Acta Tropica 82 (2002) 199–205 Use of landsat TM satellite surveillance data to measure the impact of the 1998 flood on snail intermediate host dispersal in the lower Yangtze River Basin Xiaonong Zhou a,b, *, Lin Dandan c , Yang Huiming d , Chen Honggen c , Sun Leping a , Yang Guojing a , Hong Qingbiao a , Leslie Brown e , J.B. Malone e a Jiangsu Institute of Parasitic Diseases, Wuxi 214064, People’s Republic of China b Institute of Parasitic Diseases, Chinese Academy of Preentie Medicine, Shanghai 200025, People’s Republic of China c Jiangxi Institute of Parasitic Diseases, Nanchuang, People’s Republic of China d Nanjing Hospital for Schistosomiasis Control, Nanjing, People’s Republic of China e School of Veterinary Medicine, Louisiana State Uniersity, Baton Rouge, LA, USA Abstract To assess the impact of the 1998 flood on snail distribution in the lower Yangtze River Basin, two study areas were selected, one in the Poyang Lake region, and the other along the Yangtze River in Jiangsu province. Using image analysis software, geocoded Landsat TM data were used to create TNDVI maps based on the formula TNDVI = Sqrt[(band4 -band3/band4 +band3) +0.5]. The images taken in the flood season were classified to produce a map depicting water and land. The images taken during springtime were processed and classified based on TNDVI. Composite images were created based on the time difference analysis, combining the flood season maps and spring vegetation maps to produce a map in which potential snail habitats were identified. When compared with ground survey data collected in the spring of 2000, the correspondence rate between potential snail habitats identified by image analysis of 1998–1999 Landsat TM data and ground survey data was over 90% in both regions. Results indicate that ecology based Landsat TM image analysis provides a new way to predict snail distribution under specific environmental conditions associated with the extent of the annual flood season. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Remote sensing; Oncomelania hupensis ; Schistosoma japonicum; Snail habitats; Flood www.parasitology-online.com 1. Introduction The lower reaches of the Yangtze River Basin are characterized by marshlands with seasonal summer flooding and winter drought. Habitats of Oncomelania hupensis, the snail intermediate host of Schistosoma japonicum, have expanded during recent decades because the lower reaches of the river affected by more frequent major floods, resulting in snail migration and expansion into new niches (Chen et al., 1999; Zhang et al., 1999) * Corresponding author. Tel.: +86-21-6473-8058; fax: + 86-21-64332670. E-mail address: ipdzhouxn@shib3.net (X.N. Zhou). 0001-706X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0001-706X(02)00011-6