Spatial and Temporal Variation in Susceptibility Status of Anopheles arabiensis the Malaria Vector to Insecticides in Khartoum State, Sudan

Spatial and temporal variation in the susceptibility status of
Anopheles arabiensis to five insecticides were investigated during
2011-2013 in nine sentinel sites in Khartoum State. Field-collected
larvae and pupae Anopheles in three seasons (cold dry, hot dry and wet
seasons) were reared to adult stages. Standard WHO diagnostic
bioassay for 4% DDT, 5% malathion, 0.1% propoxur, 0.75%
permethrin and 0.05% deltamethrin were used to test the susceptibility of adults An. arabiensis. A total of 6275 females of An. arabiensis were
exposed to the aforementioned insecticides. Resistances in An.
arabiensis to all insecticides were recorded in most of the sites
investigated. Most of the populations of An. arabiensis were resistant
to malathion, DDT and pyrethroids (permethrin and deltamethrin).
The results of overall revealed a clear difference pattern between the
seasons in the susceptibility status of An. arabiensis exposed to 4%
DDT and 0.1% propoxur. However, the seasonal variations in
susceptibility status in An. arabiensis from the sentinel sites did not
follow clear trends. In contrast, a significant difference were observed
between the seasons in mortality of An. arabiensis from the urban and
periurban areas exposed to 4% DDT and 5% malathion respectively.
The current study provides useful information on the distribution and
seasonal variations in the susceptibility status in An. arabiensis
populations from Khartoum State. The mortality rate in An. arabiensis
exposed to these insecticides has increased in the wet season which can
be explained by the selective insecticide pressures from the agricultural
and malaria control programme activities