Objective To understand the distribution,variance and dynamics of Oncomelania snails in the water system of the Bianmin River after the river bank being protected with concrete.Methods The snails in the water system of the Bianmin River were investigated with the systemic sampling method and environmental spot-checking method in spring from 2002 to 2005.The indexes including area with snails,area with infected snails,rate of frames with snails,density of living snails and infection rate of snails in different environments were collected,analyzed and compared year by year.Results From 2002 to 2005,in the main river of the water system of the Bianmin River,irrigation areas and the adjacent marshlands of the Yangtze River,the areas with snails were 20.94-31.88,39.30-48.08 hm2 and 275.13-292.31 hm2,respectively;the rates of frames with snails were 9.96%-21.88%,29.61%-58.54% and 62.14%-85.97%,respectively;the mean densities of snails were 0.97-1.86,0.92-3.96 snails/0.1 m2 and 7.72-11.15 snails/0.1 m2.In 2005,in the main river,irrigation areas and the adjacent marshlands,the rates of frames with snails were 21.88%,39.33% and 83.81%,respectively;the densities of living snails were 1.30,3.96 snails/0.1 m2 and 11.15 snails/0.1 m2.During the last four years,the rates of frames with snails increased quickly in the main river of the water system of the Bianmin River;the densities of snails increased by 4 times in the irrigation areas;the indexes mentioned above were stable in the adjacent marshlands of the Yangtze River.However,the rate of frames with snails in the marshlands was 2-3 times higher than that in the irrigation areas and the mean density of snails in the marshlands was 3-8 times higher than that in the irrigation areas.Conclusions The main factor causing the increase of snails is that the river beach has not been cleaned yet in the water system of the Bianmin River,and so the key of schistosomiasis control is that first,the river beach should be cleaned completely,and at the same time,strengthening the snail control in the irrigation areas and the snail surveillance and snail control with molluscicides in the outfalls of the rivers of the water system of the Bianmin River to the Yangtze River.

Objective To evaluate the mid-term effectiveness of the medium-and-long-term programme of the prevention and control of schistosomiasis in Jiangsu Province. Methods The programme was carried out in Jiangsu Province and the comprehensive measures relied mainly on snail control, detection and chemotherapy of schistosomiasis for residents and livestock. The mid-term effectiveness of the programme was observed and evaluated longitudinally. Results The coverage rate of snail control areas and the ratio of chemotherapy of schistosomiasis for residents and livestock rose year after year. The snail areas, the infected snail areas and the infection rate of schistosome for residents and livestock reduced year after year. There were negative correlations between the coverage rates of snail control and the infected snail areas, the number of settings with infected snails, the infection rate of schistosome for residents, the infection rate of schistosome for livestock and the morbidity of acute schistosomiasis, respectively (rInfected snail areas=-0.897,P=0.039;rNo. of settings with infected snail=-0.937,P=0.019;rInfection rate for residents=-0.913,P=0.031;rInfection rate for livestock=-0.991,P=0.001;rMorbidity of acute schistosomiasis=-0.894,P=0.041). There were negative correlations between the ratio of chemotherapy of schistosomiasis for residents and the infected snail areas, and between the ratio of chemotherapy of schistosomiasis for livestock and the infected snail areas (rRatio of chemotherapy for residents =-0.965,P=0.008;rRatio of chemotherapy for livestock=-0.921,P=0.027). There were negative correlations between the funds of schistosomiasis control and the infection rate of schistosome for residents livestock, respectively (rInfection rate for residents=-0.897,P=0.039;rInfection rate for livestock=-0.971,P=0.006). The multiple linear regression analysis showed that there were the linearity relationships between the infection rate of schistosome for residents and the coverage rates of snail control, and between the infection rate of schistosome for livestock and the coverage rates of snail control, and between the morbidity of acute schistosomiasis and the coverage rates of snail control. Conclusions The effect of the comprehensive strategy of schistosomiasis control which relies mainly on snail control, detection and chemotherapy of schistosomiasis for residents and livestock are remarkable. The snail control and chemotherapy are effective and immediate. The increased funds would be essential guarantee for control and elimination of schistosomiasis.

