title: Preliminary assessment of the potential role of urbanization in the distribution of carbamate and organophosphate resistant populations of Culex species in Ghana.
abstract: BACKGROUND
  Besides its role as a pathogen vector, Culex species also indirectly promotes the transmission of malaria if the use of bed nets or indoor residual spraying is discontinued due to a lack of insecticide efficacy against it. A recent survey revealed widespread occurrence of pyrethroid resistance among urban populations of this mosquito in Ghana. In order to plan and implement insecticide-based resistance management strategies, this study was carried out to assess resistance status of Culex species to organophosphate and carbamate in urban areas in Ghana and the possible mechanisms involved as well as environmental factors associated with its distribution.
  
  
  METHODS
  Mosquito larvae were sampled from various land use and ecological settings and in different seasons. In adults, susceptibility to organophosphates (fenitrothion, malathion) and carbamates (propoxur, bendiocarb) were determined. Mixed function oxidase (MFO) and α- and β-esterase assays, as well as a PCR diagnostic assay to determine ace1 mutation were performed in individual mosquitoes.
  
  
  RESULTS
  Culex quinquefasciatus as well as C. decens and other unidentified Culex species were found breeding in polluted water bodies in the study sites. Across all sites and seasons, carbamate induced mortality was 94.1% ± 15.4 whereas mortality caused by organophosphate was 99.5% ± 2.2. In addition, ace1 mutation and high levels of esterases were detected in some of the mosquito populations. There was a strong correlation between susceptibility status of the mosquitoes and the level of absorbance of β-esterase (Pearson r=- 0.841, p=0.004).
  
  
  CONCLUSIONS
  The study found low prevalence of resistance to carbamate and organophosphate insecticides among Culex species from Ghana. However, there were populations with ace1 mutations and high levels of esterases, which can confer high resistance to these classes of insecticides. Thus, it is important to monitor activities or behaviour that has the potential to select for carbamate and organophosphate resistance populations.
authors.affiliation: Center for International Health, Department of Infectious Diseases and Tropical Medicine, Ludwig-Maximilians-Universität Munich, Munich, Germany. akudom@ucc.edu.gh.|Department of Entomology and Wildlife, School of Biological Sciences, University of Cape Coast, Cape Coast, Ghana. akudom@ucc.edu.gh.
authors.forename: Andreas A
authors.initials: AA
authors.lastname: Kudom
authors.affiliation: Department of Entomology and Wildlife, School of Biological Sciences, University of Cape Coast, Cape Coast, Ghana. bmensah@ucc.edu.gh.
authors.forename: Ben A
authors.initials: BA
authors.lastname: Mensah
authors.affiliation: Center for International Health, Department of Infectious Diseases and Tropical Medicine, Ludwig-Maximilians-Universität Munich, Munich, Germany. Froeschl@lrz.uni-muenchen.de.
authors.forename: Guenter
authors.initials: G
authors.lastname: Froeschl
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, P.O. Box LG 581, Legon, Ghana. dboakye@noguchi.mimcom.org.
authors.forename: Daniel
authors.initials: D
authors.lastname: Boakye
authors.affiliation: Center for International Health, Department of Infectious Diseases and Tropical Medicine, Ludwig-Maximilians-Universität Munich, Munich, Germany. Heinz.Rinder@lgl.bayern.de.|Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit (LGL), Veterinärstraße 2, Oberschleißheim, 85762, Germany. Heinz.Rinder@lgl.bayern.de.
authors.forename: Heinz
authors.initials: H
authors.lastname: Rinder
mesh_terms: D063147:Animal Distribution; D000818:Animals; D002219:Carbamates / Q000494:pharmacology*; D003465:Culex / Q000187:drug effects*; D005869:Ghana; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D010755:Organophosphates / Q000494:pharmacology*; D010802:Phylogeny
chemical_list: D002219:Carbamates; D007306:Insecticides; D010755:Organophosphates