title: Ecological Model to Predict Potential Habitats of Oncomelania hupensis, the Intermediate Host of Schistosoma japonicum in the Mountainous Regions, China.
abstract: BACKGROUND
  Schistosomiasis japonica is a parasitic disease that remains endemic in seven provinces in the People's Republic of China (P.R. China). One of the most important measures in the process of schistosomiasis elimination in P.R. China is control of Oncomelania hupensis, the unique intermediate host snail of Schistosoma japonicum. Compared with plains/swamp and lake regions, the hilly/mountainous regions of schistosomiasis endemic areas are more complicated, which makes the snail survey difficult to conduct precisely and efficiently. There is a pressing call to identify the snail habitats of mountainous regions in an efficient and cost-effective manner.
  
  
  METHODS
  Twelve out of 56 administrative villages distributed with O. hupensis in Eryuan, Yunnan Province, were randomly selected to set up the ecological model. Thirty out of the rest of 78 villages (villages selected for building model were excluded from the villages for validation) in Eryuan and 30 out of 89 villages in Midu, Yunnan Province were selected via a chessboard method for model validation, respectively. Nine-year-average Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) as well as Digital Elevation Model (DEM) covering Eryuan and Midu were extracted from MODIS and ASTER satellite images, respectively. Slope, elevation and the distance from every village to its nearest stream were derived from DEM. Suitable survival environment conditions for snails were defined by comparing historical snail presence data and remote sensing derived images. According to the suitable conditions for snails, environment factors, i.e. NDVI, LST, elevation, slope and the distance from every village to its nearest stream, were integrated into an ecological niche model to predict O. hupensis potential habitats in Eryuan and Midu. The evaluation of the model was assessed by comparing the model prediction and field investigation. Then, the consistency rate of model validation was calculated in Eryuan and Midu Counties, respectively.
  
  
  RESULTS
  The final ecological niche model for potential O. hupensis habitats prediction comprised the following environmental factors, namely: NDVI (≥ 0.446), LST (≥ 22.70°C), elevation (≤ 2,300 m), slope (≤ 11°) and the distance to nearest stream (≤ 1,000 m). The potential O. hupensis habitats in Eryuan distributed in the Lancang River basin and O. hupensis in Midu shows a trend of clustering in the north and spotty distribution in the south. The consistency rates of the ecological niche model in Eryuan and Midu were 76.67% and 83.33%, respectively.
  
  
  CONCLUSIONS
  The ecological niche model integrated with NDVI, LST, elevation, slope and distance from every village to its nearest stream adequately predicted the snail habitats in the mountainous regions.
authors: Jiangsu Institute of Parasitic Diseases, Wuxi, People's Republic of China; Key Laboratory of Parasitic Disease Control and Prevention, Ministry of Health, Wuxi, People's Republic of China; Jiangsu Provincial Key Laboratory of Parasite Molecular Biology, Wuxi, People's Republic of China.
authors: Hong-Ru
authors: HR
authors: Zhu
authors: Jiangsu Institute of Parasitic Diseases, Wuxi, People's Republic of China; Key Laboratory of Parasitic Disease Control and Prevention, Ministry of Health, Wuxi, People's Republic of China; Jiangsu Provincial Key Laboratory of Parasite Molecular Biology, Wuxi, People's Republic of China.
authors: Lu
authors: L
authors: Liu
authors: National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, People's Republic of China; WHO Collaborating Center for Malaria, Schistosomiasis and Filariasis; Key Laboratory of Parasite and Vector Biology, Ministry of Health, Shanghai, People's Republic of China.
authors: Xiao-Nong
authors: XN
authors: Zhou
authors: Jiangsu Institute of Parasitic Diseases, Wuxi, People's Republic of China; Key Laboratory of Parasitic Disease Control and Prevention, Ministry of Health, Wuxi, People's Republic of China; Jiangsu Provincial Key Laboratory of Parasite Molecular Biology, Wuxi, People's Republic of China; Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
authors: Guo-Jing
authors: GJ
authors: Yang
mesh_terms: D000818:Animals; D002681:China; D004197:Disease Reservoirs / Q000469:parasitology; D017753:Ecosystem; D040362:Geographic Information Systems; D006801:Humans; D012549:Schistosoma japonicum / Q000502:physiology; D012554:Schistosomiasis japonica / Q000469:parasitology / Q000635:transmission; D012908:Snails / Q000254:growth & development* / Q000469:parasitology