The effect of anthropogenic activity on the occurrence of Culicoides species in the South-Western Khomas Region, Namibia

Certain species of midges in the genus Culicoides (Diptera: Ceratopogonidae) are vectors of several serious orbiviral (Reoviridae) diseases, one of which, African horse sickness (AHS), was reported in the South-Western area of Khomas Region, Namibia, where it had been believed to be absent. Culicoides imicola, AHS principal vector, was collected in several farms in the area during the winter of 2009. The objective of this study was to determine whether Culicoides midges, especially C. imicola, were favoured at anthropogenic impacted/homestead sites in the arid Khomas Region, where they were not expected to occur under natural, veld conditions. The natural 'background' Culicoides communities where determined from collections made at veld sites, which were then compared to corresponding collections made at homestead sites. Altogether, 10,178 Culicoides midges were collected at homesteads and were then compared to 1,733 individuals collected at veld sites. Culicoides midge numbers were likely boosted in anthropogenic impacted areas/homesteads. This was also the case for the Culicoides species that are vector of AHS. This study indicated the significance of human settlement in the Khomas Region in terms of Culicoides midge abundance and distribution and showed the implications that this may have on the transmission of Culicoides-vectored diseases.