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 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.

Objective To understand the effect of Schistosoma japonicum infection on Oncomelania hupensis. Methods Uninfected Oncomelania snails were collected from the marshland of the Yangtze River in Anhui Province and exposed to and infected with miracidia of S.japonicum in the laboratory. After the exposure, those snails and unexposed snails as the control were raised in the natural environment of the same field and all the snails were observed and recorded every 10 days. The survival rate and death rate were calculated, and expected survival time was also calculated with the animal life table method. Results The peak of death of the infected snails was between 60 and 70 days after the exposure, and the expected survival time was 63.46 days and the longest survival time was 135 days. The peak of death of the unexposed snails was between 80 and 90 days, and the expected survival time was 83.54 days and the longest survival time was 155 days. The expected survival time of the infected snails was 24.04% shorter compared with that of the uninfected. Conclusion The death rate of snails infected with S.japonicum increases and the survival time decreases in the natural environment.

Objective To evaluate the impact of the project diverting the Yangtze River water to the Northern Jiangsu on transmission towards the north of Oncomelania hupensis snails, in order to provide the scientific basis for the South-North Water Diversion Project (east route). Methods The running situation of the water diversion project, the data on hydrology of the waterway and the distribution of snails and schistosomiasis were investigated with the methods of epidemiology、hydrology and field test. Results There was no significant correlation between the region of waterhead and water supply on the change of snail areas. There was no significant correlation between the snail areas of the region of water supply and the volume of water diversion, either. The snail habitat was stable at the Gaoyou segment along the Grand Canal. The snail habitat in the natural place of the north of 33?15′ north latitude on the east route has not been discovered yet. Conclusion There is no sign of transmission towards north on the snail habitat at the Gaoyou segment along the Grand Canal since the project was constructed in 1961. There is no evidence that the project leads to the spread of snails and schistosomiasis, either.

Objective To identify the trend of endemic situation among surveillance sites in Jiagsu Province from 2000 to 2002. Methods Twelve schistosomiasis surveillance sites were es-tablished ,and the longitudinal, surveillance was carried out. Results The related index of snail increased in most of surveillance sites, the rates of positive snails rose rapidly in marshlands. The infection rates of Schitosoma janponicum of cattle decreased and infection rates of human were relatively steady. However, there was still the danger of heavy endemic. Conclusion Current control strategies can not effectively adapt to the endemic situation of schistosomiasis, although which have some effects on control of morbidity. We need to study the new characteristics and rule of the endemic of schistosomiasis, and make out more effective control strategies which can suit with the current society, economies and nature environment.

Objective To evaluate the eff ec t of snail control with niclosamide ethanolamine salt dustable powder (DP) in th e marshland of the Yangtze River ahead of the schedule in spring, and to underst and the impact of the low temperature to molluscicidal effect of the dusting. Methods The snail control test with niclosamide ethanolamine salt dustable powder was carried out under different te mperatures in laboratory. Then the snail control was undertaken in the marshland of the Yangtze River ahead of the schedule in spring, and the molluscicidal ef fect was observed and the temperature changes were also considered. Results When the temperature was 15 ℃ and 25 ℃ respectively, there was no significant difference on the molluscicidal effec t of niclosamide ethanolamine salt DP in laboratory. The average atmosphere temp erature in each day was 8.9-16.3 ℃ from the last ten-day of March to the fir st ten-day of April in Nanjing regions. The corrected mortality of snails and the r educed rates of density of snails were 95.38% and 99.97% respectively on the s ur face of the soil in the marshland field. The corrected mortality and the reduced rates of density of snails were 79.30% and 70.59% respectively in the surface l ayer of the soil. Conclusion The impact of air t emperature is little to the molluscicidal effect of niclosamide ethanolamine sal t DP when the average atmosphere temperature in each day was 10-15 ℃ in the ma r shland of the Yangtze River. If the snail control is undertaken ahead of the sch edule in spring, the reproduction of snails will be suppressed and the infection of Schistosma japonicum will be controlled. [