A preliminary attempt to use climate data and satellite imagery to model the abundance and distribution of Culicoides imicola (Diptera : Ceratopogonidae) in southern Africa

Abundances of Culicoides imicola, the insect vector of several livestock vi ruses, including bluetongue and African horse sickness, were recently publi shed for 34 sites in southern Africa, together with associated climate data . Here, these data are analysed statistically in combination with certain s atellite-derived variables, with the aim of developing predictive models of C. imicola abundance. Satellite-derived variables were the land surface te mperature (LST, a measure of temperature at the earth's surface) and the no rmalised difference vegetation index (NDVI, a measure of photosynthetic act ivity). Two models were developed: (1) climatic variables only and (2) sate llite-derived and climatic variables. For model I, the best model used a si ngle predictor variable (the mean daily minimum temperature) only, and acco unted for nearly 34 % of the variance in C. imicola abundance. Two variable climatic models did not perform significantly better. For model II, the be st 1-variable model used the annual minimum LST as a predictor of C. imicol a abundance, and accounted for nearly 40 % of the variance in C, imicola ab undance. The best 2-variable model, which gave a significantly better fit t han the I-variable model, combined the minimum LST and minimum NDVI as pred ictors of C, imicola abundance, and accounted for nearly 67% Qb of variance . A map of predicted C, imicola abundances is produced on the basis of this 2nd model which, despite some anomalies, agrees largely with what is curre ntly known of the prevalence of C. imicola in the region.