Direct and indirect entomological efficacy of Targeted Indoor Residual Spraying against Aedes aegypti in Iquitos, Peru.
Helvio Astete, Gissella M Vasquez, Victor M López-Sifuentes et al.
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In 30 seconds
This entomological cluster-randomized controlled trial in Iquitos, Peru, compared targeted indoor residual spraying (TIRS) with standard Ministry of Health vector-control activities. Researchers assessed indoor Aedes aegypti density in sprayed homes and untreated homes within TIRS clusters over follow-up extending to 255 days. TIRS was associated with a 96% decrease in mosquitoes captured in sprayed houses at 15 days, with a significant 40% reduction at 255 days. Indirect efficacy in untreated homes was 69% at 15 days and declined to 7% by 255 days. Effects were observed despite 57% household-level coverage.
Key findings
- Direct efficacy in sprayed houses was a 96% decrease in captured Aedes aegypti at 15 days post-spraying.
- Direct efficacy remained significant at 255 days, with a 40% reduction in sprayed houses.
- Indirect efficacy in untreated homes within TIRS clusters was 69% at 15 days and 7% at 255 days.
- Significant early direct and indirect impacts were observed despite 57% household-level TIRS coverage.
Why it matters
The findings indicate that targeting indoor resting sites can reduce indoor Aedes aegypti density in treated homes and produce measurable spillover effects in untreated homes. The persistence of a direct effect through 255 days, alongside early indirect effects, is relevant to evaluating TIRS as a vector-control option in dengue-endemic urban settings. These are entomological outcomes, not evidence of reduced dengue illness.
What to keep in mind
The study measured indoor mosquito density rather than dengue or other human health outcomes, so it does not establish an effect on disease transmission.