Malaria is endemic in Ghana as in most countries of sub-Saharan Africa. This study was
conducted to characterize
Anopheles gambiae
s.l. and determine pyrethroid resistance profiles relative to
physicochemical properties of breeding habitats in Accra, Ghana. Eight aquatic habitats containing
Anopheles larvae were identified and from each habitat, larvae and water were sampled. Adult An.
gambiae reared from larvae were morphologically identified and tested for permethrin (0.75%) and
deltamethrin (0.05%) resistance using WHO bioassay method.
An. gambiae s.s. found were identified to
their molecular levels and kdr mutation detected using PCR-based methods. Twenty-nine
physicochemical parameters of each water sample were measured and their levels connected with
pyrethroid resistance and proportions of
An. gambiae s.s. molecular forms in habitats. A total of 2,257
mosquitoes were morphologically identified as
An. gambiae s.l. and all 224 processed for PCR were
identified as
An. gambiae s.s., of which 56.46% and 43.54% were M and S-forms, respectively. Both forms
occurred in sympatry in all larval habitats and no S/M hybrids were detected. However, M-form larvae
were in high proportion in polluted habitats than the S-form.
An. gambiae s.s. was highly resistant to both
deltamethrin and permethrin with mortality rates of 42.98-70.0% and 6.5-20.0% respectively. The
frequency of kdr mutation was 60.5 % (n=195). This mutation occurred in both S and M-forms, but was
mainly associated with the S-form (X
2=10.92, df =1, P=0.001). Carbonate and pH were both selected in
discriminant function analysis as best predictors of high proportion of M-form in the habitats. The
adaptation of
An. gambiae s.s. in polluted aquatic habitats coupled with occurrence of insecticide
resistance is quite alarming particularly for urban malaria control and needs further exploration in a
wider context.
