chemical control & insectiside resistance...3/21/2016 1 chemical control & insectiside...
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Chemical control & insectiside resistance
FiocruzInstituto Oswaldo Cruz
Ademir J Martins Jr
Maceió, march 13th 2016
Suppression
XSubstitution
Target population
Control of insect populations
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Wolbachiatransgenesis
Avoid larval breeding sites
Mechanical control
SIT genetic shiftingparatransgenesisBiological control
Chemical control insecticides
predators/ parasites
Suppression
Substitution
Control of Aedes aegyptipopulations
Wolbachiatransgenesis
Avoid larval breeding sites
Mechanical control
SIT genetic shiftingparatransgenesisBiological control
Chemical control insecticides
predators/ parasites
Suppression
Substitution
Control of Aedes aegyptipopulations
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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
NNNN
IGRIGRIGR
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
0 5000 10000 15000 20000 2500030
40
50
60
70
cumulative dengue incidence
mo
rta
lity
(%) R2= 0.7372, p <0.0286
P. Prudente
Marília
CampinasRib. 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 vectorsRanson et al 2010, TropiKanet
Insecticide resistance in dengue vectorsRanson 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 detoxificationTarget 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: kdrmutations in Aedes aegypti from Brazil
Aedes aegypti SNP chipEvans 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 arbovirusesAcronym: WIN (Worldwide Insecticide-resistance Network)PI’s: Vincent Corbel (IRD, Thailand) and Jean-Philippe David (CNRS, France)
The WIN proposes to bring together 15internationally recognized institutions in vector research, providing a unique framework for trackinginsecticide resistance in mosquito vectors of arboviruses around the world. The network aims atidentifying the particular countries/regions where resistance could challenge vector controlinterventions and to provide the WHO and member states with key recommendations for improvementof insecticide resistance surveillance and deployment of alternative vector control tools.
Is it possible to revert to a susceptible stage?
Would we able to continue effectively using insecticides as one of the alternatives for vector control ???
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Selection pressureinsecticide
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 ?
0 3 6 9 12 15
0.0
0.2
0.4
0.6
0.8
1.0 cage 1 cage 2cage 3
A
generations (F)
10
16
Ile
(fre
qu
ec
y)
0 3 6 9 12 15
0.0
0.2
0.4
0.6
0.8
1.0 cage 4cage 5cage 6
B
generations (F)
10
16
Ile
(fre
qu
ec
y)
Kdr allele initial frequency(3 independent cages for each situation)
50%
75%
R2 kdr allele has a fitness cost
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0 3 6 9 12 15
0.0
0.2
0.4
0.6
0.8
1.0 cage 1 cage 2cage 3
A
generations (F)
10
16
Ile
(fre
qu
ec
y)
0 3 6 9 12 15
0.0
0.2
0.4
0.6
0.8
1.0 cage 4cage 5cage 6
B
generations (F)
10
16
Ile
(fre
qu
ec
y)
Kdr allele initial frequency(3 independent cages for each situation)
50%
75%
R2 kdr allele has a fitness cost
Awarenessmodifier genes
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- Insecticide resistance has become a serious threatento mosquito control. Merely switching insecticide whenthe current one no longer works is not effective.
- Good predictions of the dynamics of resistance innatural populations have to consider the knowledge ofgenetic, biologic and ecological aspects of the selectedmechanisms.
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
