Indoor residual spraying for preventing malaria.

Area of Science:

• Malariology
• Vector Control
• Public Health Interventions

Background:

• Large-scale malaria prevention relies on indoor residual spraying (IRS) and insecticide-treated nets (ITNs).
• The health effects of IRS have not been adequately quantified, hindering comparisons with other interventions.
• Quantifying IRS impact is crucial for effective malaria control strategies.

Purpose of the Study:

• To quantify the impact of IRS alone on malaria.
• To compare the relative effectiveness of IRS and ITNs in controlling malaria.
• To analyze effects on key malariological parameters.

Main Methods:

• Systematic search of multiple databases (Cochrane, MEDLINE, EMBASE, LILACS) and trial registries up to September 2009.
• Inclusion of cluster randomized controlled trials (RCTs), controlled before-and-after studies (CBA), and interrupted time series (ITS).
• Independent review of trials, data extraction, risk of bias assessment, and analysis, with adjustments for clustering where possible.

Main Results:

• IRS reduced malaria incidence in unstable settings (e.g., 88% PE in Pakistan).
• In stable settings, IRS showed mixed results, with some reduction in re-infection (54% PE) but limited impact on case incidence.
• Limited data suggest ITNs may be more effective than IRS in unstable malaria areas.

Conclusions:

• High-quality trial data are insufficient to fully quantify IRS effectiveness across different malaria transmission settings.
• IRS is effective in unstable malaria regions, but more randomized trials are needed for stable settings.
• Further research is required to compare IRS and ITNs directly and assess their combined effects.