As part of IVCC’s work on improving IRS, Dr. Gonzalo Vazquez-Prokopec from Emory University and Dr. Pablo Manrique-Saide of the Autonomous University of Yucatan were funded to identify residual insecticides with the longest residual power within typical surfaces found in urban settings in Merida, Mexico and to conduct a field entomological cluster randomized trial of the efficacy of targeted IRS (TIRS) for Aedes control.
Targeted indoor residual spraying (TIRS, applying residual insecticides on Aedes aegypti resting sites such as exposed low walls [<1.5 m], under furniture and on dark surfaces) is a rational vector control approach that exploits Ae. aegypti resting behavior to focalize insecticide applications with no loss in residual efficacy (thus, reducing unnecessary exposure to pesticides in applicators and residents, and the time it takes to spray a premise).
The trial, which was conducted in 2019, demonstrated significant and sustained reductions in house infestation and Ae. aegypti abundance for up to 7 months for Actellic 300CS and 6 months for SumiShield 50WDG. The proportional reduction in Ae. aegypti abundance in treatment houses compared to control houses was 50-70% for Actellic 300CS and 43-63% for SumiShield 50WDG. Applying both insecticides as TIRS led to an application time of ~9 min per house and insecticide use of 1 L per house, providing a strong operational cost-savings compared to classic IRS (which take 30 min per house, 3 L of insecticide).
An NIH-funded epidemiological trial is planned to generate additional evidence for TIRS in Aedes control, and it is hoped that lessons learned from the project can lead to a more rational, targeted-approach for Anopheles mosquito control to prevent malaria.