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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.
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Objective To investigate the reasons of natural extinction of Oncomelania hupensis snails by comparing the difference of the water chemical properties between the snail-breeding marshland and non-snail marshland in Eastern Dongting Lake areas. Methods Three adjoining marshlands in Eastern Dongting Lake areas were selected, one was a snail-breeding marshland, the second was a non-snail marshland, and the third was a boundary zone between them. During the periods of water-rising season, wet season and water-falling season, the water samples from the bottom of 0.5 m were collected by the systematic random sampling method (200 m × 200 m grid method). In addition, the water samples below the surface of 0.5 m were also collected in the wet season. The physicochemical indexes of the sampling water were detected. Results According to the Surface Water Environmental Quality Standard (GB 3838–2002), the water quality indicators which were less than the detection limit were Cr, Cd, Zn, Hg, Cu, S－ and CN－ during the three sampling seasons. The pollutants which were slightly higher than Grade III but lower than Grade IV (Hg ≤ 1 μg/L, TP ≤ 0.1 mg/L) were Hg and TP. The pollutants below the Grade III included As and F－. The temperature and pH values were within the Grade III. The oxygen consumption indicators covering DO, COD and BOD in the water-rising season and wet season were within the Grade III, while the value of BOD was beyond the scope of Grade III but was between Grade Ⅳ (≤ 6 mg/L) and Grade V (≤ 10 mg/L) in the water-falling season. The differences of the water pollution indexes between the snail-breeding marshland and non-snail marshland were statistically significant, and these indexes included F－, As and pH in the water-rising season (P < 0.05); pH, BOD and Fat the surface layer in the wet season (P < 0.05); F－ at the bottom in the wet season (P < 0.05); TP and F－ in the water-falling season. Moreover, the above-mentioned indexes in the non-snail marshland of Qianliang Lake were higher than those in the snail-breeding marshland of Junshan Park. Thus, F－ was the only index which had statistical differences in every sampling season, and the concentration of F－ at the non-snail marshland was also higher than that at the snail-breeding marshland. In the water-rising season, the pH value at the non-snail marshland exceeded the suitable range for the growth of snails (6.8 to 7.8). Conclusion In the Eastern Dongting Lake area, the high concentration of F－ and pH of water may be responsible for the natural extinction of O. hupensis snails.
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Objective To investigate the reasons of natural extinction of Oncomelania hupensis snails by comparing the difference of the water chemical properties between the snail-breeding marshland and non-snail marshland in Eastern Dongting Lake areas. Methods Three adjoining marshlands in Eastern Dongting Lake areas were selected, one was a snail-breeding marshland, the second was a non-snail marshland, and the third was a boundary zone between them. During the periods of water-rising season, wet season and water-falling season, the water samples from the bottom of 0.5 m were collected by the systematic random sampling method (200 m × 200 m grid method). In addition, the water samples below the surface of 0.5 m were also collected in the wet season. The physicochemical indexes of the sampling water were detected. Results According to the Surface Water Environmental Quality Standard (GB 3838–2002), the water quality indicators which were less than the detection limit were Cr, Cd, Zn, Hg, Cu, S－ and CN－ during the three sampling seasons. The pollutants which were slightly higher than Grade III but lower than Grade IV (Hg ≤ 1 μg/L, TP ≤ 0.1 mg/L) were Hg and TP. The pollutants below the Grade III included As and F－. The temperature and pH values were within the Grade III. The oxygen consumption indicators covering DO, COD and BOD in the water-rising season and wet season were within the Grade III, while the value of BOD was beyond the scope of Grade III but was between Grade Ⅳ (≤ 6 mg/L) and Grade V (≤ 10 mg/L) in the water-falling season. The differences of the water pollution indexes between the snail-breeding marshland and non-snail marshland were statistically significant, and these indexes included F－, As and pH in the water-rising season (P < 0.05); pH, BOD and Fat the surface layer in the wet season (P < 0.05); F－ at the bottom in the wet season (P < 0.05); TP and F－ in the water-falling season. Moreover, the above-mentioned indexes in the non-snail marshland of Qianliang Lake were higher than those in the snail-breeding marshland of Junshan Park. Thus, F－ was the only index which had statistical differences in every sampling season, and the concentration of F－ at the non-snail marshland was also higher than that at the snail-breeding marshland. In the water-rising season, the pH value at the non-snail marshland exceeded the suitable range for the growth of snails (6.8 to 7.8). Conclusion In the Eastern Dongting Lake area, the high concentration of F－ and pH of water may be responsible for the natural extinction of O. hupensis snails.
