The study, led by Fadhila Kihwele and Tegemeo Gavana of the Ifakara Health Institute together with collaborators from the Swiss Tropical and Public Health Institute, the University of Basel, and Tanzania’s National Malaria Control Programme, is part of a comprehensive evaluation of the Tanga pilot. Companion publications report on the program’s operations, entomological and epidemiological impacts, and costs. This particular investigation focused on the human dimension: how stakeholders at every level, from national officials down to village volunteers, perceived the intervention, what made it work, what got in its way, and whether it could endure beyond the pilot phase.

The scientific logic behind larviciding is straightforward. Malaria control has long depended on insecticide-treated nets and indoor residual spraying, both of which target adult mosquitoes inside homes. But malaria parasites still kill an estimated 597,000 people each year, and global progress has stalled since 2015, driven in part by mosquito behavioral adaptations and widespread pyrethroid resistance. Larval source management attacks the problem at a different stage of the mosquito life cycle, applying agents to aquatic breeding habitats to kill larvae before they ever take flight. The World Health Organization recommends larviciding as a supplementary measure, ideally where breeding sites are few, fixed, and findable. Historically, larviciding helped eradicate malaria vectors in Brazil, Egypt, and the Zambian copperbelt, but large-scale implementation in modern Africa has been rare, constrained by the difficulty of locating scattered breeding sites and questions of cost-effectiveness.

Tanzania’s pilot was distinctive in two respects. First, it used biological larvicides rather than conventional insecticides: Bactivec, containing spores of Bacillus thuringiensis var. israelensis (Bti), and Griselesf, containing spores of Bacillus sphaericus (Bs). These bacteria produce toxins that are lethal to mosquito larvae when ingested but are considered harmless to humans, livestock, fish, frogs, and the broader ecosystem. Because their mode of action differs completely from the pyrethroids used in nets and indoor spraying, they offer a way to diversify the vector control arsenal and manage insecticide resistance. Both products are manufactured in-country by Tanzania Biotech Products Limited, a government-owned enterprise created through a bilateral partnership between Tanzania and Cuba. Second, the program was delivered entirely through the existing government system, from the National Malaria Control Programme at the top down to village executive officers, using community-owned resource persons, or CORPs, selected by village leaders to identify breeding sites and apply larvicide weekly, the interval at which the products remain effective.

To capture perceptions of this ambitious undertaking, the researchers conducted a cross-sectional qualitative study in 2023, the second year of implementation. They carried out 31 in-depth interviews with government officials overseeing the project at village, ward, council, regional, and national levels, and held 13 focus group discussions with 156 community participants, including 72 CORPs and 84 other community members. The three intervention councils, Handeni District Council, Tanga City Council, and Lushoto District Council, were deliberately chosen to represent high, moderate, and low malaria risk strata and to span rural and urban settings. Interviews were conducted in Swahili, audio-recorded with consent, transcribed verbatim, and analyzed using framework analysis with NVivo software, with double coding and triangulation to reinforce rigor. Data collection continued until thematic saturation was reached.

The findings on acceptance were striking. Almost all stakeholders described the intervention as safe, and no adverse events were reported at village or ward offices across the study area. Yet the initial rollout tested community trust. When CORPs began spraying larvicide into water sources used for drinking and domestic purposes, some residents worried about their safety. The response was remarkably direct: CORPs sometimes tasted the biolarvicide or drank water from sprayed wells in front of community members to prove it was harmless. One CORP in Handeni told the researchers,

The willingness of CORPs to demonstrate the safety of the larvicide by drinking treated water illustrates a broader principle in community health programming: acceptability is not merely a passive attitude but something actively constructed through trust, demonstration, and repeated positive experience. In the Tanga pilot, this trust-building appears to have paid off. Community members across the three councils came to view the weekly applications as a routine and beneficial part of village life, and many participants in the focus group discussions linked the intervention to perceived reductions in mosquito densities and malaria episodes. Such perceptions matter for sustainability because community-based programs depend on voluntary cooperation, from granting CORPs access to private water sources to tolerating the logistical disruptions of weekly spraying campaigns.

The qualitative design of the study deserves attention for what it can and cannot reveal. Framework analysis, the method used to organize the interview and focus group data, allows researchers to systematically chart themes across stakeholder categories while preserving the context and nuance of individual accounts. By triangulating the perspectives of national officials, council health teams, ward and village officers, CORPs, and ordinary community members, the researchers could identify where perceptions converged and where they diverged. What emerges is a layered picture: national and regional officials emphasized feasibility and institutional fit, while community participants focused on tangible experiences such as the smell of the product, the reliability of CORP visits, and the visibility of results. This kind of multi-level perception mapping is increasingly recognized as essential for designing interventions that survive the transition from pilot to program.

