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https://www.arca.fiocruz.br/handle/icict/32260
LONG-TERM EXPOSURE OF AEDES AEGYPTI TO BACILLUS THURINGIENSIS SVAR. ISRAELENSIS DID NOT INVOLVE ALTERED SUSCEPTIBILITY TO THIS MICROBIAL LARVICIDE OR TO OTHER CONTROL AGENTS
Animais
Bacillus thuringiensis / crescimento e desenvolvimento
Bacillus thuringiensis / patogenicidade
Proteínas Bacterianas / Farmacologia
Brasil
Endotoxinas / farmacologia
Proteínas Hemolisinas / Farmacologia
Resistência a inseticidas
Inseticidas / farmacologia
Larva / efeitos de drogas
Controle de Mosquitos / métodos
Controle de Pragas Biológico / métodos
Author
Affilliation
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.
Abstract
Background: Bacillus thuringiensis svar. israelensis (Bti) is an effective and safe biolarvicide to control Aedes aegypti.
Its mode of action based on four protoxins disfavors resistance; however, control in endemic areas that display high
mosquito infestation throughout the year requires continuous larvicide applications, which imposes a strong
selection pressure. Therefore, this study aimed to investigate the effects of an intensive Bti exposure on an Ae.
aegypti strain (RecBti), regarding its susceptibility to Bti and two of its protoxins tested individually, to other
control agents temephos and diflubenzuron, and its profile of detoxifying enzymes.
Methods: The RecBti strain was established using a large egg sample (10,000) from Recife city (Brazil) and more
than 290,000 larvae were subjected to Bti throughout 30 generations. Larvae susceptibility to larvicides and the
activity of detoxifying enzymes were determined by bioassays and catalytic assays, respectively. The Rockefeller
strain was the reference used for these evaluations.
Results: Bti exposure yielded an average of 74% mortality at each generation. Larvae assessed in seven time
points throughout the 30 generations were susceptible to Bti crystal (resistance ratio RR ≤ 2.8) and to its individual
toxins Cry11Aa and Cry4Ba (RR ≤ 4.1). Early signs of altered susceptibility to Cry11Aa were detected in the last
evaluations, suggesting that this toxin was a marker of the selection pressure imposed. RecBti larvae were also
susceptible (RR ≤ 1.6) to the other control agents, temephos and diflubenzuron. The activity of the detoxifying
enzymes α- and β-esterases, glutathione-S-transferases and mixed-function oxidases was classified as unaltered in
larvae from two generations (F19 and F25), except for a β-esterases increase in F25.
Conclusions: Prolonged exposure of Ae. aegypti larvae to Bti did not evolve into resistance to the crystal, and no
cross-resistance with temephos and diflubenzuron were recorded, which supports their sustainable use with Bti
for integrated control practices. The unaltered activity of most detoxifying enzymes suggests that they might not
play a major role in the metabolism of Bti toxins, therefore resistance by this mechanism is unlikely to occur. This
study also highlights the need to establish suitable criteria to classify the status of larval susceptibility/resistance.
DeCS
Aedes / efeitos de drogasAnimais
Bacillus thuringiensis / crescimento e desenvolvimento
Bacillus thuringiensis / patogenicidade
Proteínas Bacterianas / Farmacologia
Brasil
Endotoxinas / farmacologia
Proteínas Hemolisinas / Farmacologia
Resistência a inseticidas
Inseticidas / farmacologia
Larva / efeitos de drogas
Controle de Mosquitos / métodos
Controle de Pragas Biológico / métodos
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