Assessment of the effect of larval source management and house improvement on malaria transmission when added to standard malaria control strategies in southern Malawi: study protocol for a cluster-randomised controlled trial

Abstract

Background: Due to outdoor and residual transmission and insecticide resistance, long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) will be insufficient as stand-alone malaria vector control interventions in many settings as programmes shift toward malaria elimination. Combining additional vector control interventions as part of an integrated strategy would potentially overcome these challenges. Larval source management (LSM) and structural house improvements (HI) are appealing as additional components of an integrated vector management plan because of their long histories of use, evidence on effectiveness in appropriate settings, and unique modes of action compared to LLINs and IRS. Implementation of LSM and HI through a community-based approach could provide a path for rolling-out these interventions sustainably and on a large scale.

Methods/design: We will implement community-based LSM and HI, as additional interventions to the current national malaria control strategies, using a randomised block, 2 × 2 factorial, cluster-randomised design in rural, southern Malawi. These interventions will be continued for two years. The trial catchment area covers about 25,000 people living in 65 villages. Community participation is encouraged by training community volunteers as health animators, and supporting the organisation of village-level committees in collaboration with The Hunger Project, a non-governmental organisation. Household-level cross-sectional surveys, including parasitological and entomological sampling, will be conducted on a rolling, 2-monthly schedule to measure outcomes over two years (2016 to 2018). Coverage of LSM and HI will also be assessed throughout the trial area.

Discussion: Combining LSM and/or HI together with the interventions currently implemented by the Malawi National Malaria Control Programme is anticipated to reduce malaria transmission below the level reached by current interventions alone. Implementation of LSM and HI through a community-based approach provides an opportunity for optimum adaptation to the local ecological and social setting, and enhances the potential for sustainability.

Trial registration: Registered with The Pan African Clinical Trials Registry on 3 March 2016, trial number PACTR201604001501493.

Keywords: Anopheles mosquitoes; Community participation; House improvement; Integrated vector management; Larval source management; Malaria transmission; Vector control.

Fig. 1

Study site map. Majete Wildlife Reserve, surrounded by 19 groups of villages known as community-based organisations (CBO). Trial villages fall under 7 of these CBOs, representing the 3 focal areas, or blocks. All villages in these 7 CBOs were enumerated into a demographic surveillance system (DSS). Reprinted with slight modification from Kabaghe et al. [90]

Fig. 2

Example showing how buffer zones were used to define contamination distance. Village A and Village B could not be assigned to different treatments without risking contamination bias. Village C is assumed to be a sufficient distance from Villages A and B to limit contamination bias

Fig. 3

Random exclusion of villages. All five maps show the 21 villages of the focal area to the west of Majete Wildlife Reserve. a shows a 400 m buffer overlaid on each of the 21 villages. Nineteen of the villages have overlapping buffers, while two villages are a sufficient distance from the others to limit contamination bias. b and c highlight two different sets of villages that could be excluded from the trial intervention allocation, so as to leave the clusters of villages shown in d and e, whereby clusters do not overlap with each other

Fig. 4

Flow chart showing the allocation of treatments to villages. HI, house improvement; LSM, larval source management; NMCP, National Malaria Control Programme

Fig. 5

Trial timeline. The red line indicates the start of the trial. Bti Bacillus thuringiensis israelensis; DSS, demographic surveillance system; D/F, draining and filling; HA, health animators; HI, house improvement; LSM, larval source management; LLIN, Long-lasting insecticidal nets; NMCP, National Malaria Control Programme