Large fluctuations in the effective population size of the malaria mosquito Anopheles gambiae s.s. during vector control cycle.
On Bioko Island, Equatorial Guinea, indoor residual spraying (IRS) has been part of the Bioko Island Malaria Control Project since early 2004. Despite success in reducing childhood infections, areas of high transmission remain on the island. We therefore examined fluctuations in the effective population size (N e ) of the malaria vector Anopheles gambiae in an area of persistent high transmission over two spray rounds. We analyzed data for 13 microsatellite loci from 791 An. gambiae specimens collected at six time points in 2009 and 2010 and reconstructed the demographic history of the population during this period using approximate Bayesian computation (ABC). Our analysis shows that IRS rounds have a large impact on N e , reducing it by 65%-92% from prespray round N e . More importantly, our analysis shows that after 3-5 months, the An. gambiae population rebounded by 2818% compared shortly following the spray round. Our study underscores the importance of adequate spray round frequency to provide continuous suppression of mosquito populations and that increased spray round frequency should substantially improve the efficacy of IRS campaigns. It also demonstrates the ability of ABC to reconstruct a detailed demographic history across only a few tens of generations in a large population.
Department of Entomology, Texas A&M University College Station, TX, USA.
Theresa K
TK
Hodges
Department of Entomology, Texas A&M University College Station, TX, USA.
Giridhar
G
Athrey
Department of Entomology, Texas A&M University College Station, TX, USA.
Kevin C
KC
Deitz
Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences Ås, Norway.
Hans J
HJ
Overgaard
Medical Care Development International Inc. Malabo, Equatorial Guinea New Haven, CT, USA.
Abrahan
A
Matias
Department of Ecology and Evolutionary Biology, Yale University New Haven, CT, USA.
Adalgisa
A
Caccone
Department of Entomology, Texas A&M University College Station, TX, USA.
Michel A
MA
Slotman
Anopheles gambiae; approximate Bayesian computation; effective population size; indoor residual spraying; malaria; vector control