First report of N1575Y mutation in pyrethroid resistant Anopheles gambiae s.l. in Nigeria

Abstract

In view of recent findings that codon 1575 mutation increases the L1014F-mediated resistance in Anopheles mosquitoes, we investigated the presence of this mutation in four States with intense pyrethroid resistance in Nigeria. Permethrin and deltamethrin susceptibility tests were carried out using 2–3 day old adult female Anopheles from larval collections. Based on the susceptibility test results, intensity tests with 5x and 10x concentrations were carried out at sites with high resistance (% mortality>85). Resistant specimen were identified by PCR and screened for the presence of L1014F and N1575Y mutations using allele specific PCR and Taqman assay respectively. The frequency of kdr mutation for permethrin varied from 0.71–0.75 for 5x and 0.73–0.75 for 10x. The kdr frequency for deltamethrin was not significantly different (P = 0.157): 0.54–0.60 for 5x and 0.66–0.71 for 10x. Percentage increase in kdr frequency between 1x and 5x permethrin doses ranges from 1.4% to 11.9% in all sites except Edo and Anambra; while only Lagos had percentage increase of 1.4% between 5x and 10x. For deltamethrin, Lagos and Niger had the same (3.8%) percentage increase in kdr frequency between 1x and 5x, while 5x and 10x gave 23.6% and 31.5% respectively. Resistant Anopheles gambiae at 5x and 10x concentrations of permethrin showed the presence of homozygous (Y) and heterozygous (NY) mutant allele in two sites. From this study, the mutation has no significant association with resistance intensity (χ2=0.8, P = 0.3711). There is need for frequent monitoring to forestall the effect this may have on national malaria control programs.