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Research Article
Received: 31 December 2016 Revised: 2 May 2017 Accepted article published: 9 May 2017 Published online in Wiley Online Library:
(wileyonlinelibrary.com) DOI 10.1002/ps.4609
Assessing the effect of selection with
deltamethrin on biological parameters
and detoxifying enzymes in Aedes aegypti (L.)
Leslie C Alvarez-Gonzalez,a,b Arelis Briceño,bGustavo Ponce-Garcia,a
O Karina Villanueva-Segura,aJesus A Davila-Barboza,a
Beatriz Lopez-Monroy,aSelene M Gutierrez-Rodriguez,a
Yamili Contreras-Perera,aIram P Rodriguez-Sancheza
and Adriana E Floresa*
Abstract
BACKGROUND: Resistance to insecticides through one or several mechanisms has a cost for an insect in various parameters of
its biological cycle. The present study evaluated the effect of deltamethrin on detoxifying enzymes and biological parameters in
a population of Aedes aegypti selected for 15 generations. The enzyme activities of alpha- and beta-esterases, mixed-function
oxidases and glutathione-S-transferases were determined during selection, along with biological parameters.
RESULTS: Overexpression of mixed-function oxidases as a mechanism of metabolic resistance to deltamethrin was found. There
were decreases in percentages of eggs hatching, pupation and age-specific survival and in total survival at the end of the
selection (F16). Although age-specific fecundity was not affected by selection with deltamethrin, total fertility, together with
lower survival, significantly affected gross reproduction rate, gradually decreasing due to deltamethrin selection. Similarly, net
reproductive rate and intrinsic growth rate were affected by selection.
CONCLUSION: Alterations in life parameters could be due to the accumulation of noxious effects or deleterious genes related to
detoxifying enzymes, specifically those coding for mixed-function oxidases, along with the presence of recessive alleles of the
V1016I and F1534C mutations, associating deltamethrin resistance with fitness cost in Ae. aegypti.
© 2017 Society of Chemical Industry
Supporting information may be found in the online version of this article.
Keywords: Aedes aegypti; fitness cost; deltamethrin; mixed-function oxidases
1 INTRODUCTION
Deltamethrin, like other type II pyrethroids, acts on the nervous
system, specifically on voltage-dependent sodium channels,
where it causes alterations in channel opening kinetics, delaying
their activation and inactivation, causing paralysis and death
of an insect.1A number of studies have demonstrated that
the mechanisms responsible for pyrethroid resistance involve
detoxifying enzymes such as carboxylesterases, cytochrome P450
mixed-function oxidases (MFOs) and glutathione-S-tranferases
(GSTs)2–7and various mutations in the para gene coding for the
voltage-gated sodium channel protein.8–10 This ability to resist
insecticides through one or both mechanisms has a cost to an
insect, affecting its longevity, infective capacity and reproduction
or inducing changes in its behaviour.11 Insecticide resistance is
a heritable trait and thus subject to natural selection.12 In the
absence of insecticides, mosquitoes carrying resistant alleles fre-
quently exhibit a diminished fitness relative to susceptible ones;
but fitness costs vary between species, even between populations
of the same species in time and space.13,14 Studies of Aedes aegypti
(Linnaeus, 1762) exposed to LD30 of Bacillus thuringiensis israelensis
H-14 Vectobac‸AS have shown shortening of the development
cycle, increased fecundity and reduced longevity in F1compared
to the results obtained with LD50 and LD70.15 Martins et al.16 in
Brazil evaluated the life cycle parameters larval development,
sex ratio, adult longevity, relative amount of blood ingested,
oviposition rate, egg size and viability in five populations of Ae.
aegypti resistant to field organophosphates and pyrethroids and
a strain selected in the laboratory with deltamethrin; the authors
∗Correspondence to: AE Flores, Universidad Autonoma de Nuevo Leon, Fac-
ultad de Ciencias Biologicas, San Nicolas de los Garza, NL 66455, Mexico.
E-mail: adriana.floressr@uanl.edu.mx
aUniversidad Autonoma de Nuevo Leon, Facultad de Ciencias Biologicas, San
Nicolas de los Garza, Mexico
bUniversidad de los Andes, Nucleo Universitario Rafael Rangel, Pampanito,
Trujillo, Venezuela
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found discrete and proportional alterations to the level of resis-
tance, suggesting that the resistance mechanisms selected for
organophosphate and pyrethroid resistance cause accumulation
of alleles with negative effects on various biological parameters.
