The Effect of Volatile Pyrethroid Insecticides on Pyrethroid-Resistant Aedes aegypti in Mérida, Mexico Open Access

Ramos, Raquel (Spring 2021)

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Aedes aegypti is the principal vector transmitting dengue, chikungunya, and Zika viruses in the Americas. They live in close association with humans, primarily in urban areas. Due to the low cost and low mammalian toxicity, pyrethroid insecticides for vector control have been widespread in order to decrease the spread of Aedes born viruses. There have been significant barriers with the use of common protective measures and an increase in insecticide resistance. One of the main resistance mechanisms is knockdown resistance which occurs by reducing the sensitivity of sodium channels to pyrethroids. Advancements in insecticides, specifically polyfluorinated pyrethroids have been made, but more research on insecticide resistant mosquito control is needed. This study was conducted to measure the effectiveness of volatile pyrethroid metofluthrin emanators on field and lab resistant Ae. Aegypti mosquitoes (New Orleans, Cienega de Flores, Itzincab, and Juan Pablo), with mutations in Mérida, Mexico. A total of 1,099 mosquitoes were used and three different levels emanators (0,1,4). Houses and apartments were the unit of treatment and the endpoint of focus was mosquito survival after treatment. Experiment One: statistical difference among resistant and susceptible strains, (1, 147) =78.62, p = <0.0001. Experiment Two: statistically significant interaction between the effects of strain and treatment level on survival, (2, 322) = 10.55 p = <0.0001. Experiment Three: statistically significant interaction between the effects of genotype and treatment level on survival was confirmed ((8, 457) = 3.73 p = 0.0003). Survival increased with mutation. 40% of mosquitoes with genotype WT, WT survived versus 72.55% of mosquitoes with genotype Mut, Mut. Our trials experimental study deliver important proof effectiveness of emanators is limited in populations with high levels of resistance and mutation. Survival increased with mutation. Mosquitoes with one or two mutations had higher percentage of survival versus mosquitoes without mutation. Probability of survival had a similar result. The estimated probability of survival for WT, WT is 0.31 (0.24-0.39) versus 0.71 (0.64-0.77) for Mut, Mut. We acknowledge the need to implement strategies that involve understanding knockdown resistance frequencies in monitoring and management programmes in complex urban areas.

Table of Contents

Table of Contents


Introduction                                                                                                                       1


I. Pyrethroids and Resistance                                                                                          2

II. Aedes aegypti Problems and Control                                                                        2


III.  Emanators                                                                                                         3


IV.  Our Study                                                                                                                    4



Materials and Methods                                                                                                    4


Ethics Statement                                                                                                             4


Study Area                                                                                                                          4


Metofluthrin Emanators                                                                                                 5


Experimental Design                                                                                                       5


Experiment One: Preparatory Study                                                                             6


Experiment Two: Preliminary Analysis in Experimental Houses                            6


Experiment Three: Evaluation of the Impact of Strains and Mechanisms of Resistance 7


Detection of kdr Alleles                                                                                                    8


Statistical Analysis                                                                                                            8


Single Mutation and Mutation in Combination Analysis                                         9



Results                                                                                                                                 9


Experiment One: Preparatory Study                                                                             9


Experiment Two: Preliminary Analysis in Experimental Houses                         10


Experiment Three: Evaluation of the Impact of Strains and Mechanisms of Resistance 10



Discussion                                                                                                                            11


Conclusion                                                                                                                            14


References                                                                                                                             15


Tables and Figures                                                                                                                18







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