Objective To evaluate the effectiveness of the current measure of Oncomelania hupensis control in Jiangsu Province. Methods The snail control was carried out with molluscicides in the high transmission areas every year. Some snail habitat areas were modified. The snail areas within three years were re-treated with molluscicides in the maintenance phase. The snail survey was carried out every spring, and the data were analysed with SAS software. Results From 1995 to 2001, 14519.17 hm 2 of snail habitats were molluscicided, 2768.57 hm 2 were modified, and 8803.64 hm 2 were re-treated with molluscicides in the maintenance phase. The coverage rates of snail control areas dropped by 19.14% every year. The snail areas increased by 6.25% every year from 1995 to 2002. In which, the areas of infected snails increased by 18.52% every year. The correlation analysis showed that the areas of infected snails increased with the increasing of the total snail areas. At the same time, the areas of infected snails increased with the fall of the coverage rates of snail control areas. The analysis of the snail distribution showed that the main problem was poor snail control. Conclusion In recent years, the rise of area of snail habitats is serious in Jiangsu Province. The present measures of the snail control have not effectively stopped the spreading and increasing of snails. The research on the new molluscicides, the new methods of snail control and the better policies are very important.

Objective To explore the aestivation and lethal hyperthermy temperature of Oncomelania hupensis in summer,which is one of important ecology indexes,in order to understand the potential impact of global warming on the distribution of Oncomelania snail in mainland China. Methods Oncomelania hupensis hupensis snails were collected from the marshland region in Jiangsu Province and the aestivation and lethal hyperthermy temperature were examined by increasing temperature gradually in laboratory. Results The lethal hyperthermy temperatures of 50% Oncomelamia snails in dry and wet environment was 40.01℃ ( 95% of confidence interval from 39.76-40.27℃) and 42.13℃( 95% of confidence interval from 41.59-42.68℃), respectively. The logistic regression equations between temperature and mortality were d=101/(1+e 61.402269-1.535058X) (F=69.997,P

Objective To understand the distribution and fluctuation tendency of infected Oncomelania snails in marshland areas of Jiangsu Province in order to provide the scientific basis for acute schistosomiasis control. Methods In each county(city, district) 5-10 marshland areas with snails were sampled randomly, and of which 5-10 sites were selected. Fifty to one hundred snails were collected in each site and dissected by professionals to determine the natural infection rate. At the same time, the mollusiciding actions were carried out in the schistosome-positive snail sites and beaches. Results In 5 years, a total of 467 beaches have been checked and 102 positive beaches were find out and the snails detected. The positive rate of beaches was 21.84%(102/467). A total of 169200 snails were dissected , and of which 433 were positive snails. The natural infection rate was 0.2559%(433/169200). The infested areas and the number of positive snails in 2002 were 2.71 and 18.33 times of those in 1998 in Jiangsu Province. Conclusion In the continuous 5 years observation, the tendency of the population of positive snails and the infested areas were significantly growing, and there is a apotential threat for the acute infections. So, the keys of the following work should be controlling snails seriously in the marshlands and the rivers in connection with the Yangtze River, increasing the mollusiciding cover rate and improving the quality in the positive beaches, and surveying and treating the cattle time by time.

