title: Insecticide resistance profiles for malaria vectors in the Kassena-Nankana district of Ghana.
abstract: BACKGROUND
  Malaria is a major public health problem in Ghana. The current strategy of the National Malaria Control Programme is based on effective case management and the use of insecticide treated bed nets among vulnerable groups such as children under-five years of age and pregnant women. Resistance to pyrethroids by Anopheles gambiae s.l. and Anopheles funestus has been reported in several African countries including neighbouring Burkina Faso.
  
  
  METHODS
  Indoor resting Anopheles mosquitoes were collected. Blood-fed and gravid females were allowed to oviposit, eggs hatched and larvae reared to 1-3 days old adults and tested against permethrin 0.75%, deltamethrin 0.05%, cyfluthrin 0.15%, lambdacyhalothrin 0.1% and DDT 4%, based on WHO methodology. PCR analyses were carried out on a sub-sample of 192 of the An. gambiae for sibling species complex determination. Resistance to pyrethroids and DDT was determined by genotyping the knock-down resistance kdr gene mutations in the study area.
  
  
  RESULTS
  A total of 9,749 1-3 days-old F1 female Anopheles mosquitoes were exposed to the insecticides. Among the pyrethroids, permethrin, 0.75% had the least knockdown effect, whilst cyfluthrin 0.15%, had the highest knock-down effect. Overall, no difference in susceptibility between An. gambiae 93.3% (95% CI: 92.5-94.1) and An. funestus 94.5% (95% CI: 93.7-95.3) was observed when exposed to the pyrethroids. Similarly, there was no difference in susceptibility between the two vector species (An. gambiae = 79.1% (95% CI: 76.6-81.8) and An. funestus = 83.5% (95% CI: 80.2-86.4) when exposed to DDT. Overall susceptibility to the insecticides was between 80% and 98%, suggesting that there is some level of resistance, except for cyfluthrin 0.15%. The kdr PCR assay however, did not reveal any kdr mutations. The analysis also revealed only the molecular M (Mopti) form.
  
  
  CONCLUSIONS
  The findings in this study show that An. gambiae and An. funestus, the main malaria vector mosquitoes in the Kassena-Nankana district are susceptible to the insecticides being used in the treatment of bed nets in the malaria control programme. There is however, the need for continuous monitoring of the pyrethroids as the efficacy is not very high.
authors.affiliation: Navrongo Health Research Centre, Navrongo Health Research Centre, Ghana Health Service, P O Box 114, Navrongo, Upper East Region, Ghana. franciskanto@yahoo.com
authors.forename: Francis
authors.initials: F
authors.lastname: Anto
authors.forename: Victor
authors.initials: V
authors.lastname: Asoala
authors.forename: Thomas
authors.initials: T
authors.lastname: Anyorigiya
authors.forename: Abraham
authors.initials: A
authors.lastname: Oduro
authors.forename: Martin
authors.initials: M
authors.lastname: Adjuik
authors.forename: Seth
authors.initials: S
authors.lastname: Owusu-Agyei
authors.forename: Dominic
authors.initials: D
authors.lastname: Dery
authors.forename: Langbong
authors.initials: L
authors.lastname: Bimi
authors.forename: Abraham
authors.initials: A
authors.lastname: Hodgson
mesh_terms: D000818:Animals; D000852:Anopheles / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000469:parasitology; D016001:Confidence Intervals; D003634:DDT / Q000494:pharmacology; D005260:Female; D055785:Gene Knockdown Techniques; D005838:Genotype; D005869:Ghana; D007303:Insect Vectors / Q000187:drug effects* / Q000235:genetics / Q000469:parasitology; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D008288:Malaria / Q000517:prevention & control / Q000635:transmission*; D009032:Mosquito Control / Q000379:methods; D009154:Mutation / Q000187:drug effects; D009570:Nitriles / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011722:Pyrethrins / Q000494:pharmacology
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; D003634:DDT