Significant fitness cost was observed in response to insecticide
selection of adults of an Ae. aegypti population from Colombia
with lambda-cyalothrin for nine and ten generations of selection.
The median survival of the selected generations F9and F10 was
significantly lower than the non-selected lines (F9and F10), which
were very similar to the susceptible strain Rockefeller. Fecun-
dity although shown to be different between selected lines (F9
and F10) from the susceptible Rockefeller strain, there were no
differences between the selected and non-selected lines. Life
table parameters like net reproductive rate per generation (Ro)
and the intrinsic rate of increase in days (rm) showed significant
differences between the non-selected and selected lines; besides
the rmparameter did not show differences with the Rockefeller
strain.17 In two populations of Ae. aegypti resistant to temephos,
Belinato et al.18 observed changes in the acceptance of the blood
source, amount of blood ingested, number of eggs laid and fre-
quency of inseminated females, which were proportional to the
degree of resistance, suggesting that the alterations were not due
exclusively to resistance to temephos, since the populations also
showed resistance to deltamethrin and carried the kdr mutation
V1016I. Also, the fitness cost of V1016I and F1534C kdr mutations
was assessed in Ae. aegypti resistant to pyrethroids. The popula-
tion showed with respect to development and reproduction an
increase in larval development time and locomotor capacity in
adults, a decrease in the number of females and a decrease in the
number of eggs as well.19 Evidence has shown that pyrethroid
resistance in Ae. aegypti from Mexico caused by mutations in
the voltage-gated sodium channel gene requires the sequential
evolution of two mutations, F1534C and V1016I, in that particular
order caused by the low fitness of I1016/F1534 haplotype.20
In the present study, we evaluated the effect of deltamethrin
on some biological parameters in a strain of Ae. aegypti from
Venezuela, the Pampanito population, selected in the laboratory
for 15 generations with this pyrethroid, and the changes in levels
of detoxifying enzymes throughout the selection. It should be
mentioned that in a previous study, the increase in frequency and
co-occurrence of V1016I and F1534C kdr mutations in the F1,F
8
and F15 generations of the same population included in this study
was reported.21
2METHODS
In the present study, we used a strain of Ae. aegypti from Pam-
panito (9∘24′42′′ N, 70∘29′39′′ E) in the state of Trujillo, western
Venezuela collected in 2010. Larvae were collected from natural
breeding sites and transported to the insectary of the Institute
Experimental JW Torrealba, Universidad de los Andes, Venezuela.
Colonies were maintained at 25 ±4∘C and 12:12 (L:D). The females
reared from these larvae were fed on chickens (Gallus gallus domes-
ticus Brisson) and males with 10% sucrose. The eggs obtained
were partially dried after embryogenesis, stored at room temper-
ature and transferred to the Laboratorio de Entomologia Medica,
Universidad Autonoma de Nuevo Leon, Mexico. The eggs were
placed in plastic containers with dechlorinated water for hatching
and subsequently provided with a 50% solution of liver protein
for subsequent stages. When they reached the pupa stage they
were placed in 250 mL containers inside cages (30 cm ×30 cm)
until the adults emerged. The females were fed on rats (Rat-
tus norvegicus Berkenhout) for the production of eggs corre-
sponding to the F1filial generation, and the males with a 10%
sucrose solution. All specimens were maintained at 25 ±2∘Cand
70 ±2% relative humidity, with a 12:12 h light/dark photoperiod.
The Pampanito strain was characterized with regard to resistance
to deltamethrin by the bottle bioassay in 2008 and 2010, and the
metabolic and non-metabolic (V1016I and F1534C kdr mutations)
mechanisms of resistance were evaluated in the field population
in both periods and in a strain selected in the laboratory with
deltamethrin.21,22
2.1 Selection of population with deltamethrin
Approximately 400 adults of both sexes of F1at 2 to 5 days
after emergence were exposed to LC50 (0.14 μgmL
−1)of
deltamethrin, determined in previous studies for 1 h, using
the bottle bioassay.21,23 The mosquitoes were then transferred
to breeding cages, and after 24 h, they were fed on rats and 10%
sucrose solution for oviposition, which corresponded to the F2
generation. Once the eggs were obtained, they were hatched in
dechlorinated water until F2adults were obtained. Adults of both
sexes of F2were again exposed to 0.14 μgmL
−1deltamethrin for
1 h, continuing the selection uninterrupted until F15 , following
the previously described method. Approximately 40 females of
the F1,F
2,F
5,F
8,F
11 and F15 generations without blood ingestion
were individually stored in Eppendorf tubes at −80 ∘C for later
determination of detoxifying enzymes.
