title: Identification of optimum scopes of environmental factors for snails using spatial analysis techniques in Dongting Lake Region, China.
abstract: BACKGROUND
  Owing to the harmfulness and seriousness of Schistosomiasis japonica in China, the control and prevention of S. japonica transmission are imperative. As the unique intermediate host of this disease, Oncomelania hupensis plays an important role in the transmission. It has been reported that the snail population in Qiangliang Lake district, Dongting Lake Region has been naturally declining and is slowly becoming extinct. Considering the changes of environmental factors that may cause this phenomenon, we try to explore the relationship between circumstance elements and snails, and then search for the possible optimum scopes of environmental factors for snails.
  
  
  METHODS
  Moisture content of soil, pH, temperature of soil and elevation were collected by corresponding apparatus in the study sites. The LISA statistic and GWR model were used to analyze the association between factors and mean snail density, and the values in high-high clustered areas and low-low clustered areas were extracted to find out the possible optimum ranges of these elements for snails.
  
  
  RESULTS
  A total of 8,589 snail specimens were collected from 397 sampling sites in the study field. Besides the mean snail density, three environmental factors including water content, pH and temperature had high spatial autocorrelation. The spatial clustering suggested that the possible optimum scopes of moisture content, pH, temperature of the soil and elevation were 58.70 to 68.93%, 6.80 to 7.80, 22.73 to 24.23°C and 23.50 to 25.97 m, respectively. Moreover, the GWR model showed that the possible optimum ranges of these four factors were 36.58 to 61.08%, 6.541 to 6.89, 24.30 to 25.70°C and 23.50 to 29.44 m, respectively.
  
  
  CONCLUSIONS
  The results indicated the association between snails and environmental factors was not linear but U-shaped. Considering the results of two analysis methods, the possible optimum scopes of moisture content, pH, temperature of the soil and elevation were 58.70% to 68.93%, 6.6 to 7.0, 22.73°C to 24.23°C, and 23.5 m to 26.0 m, respectively. The findings in this research will help in making an effective strategy to control snails and provide a method to analyze other factors.
authors.forename: Jin-Yi
authors.initials: JY
authors.lastname: Wu
authors.affiliation: Department of Epidemiology, School of Public Health, Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, China. z_yibiao@hotmail.com.
authors.forename: Yi-Biao
authors.initials: YB
authors.lastname: Zhou
authors.forename: Lin-Han
authors.initials: LH
authors.lastname: Li
authors.forename: Sheng-Bang
authors.initials: SB
authors.lastname: Zheng
authors.forename: Song
authors.initials: S
authors.lastname: Liang
authors.forename: Ashley
authors.initials: A
authors.lastname: Coatsworth
authors.forename: Guang-Hui
authors.initials: GH
authors.lastname: Ren
authors.forename: Xiu-Xia
authors.initials: XX
authors.lastname: Song
authors.forename: Zhong
authors.initials: Z
authors.lastname: He
authors.forename: Bin
authors.initials: B
authors.lastname: Cai
authors.forename: Jia-Bian
authors.initials: JB
authors.lastname: You
authors.forename: Qing-Wu
authors.initials: QW
authors.lastname: Jiang
mesh_terms: D063147:Animal Distribution; D000818:Animals; D002681:China / Q000453:epidemiology; D004197:Disease Reservoirs; D017753:Ecosystem; D019353:Endemic Diseases; D004784:Environmental Monitoring / Q000379:methods*; D006801:Humans; D060106:Lakes; D015999:Multivariate Analysis; D012554:Schistosomiasis japonica / Q000453:epidemiology; D012908:Snails / Q000469:parasitology / Q000502:physiology*