X Substitution Target population 1 3/21/2016 Control of Aedes - - PDF document

3/21/2016 1

Chemical control & insectiside resistance

Fiocruz Instituto Oswaldo Cruz

Ademir J Martins Jr Maceió, march 13th 2016

Suppression

X

Substitution Target population

Control of insect populations

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Wolbachia transgenesis Avoid larval breeding sites

Mechanical control

SIT genetic shifting paratransgenesis

Biological control Chemical control

insecticides predators/ parasites

Suppression Substitution

Control of Aedes aegypti populations

Wolbachia transgenesis Avoid larval breeding sites

Mechanical control

SIT genetic shifting paratransgenesis

Biological control Chemical control

insecticides predators/ parasites

Suppression Substitution

Control of Aedes aegypti populations

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Bass et al 2014 – Insect Biochem Mol Biol

The Brazilian National Program for Dengue Control only applies insecticides approved by the WHO Pesticide Evaluation Scheme (WHOPES)

Insecticides

updated 5 February 2016

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The Brazilian National Program for Dengue Control only applies insecticides approved by the WHO Pesticide Evaluation Scheme (WHOPES)

Insecticides

updated 5 February 2016

N N N N IGR IGR IGR N Bio

The Brazilian National Program for Dengue Control only applies insecticides approved by the WHO Pesticide Evaluation Scheme (WHOPES)

Insecticides

updated 5 February 2016

Pyr Pyr Pyr Pyr OP

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The Brazilian National Program for Dengue Control only applies insecticides approved by the WHO Pesticide Evaluation Scheme (WHOPES)

Insecticides

updated 5 February 2016

Insecticides against Ae. aegypti In Brazil

• Larvicide temephos (OP) and adulticides fenitrothion and malathion

(OPs) until 2009

• Resistance to OPs started being detected in1998
• Inauguration of a National Monitoring Network for Insecticide Resistance in

Aedes aegypti

• Substitution of the larvicide to Bti (biol), JH and BPUs IGRs and the

adulticides to deltamethrin (Pyr)

• Soon after, resistance to Pyr was detected and then we returned to the OP

malathion.

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Insecticides against Ae. aegypti In Brazil

Currently indicated by the Brazilian National Program for Dengue Control Larvicide: pyriproxyfen (JH) Adulticides: malathion (OP) – spatial bendiocarb (CA) – residual

• Larvicide temephos (OP) and adulticides fenitrothion and malathion

(OPs) until 2009

• Resistance to OPs started being detected in 1998
• Inauguration of a National Monitoring Network for Insecticide Resistance in

Aedes aegypti

• Substitution of the larvicide to Bti (biol), JH and BPUs IGRs and the

adulticides to deltamethrin (Pyr)

• Soon after, resistance to Pyr was detected and then we returned to the OP

malathion.

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Insecticide resistance can contribute to an increase in the incidence of arboviruses

5000 10000 15000 20000 25000 30 40 50 60 70

cumulative dengue incidence mortality (%) R2= 0.7372, p <0.0286

• P. Prudente

Marília Campinas

• Rib. Preto

Santos SJR Preto Exemple: reduced mortality of Ae. aegypti to pyrethroids showed a significant correlation with dengue incidence in localities from São Paulo Insecticide resistance can contribute to an increase in the incidence of arboviruses Macoris, not published

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Insecticide resistance in dengue vectors Ranson et al 2010, TropiKanet Insecticide resistance in dengue vectors Ranson et al 2010, TropiKanet

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2005 – 2015 published data on Anopheles resistance

source: IR Mapper

How to evaluate insecticide resistance?

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How to evaluate insecticide resistance?