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Objective To investigate the seasonal fluctuations of mosquitoes in Taibai Lake area of Jining City,and evaluate the application effects of two mosquito trapping tools(Gongfu Xiaoshuai mosquito lamp and WJ-C mosquito sampler),so as to provide references for the effective surveillance,prevention and control of local mosquito vectors.Methods The overnight cap-ture of mosquitoes with a man-bait net trap,Gongfu Xiaoshuai mosquito lamp,and WJ-C mosquito sampler was performed to col-lect mosquitoes.The species of adult mosquitoes and seasonal fluctuations were investigated and analyzed.Results A total of 10 914 mosquitoes belonging to 13 species,5 genera were collected with the overnight capture of mosquitoes with the man-bait net trap,and Culex tritaeniorhynchus,Cx.pipiens palllen and Mansonia uniformis were the dominant species,accounting for 77.41％of the total.The proportion of Coquillettidia ochracea increased significantly.All the adult mosquitoes appeared in June,and reached the density peak in July and August.Both of the two surveillance tools showed relatively sensitive capture perfor-mance against mosquitoes.The trapping results of WJ-C mosquito sampler were basically the same as the man-bait trapping meth-od,however,the amount of Mansonia uniformis and Coquillettidia ochracea collected by Gongfu Xiaoshuai mosquito lamp was significantly lower than that of the man-bait trapping method.Conclusions The mosquito species are varied in Taibai Lake area of Jining City.Therefore,monitoring should be strengthened.In addition,the two mosquito trapping tools are sensitive,but they have both advantages and disadvantages,thus we should better pay attention to the consistency of monitoring methods in use.
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Objective To understand the present situation of the chronic schistosomiasis patients'knowledge,attitude and practice on schistosomiasis control in Nanchang City. Methods The knowledge,attitude and values on schistosomiasis control of 523 chronic schistosomiasis patients in Nanchang County,Jinxian County and Xinjian District in the Poyang Lake District were investigated with questionnaires. And the accuracy rates of the knowledge,attitude and practice among the patient groups of different counties,genders,age groups,occupations and educational levels were analyzed. Results The accuracy rates of the knowledge,attitude and practice of patients on schistosomiasis control were 95.76%,82.80%,and 81.73% in Nanchang County;91.37%,93.32%,and 76.48%in Jinxian County;88.25%,67.56%,and 49.40%in Xinjian District. In the accuracy rates of knowledge,attitude and practice,the differences among the three counties (districts) were statistically significant (χ2=57.511-301.378,all P<0.05). Conclusions The accuracy rates of chronic schistosomiasis patients'attitude and prac-tice on schistosomiasis control in Nanchang City remain low. Therefore,the intensity of attitude and practice intervention should be strengthened in the Poyang Lake District in order to enhance the self-protection awareness of the patients.
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Objective To evaluate the long?term effect of the comprehensive control strategy for schistosomiasis with empha?sis on infectious source control in marshland?type endemic areas of Poyang Lake. Methods Three heavy endemic villages with schistosomiasis in the lake areas were selected as pilots for the comprehensive control strategy which included replacing bovine with tractors and forbidding grazing on marshlands. The data of schistosome infections of residents and Oncomelania hupensis snails were collected and analyzed statistically from 2009 to 2014. Results There were no patients with schistosomiasis through feces examinations in the 3 pilot villages. The average density of live snails in Niuzhou marshland showed a decline trend and the density was stable in Liulingwei marshland. There were no infected snails in the 2 marshlands and no schistosome adult worms were found in the sentinel rats Conclusion The implantation of the comprehensive control strategy for schistosomiasis with em?phasis on infectious source control can control the prevalence of schistosomiasis during a long period.
