Fitness cost in field and laboratory Aedes aegypti populations associated with resistance to the insecticide temephos

Abstract

BackgroundThe continued use of chemical insecticides in the context of the National Program of Dengue Control in Brazil has generated a high selective pressure on the natural populations of Aedes aegypti, leading to their resistance to these compounds in the field. Fitness costs have been described as adaptive consequences of resistance. This study evaluated the biological and reproductive performance of A. aegypti strains and a field population resistant to temephos, the main larvicide used for controlling mosquitoes.MethodsComparative tests were performed with a resistant field population from the municipality of Arcoverde, Pernambuco State, Brazil, with a high rate of temephos resistance (RR = 226.6) and three isogenetic laboratory strains from the same origin (Araripina municipality, Pernambuco): RecR (RR = 283.6); RecRNEx (RR = 250.5), a strain under a process of resistance reversion; and RecRev (RR = 2.32), a reversed susceptible strain used as an experimental control.ResultsOur study revealed that the absence of selective pressure imposed by exposure to temephos, for five consecutive generations, led to a discrete reduction of the resistance ratio and the response of the detoxifying enzymes. Most of the 19 biological parameters were impaired in the resistant strains and field population. The analysis of the fertility life table confirmed the presence of reproductive disadvantages for the resistant individuals. Similarly, the longevity, body size, and total energetic resources were also lower for the resistant females, except for the last two parameters in the field females (Arcoverde). In contrast, the sex ratio and embryonic viability suffered no interference in all strains or population evaluated, regardless of their status of resistance to temephos.ConclusionsThe reproductive potential and survival of the resistant individuals were compromised. The parameters most affected were the larval development time, fecundity, net reproduction rate, and the generational doubling time. These fitness costs in the natural population and laboratory strains investigated are likely associated with maintaining the metabolic mechanism of resistance to temephos. Our results show that despite these costs, the highly temephos resistant populations can compensate for these losses and successfully overcome the control actions that are based on the use of chemical insecticides.

Insecticide resistance, associated mechanisms and fitness aspects in two Brazilian Stegomyia aegypti (= Aedes aegypti) populations

“…Insemination performance and, consequently, mating efficiency in both Aracaju and Crato males were affected in a significant and equivalent measure in comparison with Rockefeller mosquitoes. Impairment of these functions as a result of insecticide resistance has been reported previously in S. aegypti and in Culex pipiens (Diptera: Culicidae) populations (Antonio et al ., ; Belinato et al ., ; Diniz et al ., ). Partial reversion of this liability was achieved in the dengue vector after laboratory rearing in the absence of insecticides (Belinato & Valle, ).…”

“…The amount of blood ingested is critical to mosquito vector capacity because it directly influences the quantity of ingested parasites and the number of eggs laid (Belinato et al ., , ; Belinato & Valle, ). Despite its relevance, this parameter is generally neglected when fitness evaluations are concerned (Jaramillo‐O et al ., ; Diniz et al ., ). The present data indicate a decreased ability of Aracaju females to ingest blood in comparison with the control Rockefeller strain.…”

“…This parameter was affected only in the Aracaju population. In S. aegypti, speed of larval development has been previously related to high levels of temephos resistance in field populations, as well as to deltamethrin and temephos selection under laboratory conditions Brito et al, 2013;Diniz et al, 2015).…”

“…In these cases, although resistant insects are more likely to survive in the face of exposure to the insecticide, in its absence resistant specimens tend to be less competitive (Brito et al, 2013). Indeed, there are several registers of adaptive costs associated with insecticide resistance in disease vector mosquitoes (Berticat et al, 2002;Rivero et al, 2010;Belinato et al, 2012;Jaramillo-O et al, 2014;Diniz et al, 2015).…”

Assessing the effect of selection with deltamethrin on biological parameters and detoxifying enzymes in Aedes aegypti (L.)

“…aegypti resistant to deltamethrin. It is likely that in the case of the metabolic resistance found, the increase in MFO production implies a commitment of resources which would be important for the longevity of the population under study, as suggested by Diniz et al ., who found that the reproductive potential and survival of temephos‐resistant Ae. aegypti were compromised due to the maintenance of metabolic resistance.…”