Bed Bugs: What Strain Do You Have? The Importance of Resistance Profiling for Insecticide Efficacy Trials Sydney Medical School, Westmead Hospital
Lilly, D.G., K. Dang, C.E. Webb, & S.L. Doggett
Background Monheim LD 50 Sydney LD 50 Group (mg/mL) ( m g/ mL)
Resistance Ratio
Imidacloprid
4A
0.0057
0.015
2.6
Pirimiphos methyl
1B
0.11
0.29
2.6
Bendiocarb
1A
0.027
6.85
250
Deltamethrin
3A
0.00057
210
≈370,000
Permethrin
3A
0.00044
544
≈1,235,000
2
Background Products Registered in Australia
Resistance Internationally
Resistance in Australia
Organophosphates
Yes
Yes (Denmark)
No
Carbamates
Yes
Yes (EU)
Yes
Pyrethroids
Yes
Yes (EU, US)
Yes
Neonicotinoids
Yes
No
No
Group
3
Field Screening Methods 1. Screening test of field strains with 2.5 g/L deltamethrin a. Represents 7,500x susceptible LD50 b. 1 l of insecticide in acetone c. Applied ventrally d. Mortality recorded at 24h
2. Selective test of low mortality strains from above with PBO a. 2-hour pre-treatment with 50 g/L piperonyl butoxide
3. Selective test of injection vs topical application
4
100%
C. lectularius Field Screening g/L deltamethrin Field Strain 2.5 Screening Results
90%
Cumulative Percentage Mortality
1. Screening test of field strains with 2.5 g/L deltamethrin 80%
a.
1 l of insecticide in acetone
60% b.
Applied ventrally
70%
50%
c.
Mortality recorded at 24h
40%
2. 30% Selective test of low mortality strains from above with PBO 20%
a.
2-hour pre-treatment with 50 g/L piperonyl butoxide (otherwise as above)
10%
3. 0% Selective test of injection vs topical application
Strain Source Location (Suburb & State)
5
100%
C. lectularius Field Screening 2.5 g/L deltamethrin The Resurgence A
??
90%
Cumulative Percentage Mortality
Reasons?
B
A = None B = L925I C = V419L / L925I ?? = TBC
B/C
80%
B
B/C
› Increased international travel??
??
70%
› Prevalence of cheap accommodation 60% ??
??
› Phase out of organochlorines and organophosphates 50% 40% › Development of IPMB
?? ??
B
B
B
??
30% › Insecticide resistance 20%
??
B
› Lack ofB research or knowledge of the pest 10%
?? B
B
0%
Strain Source Location (Suburb & State)
6
C. lectularius Field Screening 2.5 g/L deltamethrin The Resurgence
100%
B
B
90%
Cumulative Percentage Mortality
Reasons? 80%
› Increased international travel 70%
› Prevalence of cheap accommodation 60% › Phase out of organochlorines and organophosphates 50% 40% › Development of IPMB
B
30% › Insecticide resistance 20%
B
B
› Lack ofB research or knowledge of the pest 10%
B
B
B
0%
Strain Source Location (Suburb & State)
7
C. lectularius Field Screening 2.5 g/L deltamethrin
Cumulative Percentage Mortality
100%
B
B
90% 80% 70% 60% 50% 40%
B
30% 20% 10%
B
B
B
B B
B
B
0%
Strain Source Location (Suburb & State)
8
100% 90%
Cumulative Percentage Mortality
80% 70% 60% 50%
Alice Springs NT Parramatta NSW
40% 30% 20%
10% 0% Deltamethrin (2.5g/L)
Deltamethrin (2.5g/L) + PBO (50g/L)
Treatment
9
100% 90%
Cumulative Percentage Mortality
80% 70% 60% 50%
Alice Springs NT Parramatta NSW
40% 30% 20%
10% 0% Deltamethrin (2.5g/L)
Deltamethrin (2.5g/L) + PBO (50g/L)
Treatment
10
100% 90%
Cumulative Percentage Mortality
80% 70% 60% 50% Parramatta NSW 40% 30% 20%
10% 0% Topical (Deltamethrin 2.5g/L)
Injection (Deltamethrin 2.5g/L)
Treatment
11
Implications
› High degree of variability in susceptibility of field strains
› By itself, presence of kdr-type may not be an indicator of magnitude - Possibly confers lower degree of resistance to other mechanisms
› Strains present in Australia with multiple resistance mechanisms - And potentially in different combinations
