Spatio-temporal distribution of emerging snail-infested sites in different environmental types in Yunnan Province / 中华地方病学杂志

ABSTRACT

Objective:To explore the spatial and temporal distribution patterns of emerging snail-infested sites in different environmental types in Yunnan Province.Methods:The data of snail-infested sites in Yunnan Province from 1950 to 2014 (from Yunnan Institute for Endemic Diseases Control and Prevention), were collected and sorted out, a spatial and temporal database on the distribution of emerging snail-infested sites were established, and the changes in the spatial and temporal distribution of emerging snail-infested sites in different environments types (ditches, tangerines, paddy fields, dry land, beaches and other environments) were studied by using spatial autocorrelation analysis and scanning statistics analysis.Results:From 1950 to 2014, the annual number of emerging snail-infested sites in Yunnan Province reached a peak (1 730) in 1955 and then showed a fluctuating downward trend. From 1993 to 2014, the number of emerging snail-infested sites remained below 100, and increased to 160 and 131, respectively, in 2004 and 2013. The longest mean duration of 43.85 years was recorded for the beaches environment for emerging snail-infested sites, followed by the paddy fields environment with a mean duration of 37.01 years, and the shortest mean duration of 20.44 years for the tangerines environment. Spatial autocorrelation analysis showed that there was a positive spatial correlation between the duration of emerging snail-infested sites of different environmental types (global Moran's I ranged from 0.43 to 0.64, P < 0.05). Scanning statistics analysis showed that emerging snail-infested sites of different environmental types had spatial and temporal aggregation ( P < 0.001), with 3- 6 clusters of statistically significant aggregation detected respectively. Conclusion:The emerging snail-infested sites in different environments types in Yunnan Province have spatial and temporal aggregation, and it is necessary to strengthen monitoring and prevention and control of the aggregation areas of different environment types to prevent further spread of the snail.