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 observe hibernation phenomena of Oncomelanai hupensis and explore the way of inducing the hibernation in laboratory. \ Methods\ Snails, O\^hupensis hupensis, were collected from marshland of Jiangsu. The snail hibernation was induced by the way of cultivation at a mimic natural environment in the laboratory with gradually changing temperature. The amount of oxygen consumed by snails was tested by iodine titration, and their hibernation was tested by pin puncture followed by warm water. \ Results \ There was no significant difference on the rate of snail \{hibernation\} when the temperature was reduced by 1 ℃ per 24 hrs and by 1 ℃ per 48 hrs. The hibernation rate \{increased\} with the decreasing temperature. There was a significant regression relationship between hibernation rate and temperature with R\+2=0\^967 (F=207\^72, P

Objective To study the impact of environmental temperature on the development of Schistosoma japonicum larvae within the Oncomelania hupensis. Methods Oncomelania snails, collected from the field and free of S. japonicum infection, were exposed to miracidiae of S. japonicum in a ratio of 1∶20 and raised at 30 ℃, 27 ℃, 24 ℃, 21 ℃ and 18 ℃, respectively. The prepatent period of larvae within the Oncomelania hupensis and the developmental velocity were determined, of which the relationship with the temperature was analysed. Results The average prepatent period of cercariae in snail was (128.89?16.05) d,(95.00?21.03) d,(71.93?12.74) d and (62.74?14.19) d at 21 ℃, 24 ℃, 27 ℃, 30 ℃, respectively. The regression formulation between prepatent period and temperature was y =730.68x -0.8918 (r=0.9976, P

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 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