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Objective To classify and grade the environments with Oncomelania hupensis snails inside embankment in marsh-land and lake areas,so as to improve the work efficiency and realize the systematic management. Methods The schistosomiasis endemic area Liaodi and Xiongdi villages in Jiangling County,Hubei Province were selected as the experiment villages,and the environments with snails in the two villages were divided into sections with a length of 500m,then the snail situation were sur-veyed by the systematic sampling method with 10m and 50m a frame respectively. The environments were classified according to the discovery of infected snails and wild fecal contamination,and the numbers of sites with snails and their areas in different class-es were recorded. Meanwhile,the data of sites with infected snails in Jingzhou City during the recent 5 years were collected and graded according to the average density of snails,so as to discuss the correlativity between the grades of environments with snails and the numbers of sites with infected snails and the occurrence rate of frames with snails. Results There were 1 967 sites with in-fected snails in Jingzhou City during the recent 5 years,and there was a positive correlation between the grades of environments with snails and the occurrence rate of frames with snails(rs=0.77,P0.05),but the time-consuming of the former was 3 times of the latter. Conclusions The classification and grading of the environments with snails inside embankment in marshland and lake areas can master the key point of the snail survey. The subsection and setting frames at a suitable distance can save time and manpower,improve work efficiency,as well as understand the distribution of snail status of the environment with snails,which can realize the sort management of the snail envi-ronments inside embankment.
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Objective To understand the characteristics of schistosome cercarial infested water contact of residents in Poyang Lake endemic areas after the operation of Three Gorges Project,so as to provide the evidence for formulating a well-directed con-trol strategy. Methods The residents in two villages in schistosomiasis endemic areas were selected and surveyed for their activi-ties of infested water contacts by questionnaire. Results The proportion and frequency of infested water contacts of residents in Poyang Lake region were high and the average rate of infested water contacts was 69.77%,and 98.96%of infested water contacts occurred in spring,summer and autumn. The main ways of infested water contacts were fishing/swimming/playing for adult men, washing clothes/fishing for adult women,and swimming/playing for school children,respectively. The rates of infested water con-tacts were 73.33%,71.63%and 61.87%in adult men,women and school children,respectively. The frequencies of infested water contacts>1 time/week,1 time/week-1 time/month,and<1 time/month were 62.61%,23.74%and 13.66%respectively. Conclu-sions The infested water contacts mainly occurs in spring,summer and autumn,and the main way of infested water contacts was fishing. Farming and mowing grass,which had been the primary way,now become the secondary way for the adult residents.
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Objective To detect the snail habitats from the marshland of Eastern Dongting Lake Area, using the Remote Sensing (RS) and Geographic Information System (GIS) technology based on the China-Brazil Earth Resources Satellite-02B (CBERS-02B) CCD images. Methods According to the two typical traits of snail habitats in marshland including "water in summer and land in winter" and "no grass, no snails" , the "water in summer and land in winter" region and the vegetation coverage region were calculated by RS image processing respectively. The two regions mentioned above were then overlapped to confirm the snail habitats through comparing with the data from field survey under spatial overlapping of Arcgis as the last step. Results In Eastern Dongting Lake area, the "water in summer and land in winter" region and vegetation coverage region were predicted based on the formula normalized difference water index (NDWI) >0.01 and normalized difference vegetation index (NDVI) >0.36, respectively. The snail habitat was determined by theme overlay of the two regions said above.The agreement rate between the prediction and the geospatial data of field survey was 93.55% , which demonstrated the final results were credible and reliable. Conclusion CBERS-02B image could be used to detect the snail habitats and to monitor the changes of them, so as to find out the characteristics of distribution and the trends of diffusion. The snail index (discriminant 1 and 2) seemed to be suitable for the detection of snail habitats in the marshland of Lake area and used for the programs of snail control.
