A random forest approach for predicting the presence of intermediate host . presence in relation to landscape characteristics in western China.

Understanding distribution patterns of hosts implicated in the transmission of zoonotic disease remains a key goal of parasitology. Here, random forests are employed to model spatial patterns of the presence of the plateau pika (.) small mammal intermediate host for the parasitic tapeworm which is responsible for a significant burden of human zoonoses in western China. Landsat ETM+ satellite imagery and digital elevation model data were utilized to generate quantified measures of environmental characteristics across a study area in Sichuan Province, China. Land cover maps were generated identifying the distribution of specific land cover types, with landscape metrics employed to describe the spatial organisation of land cover patches. Random forests were used to model spatial patterns of . presence, enabling the relative importance of the environmental characteristics in relation to . presence to be ranked. An index of habitat aggregation was identified as the most important variable in influencing . presence, with area of degraded grassland the most important land cover class variable. 71% of the variance in . presence was explained, with a 90.98% accuracy rate as determined by 'out-of-bag' error assessment. Identification of the environmental characteristics influencing . presence enables us to better understand distribution patterns of hosts implicated in the transmission of Em. The predictive mapping of this Em host enables the identification of human populations at increased risk of infection, enabling preventative strategies to be adopted.