Effect Of Water Level Changes In Anhui Section Of Yangtze River On Schistosomiasis After Implementation Of The Three Gorges Project(TGP)

Objective To study the effect of the changes of water level in Anhui section of the Yangtze river after the operation of the Three Gorges Project(TGP)on the distribution of snails and the epidemic of schistosomiasis in the areas along the Yangtze river in Anhui Province.Methods The combination of macro research and micro research was used.First,the work data of schistosomiasis endemic areas along the Yangtze river in Anhui from 1990 to 2016 were collected,and the annual snail area,the annual snail control area,the annual infection of residents and cattle,as well as annual chemotherapy for residents and cattle were analyzed,and then explorer the possible relationship between water level and snail distribution as well as schistosomiasis endemic.Second,three typical marshland including Xinzhou marshland in Anqing City,Laozhou marshland in Yian District as well as Chenqiaozhou marshland in He County were selected from upstream to downstream in the Anhui section of the Yangtze river,and field investigation were conducted to understand the current utilization of the marshland,snail distribution and infection status of residents.Besides,the daily water level,annual snail area,annual snail density,serological positive rate of residents,pathogeny positive rate of residents,coverage rate of snail control,coverage rate of chemotherapy measures and infection control measures were all collected from 1990 to 2015,and discuss the relationship between water level near the marshland and these indicators.Results (a)The water level in Anhui section of Yangtze River has generally declined after implementation of the TGP.Take the Anqing Hydrometric Station on the Yangtze River as an example,the average value of annual maximum water level,annual average water level,average water level during the flood season,and difference value between highest and lowest water level have decreased by 1.45m,0.77m,0.94m and 1.52,respectively,except for the lowest water level.Before and after implementation of the TGP,the median value of annual snail area in the endemic areas along Yangtze River was 24,917 hm~2 and 25,500 hm~2,respectively,and the snail area rose first and then decreased after implementation of the TGP;The median value of total coverage rate of snail control was 18.10%and 23.21%,respectively;the median value of positive rate of inhabitants'fecal tests was 5.44%and 1.11%,respectively,which showed a rapid decline since 2006;the median value of annual acute schistosomiasis case were 206 and 17,respectively.No acute schistosomiasis case had been reported since 2013;the median value of chemotherapy coverage rate of inhabitant were 18.99%and 16.12%respectively;the median value of chemotherapy coverage rate of cattle were 37.50%and 58.84%respectively.(b)After implementation of the TGP,the annual flooding days of three marshland was significantly reduced.the median value of annual flooding days calculated by the average elevation at Xinzhou marshland,Laozhou marshland,Chenqiaozhou marshland were reduced from 62 days,73 days,and 61.5 days to 32 days,35 days and 20.5 days,respectively.In the three marshland,the development and utilization of Laozhou and Chenqiaozhou were significantly increased.Take Laozhou as an example.Before and after implementation of the TGP,the development and utilization area of Laozhou was 63hm~2 and 287hm~2,respectively.The snail density of marshland decreased significantly,especially higher elevation of each survey marshland.The snail area decreased slowly.The serology and etiology positive rate of inhabitant declined rapidly after implementation of the TGP.For snail control,taking the representative marshland of Xinzhou,Laozhou,and Chenqiaozhou as examples,the coverage rate of snail control decreased from 7.8%,80%,and 39.58%to 3.0%,49%,and 3.56%,respectively.The inhabitant chemotherapy coverage of typical villages in Xinzhou,Laozhou,and Chenqiaozhou dropped(rose)from 17.40%(Qinglong Village),12.60%(Guanghui Village),and12.9%(Chenqiaozhou Village)to 16.95%,10.4%and 16.8%,respectively.After implementation of the TGP,all regions have implemented the infection source control measures after 2006,such as replace cattle with machine.Conclusion The TGP decreased water level in Yangtze river,resisted the floods effectively,reduced annual flooding days of marshland significantly,promoted the development and utilization of the marshland,changed breeding environment of Oncomelania snails,and reduced the infection rate of inhabitant.The TGP is beneficial to the prevention and control of schistosomiasis in the middle and lower reaches of the Yangtze river in the short term.