title: [Oncomelania hupensis snail situation in wetlands surrounding reservoirs in hilly areas in Danling County].
abstract: OBJECTIVE
  To master the Oncomelania hupensis snail situation in wetlands surrounding reservoirs in hilly areas in Danling County, Sichuan Province, so as to provide the reference for improving the snail control in these areas.
  
  
  METHODS
  A medium-sized reservoir (Meiwan Reservoir) and a small-sized reservoir (Zhulinkan Reservoir) were chosen respectively , and the snail situation of the environments surrounding the reservoirs were investigated , the indexes such as the occurrence rate of frames with snails and the density of living snails at the upstream and downstream of the reservoirs as well as the surrounding environments were calculated and compared. Meanwhile , the data of the snail situation of the adjacent villages in the irrigation district at the downstream of the reservoirs year by year were collected to analyze the variation trend.
  
  
  RESULTS
  The Meiwan Reservoir was located in the deep hill, the occurrence rate of frames with snails was 4.29%, the highest and average densities of living snails were 28.00 snails/0.1 m2 and 0.38 snails/0.1 m2, respectively. There was a statistically significant difference between the occurrence rates of frames with snails at the upstream and downstream, which were 0.17% and 22.16%, respectively (χ2 = 1,267.40, P < 0.05), and the rate of spillway was the highest (51.69%). The highest and average densities of living snails in the downstream were 7.00 and 656.10 times higher than those in the upstream respectively. The Zhulinkan Reservoir was located in the shallow hill, the occurrence rate of frames with snails was 17.29%, and the highest and average densities of the living snails were 38.00 snails/0.1 m2 and 0.61 snails/0.1 in 2, respectively. There was a statistically significant difference between the occurrence rates of frames with snails at the upstream and the downstream, which were 12.95% and 50.92% respectively (χ2 = 194.68, P < 0.05), and the rate of spillway was the highest (65.74%). The highest and average densities of living snails in the downstream were 5.43 and 10.00 times higher than those in the upstream respectively. After the construction of the two reservoirs, the snail area in the irrigation districts of the adjacent villages at the downstream was 57.26% of that before and after the construction (398,030 m2/695 160 m2). The snail area showed a down-ward tendency with repeatedly rebound since the 1990s.
  
  
  CONCLUSIONS
  The wetland surrounding the reservoir in hilly region is suitable for snail breeding, and the snail situation in the shallow hill is more serious than that in the deep hill. There exists a risk for the repeatability of snail situation in this type of area where the snails can easily diffuse.
authors.forename: Meng
authors.initials: M
authors.lastname: Tang
authors.forename: Hui-bin
authors.initials: HB
authors.lastname: Zhu
authors.forename: You-ping
authors.initials: YP
authors.lastname: Hu
authors.forename: Jian-ru
authors.initials: JR
authors.lastname: Fan
authors.forename: Liang
authors.initials: L
authors.lastname: Xu
authors.forename: Feng
authors.initials: F
authors.lastname: Luo
authors.forename: Yi
authors.initials: Y
authors.lastname: Huang
authors.forename: Zi-song
authors.initials: ZS
authors.lastname: Wu
mesh_terms: D000818:Animals; D004197:Disease Reservoirs; D011156:Population Density; D012552:Schistosomiasis / Q000635:transmission*; D012908:Snails / Q000254:growth & development*; D053833:Wetlands