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Objective To explore the impact and regularity of snail population after changing of water level and to develop effective control and prediction programs. Methods A typical snail habitat closed to Changjiang county in Yueyang city, Hunan province was selected as the survey field.Data on water level and the changing trend of snail population during 2001-2009 including the average water level, maximum and minimum water levels, snail and infected snail densities,proportion of sampling frames with living and infected snails etc. were collected. The distribution of water level and snail indexes were described and a general additive model(GAM)for the relationships between these indexes were also fitted. Results Impacts of the average water level and the watered-out days in current year in the surveyed field on the snail density were statistically significant(P＜0.01), showing a quadratic curve association. The snail density remained at the lowest level when the average water level was at 25.0 m and the surveyed field watered-out days was 120. The average water level in current year and the field watered-out days in the past year showed statistically significant impacts on the infected snail density(P＜0.001), the proportion of sampling frames with infected snails(P＜0.05)and living snails(P value neared 0.05), presented a quadratic curve, a cubic curve or even a more complicated piecewise curve association. Both the infected snail density and the proportion of sampling frames with infected snails remained at the lowest level when the average water level was at 25.0 m and the watered-out days in the past year was 110, while the proportion of sampling frames with living snails kept the lowest level when the average water level was at 25.0 m and the watered-out days in the past year was 160. Conclusion The water level and the field watered-out days affected the development of snail population directly. The changing water level had an impact on snail population change, which mainly presented as nonlinear smooth function relation. Impact of the field watered out days on the infected snail density and the proportion of sampling frames with living snails and infected snails showed a hysteresis effect. The snail density was predicted to be retaining a high level when the water level was 24.0 m and the field watered-out days was 3 months. It had obvious advantages to fit the relationship of the changing water level and the snail indexes with a GAM which could get closer to the reality as well as easier to find and explain the potential associations and regulations.
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Objective To explore the relationships between micro-ecological environmental factors and the density of Snails so as to provide information for the elimination of Snails and control of Schistosomiasis disease,under ecological methods.Methods A bottomland close to Junshan Park in Yueyang city,Hunan province was selected as the field for survey during 10,2007-10,2008,and a systematic sampling method was applied to determine the specific sites of Snail investigation.All the Snails in each frames were collected and the soil surface temperature and vegetation coverage in several frames were measured.30 g soil sample in each selected frames were also collected simultaneously.The number of live Snails in each frame was counted by dissection,and soil measured pH value and soil moisture were tested in the laboratory.The distribution of Snails and microecological environmental factors,fitted general additive model for the relationship of these factors and the Snail density were described.Results 104 frames were surveyed,with pH value as between 4.70-7.92,vegetation coverage as in 1% to 96%,soil surface temperature as in 14.5-32.7℃,the soil moisture as in 0.07-2.00.Under General additive model,data showed that there was no significant difference for vegetation coverage.However,other factors were all significantly different(P＜0.001).It was found that a nonlinear relationship was existing between these factors and the Snail density.Conclusion Smoothing function relationship was noticed between the Snail density and micro-ecological environmental factors.It's suggested to fit general additive model to study the relationship between the distribution of Snails and its influencing factors,so as to adopt appropriate measures to change the related ecology to control the diffusion and reproduction of Snails.
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Objective To study the impact of precipitation and water level on acute schistosomiasis for providing reference to control acute schistosomiasis in advance. Methods The historical data on precipitation and water level as well as acute schistosomiasis from 2003 to 2007 in Eastern, Southern and Western Dongting Lake regions were collected and analysed for the correlation between acute schistosomiasis and precipitation and water level in local areas. Results Acute schistosomiasis gradually decreased year by year from 2003 to 2007. Compared with 2003, the number of acute schistosomiasis in 2007 reduced by 95.37%. There was no outbreak of acute schistosomiasis from 2005 to 2007.In the period of peak acute schistosomiasis, the average monthly rainfall reduced from year to year for the successive 5 years. There was a significantly correlation between acute schistosomiasis and monthly average water level. Conclusions The acute schistosomiasis is directly affected by nature factors and has a close correlation with the rainfall and water level in Dongting Lake regions.