HPGDS and malaria: Using the recent L119F-GSTe2 diagnostic tool for glutathione S-transferase metabolism of pyrethroids/DDT resistance in the resistant African malaria vector An. funestus, we showed in this study using mosquitoes collected in the same location that metabolic resistance could incur fitness costs in resistant mosquitoes but also provide a fitness advantage to resistant mosquitoes; although further work is needed to assess any possible effects associated with closely linked genes.