Click here for updated information on the progress of our TIRS trials.
TARGETED INDOOR RESIDUAL SPRAYING (TIRS)
Targeted Indoor Residual Spraying (TIRS) refers to the selective application of residuals insecticides on indoor Aedes aegypti resting locations. Funded by the National Institutes of Health (NIH, U01AI148069; Vazquez-Prokopec, PI), these trials will evaluate the epidemiological impact of TIRS on Aedes-borne diseases, such as dengue, Chikungunya, and Zika, using clustered randomized controlled trials.
WHAT IS TIRS?
Mosquitoes spend the majority of their time resting in spaces referred to as resting sites. These surfaces are targeted as areas with a high degree of contact with targeted mosquitoes and act as conduits for delivering residual insecticides.
Image developed by GM Vazquez-Prokopec, Emory University
In urban environments, houses are primarily built of brick and cement. Aedes aegypti mosquitoes preferentially rest on surfaces of the house below 1.5 m in height. Spraying residual insecticides on walls below 1.5 m and in other key resting sites such as under furniture (1) will eventually kill Ae. aegypti that may be emerging from immature larval habitats outdoors (2) as they move indoors and rest on treated surfaces (3). After insecticide exposure, mortality can occur immediately (4) or after several hours or days (5). Therefore, TIRS epidemiological impact is driven by a reduction in vector abundance and by a shift in the age structure of the remaining population towards younger females (<7 days).
WHAT WILL THE TIRS TRIAL DO?
We will conduct a two-arm, parallel, unblinded, cluster randomized controlled trial to quantify the overall efficacy of TIRS in reducing the burden of laboratory-confirmed arbovirus (ABV) clinical disease (primary endpoint).
The trial will be conducted in the city of Mérida, Yucatán State, Mexico (population ~1 million), where we will prospectively follow 4,600 children aged 2-15 years at enrollment, distributed in 50 clusters of 5x5 city blocks each. Clusters will be randomly allocated (n= 25 per arm) using covariate-constrained randomization.
A “fried egg” design, in which all blocks of the 5x5 cluster receive the intervention, but all sampling to evaluate the epidemiological and entomological endpoints will occur in the “yolk,” the center 3x3 city blocks of each cluster.
TIRS will be implemented as a preventive application about 1-2 months prior to the beginning of the ABV season. Active monitoring for symptomatic ABV illness will occur through weekly household visits and enhanced surveillance. Annual serological surveys will be performed after each transmission season and entomological evaluations of Ae. aegypti indoor abundance and ABV infection rates monthly during the period of active surveillance. Epidemiological and entomological evaluation will continue for up to three transmission seasons.
In 2019, we collaborated with the Pan American Health Organization (PAHO) and a team of talented scientists to publish the new Manual for Indoor Residual Spraying in Urban Areas for Aedes aegypti Control. Click on the image for more information about our work with mosquito control and surveillance.