training strategies for O. hupensis image recognition. Methods A total of 2 614 datasets of O. hupensis snails and 4 similar snails were generated through field sampling and internet capture, and were divided into training sets and test sets. An intelligent recognition model was created based on deep learning, and was trained and tested. The precision, sensitivity, specificity, accuracy, F1 score and Youden index were calculated. In addition, the receiver operating characteristic (ROC) curve of the model for snail recognition was plotted to evaluate the effects of “new learning”, “transfer learning” and “transfer learning + data enhancement” training strategies on the accuracy of the model for snail recognition. Results Under the “transfer learning + data enhancement” strategy, the precision, sensitivity, specificity, accuracy, Youden index and F1 score of the model were 90.10%, 91.00%, 97.50%, 96.20%, 88.50% and 90.51% for snail recognition, which were all higher than those under both “new learning” and “transfer learning” strategies. There were significant differences in the sensitivity, specificity and accuracy of the model for snail recognition under “new learning”, “transfer learning” and “transfer learning + data enhancement” training strategies (all P values < 0.001). In addition, the area under the ROC curve of the model was highest (0.94) under the “transfer learning + dataenhancement” training strategy. Conclusions This is the first visual model for intelligent recognition of O. hupensis based on deep learning, which shows a high accuracy for snail image recognition. The “transfer learning + data enhancement” training strategy is helpful to improve the accuracy of the model for snail recognition.