[Application of space-time scan statistics in the analysis of spatial and temporal distribution of Oncomelania hupensis snails in Gaoyou County, Jiangsu Province].

Objective To investigate the distribution features of Oncomelania hupensis infested areas in Gaoyou County so as to formulate surveillance and intervention strategies. Methods A database was established through collecting data of the snail infested areas during 1970-2009 in the County. The data were input into SaTScan 9.2 software for spatial-temporal cluster analysis to determine the spatial and temporal cluster of the snail habitats. The results were displayed by ArcGIS 10.1 software. Results There were historically 720 snail habitats in the County in 1970-2009 including 521 in plain region with water networks and 199 in lake marshland region. Those in water networks covered an area of 456.62 ha distributing mainly in the northern towns/townships of the County, and the latters distributed in the Xinmin Beach between Gaoyou Lake and Shaobo Lake, and Qiaojian Beach close to Tianchang County of Anhui Province with an area of 4 495.75 ha. The spatial-temporal cluster analysis revealed that among all the historical snail habitats, there were two prominent spatial-temporal clusters with a relative risk of 3. One cluster appeared in Xinmin Beach in 1983-2002 and another one located in the north of Gaoyou in 1970-1973. Separate analysis was performed by the regions of water network or lake marshland, indicating 2 clusters in each of the regions. During 1970-2009, 244 snail habitats were newly found in the County with 130 in water network region and 114 in lake marshland region. Again, the spatial-temporal cluster analysis displayed 2 prominent clusters. By separate analysis, 2 clusters existed in each of the regions. Conclusion The space-time scan statistics can be applied in detecting the cluster of snail infested areas in two dimensions, which will provide information for guiding specific measures of surveillance and control.