ASTMH 2016, Elizabeth Hemming-Schroeder: “Landscape genetics of pyrethroid resistance in Anopheles arabiensis in Kenya”

In collaboration with ASTMH, Image Audiovisuals, and session presenters, MESA brings you this webcast from the 65th ASTMH annual meeting in Atlanta, November 2016.

Title: “Landscape genetics of pyrethroid resistance in Anopheles arabiensis in Kenya”

Speaker: Elizabeth Hemming-Schroeder, University of California, Irvine

Session information: Scientific Session 144: “Mosquitoes: Molecular Genetics and Genomics”

Wednesday, 16 November, 1:45 – 3:30, Marriott – Room A602

Abstract:

Anopheles arabiensis have become increasingly abundant in Africa and are playing an important role in maintaining residual malaria transmission in sub-Saharan Africa. Overall, insecticide resistance in An. arabiensis has remained relatively low with respect to An. gambiae. However, recent studies suggest that resistance in An. arabiensis is emerging in Africa. Resistance could potentially increase and spread rapidly if gene flow between populations is large. Knowledge of An. arabiensis population genetic structure is critical to understanding insecticide resistance spread. We test how various ecological variables affect gene flow (dispersal) using a landscape genetics approach utilizing techniques from population genetics, landscape ecology, and spatial statistics. We genotyped An. arabiensis collected from 14 study sites across Kenya at 10 microsatellite loci and at kdr L1014F/S. We created resistance surfaces in ArcGIS for key environmental and landscape variables hypothesized to influence gene flow of An. arabiensis. We optimized resistance surfaces using the ResistanceGA package in R which utilizes a genetic algorithm to optimize surfaces based on pairwise genetic distances and CIRCUITSCAPE resistance distances. Lastly, mixed effects models were fit by maximum likelihood in the lme4 package in R. We observed both kdr 1014F and 1014S alleles. Kdr mutation frequencies were 0.023 and 0.103 at two sites in western Kenya and were absent from other sites. We hypothesize that forest cover and elevation provide the greatest barriers to gene flow and population density and roads largely promote gene flow. Understanding the factors promoting gene flow and insecticide resistance spread is critical to informing antimalarial interventions, especially since pyrethroid resistance in An. arabiensis is relatively low and patchily distributed.