The need to harmonize insecticide resistance testing: methodology, intensity concentrations and molecular mechanisms evaluated inAedes aegyptipopulations in Central America and Hispaniola
Authors: Ledoux Sarah , Gutierrez Carolina Torres , Lobo Neil F. , Murillo Elizabeth Melany , Pérez Silvia , Guerra Rocío , Avendano Sayra Chanquin , Orellana Herrera Ángel Gabriel , Mendoza Aarón , Escobar Denis , Contreras Gavino Guzmán , Rivera Magdiel , Ventura Gilda , Anagonou Rodrigue , Pierre-Louis Eliane , Yurrita Carmen , López Hun Francisco J. , Duque Camilo , Romero Eduardo , Lovin Diane D. , Cunningham Joanne M. , Dengela Dereje , Belemvire Allison , Stewart Kellie , Grisales Nelson 
Published: February 2020

Background

The Zika AIRS Project, a USAID-funded initiative worked across the Latin America and Caribbean regions from 2016 to 2019, as an emergency to contain the spread of the Zika virus. All entomological records in the target countries showed wide distribution and high abundance ofAedes aegyptipopulations, however the susceptibility profiles of these insects to insecticides commonly employed by vector control campaigns were in most cases incomplete or inexistent. In close collaboration with the Ministries of Health of individual countries, Zika-AIRS teams conducted insecticide susceptibility testing of an array of insecticides inA. aegyptipopulations of each country. Procedures applied met the standard international protocols instructed by the World Health Organization and Centers for Disease Control and Prevention.

Methodology and main findings

The insecticides tested were selected under categories such as pyrethroids, organophosphates and carbamate. Results showedA. aegyptipopulations displaying high and widely distributed resistance to all pyrethroids across countries, tolerance to organophosphates and full susceptibility to a carbamate. Key inconsistencies between testing methods are presented and discussed. Additionally, fourkdrmutations were analyzed to detect molecular mechanisms of insecticide resistance. The screening forkdrmutations suggested the widespread nature of V1016I mutation, linked to pyrethroid resistance inA. aegyptipopulations distributed and sampled in the above mentioned regions.

Conclusions and perspectives

This multi-country study contributes with updated information to the public health decision-makers across Central America and the Caribbean. This study provided training and established technical networks for more effective and sustainable insecticide surveillance programs. Most but not all records of insecticide resistance inA. aegyptiwere consistent between methodologies, thus inconsistent issues are discussed here to call for further improvement in procedures and convey more practical guidelines for surveillance teams in countries whereAedes-borne diseases are endemic.

Author summary

At the forefront of the fight against arboviruses transmission is the insecticide-based vector control. All countries in the Latin American and Caribbean region invest valuable resources from their limited budget to acquire and implement insecticide-based tools, with non-existent or weak insecticide resistance monitoring programs. Hence, the USAID-funded Zika AIRS Project (ZAP) collaborated with the Ministries of Health of multiple countries to update the profile of susceptibility to insecticides inAedes aegyptipopulations. We found widespread resistance to pyrethroid and organophosphate insecticides, which account to almost 100% of the products available to control adult mosquitoes. As we used both of World Health Organization and Centers for Disease Control and Prevention standard methods, we found many similarities and some inconsistencies in the susceptibility profiles obtained for the very same vector populations. Additionally, we obtained insight on potential molecular mechanisms of resistance across the countries, finding thekdrmutation V1016I possibly involved in loss of susceptibility.

This study is the biggest cross-country update of insecticide resistance forAedes aegyptiin years, and it should be used as evidence for improving the selection of insecticides in these countries and a call for further support to maintain insecticide resistance monitoring programs.