The challenges identified in the study are not unique to larviciding, but they carry particular weight for this intervention model. The unpleasant odor of the larvicide, repeatedly mentioned by participants, is more than a cosmetic nuisance; in community-based programs, sensory characteristics of a product can shape rumors, resistance, and ultimately coverage. High turnover among CORPs poses a parallel threat, because these volunteers embody the institutional memory of the program. Each departure means retraining, re-mapping of breeding sites, and re-establishing relationships with village leaders and residents. The study’s finding that turnover was driven partly by irregular or inadequate incentives echoes a well-documented problem in community health worker programs across sub-Saharan Africa, where volunteer cadres are often asked to perform substantial labor without reliable compensation.

Discontinuous implementation emerged as another recurring concern. Larviciding, unlike bed net distribution, requires sustained, rhythmical application: the biological toxins in Bti and Bs products degrade in the environment within roughly a week, so any pause in the spraying cycle allows larvae in treated habitats to complete their development and replenish the adult mosquito population. Interruptions caused by funding delays, stockouts, or seasonal gaps in supervision therefore have direct entomological consequences. This characteristic makes larviciding operationally more demanding than some other vector control tools, and it underscores why the study’s participants stressed the importance of predictable financing and supply chains for any future scale-up.

The Tanga pilot also offers a case study in implementation through government structures rather than parallel project systems. Delivering the program through local government authorities, with the National Malaria Control Programme providing national supervision, was a deliberate choice intended to produce a model that could be replicated if the government decided to expand. This design has implications for sustainability: interventions embedded in existing administrative structures are generally better positioned to survive the withdrawal of external donors and technical partners. The involvement of the President’s Office–Regional Administration and Local Government signals that the program was conceived from the outset as a potential public service rather than a research demonstration, which may explain the strong institutional buy-in reported by officials at multiple levels.

The broader context of malaria control in Tanzania lends urgency to these findings. Sub-Saharan Africa carries roughly 95 percent of global malaria cases and deaths, and the continent faces mounting threats from insecticide resistance, invasive vector species such as Anopheles stephensi that thrive in urban environments, and changing mosquito behaviors that reduce the effectiveness of indoor tools. Biological larvicides, with their distinct mode of action, offer a way to relieve selection pressure on pyrethroids while targeting outdoor-biting and outdoor-breeding vectors. The renewed interest in larval source management across countries such as Rwanda, Kenya, Burkina Faso, and The Gambia reflects this strategic logic, and the Tanzanian experience provides one of the few large-scale, government-implemented evidence bases available to inform those efforts.

For policymakers weighing a national rollout, the qualitative findings suggest that the technical questions about larviciding are increasingly inseparable from social and organizational ones. The Tanga evidence indicates that communities will accept and even champion larviciding when it is delivered by trusted local actors and perceived as safe and effective. But it equally indicates that the same community-based model is fragile in the face of volunteer attrition, supply disruptions, and product characteristics that irritate the very people it protects. Addressing these operational vulnerabilities, through sustainable incentive structures for CORPs, reliable procurement of biolarvicide, improved product formulation or masking of odor, and continuous rather than episodic implementation, will likely determine whether the promise demonstrated in Tanga can be translated into durable malaria reduction across Tanzania and beyond.

Subject of Research: Stakeholder perceptions, acceptability, and sustainability of a community-based mosquito larviciding intervention for malaria control in Tanga Region, Tanzania

Article Title: Stakeholders’ perceptions, acceptability, and sustainability of a larviciding intervention in Tanga Region, Tanzania

Article References: Kihwele, F., Gavana, T., Kailembo, D., Kasagama, E., Mwalimu, C. D., Bernard, J., Yoram, B., Ndekuka, L., Kajange, S., Lazaro, S., Kisoka, N., Chaki, P., Lengeler, C., & Dillip, A. (2025). Stakeholders’ perceptions, acceptability, and sustainability of a larviciding intervention in Tanga Region, Tanzania. Frontiers in Malaria, 3, Article 1693543. https://doi.org/10.3389/fmala.2025.1693543

Image Credits: AI Generated

DOI: 10.3389/fmala.2025.1693543

Keywords: malaria, larviciding, Tanzania, vector control, biolarvicide, Bacillus thuringiensis israelensis, community health workers, Tanga Region, insecticide resistance, larval source management, public health, qualitative research