Environmental Engineering Reference
In-Depth Information
It has been suggested that insecticide resistance could be accentuated by the
exposure of mosquito populations to pollutants and pesticides used in agriculture [14,
15, 54, 55]. In Martinique, bananas, sugar cane, and pineapple represent important
cultured surface areas often localized near mosquito breeding sites. These cultures
have been submitted for decades to heavy use of insecticides such as the organochlo-
rates aldrin, dieldrin and chlordecone and herbicides such as the triazine simazine,
the pyridines paraquat, and glyphosate [56]. This particular situation is likely to have
contributed to the high resistance of
Ae. aegypti
to chemical insecticides and to the
selection of particular detoxifi cation genes in Martinique.
MATERIAL AND METHODS
Mosquito Strains
Two strains of
Ae. aegypti
were used in this study. The susceptible reference Bora-Bora
strain, originating from Bora-Bora (French Polynesia) is free of any detectable insec-
ticide resistance mechanism. An
Ae. aegypti
colony was established from wild field-
caught mosquito larvae collected from individual houses in the community of Vauclin
in Martinique (Vauclin strain). Larvae and adults obtained from the F1 progeny were
used for bioassays, biochemical, and molecular studies.
Insecticides and Detoxification Enzyme Inhibitors
Two technical grade compounds were used, representing organophosphate and pyre-
throid classes of insecticides, temephos (97.3%; Pestanal™, Riedel-de-Haën, Seelze,
Germany) and deltamethrin (100%; AgreEvo, Herts, United Kingdom). In addition,
three classical detoxification enzyme inhibitors were used for larval and adult bioas-
says; piperonyl butoxide (PBO; 5-((2-(2-butoxyethoxy)ethoxy) methyl)-6-propyl-1,3-
benzodioxole; 90% Fluka, Buchs, Switzerland) an inhibitor of mixed-function oxidas-
es, tribufos (DEF; S,S,S-tributyl phosphorotrithioate; 98.1% Interchim, Montluçon,
France) an inhibitor of carboxylesterases and in a lesser extent of GSTs and chlor-
fenethol (DMC; 1,1-bis (4-chlorophenyl) ethanol; 98% Pestanal™, Riedel-de-Haën,
Seelze, Germany) a specific inhibitor of GSTs.
Larval Bioassays
Larval bioassays were performed using a standard protocol described by the World
Health Organization [58]. Bioassays were carried out using late third and early fourth-
instar larvae of the Bora-Bora and Vauclin strains. For each bioassay, 20 larvae of
each strain were transferred to cups containing 99 ml of distilled water. Five cups
per concentration (100 larvae) and 5-8 concentrations of temephos diluted in ethanol
leading to 0-100% mortality were used. For each concentration, 1 ml of temephos at
the desired concentration was added to the cups. Control treatments of 1 ml of ethanol
were performed for each test. Temperature was maintained at 27°C ± 2°C all over the
duration of bioassays, and larval mortality was recorded 24 hr after exposure. Three
replicates with larvae from different rearing batches were made at different times and
the results were pooled for analysis. Larvae were then exposed to the insecticide plus
each enzyme inhibitor for 24 hr. Dose of enzyme inhibitors were determined according
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