2.2 Enzymes
Each mosquito was homogenized in 100 μL of 0.01 M potassium
phosphate buffer, pH =7.2, and suspended in up to 2 mL of
the s ame buffer. Aliquots of 100 μL were transferred to wells of
microtitre plates. Thirty specimens of the F1(unselected) and F2,
F5,F
8,F
11 and F15 (selected with delamethrin) generations, as well
as the insecticide susceptible strain New Orleans (NO; hereafter
referred as the control), were analysed in triplicate for enzyme
activity. Activity levels of alpha- and beta-esterases, MFO and GST
were determined.24 Absorbance values were measured with a
UVM-340 microplate reader (ASYS Hitech GmbH, Eudendorf, Aus-
tria) and averaged. Protein concentration was determined, and
in the case of variation in the size of the mosquitoes, the con-
centration of the homogenate was adjusted.25 Analysis of vari-
ance (ANOVA; P<0.05) and Tukey’s test were carried out to deter-
mine the significant difference between the enzyme levels in the
females of the selected generations (F2,F
5,F
8,F
11 and F15)with
respect to the F1strain and F1with respect to the control strain.
The resistance threshold (maximum absorbance value for each
enzyme)inF
1was evaluated to determine the percentage of indi-
viduals from each selection generation that exceeded that thresh-
old and to categorize the enzymatic mechanisms as not altered
(less than 15% exceed the resistance threshold), incipiently altered
(between 15 and 50%) and altered (more than 50% of individuals
exceed the threshold).26 In the case of F1, the reference threshold
was the maximum absorbance value for each enzyme in the con-
trol strain.
2.3 Biological parameters
A cohort of F1(370 eggs) and one of F16 (372 eggs) were placed
in plastic containers with dechlorinated water for egg hatching.
It should be mentioned that the F16 comes from the last genera-
tion of selection (F15). Once hatched, the larvae were fed 50% (w/v)
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liver protein. Daily survival of the larvae was recorded, and after
reaching the pupa stage, they were placed in emergence cham-
bers to obtain adults, which were transferred to cages, counted
and sexed. The male mosquitoes were fed a 10% sugar solution
and the females were fed on rats for the production of eggs, for
which flasks with water, lined inside with filter paper, were pro-
vided. The oviposition container was removed and replaced daily
and counts were made of the eggs and surviving females until the
death of the last female. At the same time, a cohort of the suscep-
tible NO strain (350 eggs) was taken as standard for comparison,
considered the control strain. Biological parameters were deter-
mined: egg hatching rate, mean development time (egg to adult),
sex ratio, daily survival, total survival, life expectancy, daily mean
fecundity and total fecundity. The age per interval (x), age-specific
fecundity (mx) and probability of survival (lx) were calculated to
obtain the parameters gross reproduction rate (GRR), net repro-
ductive rate (Ro), finite growth rate (𝜆), cohort time (Tc), intrin-
sic growth rate (rm), mean generation time (TG), birth rate and
death rate.27 ANOVA and Tukey’s test (P<0.05) were used to com-
pare sex ratio, development time, total and mean daily fecundity,
totalsurvivalandlifeexpectancyinF
1(without deltamethrin selec-
tion), F16 (strain resulting from F15 selected with deltamethrin)
and the control (reference strain NO). Age-specific survival curves
were built and compared using the log-rank test (Mantel– Cox test;
P<0.05).
3 RESULTS AND DISCUSSION
3.1 Deltamethrin selection
Aedes aegypti from F1had a survival rate of 18% after being
exposed to bottles impregnated with 0.14 μgmL
−1deltamethrin
(LC50) for 1 h, showing an increase in survival over gradual selection
with deltamethrin in each generation until reaching 95% survival
in F15 (Fig. 1).
