Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.

<h4>Background</h4>Insecticide use continues as the main strategy to control Aedes aegypti, the vector of dengue, Zika, chikungunya, and yellow fever. In the city of Tapachula, Mexico, mosquito control programs switched from pyrethroids to organophosphates for outdoor spatial spraying in...

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Autores principales:	Francisco Solis-Santoyo, Americo D Rodriguez, R Patricia Penilla-Navarro, Daniel Sanchez, Alfredo Castillo-Vera, Alma D Lopez-Solis, Eduardo D Vazquez-Lopez, Saul Lozano, William C Black, Karla Saavedra-Rodriguez
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2021
Materias:	Arctic medicine. Tropical medicine RC955-962 Public aspects of medicine RA1-1270
Acceso en línea:	https://doaj.org/article/6d675cf03c94478fab16618f33b97a34
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spelling	oai:doaj.org-article:6d675cf03c94478fab16618f33b97a342021-12-02T20:24:01ZInsecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.1935-27271935-273510.1371/journal.pntd.0009746https://doaj.org/article/6d675cf03c94478fab16618f33b97a342021-09-01T00:00:00Zhttps://doi.org/10.1371/journal.pntd.0009746https://doaj.org/toc/1935-2727https://doaj.org/toc/1935-2735<h4>Background</h4>Insecticide use continues as the main strategy to control Aedes aegypti, the vector of dengue, Zika, chikungunya, and yellow fever. In the city of Tapachula, Mexico, mosquito control programs switched from pyrethroids to organophosphates for outdoor spatial spraying in 2013. Additionally, the spraying scheme switched from total coverage to focused control, prioritizing areas with higher entomological-virological risk. Five years after this strategy had been implemented, we evaluated the status and variability of insecticide resistance among Ae. aegypti collected at 26 sites in Tapachula.<h4>Methodology/principal findings</h4>We determined the lethal concentrations at 50% of the tested populations (LC50) using a bottle bioassay, and then, we calculated the resistance ratio (RR) relative to the susceptible New Orleans strain. Permethrin and deltamethrin (pyrethroids), chlorpyrifos and malathion (organophosphates), and bendiocarb (carbamate) were tested. The frequencies of the substitutions V1016I and F1534C, which are in the voltage-gated sodium channel and confer knockdown-resistance (kdr) to pyrethroid insecticides, were calculated. Despite 5 years having passed since the removal of pyrethroids from the control programs, Ae. aegypti remained highly resistant to permethrin and deltamethrin (RR > 10-fold). In addition, following 5 years of chlorpyrifos use, mosquitoes at 15 of 26 sites showed moderate resistance to chlorpyrifos (5- to 10-fold), and the mosquitoes from one site were highly resistant. All sites had low resistance to malathion (< 5-fold). Resistance to bendiocarb was low at 19 sites, moderate at five, and high at two. Frequencies of the V1016I ranged from 0.16-0.71, while C1534 approached fixation at 23 sites (0.8-1). Resistance profiles and kdr allele frequencies varied across Tapachula. The variability was not associated with a spatial pattern at the scale of the sampling.<h4>Conclusion/significance</h4>Mosquito populations respond to selection pressure at a focal scale in the field. Spatial variation across sites highlights the importance of testing multiple sites within geographical regions.Francisco Solis-SantoyoAmerico D RodriguezR Patricia Penilla-NavarroDaniel SanchezAlfredo Castillo-VeraAlma D Lopez-SolisEduardo D Vazquez-LopezSaul LozanoWilliam C BlackKarla Saavedra-RodriguezPublic Library of Science (PLoS)articleArctic medicine. Tropical medicineRC955-962Public aspects of medicineRA1-1270ENPLoS Neglected Tropical Diseases, Vol 15, Iss 9, p e0009746 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Arctic medicine. Tropical medicine RC955-962 Public aspects of medicine RA1-1270
spellingShingle	Arctic medicine. Tropical medicine RC955-962 Public aspects of medicine RA1-1270 Francisco Solis-Santoyo Americo D Rodriguez R Patricia Penilla-Navarro Daniel Sanchez Alfredo Castillo-Vera Alma D Lopez-Solis Eduardo D Vazquez-Lopez Saul Lozano William C Black Karla Saavedra-Rodriguez Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.
description	<h4>Background</h4>Insecticide use continues as the main strategy to control Aedes aegypti, the vector of dengue, Zika, chikungunya, and yellow fever. In the city of Tapachula, Mexico, mosquito control programs switched from pyrethroids to organophosphates for outdoor spatial spraying in 2013. Additionally, the spraying scheme switched from total coverage to focused control, prioritizing areas with higher entomological-virological risk. Five years after this strategy had been implemented, we evaluated the status and variability of insecticide resistance among Ae. aegypti collected at 26 sites in Tapachula.<h4>Methodology/principal findings</h4>We determined the lethal concentrations at 50% of the tested populations (LC50) using a bottle bioassay, and then, we calculated the resistance ratio (RR) relative to the susceptible New Orleans strain. Permethrin and deltamethrin (pyrethroids), chlorpyrifos and malathion (organophosphates), and bendiocarb (carbamate) were tested. The frequencies of the substitutions V1016I and F1534C, which are in the voltage-gated sodium channel and confer knockdown-resistance (kdr) to pyrethroid insecticides, were calculated. Despite 5 years having passed since the removal of pyrethroids from the control programs, Ae. aegypti remained highly resistant to permethrin and deltamethrin (RR > 10-fold). In addition, following 5 years of chlorpyrifos use, mosquitoes at 15 of 26 sites showed moderate resistance to chlorpyrifos (5- to 10-fold), and the mosquitoes from one site were highly resistant. All sites had low resistance to malathion (< 5-fold). Resistance to bendiocarb was low at 19 sites, moderate at five, and high at two. Frequencies of the V1016I ranged from 0.16-0.71, while C1534 approached fixation at 23 sites (0.8-1). Resistance profiles and kdr allele frequencies varied across Tapachula. The variability was not associated with a spatial pattern at the scale of the sampling.<h4>Conclusion/significance</h4>Mosquito populations respond to selection pressure at a focal scale in the field. Spatial variation across sites highlights the importance of testing multiple sites within geographical regions.
format	article
author	Francisco Solis-Santoyo Americo D Rodriguez R Patricia Penilla-Navarro Daniel Sanchez Alfredo Castillo-Vera Alma D Lopez-Solis Eduardo D Vazquez-Lopez Saul Lozano William C Black Karla Saavedra-Rodriguez
author_facet	Francisco Solis-Santoyo Americo D Rodriguez R Patricia Penilla-Navarro Daniel Sanchez Alfredo Castillo-Vera Alma D Lopez-Solis Eduardo D Vazquez-Lopez Saul Lozano William C Black Karla Saavedra-Rodriguez
author_sort	Francisco Solis-Santoyo
title	Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.
title_short	Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.
title_full	Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.
title_fullStr	Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.
title_full_unstemmed	Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.
title_sort	insecticide resistance in aedes aegypti from tapachula, mexico: spatial variation and response to historical insecticide use.
publisher	Public Library of Science (PLoS)
publishDate	2021
url	https://doaj.org/article/6d675cf03c94478fab16618f33b97a34
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Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.

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