 There is an increasing number of validated methods for evaluating insecticide resistance levels and their selected physiological mechanisms CDC bottle bioassay WHO tubes bioassay

How to evaluate insecticide resistance? Bioassays

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Behavioral changes Reduced penetration (cuticle) Increase in enzymatic detoxification Target site insensitivity

Main mechanisms selected for insecticide resistance

How to evaluate insecticide resistance? Biochemical and molecular assays

Biochemical assays of enzymatic activity

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Mechanisms for insecticide resistance: metabolic resistance in Aedes aegypti from Brazil

High-throughput identification of resistance genes

Faucon et al 2015 – Genome Research

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Mechanisms for insecticide resistance: kdr mutations in Aedes aegypti from Brazil

Aedes aegypti SNP chip Evans et al 2015 – Genes, Genomics, Genetics

• Wide genome analysis (GWAS) comparing susceptible and

resistant individuals of several Brazilian populations Bioasays with insecticide Resistant Susceptible

• 32K biallelic, mendelian and validated

SNPs for each individual in one reaction Aedes aegypti SNP chip

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Worldwide insecticide resistance network in mosquito vectors of arboviruses

Acronym: WIN (Worldwide Insecticide-resistance Network) PI’s: Vincent Corbel (IRD, Thailand) and Jean-Philippe David (CNRS, France) The WIN proposes to bring together 15 internationally recognized institutions in vector research, providing a unique framework for tracking insecticide resistance in mosquito vectors of arboviruses around the world. The network aims at identifying the particular countries/regions where resistance could challenge vector control interventions and to provide the WHO and member states with key recommendations for improvement

• f insecticide resistance surveillance and deployment
• f alternative vector control tools.

Is it possible to revert to a susceptible stage? Would we able to continue effectively using insecticides as

• ne of the alternatives for vector control ???

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Selection pressure insecticide

time

Is it possible to revert to a susceptible stage?

• Comparisons between Rock and Rock-kdr (R2R2)

Time of larval development Pupation rate Adults longevity Blood feeding Fecundity: rate of inseminated females Fecundity: number of eggs Locomotor activity Circadian rhythm Fertility: eggs’ viability Competition during larval development Competition for copula

   

R2 kdr allele has a fitness cost

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• Comparisons between Rock and Rock-kdr (R2R2)

Time of larval development Pupation rate Adults longevity Blood feeding Fecundity: rate of inseminated females Fecundity: number of eggs Locomotor activity Circadian rhythm Fertility: eggs’ viability Competition during larval development Competition for copula

   

R2 kdr allele has a fitness cost

Enough to diminish the frequency of the mutant allele in an insecticide-free environment ?

3 6 9 12 15 0.0 0.2 0.4 0.6 0.8 1.0

cage 1 cage 2 cage 3 A generations (F) 1016 Ile (frequecy)

3 6 9 12 15 0.0 0.2 0.4 0.6 0.8 1.0

cage 4 cage 5 cage 6 B generations (F) 1016 Ile (frequecy)

Kdr allele initial frequency (3 independent cages for each situation)

50% 75%

R2 kdr allele has a fitness cost

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3 6 9 12 15 0.0 0.2 0.4 0.6 0.8 1.0

cage 1 cage 2 cage 3 A generations (F) 1016 Ile (frequecy)

3 6 9 12 15 0.0 0.2 0.4 0.6 0.8 1.0

cage 4 cage 5 cage 6 B generations (F) 1016 Ile (frequecy)

Kdr allele initial frequency (3 independent cages for each situation)

50% 75%

R2 kdr allele has a fitness cost

Awareness modifier genes

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• Insecticide resistance has become a serious threaten

to mosquito control. Merely switching insecticide when the current one no longer works is not effective.

• Good predictions of the dynamics of resistance in

natural populations have to consider the knowledge of genetic, biologic and ecological aspects of the selected mechanisms. Conclusions

Challange #1 : knowledge of the selected mechanisms

• Metabolic
• target site
• cuticle thickening
• behavioural

Challenge #2 : knowledge of the dynamics of resistance genes in the population Avoid the increase and dispersion of resistance Avoid cross resistance among different class of insecticides Maintain insecticides as one of the possible strategies for mosquito control

• R allele frequencies
• dominance relationships
• epistatic effects on fitness

Remarks for studying a resistant population

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Thank you! Ademir J Martins ademirjr@ioc.fiocruz.br