Combining indoor residual spraying and long-lasting insecticidal nets for preventing malaria: Cluster randomized trial in Ethiopia

The project "Combining indoor residual spraying and long-lasting insecticidal nets for preventing malaria: Cluster randomised trial in Ethiopia" aims to inform national and global policy-makers on the combined use of indoor residual spraying (IRS) and Long Lasting Insecticidal Net (LLIN) in controlling malaria. The current main malaria control strategies are LLINs and IRS. Most often, these interventions have proven to be effective when applied as a single intervention. The MalTrials study aims to evaluate if a combination of the two interventions is more efficient and cost-effective and that using them alone. During the first year of the study, there was a low incidence of malaria cases in the study area, potentially as a result of severe drought in the Rift Valley of Ethiopia. This cluster randomized controlled trial was done in the Adami Tullu district in south-central Ethiopia for 119 weeks, from September 2014 to January 2017. Prior to the trial, we did a pilot study to estimate the sample size, and registered 8 malaria episodes per 10,000 person-weeks of observation (PWO). 6072 households (HHs) were randomly assigned to four intervention arms: LLINs + IRS, LLINs, IRS, and no intervention implemented by the project (control). The primary outcome was malaria incidence. Analysis was based on an intention-to-treat principle. Each arm had 44 clusters with an average of 35 HHs per cluster; the total population was 34,548. PermaNet 2.0 LLINs were distributed in September 2014, and IRS (with propoxur) was carried out yearly. Active and passive case detection were done weekly. Malaria was diagnosed using a rapid diagnostic test (CareStartTM). Anaemia was assessed through yearly surveys on children. The yearly rainfall was 60% of expected in 2015 (El Nino effect), entomological studies were simultaneously conducted. The overall malaria incidence was 2.91 per 10,000 PWO (37% of pre-intervention incidence), and similar in the four arms with 2.99 (LLINs + IRS), 2.92 (LLINs), 3.01 (IRS) and 2.72 (control). Entomological findings showed greater outdoor mosquito human-biting activities than indoor. The yearly mean haemoglobin concentrations were similar among the trial arms. The malaria incidence was low and similar in the intervention arms. The severe drought might have contributed in too few malaria cases to evaluate the interventions. However, residual transmission could be an important cause of malaria transmission in the area. Our results could be relevant for situations with low malaria incidence, such as during work to eliminate malaria.

The proposal aims to assess whether the combined use of mosquito nets and indoor residual spraying (IRS) increases protection against malaria. The proposal is to conduct a two-armed cluster randomised controlled trial in Ethiopia to measure malaria incide nce and transmission, insecticide resistance, and to assess whether mosquito nets result in an age shift in malaria morbidity before and after trials. We shall also measure the entomological inoculation rates (EIR). We will use a cluster randomised cont rolled study design in the Adami Tullu area in the Ethiopian Rift Valley. The village will be the unit for randomisation. The intervention will consist of villages (clusters) receiving both IRS and long-lasting insecticidal nets (LLINs) while the control communities will use LLINs only. The cost-effectiveness study will be performed prospectively alongside the trial. Our proposal addresses the core areas of the call by targeting malaria, a disease that contributes substantially to ill health and death i n children and adults in sub-Saharan Africa. More than just an intervention development programme by conducting epidemiological studies of malaria in Ethiopia, the research addresses important topics for the delivery of Millennium Development Goals (MDG 4 and 6).