Efficacy of novel indoor residual spraying methods targeting pyrethroid-resistant aedes aegypti within experimental houses

• Authors: Mike W. Dunbar, Emory University; Fabian Correa-Morales, Secretaria de Salud; Felipe Dzul-Manzanilla, Secretaria de Salud; Anuar Medina-Barreiro, Universidad Autónoma de Yucatán; Wilbert Bibiano-Marín, Universidad Autónoma de Yucatán; Evaristo Morales-Ríos, Universidad Autónoma de Yucatán; Jose Vadillo-Sánchez, Secretaria de Salud; Beatriz López-Monroy, Universidad Autónoma de Nuevo León; Scott A. Ritchie, James Cook University; Audrey Lenhart, Centers for Disease Control and Prevention; Pablo Manrique-Saide, Emory University; Gonzalo Vazquez Prokopec, Emory University
• Journal Title: PLoS Neglected Tropical Diseases
• Volume: Volume 13, Number 2
• Publisher: Public Library of Science | 2019-02-01, Pages e0007203-e0007203
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1371/journal.pntd.0007203
• Subjects: Environmental Sciences; Biology, Entomology; Biology, Parasitology
• Keywords: Aedes; Animals; Female; Housing; Insecticide Resistance; Insecticides; Mexico; Mosquito Control; Phenylcarbamates; Pyrethrins

Abstract

Challenges in maintaining high effectiveness of classic vector control in urban areas has renewed the interest in indoor residual spraying (IRS) as a promising approach for Aedes-borne disease prevention. While IRS has many benefits, application time and intrusive indoor applications make its scalability in urban areas difficult. Modifying IRS to account for Ae. aegypti resting behavior, named targeted IRS (TIRS, spraying walls below 1.5 m and under furniture) can reduce application time; however, an untested assumption is that modifications to IRS will not negatively impact entomological efficacy. We conducted a comparative experimental study evaluating the residual efficacy of classically-applied IRS (as developed for malaria control) compared to two TIRS application methods using a carbamate insecticide against a pyrethroid-resistant, field-derived Ae. aegypti strain. We performed our study within a novel experimental house setting (n = 9 houses) located in Merida (Mexico), with similar layouts and standardized contents. Classic IRS application (insecti-cide applied to full walls and under furniture) was compared to: a) TIRS: insecticide applied to walls below 1.5 m and under furniture, and b) Resting Site TIRS (RS-TIRS): insecticide applied only under furniture. Mosquito mortality was measured eight times post-application (out to six months post-application) by releasing 100 Ae. aegypti females/house and collecting live and dead individuals after 24 hrs exposure. Compared to Classic IRS, TIRS and RS-TIRS took less time to apply (31% and 82% reduction, respectively) and used less insecticide (38% and 85% reduction, respectively). Mortality of pyrethroid-resistant Ae. aegypti did not significantly differ among the three IRS application methods up to two months post application, and did not significantly differ between Classic IRS and TIRS up to four months post application. These data illustrate that optimizing IRS to more efficiently target Ae. aegypti.