Abstract:

【Abstract】 Objective To investigate the spatial-temporal variation pattern of infected snails in Hunan province in order to evaluate the effects of the integrated control strategies on prevention and control of schistosomiasis for scientific evidence in following plan decision. Methods  Data on the areas with infected snails were collected on town basis from 2004 to 2011. The electric map was prepared on town polygon, and spatial database was developed to match the polygon. The total index ,the spatial autocorrelation and spatial scan statistics at town level were included to quantify the spatial-temporal characteristics in the endemic areas. Results  The areas with infected snails tended to decline in general between 2004 and 2011. The decrease was from 2 627.9hm2 in 2004 to 664.6hm2 in 2011, and the corresponding P50, P75 and P90 was decreased sharply. However, the P90 was still at high level in 2011(5.9 h㎡), and the high level areas were associated with towns near the rivers with infected snails. Simulation analysis of the spatial weight matrix by Moran’s I between 20014 and 2011 indicated the index was greater than the expected one, which fell in 0.13-0.28, and the difference was statistically significant(Z>3.77, P<0.05). The number of towns, clustered primarily along the banks of Dongting Lake, with H-H types of auto-correlation was between 23-41. Conclusion  The areas with infected snails were significantly reduced in Hunan Province from 2004 through 2011, suggesting that the integrated measures with emphasis on infectious sources control appear effective for schistosomiasis control. However, distribution of the areas with infected snails tends to be positive auto-correlation, and the snail burden is still heavy in some towns in 2011. This needs further consolidated comprehensive prevention and control, particularly in areas with H-H types of distribution. 

Key words: Schitosomiasis, Dongting Lake, Oncomelania hupensis, Spatial-temporal distribution, Spatial Autocorrelation, Hunan Province