Abstract
<jats:title>Abstract</jats:title> <jats:p>The effectiveness of malaria vector control is increasingly threatened by widespread insecticide resistance, particularly to pyrethroids. In response, the World Health Organization recommends dual-active ingredients (dual-A.I.) insecticide-treated nets (ITNs) in resistant settings. This study evaluated the efficacy of several dual-A.I. ITNs in two experimental hut trial sites an area with high insecticide resistant malaria vectors in Tanzania with differing vector species composition and bionomics.</jats:p> <jats:p> Five ITNs were evaluated: a pyrethroid-only net (MAGNet®), three pyrethroid-piperonyl butoxide (PBO) nets (OlysetTM Plus, Veeralin®, and PermaNet® 3.0), one dual-A.I. net (Interceptor® G2; chlorfenapyr + alpha-cypermethrin), and an untreated control net. Mosquitoes were collected from huts, morphologically identified, and monitored for mortality up to 72 h. WHO cone and tunnel tests using susceptible <jats:italic>An. gambiae</jats:italic> s.s. were conducted for quality control, while field-collected mosquitoes were used for bio-efficacy monitoring. Molecular species identification was performed using PCR assays, and genomic DNA was extracted from <jats:italic>An. funestus</jats:italic> s.l. and <jats:italic>An. gambiae</jats:italic> s.l. collected from the trials. </jats:p> <jats:p> All ITNs met WHO bio-efficacy criteria in cone and tunnel tests. <jats:italic>An. gambiae</jats:italic> s.l. predominated in Mwagagala (77%) but was rare in Magu (4%), where <jats:italic>An. funestus</jats:italic> complex was dominant. In Magu, Interceptor® G2 and Veeralin® achieved significantly higher mortality than MAGNet® at 24 h (53% and 45% vs 24%) and 72 h (61% and 53% vs 24%). In contrast, no significant mortality differences were observed among ITNs in Mwagagala. High resistance intensity was detected in both vector groups (mortality <20% in bioassays). In <jats:italic>An. funestus</jats:italic> from Magu, the 4.3 kb-SV resistant genotype was fixed, while G454A-CYP9K1 resistance was highly prevalent (RR: 0.70– 1.00). </jats:p> <jats:p> Interceptor® G2 and Veeralin® outperformed the pyrethroid-only reference net against <jats:italic>An. funestus</jats:italic> complex but not against predominantly <jats:italic>An. arabiensis</jats:italic> populations. </jats:p>