Abstract:
BACKGROUND: The use of insecticides to control malaria vectors is essential to reduce the prevalence of malaria
and as a result, the development of insecticide resistance in vector populations is of major concern. Anopheles
arabiensis is one of the main African malaria vectors and insecticide resistance in this species has been reported in a
number of countries. The aim of this study was to investigate the detoxification enzymes that are involved
in An. arabiensis resistance to DDT and pyrethroids.
METHODS: The detoxification enzyme profiles were compared between two DDT selected, insecticide resistant
strains of An. arabiensis, one from South Africa and one from Sudan, using the An. gambiae detoxification chip, a
boutique microarray based on the major classes of enzymes associated with metabolism and detoxification of
insecticides. Synergist assays were performed in order to clarify the roles of over-transcribed detoxification genes in
the observed resistance phenotypes. In addition, the presence of kdr mutations in the colonies under investigation
was determined.
RESULTS: The microarray data identifies several genes over-transcribed in the insecticide selected South African
strain, while in the Sudanese population, only one gene, CYP9L1, was found to be over-transcribed. The outcome
of the synergist experiments indicate that the over-transcription of detoxification enzymes is linked to
deltamethrin resistance, while DDT and permethrin resistance are mainly associated with the presence of the
L1014F kdr mutation.
CONCLUSIONS: These data emphasise the complexity associated with resistance phenotypes and suggest that
specific insecticide resistance mechanisms cannot be extrapolated to different vector populations of the
same species.
