Modelling the impact of larviciding as a supplementary malaria vector control intervention in rural south-eastern Tanzania: A district-level simulation study
Loading...
Date
2025-11-15
Journal Title
Journal ISSN
Volume Title
Publisher
medRxiv
Abstract
Combining larviciding with insecticide treated nets (ITNs) can reduce malaria transmission, but
42 most modelling analyses use generalized scenarios rather than local contexts. In Tanzania and
43 other countries, larviciding is increasingly being prioritized in national strategies, with growing
44 advocacy for its broader implementation, to achieving sustained malaria reduction. District-
45 specific modelling is therefore essential to capture variation in transmission ecology, seasonality,
46 and varying coverage levels, providing evidence that is both rigorous and actionable for malaria
47 control programs. The Vector Control Optimization Model (VCOM) was adapted and extended to
48 incorporate local seasonality, simulating the impact of larviciding across a range of coverage levels
49 combined with ITNs. The model was parameterized using district-level field-data on mosquito
50 mortality collected before (2016-2017) and after (2019-2021) larviciding implementation.
51 Mosquito mortality rates were estimated using Bayesian inference. Outcomes were evaluated
52 specifically for Anopheles gambiae s.l. including annual entomological inoculation rates (EIR) and
53 mosquito density. Sensitivity analysis explored the influence of key parameters driving
54 transmission in this scenario study. The immature mosquito mortality rate due to larviciding is
55 estimated to be 61% based on field data. VCOM simulation showed that, at 80%, ITNs coverage,
56 larviciding substantially reduced mosquito densities and EIR. Specifically, combining ITNs at
57 80% and larviciding coverage ≥ 60% lowered EIR below 1, the threshold required to interrupt
58 malaria transmission. Sensitivity analyses highlighted the high impact of targeting immature
59 mosquitoes, suggesting larviciding can effectively complement ITNs to control vectors, including
60 invasive species like An. stephensi, regardless of feeding preference, resting, and biting behaviors,
61 which hinder the effectiveness of most vector control tools. This study provides local evidence
62 that larviciding is an effective complement to ITNs for interrupting malaria transmission.
63 Implementation should leverage innovative approaches, such as drones for precise mapping and
64 targeted application of biological larvicides, to maximize coverage, and scalability for district-
65 level malaria control and elimination
Sustainable Development Goals
SDG 3: Good Health and Well-Being
SDG 9: Industry, Innovation and Infrastructure
SDG 10: Reduced Inequalities
Keywords
Larviciding, ITNs, VCOM, malaria transmission, district-level modeling