3.2 Enzymes
Figure 2 displays the protein-corrected absorbance values for each
enzyme in females of Ae. aegypti starting with F1(initial popula-
tion) and during deltamethrin selection, and for the control strain
(NO) as well. The percentage of individuals from each genera-
tion for each enzyme that exceeded the resistance threshold with
respect to F1is shown in Fig. 3. F1and NO strain did not differ
for all enzymes analysed. The levels of alpha-esterases fluctuated
during selection, where there was only a significant difference
between F1with F2,F
5and F11. However, this enzyme was con-
sidered as incipiently altered in the three generations of selec-
tion, according to the Montella classification (Fig. 3). In the case of
beta-esterases, a significant difference was only found between F1
and F2,F
5and F11, but only for F11 selection generation was this
mechanism classified as altered. In the case of MFO, we observed
a gradual increase in mean absorbance values from F2to F15.How-
ever, the values were significant (P<0.01) starting with F8;per-
centages for F8,F
11 and F15 exceeded the threshold set by F1,
which were 43, 80 and 83%, respectively, classifying this mecha-
nism incipiently altered for F8and altered for F11 and F15.GSTswere
not overexpressed in any of the selection generations. Overexpres-
sion of nonspecific esterases and MFOs has been associated with
resistance to deltamethrin in Ae. aegypti.28 –33 Our results showed
overexpression of MFO induced by deltamethrin, and although
they decreased significantly at the end of selection (F15), it is impor-
tant to note that starting with F8, the levels were higher than those
Figure 1. Percentagesurvival of Ae. aegypti Pampanito field population and
each generation of selection with 0.14 μgmL
−1of deltamethrin.
exhibited by F1and the susceptible strain (control), suggesting its
participation in pyrethroid resistance, unlike that observed with
alpha- and beta-esterases. The mechanism of resistance involving
P450 oxidases is very complex; 160 detoxification genes have been
detected in the genome of Ae. aegypti,34 and it is likely that this
mechanism is not the main cause of the resistance exhibited by our
selected population with deltamethrin, because the V1016I and
F1534C mutations were present in the population at the beginning
of the selection and were co-selected, gradually increasing the fre-
quency of the mutant I1016 allele from 0.02 in F1to 0.50 in F15 and
of C1534 from 0.35 to 1.0, which was previously reported by our
group.22
3.3 Biological parameters
Six parameters were evaluated to examine the fitness cost: egg
hatching rate, mean development time (egg to adult), sex ratio,
daily survival and total survival, life expectancy, and daily mean
fecundity and total fecundity. The components were measured
under ideal conditions in the laboratory and focused on the
difference between two strains, the Pampanito population of
Ae. aegypti (F1) and the selected strain for 15 generations with
deltamethrin (F16). The comparison with the susceptible NO strain
is later discussed.
3.3.1 Eggs
The percentage of eggs hatching for the F1generation was 67.1%,
higher than that observed in F16 (52.9%), but in both cases smaller
compared to the control strain (NO, 84.84%). This suggests then
a lower viability of the eggs produced as result of selection
with deltamethrin, in agreement with the results reported for
permethrin-resistant Ae. aegypti.16,35
3.3.2 Development cycle
The mean time of the development cycle of Ae. aegypti in F1
was 6 ±1 days, while 6.5 ±1.04 days in F16 and 8.5 ±1.19 days in
the NO strain. Despite the apparent shortening of the cycle in
the field strain (F1) and the resulting strain of 15 generations of
selection with deltamethrin (F16) with respect to the control strain,
there was no significant difference (P<0.05) between the values
(Table 1). The percentage of pupal formation in the control strain
was 96.7%, while it was 96.1% in F1, higher than that found in
F16 (89.9%), coinciding with the investigations carried out of Ae.
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Figure 2. Profiles of protein-corrected absorbance values for each enzyme in females of Ae. aegypti Pampanito field population and during selection with
deltamethrin and in comparison with the susceptible New Orleans strain.
Figure 3. Percentage of individuals from each generation of selection with
deltamethrin for each enzyme that exceeded the resistance threshold with
respect to F1.
aegypti resistant to deltamethrin and Ae. albopictus resistant to
permethrin (Table 1).16,36
3.3.3 Sex ratio
Regarding the sex ratio, males (52.22% NO, 61.04% F1and 61.59%
F16) were predominant to females (47.78% NO, 38.96% F1and
38.41% F16), with similar female-to-male proportions of 1:1.57 for
F1and 1:1.60 for F16. Although the proportion of females to males
was lower in the control group (1:1.09), no significant difference
was found (Table 1). Our results suggest that deltamethrin had
no effect on sex ratio, and male dominance could be due to
an intrinsic condition of the studied population, which places it
at a reproductive disadvantage, in agreement with the results
obtained for Ae. aegypti exposed to sublethal doses of temephos
and Bti.15,37
3.3.4 Survivorship
The survival curves of the Pampanito population prior to selection
with deltamethrin (F1) and after selection (F16),alongwiththat
of the NO strain, are shown in Fig. 4. When comparing the curves
using the log-rank test, a highly significant difference was found in
age-specific survival rate between the three groups (susceptible
strain, F1and F16 resulting from 15-generation selection with
deltamethrin) (X2=16.16, df =2, P<0.0003). When analysing
total survival, a highly significant difference was found between
the control with respect to F1and F16 (P<0.01), with mean
survival values of 23 ±1.96 days for F1,20±1.83 days for F16 and
40.50 ±2.6 days for control.
