Detoxification enzymes associated with insecticide resistance in laboratory strains of Anopheles arabiensis of different geographic origin.
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.
Vector Control Reference Unit, Centre for Opportunistic, Tropical and Hospital Infections, National Institute for Communicable Diseases of the National Health Laboratory Services, Johannesburg, South Africa. luisan@nicd.ac.za
Luisa
L
Nardini
Riann N
RN
Christian
Nanette
N
Coetzer
Hilary
H
Ranson
Maureen
M
Coetzee
Lizette L
LL
Koekemoer
D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000201:enzymology*; D003634:DDT / Q000494:pharmacology*; D003710:Demography; D005260:Female; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D008297:Male; D009032:Mosquito Control; D010574:Pesticide Synergists / Q000494:pharmacology; D011722:Pyrethrins / Q000494:pharmacology*; D060888:Real-Time Polymerase Chain Reaction
D007306:Insecticides; D010574:Pesticide Synergists; D011722:Pyrethrins; D003634:DDT