RESUMO
Objective To study the reasons of natural death of Oncomelania hupensis snails by comparing the differences of the indicator days covered with water DCW in snail marshland and non?snail marshland around the build of Three Gorges Dam in Eastern Dongting Lake areas. Methods Two marshlands were selected one was a non?snail marshland Qianliang Lake and another was a snail marshland Junshan Park . The measuring points were set through the mechanical sampling. The snails and elevation of the points were surveyed and the data of the water levels from the hydrological station were collected and then DCWs were calculated. Results From 1995 to 2013 DCWs of the marshland of natural death of snails were all more than that of the snail marshland P<0.01 . In Qianliang Lake marshland the difference between DCW before natural death and DCW from natural death until the dam was not significant P=0.23 while DCWs of the two stages both were more than that after the dam P1=0.045 P2=0.002 . Before the build of the dam DCW of the Qianliang Lake marshland of natural death of snails was more than that after the build of the dam P=0.013 and there was the same situation in Junshan Park marshland P=0.005 . The relationship between snail density and DCW was not significant in Junshan Park marshland rs=0.008 P=0.914 and the reference range of DCW of all the measuring points was 76-251 days. Conclusion In the eastern Dongting Lake district the build of Three Gorges Dam and DCW may be not the direct factors affecting the natural death of snails and the latter may change the distribution of snails.
RESUMO
A typical lake region with serious schistosomiasis endemic areas was selected as the study field. In the study,the 10 years (1985 - 1994) data about the agriculture sturcture and schistosomiasis prevalence was collected and analyzed. The results showed significant posi-tive correlationships among the infection rate,the total area of snail habitat and paddy field. The infection rate of human had a close relation to the infection rate of domestic animals.
RESUMO
Possible impact of ecological and social environmental changes due to the construction of the Three Gorges Dam on the transmission of schistosomiasis draws great attention of the health authority and publics. This article reviews the situation and progress of research on schistosomiasis transmission in reservoir area from three aspects: the possibility of snail spreading and breeding, imported infection sources and social behavioral factors of the people.