3.3.5 Fecundity
Mean daily fecundity did not differ significantly between females
from F16 and unselected (F1and NO) strains: 5.8 eggs/female/day
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Table 1. Development time in days, mean ±SE, percentage of pupation and sex ratio in Aedes aegypti F1(field strain) and after 15 generations of
selections with 0.14 mg mL−1of deltamethrin (F16) in comparison with a control (New Orleans strain without selection).
Strain Days Mean ±SE CI 95% Pupation (%) Females (%) Males (%) Sex ratio, females:males
New Orleans 16 8.5 ±1.19a 5.96– 11.04 96.7 47.78 52.22 1:1.09a
F111 6.0 ±1.00a 3.78– 8.23 96.1 38.96 61.04 1:1.57a
F16 12 6.5 ±1.04a 4.21– 8.9 89.9 38.41 61.59 1:1.60a
Values in the same column with the same letter did not differ significantly (P=0.05).
Figure 4. Survival analysis. Curves represent the daily survival of females of
the Ae. aegypti Pampanito field strain prior to selection with deltamethrin
(F1) and 15 generations of selection (F16), along with that of the susceptible
New Orleans strain.
in F1, 4.9 eggs/female/day in F16 and 6.0 eggs/female/day in the
control. But we did find a difference in mean daily fecundity
and total fecundity between the three strains, reflected later in
GRR. In the case of F1, the maximum mean fecundity value was
ca 38 eggs/female/day reached on day 45, and for F16,ca 25
eggs/female/day on day 33. The control showed the maximum
value on day 52 with ca 33 eggs/female/day (Fig. S1).
It is important to notice that the susceptible NO strain and the
Pampanito population do not share a genetic background, but
the Pampanito population and the selected strain for 15 genera-
tions with deltamethrin (F16) share the same genetic background.
In relation to this, there were no other intrinsic triggers of mortality
and fecundity between the F1and F16 than insecticide resistance,
and, consequently, it suggests costs in age-specific survival and
fecundity of females resistant to deltamethrin. These was assessed
before regarding the selection forward and reverse for 20 genera-
tions with lambda-cyhalothrin in a strain of Ae. aegypti.17
3.3.6 Growth parameters
The results obtained are presented in Tables 2 and 3 which were
determined on the basis of survival and fecundity tables and the
standard procedures of life tables.32 Theresultsshowadecrease
in GRR according to the generation of selection with deltamethrin,
with values of 266.8 for F1and 194.7 for F16, both lower than that
shown by the control strain of 466.3. The decrease in GRR with
selection generation in this case showed that the females had
reduced reproductive potential; however, it must be considered
that the impact on GRR was due in large part to a greater survival
of the control, followed by F1and F16,wherethelatterhada
significantly lower survival (P<0.01) with respect to the control
Table 2. Life-table attributes of Aedes aegypti field strain (F1)and
after 15 generations of selection with 0.14 mg mL−1of deltamethrin
(F16) in comparison with a control (New Orleans strain without
selection).
Attribute New Orleans F1F16
Grossreproductiverate(GRR) 466.3 266.8 194.7
Finite growth rate (𝜆) 1.18 1.17 1.12
Time of cohor t (Tc) (days) 39.44 24.5 24.6
Mean generation time (TG) (days) 26.2 21.7 23.3
Birth rate (B) 0.142 0.220 0.218
Death rate (D) 0.024 0.060 0.102
rm/B1.17 0.73 0.53
B/D5.91 3.66 2.14
Longevity (days) 79 44 38
Table 3. Relative fitness with respect to New Orleans strain of F1and
F16 according to the net reproductive rate (Ro), intrinsic growth rate
(rm) and generation time.
