Durability of the insecticidal activity of next-generation insecticide treated nets distributed for malaria control in Mozambique: Findings from the New Nets Project (2020–2022)
Bibliographic record
Abstract
Abstract Background As next-generation insecticide-treated nets (ITNs) are increasingly deployed, it is essential to monitor their durability over time under operational conditions to support evidence-based procurement and replacement strategies by national malaria programs. This study evaluated the insecticidal durability of next-generation ITNs distributed in Mozambique through the New Nets Project (2020–2022), with a focus on bioefficacy and chemical content over 24 months of household use. Methods An ITN insecticidal durability study was conducted with nets from four districts of Mozambique to evaluate four ITN product types: pyrethroid-only (MAGNet ® , DuraNet ® , Olyset ® Net), pyrethroid-PBO (Olyset ® Plus), pyrethroid-pyriproxyfen (Royal Guard ® ), and pyrethroid-chlorfenapyr (Interceptor ® G2). ITNs were withdrawn from households at 6, 12, and 24 months post-distribution. Bioefficacy was assessed via WHO cone and tunnel bioassays using insecticide-susceptible and pyrethroid-resistant laboratory strains of Anopheles gambiae s.l., and through experimental hut trials in Cove, Benin against wild, pyrethroid-resistant An. gambiae s.l. populations. Chemical analysis was conducted to quantify active ingredient content over time. Results The pyrethroid components of all ITN types retained high efficacy, with 100% of nets meeting WHO bioefficacy criteria at 6, 12, and 24 months in bioassays using the susceptible An. gambiae KISUMU strain. However, the proportion of Olyset ® Plus nets meeting WHO thresholds in bioassays assessing the bioefficacy of the PBO component against the pyrethroid-resistant An. gambiae s.l. AKRON strain, declined from 73% at 6 months to 40% at 24 months. Royal Guard ® showed variable performance for pyriproxyfen bioefficacy, with pass rates increasing from 43% to 87% over the same period. Interceptor ® G2 maintained high bioefficacy against the pyrethroid-resistant VKPER strain, with ≥92% of nets meeting WHO efficacy criteria across all time points. Experimental hut trials confirmed the superior field performance of Interceptor ® G2 compared to pyrethroid-only nets, though mortality declined from 55% to 39% and blood-feeding inhibition from 72% to 19% between 6 and 24 months. Chemical analysis showed substantial degradation of PBO and chlorfenapyr by 24 months, with residual levels at 8% and 32% of baseline, respectively. Conclusion Next-generation ITNs provide improved protection against pyrethroid-resistant malaria vectors, but the durability of their enhanced efficacy varies by active ingredient. Interceptor ® G2 demonstrated the most consistent performance over 24 months, reinforcing its utility for control of pyrethroid resistant malaria vectors. However, declining personal protection and insecticide content underscore the need for long-term monitoring. These findings support the implementation of extended, context-specific durability studies to guide ITN selection, replacement strategies, and policy decisions for sustained malaria control.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".