The effect of community-driven larval source management and house improvement on malaria transmission when added to the standard malaria control strategies in Malawi: a cluster-randomized controlled trial

Abstract

Background Current standard interventions are not universally sufficient for malaria elimination. The effects of community-based house improvement (HI) and larval source management (LSM) as supplementary interventions to the Malawi National Malaria Control Programme (NMCP) interventions were assessed in the context of an intensive community engagement programme. Methods The study was a two-by-two factorial, cluster-randomized controlled trial in Malawi. Village clusters were randomly assigned to four arms: a control arm; HI; LSM; and HI + LSM. Malawi NMCP interventions and community engagement were used in all arms. Household-level, cross-sectional surveys were conducted on a rolling, 2-monthly basis to measure parasitological and entomological outcomes over 3 years, beginning with one baseline year. The primary outcome was the entomological inoculation rate (EIR). Secondary outcomes included mosquito density, Plasmodium falciparum prevalence, and haemoglobin levels. All outcomes were assessed based on intention to treat, and comparisons between trial arms were conducted at both cluster and household level. Results Eighteen clusters derived from 53 villages with 4558 households and 20,013 people were randomly assigned to the four trial arms. The mean nightly EIR fell from 0.010 infectious bites per person (95% CI 0.006–0.015) in the baseline year to 0.001 (0.000, 0.003) in the last year of the trial. Over the full trial period, the EIR did not differ between the four trial arms (p = 0.33). Similar results were observed for the other outcomes: mosquito density and P. falciparum prevalence decreased over 3 years of sampling, while haemoglobin levels increased; and there were minimal differences between the trial arms during the trial period. Conclusions In the context of high insecticide-treated bed net use, neither community-based HI, LSM, nor HI + LSM contributed to further reductions in malaria transmission or prevalence beyond the reductions observed over two years across all four trial arms. This was the first trial, as far as the authors are aware, to test the potential complementary impact of LSM and/or HI beyond levels achieved by standard interventions. The unexpectedly low EIR values following intervention implementation indicated a promising reduction in malaria transmission for the area, but also limited the usefulness of this outcome for measuring differences in malaria transmission among the trial arms. Trial registration PACTR, PACTR201604001501493, Registered 3 March 2016, https://pactr.samrc.ac.za/.

Cost of community-led larval source management and house improvement for malaria control: a cost analysis within a cluster-randomized trial in a rural district in Malawi

“…Whereas previous studies often reported ‘cost per person protected ’, i.e. interventions protected (or were assumed to protect) the target population [ 14 , 15 , 33 ], this study used ‘cost per person’ as there was no statistical evidence of a protective effect of HI or LSM on primary entomological and epidemiological outcomes [ 24 ]. Thus, these annual per person costs are best interpreted as the average annual cost of implementing the interventions, as in the Majete trial study area.…”

“…For example, while proportions of water bodies treated with larvicide may be similar across settings, e.g. 86% in the rural Tanzania study [ 33 ] versus 84% in the MMP LSM/HI trial [ 24 ], also see Additional file 5 ), the costs of draining and filling, not reported in the Tanzania study, may underlie observed differences. Similarly for house improvement interventions, previous studies have reported closing eaves and screening windows, but varied in terms of additional modifications, e.g.…”

“…In 2015, the MMP study area catchment population was estimated at 25,000 people. From April 2015 to April 2016, malaria parasite prevalence in children aged 6–59 months was 33.8% (95% confidence interval 30.8–36.9%) [ 24 ]. The main source of income for the communities surrounding MWR is subsistence farming [ 25 ].…”

“…The MMP LSM/HI trial used a cluster-randomized 2 × 2 factorial design to assess the effect of LSM and HI on malaria transmission when added to standard national malaria control programme (NMCP) interventions at scale-up for impact targets, over a 2-year period. The village was the unit of intervention implementation, so that all households in each village were targeted to receive the trial intervention, as per the cluster’s treatment arm [ 24 ]. The four trial arms were: (1) NMCP + HI; (2) NMCP + LSM; (3) NMCP + HI + LSM; (4) NMCP only (control arm); hereinafter HI, LSM, HI + LSM and control arms, respectively.…”

“…No IRS was implemented in the study area during the trial period [ 23 ]. The MMP was not responsible for implementation of NMCP interventions; rather, these interventions were implemented by the Chikwawa DHO as done throughout the district [ 24 ].…”