Environmental Engineering Reference
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pyrethroid deltamethrin at the adult stage [30]. The use of specifi c detoxifi cation en-
zyme inhibitors suggested that resistance of larvae to temephos is linked to carboxy-
lesterases and to a lesser extent P450s and GSTs. In adults, resistance to deltamethrin
appeared principally linked to P450s and GSTs. Comparison of global detoxifi cation
enzyme activities between the two strains revealed elevated P450s, GSTs, and in a
lesser extent CCEs activities in the Vauclin strain at both life-stages, confi rming the
importance of metabolic resistance mechanisms in Martinique.
Carboxylesterases based-resistance mechanism is a major mechanism for organo-
phosphate resistance in insects [12]. Several examples of
Ae. aegypti
resistance to
organophosphates in the Caribbean linked to elevated carboxylesterases activities
have been described [25, 31]. Our toxicological and biochemical data confi rms these
observations despite a moderate elevated level of CCEs activities in the Vauclin strain.
Among detoxifi cation enzymes, P450s have been shown to play a major role in pyre-
throid resistance in insects [8, 10, 32]. In Martinique, Marcombe et al. [30] suggested
the involvement of P450s in the reduced effi cacy of deltamethrin space-spray opera-
tions. Elevated GST levels have also been frequently associated with insect resistance
to insecticides such as DDT and pyrethroids [33-35]. Our toxicological and biochemi-
cal data support the role of P450s and GSTs in insecticide resistance in Martinique.
At the molecular level, several mutations in the voltage-gated sodium channel
gene have been associated with pyrethroid resistance in
Ae. aegypti
from Asian, Latin
American, and Caribbean countries [27, 29, 36]. Our results revealed a high frequency
(71%) of the V1016I
kdr
mutation in
Ae. aegypti
populations from the community of
Vauclin. The role of this mutation in pyrethroid resistance was clearly demonstrated
by genotype-phenotype association studies [37]. The high frequency of the mutation,
together with the incomplete effect of enzyme inhibitors in adults, supports a contribu-
tion of this
kdr
mutation in deltamethrin resistance.
Acetylcholinesterase (AChE) is critical for hydrolysis of acetylcholine at cholin-
ergic nerve synapses and is a target for organophosphate and carbamate insecticides
[38]. Altered AchE is an important resistance mechanism to organophosphates in
many insects. Following the methods of Alout et al. [39] and Bourguet et al. [40], the
AChE activities of Vauclin mosquitoes were determined to investigate the presence of
the G119S and/or F290V mutations. No insensitive AChE phenotypes were found in
any of the mosquitoes tested (Corbel V., unpublished data), suggesting that organo-
phosphate resistance of the Vauclin strain is rather due to detoxifi cation enzymes un-
less other mutations occurred elsewhere in the Ace gene.
Our microarray screening identifi ed 14 and nine over-transcribed detoxifi cation
genes in larvae and adults of the Vauclin strain respectively. Among them, four P450s
(
CYP6M6, CYP6Z6, CYP9J23
and
CYP9J22
), the glutathione S-transferase
GSTe7
and the carboxy/cholinesterase
CCEae3A
were all confi rmed to be over-transcribed
at both life-stages, supporting their involvement in insecticide-resistance. Other genes
appeared more highly over-transcribed in adults (
CYP9J22, CYP9M9, CYP6M11,
CCEae3A
) or in larvae (
CYP6M6
), suggesting that particular enzymes might be more
specifi cally involved in resistance to one insecticide during a particular life-stage as
argued by Paul et al. [41]. Validation of transcription profi les by real-time quantitative
RT-PCR was successful for the 10 genes tested although expression ratios obtained
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