title: Spatial variation of insecticide resistance in the dengue vector Aedes aegypti presents unique vector control challenges.
abstract: BACKGROUND
  Dengue is a major public health problem in Mexico, where the use of chemical insecticides to control the principal dengue vector, Aedes aegypti, is widespread. Resistance to insecticides has been reported in multiple sites, and the frequency of kdr mutations associated with pyrethroid resistance has increased rapidly in recent years. In the present study, we characterized patterns of insecticide resistance in Ae. aegypti populations in five small towns surrounding the city of Merida, Mexico.
  
  
  METHODS
  A cross-sectional, entomological survey was performed between June and August 2013 in 250 houses in each of the five towns. Indoor resting adult mosquitoes were collected in all houses and four ovitraps were placed in each study block. CDC bottle bioassays were conducted using F0-F2 individuals reared from the ovitraps and kdr allele (Ile1016 and Cys1534) frequencies were determined.
  
  
  RESULTS
  High, but varying, levels of resistance to chorpyrifos-ethyl was detected in all study towns, complete susceptibility to bendiocarb in all except one town, and variations in resistance to deltamethrin between towns, ranging from 63-88% mortality. Significant associations were detected between deltamethrin resistance and the presence of both kdr alleles. Phenotypic resistance was highly predictive of the presence of both alleles, however, not all mosquitoes containing a mutant allele were phenotypically resistant. An analysis of genotypic differentiation (exact G test) between the five towns based on the adult female Ae. aegypti collected from inside houses showed highly significant differences (p < 0.0001) between genotypes for both loci. When this was further analyzed to look for fine scale differences at the block level within towns, genotypic differentiation was significant for both loci in San Lorenzo (Ile1016, p = 0.018 and Cys1534, p = 0.007) and for Ile1016 in Acanceh (p = 0.013) and Conkal (p = 0.031).
  
  
  CONCLUSIONS
  The results from this study suggest that 3 years after switching chemical groups, deltamethrin resistance and a high frequency of kdr alleles persisted in Ae. aegypti populations. The spatial variation that was detected in both resistance phenotypes and genotypes has practical implications, both for vector control operations as well as insecticide resistance management strategies.
authors: Department of Environmental Sciences, Emory University, Atlanta, GA, USA. rldeming@gmail.com.
authors: Regan
authors: R
authors: Deming
authors: Unidad Colaborativa para Bioensayos Entomológicos, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Mexico. Pablo_manrique2000@hotmail.com.
authors: Pablo
authors: P
authors: Manrique-Saide
authors: Unidad Colaborativa para Bioensayos Entomológicos, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Mexico. anuar116@hotmail.com.
authors: Anuar
authors: A
authors: Medina Barreiro
authors: Unidad Colaborativa para Bioensayos Entomológicos, Campus de Ciencias Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Mexico. edgarkoyoc@gmail.com.
authors: Edgar Ulises Koyoc
authors: EU
authors: Cardeña
authors: Servicios de Salud de Yucatán, Gobierno del Estado de Yucatán, Mérida, Mexico. achemendoza_vectores@hotmail.com.
authors: Azael
authors: A
authors: Che-Mendoza
authors: Department of Environmental Sciences, Emory University, Atlanta, GA, USA. bdjone3@emory.edu.
authors: Bryant
authors: B
authors: Jones
authors: Division of Parasitic Diseases and Malaria, Entomology Branch, Centers for Disease Control and Prevention, Center for Global Health, Atlanta, GA, USA. Kelly.liebman@gmail.com.
authors: Kelly
authors: K
authors: Liebman
authors: Division of Parasitic Diseases and Malaria, Entomology Branch, Centers for Disease Control and Prevention, Center for Global Health, Atlanta, GA, USA. VTB6@cdc.gov.
authors: Lucrecia
authors: L
authors: Vizcaino
authors: Department of Environmental Sciences, Emory University, Atlanta, GA, USA. gmvazqu@emory.edu.
authors: Gonzalo
authors: G
authors: Vazquez-Prokopec
authors: Division of Parasitic Diseases and Malaria, Entomology Branch, Centers for Disease Control and Prevention, Center for Global Health, Atlanta, GA, USA. AJL8@cdc.gov.
authors: Audrey
authors: A
authors: Lenhart
mesh_terms: D000330:Aedes / Q000187:drug effects*; D000818:Animals; D001681:Biological Assay; D003430:Cross-Sectional Studies; D005787:Gene Frequency; D007303:Insect Vectors / Q000187:drug effects*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D008800:Mexico; D009032:Mosquito Control / Q000379:methods*; D016019:Survival Analysis
chemical_list: D007306:Insecticides