Process Evaluation of a Community-Based Microbial Larviciding Intervention for Malaria Control in Rural Tanzania

Abstract

Microbial larviciding can be an effective component of integrated vector management malaria control schemes, although it is not commonly implemented. Moreover, quality control and evaluation of intervention activities are essential to evaluate the potential of community-based larviciding interventions. We conducted a process evaluation of a larval source management intervention in rural Tanzania where local staff were employed to apply microbial larvicide to mosquito breeding habitats with the aim of long-term reductions in malaria transmission. We developed a logic model to guide the process evaluation and then established quantitative indicators to measure intervention success. Quantitative analysis of intervention reach, exposure, and fidelity was performed to assess larvicide application, and interviews with larviciding staff were reviewed to provide context to quantitative results. Results indicate that the intervention was successful in terms of reach, as staff applied microbial larvicide at 80% of identified mosquito breeding habitats. However, the dosage of larvicide applied was sufficient to ensure larval elimination at only 26% of sites, which does not meet the standard set for intervention fidelity. We propose that insufficient training and protocol adaptation, environment and resource issues, and human error contributed to low larvicide application rates. This demonstrates how several small, context-specific details in sum can result in meaningful differences between intervention blueprint and execution. These findings may serve the design of other larval source management interventions by demonstrating the value of additional training, supervision, and measurement and evaluation of protocol adherence.

Local resource mobilization for malaria vector control among Rwandan rice farmers: a pilot study into the role of community ownership

“…In case the slow onset of effectiveness observed in CB is inherent to community self-organization, the monitoring data suggest that LSM application of larval source management by well-trained professionals had advantages over implementation by rice farming communities themselves, implying a trade-off between community agency and effectiveness. This aligns with the underdosage problem identified during community-based larviciding in rural Tanzania [33], but is at odds with Chaki et al 's [65] finding in urban Tanzania that CORPs who were recruited through the program administrative staff performed rather poorly when compared to those who were selected at the community level, specifically in relation to the task of mosquito habitat coverage. It should be pointed out, however, that our outcome effectiveness analysis did not extend beyond the intervention period, so we are unable to check the precise window of effectiveness in both groups in an objective sense, nor did we track to what extent lower larval and pupal densities translated into lower rates of entomological inoculation or malaria positivity.…”

“…Tanzania (urban) [2006–2008] Non-random trial with control [12/67 neighbourhoods] Sensitization: No Spraying: Yes Supervision: Yes [ 34 , 38 ] #2. Tanzania (rural) [2012–2013] Randomised 2 × 2 factorial design; (1) LSM; (2) early detection and treatment [12/24 villages] Sensitization: Yes Spraying: Yes Supervision: No [ 29 , 33 ] #3. Burkina Faso (rural/semi-urban) [2013–2015] Cluster-randomised trial with control; treatment varied by intensity (50% or 100% of sites sprayed) [85/127 villages] Sensitization: Yes Spraying: Yes Supervision: No [ 28 , 36 , 40 , 41 ] #4.…”

“…The limits of community engagement are reflected most clearly in the supervision of the larviciding campaign, which often falls to outside experts. For example, the trial in the border region of Botswana and Zimbabwe made sure that “community volunteers […] worked under the full supervision of an entomologist seconded to the study by the Ministry of Health” [ 32 ] and in rural Tanzania “a trained entomology supervisor was on-site throughout the three-month intervention period in each year to […] conduct quality control spot checks” [ 33 ]. Occasionally, supervision became more hybrid, as in Ethiopia, where the ‘mosquito scouts’ who were primarily sprayers in 2013–2015 (#4) gained a more supervisory role in 2016–2018 (#6), even though the involved research institute carried the final responsibility for surveillance [ 30 ].…”

“…Yet, a trade-off between the delegation of Bti spraying to the community level on the one hand, and effectiveness on the other, was observed in rural Tanzania. Berlin Rubin et al [ 33 ] observed a satisfactory coverage rate of community-based spraying teams (80% of the mosquito breeding habitats identified), but under-dosing of larvicide occurred in almost three out of every four sites inspected. While acknowledging incomplete adherence to protocols in the urban context of Dar es Salaam, Geissbühler et al [ 38 ] nonetheless conclude that “larval control can have such clear benefits, even when applied sub-optimally”, which in turn “questions the assumption that very high levels of programmatic performance are essential for this approach to deliver epidemiological impact” (p. 10).…”

The Laboratory and Semi-Field Larvicidal Effects of Essential Oil Extracted from Feronia limonia against Anopheles arabiensis Patton

“…The modification of the plant-based biolarvicides is of paramount importance to extend its longevity in environment by making it in slow-release technology. This technology has been practical to Bacillus thuringiensis israelensis (Bti), which in application lasts for 5–7 days [ 14 , 15 ], but with improved slow-release technology, it has lasted active against larvae for 6 months with no effects to non-targeted organisms [ 3 , 16 ].…”