RormTGRelative fitness
New Orleans 75.71a 0.166a 26.20 1
F132.43b 0.160ab 21.70 0.74
F16 14.86c 0.116c 23.30 0.59
Different letter in each row means significate difference (P<0.05).
and F1. Net reproductive rate (Ro) was 32.43 in F1, which decreased
by more than 50% in F16, down to 14.86, which could have been
due to selection with deltamethrin. This indicated that each female
in F16 would be replaced by 14.86 females in the period of one
generation, with this value being much lower than that observed
in the control strain (75.71). In turn, the intrinsic growth rate (rm)
was also affected by selection with deltamethrin being lower in F16
with respect to F1and the control group (Table 3). In Brazil, Diniz
et al.38 found in Ae. aegypti resistant to temephos, decreased net
reproductive rate and duration of the cohort, in agreement with
the findings of the present investigation.39
TGfor F1was 21.7 days, increasing the daily population 1.17
times. For F16 it was 23.3 days, increasing the population 1.12
times, and in the case of the control, TGwas greater at 26.5 days,
increasing the population 1.18 times (Tables 2 and 3). The birth
rate (B) in all cases was higher than the death rate (D) although the
calculated rm/Band B/Dratios were higher in the control strain in
comparison with F1and the lowest for F16, indicating a low growth
potential for the strain resulting from 15 generations of selection
with deltamethrin ( Table 2). The low rm/Band B/Dratios indicate
the slow population growth and reduced colonizing ability, as
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previously reported for anopheline mosquitoes.39 In contrast, high
ratios of these variables indicate very high colonizing ability and
rapid population growth as was reported for Ae. albopictus.40
The estimated life expectancy showed that the individuals from
F16 had a significantly shorter life span than individuals from F1
(P<0.01). In the case of the NO strain this parameter was higher
in comparison with F1, and gradually decreased for all strains
with increasing age to death (P<0.01) (Fig. S2). The Pampanito F1
population had a maximum value of 22.1 at day 12, for F16 15.52 at
day 2 and the control group 35.81 at day 14.
Relative to the NO strain, the fitness, which was calculated from
Ro,rmand TG, was 0.74 and 0.59 for the field strain and F16
(selected strain for 15 generations with deltamethrin) (Table 3).
Fitness cost due to survival and fecundity in Ae. aegypti associated
with insecticide resistance has been reported,16,18,19,41,42 but few
reports include the growth estimators such as Roand rmrelated
to relative fitness. This was previously reported in Ae. aegypti
in relation to artificial selection with lambda-cyalothrin for ten
generations. The results showed a reduction of the fitness cost
of the selected strain by 21% with respect to the susceptible
Rockefeller strain meanwhile the reduction for the non-selected
strain was only 4%.17 In our case, setting a relative fitness value
of 1 to the NO strain, the selected strain with deltamethrin (F16)
reduced its fitness by 41%, and the Pampanito strain (F1) by 26%
(Table 3).
3.3.7 Longevity
The longevity of the females of the Pampanito population at the
beginning and at the end of the selection (F1and F16)wassignif-
icantly lower (P<0.01) than that of the control (NO strain), with
values of 44 days for F1, 38 days for F16 and 70 days for control
(Table 2). Although the frequencies of the kdr mutations V1016I
and C1534F, previously reported,22 increased in the selected pop-
ulation, the decrease in longevity could have been due to MFO
overexpression, according to Chan and Zairi,36 who believed that
MFOs exacerbate the oxidative stress induced by the insecticide in
insect cells, accelerating the aging process, and considering that
Brito et al.19 found no evidence that kdr mutations interfered with
the longevity of Ae. 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 sug-
gested by Diniz et al.,43 who found that the reproductive potential
and survival of temephos-resistant Ae. aegypti were compromised
due to the maintenance of metabolic resistance. The decrease in
longevity and the relation to period of extrinsic incubation of the
pathogen are very important aspects, since they would influence
the vector capacity of the mosquito, which would be advanta-
geous in reducing the transmission of arbovirosis.
Resistance to insecticides can lead to a number of side effects
during an insect’s life cycle, either as a result of pleiotropic effects
on resistance genes or as a consequence of increased alleles of
a gene strongly linked with the resistance gene under selection.
In our study, we established a population of Ae. aegypti resistant
to deltamethrin conferred by MFO and kdr mutations, in which
alterations were observed in some biological and population
parameters, demonstrating the existence of a fitness cost for Ae.
aegypti associated with pyrethroid resistance, possibly due to two
events together: accumulation of harmful or deleterious effects,
genes related to detoxifying enzymes, especially those encoding
MFO, and the co-occurrence of the V1016I and F1534C mutations
previously reported.16,20,22
SUPPORTING INFORMATION
Supporting information may be found in the online version of this
article.
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