Objective To understand the impact of environmental temperature on the infection of miracidia of Schistosoma japonicum to Oncomelania snails, and to estimate the lowest critical temperature for infection of snails with miracidia. Methods Oncomelania snails free of S.japonicum were collected from field,and exposed to miracidia at the ratio of 1∶20 under the different temperatures, such as 5,6,8,10,15,20℃.Snails were dissected to check if infected after exposured and kept in 25℃ for another 70 days. Results The infection rate of snails were 0,0.92,1.43,2.40,8.96,17.39% under the temperature of 5,6,8,10,15,20℃, respectively. The relationship between snail infection rate and temperature for infection was showed in the regression formulation of y=0.0622x 2-0.4035x+0.6703 (r=0.9988,P

Objective To determine the effective accumulated temperature of Oncomelania hu-pensis during the period of development of generations in the natural environment. Methods The snails, Oncumelania hupensis, were raised in natural breeding site, the developing duration and accumulated temperature for .snails' development from eggs to adult that began to lay eggs were estimated based on the formula T=?(Ti-C). Results The average developing duration was (334.22?7. 52) days, average accumulated temperature was (5 821.38?70.05) day degree, and average effective accumulated temperature was (3 846.28?32. 59) day degree. Conclusion The method to estimate the effective accumulated temperature is quite accuracy, which provides theoretical parameters in developing the prediction model on transmission of schistosomiasis japonica affected by weather warming.

Objective To evaluate the molluscicidal effect of niclosamide ethanolamine salt clustable powder (DP). Methods A comparative molluscicidal experiment was carried out by spraying method with niclosamide ethanolamine salt 4% DP. The experiments were respectively done in the labatory and field. The spraying with niclosamide ethanolamine salt 50% wettable power (WP) was used as the control. Results The molluscicidal effects of niclosamide ethanolamine salt 4% DP and 50% WP were similar in the laboratory. In the field, the effect of niclosamide ethanolamine salt 4% DP was lower than that of 50% WP in 3 d. However, the molluscicidal effects of the two formulations had not significant difference after 7 d. Conclusion The molluscicidal effects of niclosamide ethanolamine salt 4% DP and 50% WP were almost the same. DP is suitable for some areas where water are lack, or the water level are difficult to control.

0.05.Therefore,the average EGDD of S.japonicum developing in snails from the Yangtze River basin was 631.44 degree days, with its 95% confidence interval from (426.76 - 836.12) degree days. Conclusion The EGDD of S.japonicum developing in different snail populations along the Yangtze River are quite similar.

Objective To evaluate the molluscicidal effect and the using value of qiangluocide powder by dusting in the fields. Methods The two different ways of dusting with qiangluocide and spraying with luomiecide for controlling snails were compared in the fields, and the cost-effectiveness was analysed. Results The corrected mortalities and the reduced rates for density of snails were 88.48%, 96.26%, 96.96%, 95.67%, and 87.58%, 95.40%, 96.14%, 96.67%, respectively, on the marshland in Longtan, Nanjing, 73. 65% , 98. 31% , 99. 22% , 99. 26% and 69. 30% , 98.14%, 98.84%, 98. 60% , respectively, on the marshland in Yizheng, Yangzhou, on 1 d, 3d, 7 d, 15 d after dusting with qiangliocide power; and those on 1d, 3d, 7d, 15d after the spraying with luomiecide were 69.15%, 88.01%, 86.46%, 85.56% and 75.27%, 84.99%, 87.50%, 87.96% on the marshland in Longtan, Nanjing, 18.70%, 63.11%, 1.25%, 12.60% and 34. 88% , 89. 02% , 45.37% , 46. 59% , respectively, on the marshland in Yizheng, Yangzhou. The st of dusting with qiangluocide powder was 0. 20 yuan/m2, and that of spraying with luomiecide as 0. 21 yuan/m2 for snail control in the fields. The costs of reduced one percentage for the cor rected mortalities and the density of snail were 6. 27-10. 07 yuan and 6. 21-10. 14 yuan, respectively, on 15 d after dusting with qiangluocide power and those on 15 d after spraying with luomiecide were 7. 36-83. 33 yuan and 7. 16-22. 54 yuan , respectively. Conclusion The dusting with qiangluocide powder is a promising new formulation, which is suitable for the areas without water resource and possessed of high effectiveness against snails. The method ofdusting with qian-gluocide powder for controlling snails is simple, convenient, cheap and easy to be carried out for the inspection and quality control.