Published in PLOS One on 2026-05-19, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original authors: GloriaSalome Shirima, Emma L. Fairbanks, Tegemeo Gavana, Gerald Kiwelu, Ismail Nambunga, Yeromin P. Mlacha, Silas Mirau, Prosper Chaki, Nakul Chitnis, Samson Kiware
Source: PLOS One • DOI 10.1371/journal.pone.0337662
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
Combining larviciding with insecticide treated nets (ITNs) can reduce malaria transmission. However, most modelling analyses use generalized scenarios rather than incorporating local epidemiological and ecological contexts. In Tanzania and other countries, larviciding is increasingly being prioritized in national strategies, with growing advocacy for its broader implementation, to achieving sustained malaria reduction. District-specific modelling is therefore essential to capture variation in transmission ecology, seasonality, and varying coverage levels, providing evidence that is both rigorous and actionable for malaria control programs. The Vector Control Optimization Model (VCOM) was adapted and extended to incorporate local seasonality, simulating the impact of larviciding across a range of coverage levels combined with ITNs. The model was parameterized using district-level field-data on mosquito mortality collected before (2016–2017) and after (2019–2021) larviciding implementation. Mosquito mortality rates were estimated using Bayesian inference. Outcomes were evaluated specifically for Anopheles gambiae s.l. including annual entomological inoculation rates (EIR) and mosquito density. Sensitivity analysis explored the influence of key parameters driving transmission in this scenario study. The immature mosquito mortality rate due to larviciding was 61% based on field data. VCOM simulation showed that, at 80%, ITNs coverage, larviciding substantially reduced mosquito densities and EIR. Specifically, combining ITNs at 80% and larviciding coverage ≥ 60% lowered EIR below 1 ib/p/year, the threshold required to interrupt malaria transmission. Sensitivity analyses highlighted the high impact of targeting immature mosquitoes, suggesting larviciding can effectively complement ITNs to control vectors, including invasive species like An. stephensi, regardless of feeding preference, resting, and biting behaviors, which hinder the effectiveness of most vector control tools. This study provides local evidence that larviciding is an effective complement to ITNs for interrupting malaria transmission. Implementation should leverage innovative approaches, such as drones for precise mapping and targeted application of biological larvicides, to maximize coverage, and scalability for district-level malaria control and elimination.
Background
Malaria, remains a significant global health threat, particularly in sub-Saharan Africa [1]. In 2023, there were an estimated 263 million cases globally, with the African region accounting for 89.7% of this burden [2]. In Tanzania, malaria ranks among the top causes of mortality and morbidity; malaria case incidence increased by 5.6% from 121 in 2022–128 per 1000 of the population at risk [2–4]. The Rufiji district, is in south-eastern Tanzania, a malaria hotspot within the country [5] that needs some interventions to ensure malaria reduction. The World Health Organization (WHO) recommends chemoprevention, case management, and vector control as core malaria interventions. However, the primary vector control tools, notably insecticide-treated nets (ITNs) and indoor residual spraying (IRS), are facing challenges. This is due to several factors, including insecticide resistance and changes in mosquito behavior, such as increased outdoor and early-evening biting, which reduce the effectiveness of these indoor-targeted tools [6]. These challenges have contributed to a shortfall in achieving national and global targets such as the WHO’s 2030 goal to reduce malaria incidence and mortality by at least 90% from 2015 levels. As of 2023, globally, there were 60 cases per 1,000 people at risk and 13.7 deaths per 100,000 people at risk, compared to the targeted figures of 21.3 cases per 1,000 and 5.5 deaths per 100,000 people at risk [2,7].
Reading this evidence
Use the full paper to check the study design, participant selection, comparator and outcome definitions before drawing a practical conclusion. An association does not by itself show cause and effect. A reported performance measure needs its denominator and uncertainty. A finding from a particular facility, sample or time period should retain that scope when it is discussed elsewhere.
This briefing makes the source accessible within the wider public health desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2026 GloriaSalome Shirima, Emma L. Fairbanks, Tegemeo Gavana, Gerald Kiwelu, Ismail Nambunga, Yeromin P. Mlacha, Silas Mirau, Prosper Chaki, Nakul Chitnis, Samson Kiware. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
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