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The Impact of Selection with Diflubenzuron, a Chitin Synthesis Inhibitor, on the Fitness of Two Brazilian Aedes aegypti Field Populations.

Belinato TA, Valle D - PLoS ONE (2015)

Bottom Line: Diflubenzuron was effective against the two Ae. aegypti field populations evaluated, regardless of their resistance level to neurotoxic insecticides.Several aspects of mosquito biology were affected in both selected populations, indicating that diflubenzuron resistance acquisition is associated with a fitness cost.We believe that these results can significantly contribute to the design of control strategies involving the use of insect growth regulators.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro (RJ), Brasil.

ABSTRACT
Several Aedes aegypti field populations are resistant to neurotoxic insecticides, mainly organophoshates and pyrethroids, which are extensively used as larvicides and adulticides, respectively. Diflubenzuron (DFB), a chitin synthesis inhibitor (CSI), was recently approved for use in drinking water, and is presently employed in Brazil for Ae. aegypti control, against populations resistant to the organophosphate temephos. However, tests of DFB efficacy against field Ae. aegypti populations are lacking. In addition, information regarding the dynamics of CSI resistance, and characterization of any potential fitness effects that may arise in conjunction with resistance are essential for new Ae. aegypti control strategies. Here, the efficacy of DFB was evaluated for two Brazilian Ae. aegypti populations known to be resistant to both temephos and the pyrethroid deltamethrin. Laboratory selection for DFB resistance was then performed over six or seven generations, using a fixed dose of insecticide that inhibited 80% of adult emergence in the first generation. The selection process was stopped when adult emergence in the diflubenzuron-treated groups was equivalent to that of the control groups, kept without insecticide. Diflubenzuron was effective against the two Ae. aegypti field populations evaluated, regardless of their resistance level to neurotoxic insecticides. However, only a few generations of DFB selection were sufficient to change the susceptible status of both populations to this compound. Several aspects of mosquito biology were affected in both selected populations, indicating that diflubenzuron resistance acquisition is associated with a fitness cost. We believe that these results can significantly contribute to the design of control strategies involving the use of insect growth regulators.

No MeSH data available.


The sex ratio of mosquitoes both pre- (Panel A) and post-selection, (Panel B) showing the proportion of male (blue) and female (pink) adults in each group.The value at the bottom of each bar represents the total number of adults that eclosed in that particular treatment. Diflubenzuron-selected (dfb) and control (cont) strains are shown for the Boa Vista (BVT) and Aparecida de Goiânia (APG) populations.
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pone.0130719.g002: The sex ratio of mosquitoes both pre- (Panel A) and post-selection, (Panel B) showing the proportion of male (blue) and female (pink) adults in each group.The value at the bottom of each bar represents the total number of adults that eclosed in that particular treatment. Diflubenzuron-selected (dfb) and control (cont) strains are shown for the Boa Vista (BVT) and Aparecida de Goiânia (APG) populations.

Mentions: Dose-response assays confirmed DFB inhibits Ae. aegypti adult emergence in a dose-dependent manner (S1 Fig). Table 1 depicts the EI values and DFB resistance ratios for both Brazilian populations and the Rockefeller strain, and reveals a higher RR for APG compared to BVT. Evaluation of mortality at each stage shows that the proportion of specimens that died as larvae increased after exposure to higher DFB concentrations. Adult emergence was observed for all CSI concentrations for APG mosquitoes, but not for the three highest concentrations for BVT (Fig 1A). In general, the number of viable adults was very low, and the majority of survivors at high DFB concentrations were males (Fig 2A).


The Impact of Selection with Diflubenzuron, a Chitin Synthesis Inhibitor, on the Fitness of Two Brazilian Aedes aegypti Field Populations.

Belinato TA, Valle D - PLoS ONE (2015)

The sex ratio of mosquitoes both pre- (Panel A) and post-selection, (Panel B) showing the proportion of male (blue) and female (pink) adults in each group.The value at the bottom of each bar represents the total number of adults that eclosed in that particular treatment. Diflubenzuron-selected (dfb) and control (cont) strains are shown for the Boa Vista (BVT) and Aparecida de Goiânia (APG) populations.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481264&req=5

pone.0130719.g002: The sex ratio of mosquitoes both pre- (Panel A) and post-selection, (Panel B) showing the proportion of male (blue) and female (pink) adults in each group.The value at the bottom of each bar represents the total number of adults that eclosed in that particular treatment. Diflubenzuron-selected (dfb) and control (cont) strains are shown for the Boa Vista (BVT) and Aparecida de Goiânia (APG) populations.
Mentions: Dose-response assays confirmed DFB inhibits Ae. aegypti adult emergence in a dose-dependent manner (S1 Fig). Table 1 depicts the EI values and DFB resistance ratios for both Brazilian populations and the Rockefeller strain, and reveals a higher RR for APG compared to BVT. Evaluation of mortality at each stage shows that the proportion of specimens that died as larvae increased after exposure to higher DFB concentrations. Adult emergence was observed for all CSI concentrations for APG mosquitoes, but not for the three highest concentrations for BVT (Fig 1A). In general, the number of viable adults was very low, and the majority of survivors at high DFB concentrations were males (Fig 2A).

Bottom Line: Diflubenzuron was effective against the two Ae. aegypti field populations evaluated, regardless of their resistance level to neurotoxic insecticides.Several aspects of mosquito biology were affected in both selected populations, indicating that diflubenzuron resistance acquisition is associated with a fitness cost.We believe that these results can significantly contribute to the design of control strategies involving the use of insect growth regulators.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro (RJ), Brasil.

ABSTRACT
Several Aedes aegypti field populations are resistant to neurotoxic insecticides, mainly organophoshates and pyrethroids, which are extensively used as larvicides and adulticides, respectively. Diflubenzuron (DFB), a chitin synthesis inhibitor (CSI), was recently approved for use in drinking water, and is presently employed in Brazil for Ae. aegypti control, against populations resistant to the organophosphate temephos. However, tests of DFB efficacy against field Ae. aegypti populations are lacking. In addition, information regarding the dynamics of CSI resistance, and characterization of any potential fitness effects that may arise in conjunction with resistance are essential for new Ae. aegypti control strategies. Here, the efficacy of DFB was evaluated for two Brazilian Ae. aegypti populations known to be resistant to both temephos and the pyrethroid deltamethrin. Laboratory selection for DFB resistance was then performed over six or seven generations, using a fixed dose of insecticide that inhibited 80% of adult emergence in the first generation. The selection process was stopped when adult emergence in the diflubenzuron-treated groups was equivalent to that of the control groups, kept without insecticide. Diflubenzuron was effective against the two Ae. aegypti field populations evaluated, regardless of their resistance level to neurotoxic insecticides. However, only a few generations of DFB selection were sufficient to change the susceptible status of both populations to this compound. Several aspects of mosquito biology were affected in both selected populations, indicating that diflubenzuron resistance acquisition is associated with a fitness cost. We believe that these results can significantly contribute to the design of control strategies involving the use of insect growth regulators.

No MeSH data available.