RESUMO
Objective To study the relationship between land use/cover structure and changes and risk of plague prevalence.Methods Chifeng,Aohan,Alukeerqin and Wengniute were selected as typical areas of Spermophilus Dauricus plague foci in Inner Mongolia,density of Spermophilus Dauricus,plague epidemic and land use data in 1986,1995,2000 were collected,and risk of plague prevalence was represented by the density of Spermophilus Dauricus and epizooty of Spermophilus Dauricus.The percentage of land type structure,change degree of integrated land cover,division index of grassland for plague suitable habitat were calculated with ArcGIS 9.3.The relationship between the land use,cover change and the plague epidemic were analyzed by the methods of comparative.Results From 1982 to 2000,the density of Spermophilus Dauricus was lower than 0.4/hm2 and no epizooty of Spermophilus Dauricus was observed both in Aohan Banner and Chifeng City,which indicated low risk of plague prevalence.Contrarily,from 1982 to 2000,the density of Spermophilus Dauricus was higher than 1.0/hm2,and epizooty of Spermophilus Dauricus was prevalent in Alukerqin Banner,which implied high risk of plague prevalence.In Wenguiute Banner,the density of Spermophilus Dauricus was lower than 0.3/hm2 from 1982 to 1990,after then showed a rising trend,reached higher than 1.0/hm2 in 1991,1995-1997,and epizooty of Spermophilus Dauricus was also monitored,which denoted high risk of plague prevalence;In 1986,1995 and 2000,the proportions of grassland of Wengniute Banner,Alukerqinqi Banner (51.36％,49.14％,48.28％;56.97％,57.48％,57.44％) were much higher than Chifeng and Aohan Banner (35.99％,33.24％,32.95％;38.94％,34.46％,31.31％),but those of arable land (16.81％,18.78％,20.22％;13.28％,14.92％,15.15％) were lower than Chifeng and Aohan Banner (39.73％,42.25％,42.67％;41.21％,43.99％,49.53％).The highest of comprehensively dynamic degree of land cover changes appeared in Aohan Banner,and it was 0.53 and 1.11 in 1986 vs.1995 and 1995 vs.2000,respectively,and the lowest in Alukeerqin Banner,it was 0.22 and 0.05 during those periods.The grassland division index in Alukeerqin Banner was the lowest,which was 0.29 in 1986,0.28 in 1995,and 0.29 in 2000.The grassland division index was higher and showed a upward trends in Aohan Banner,which was 0.57 in 1986,0.69 in 1995 and 0.71 in 2000.Conclusion There is a certain relation between risk of plague prevalence and land use/cover structure and changes.
RESUMO
The association between land use and land cover changes between 1979-2004 in a 2.26-million-hectare area south of the Gran Chaco region and Trypanosoma cruzi infection in rural communities was analysed. The extent of cultural land, open and closed forests and shrubland up to 3,000 m around rural communities in the north, northwest and west of the province of Córdoba was estimated using Landsat satellite imagery. The T. cruzi prevalence was estimated with a cross-sectional serological survey conducted in the rural communities. The land cover showed the same patterns in the 1979, 1999 and 2004 satellite imagery in both the northwest and west regions, with shrinking regions of cultured land and expanding closed forests away from the community. The closed forests and agricultural land coverage in the north region showed the same trend as in the northwest and west regions in 1979 but not in 1999 or 2004. In the latter two years, the coverage remote from the communities was either constant or changed in opposite ways from that of the northwest and west regions. The changes in closed forests and cultured vegetation alone did not have a significant, direct relationship with the occurrence of rural communities with at least one person infected by T. cruzi. This study suggests that the overall decrease in the prevalence of T. cruzi is a consequence of a combined effect of vector control activities and changes in land use and land cover.