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Research
Joseph Chabi
University of Ghana Noguchi Memorial Institute for Medical Research
Corresponding Author
ORCiD: https://orcid.org/0000-0003-1988-5403
License:
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Background : Pyrethroid-treated mosquito nets are currently the mainstay of vector control in Côte d’Ivoire. However, resistance to pyrethroids has been reported across the country, limiting options for insecticide resistance management due to the paucity of alternative insecticides. Two types of insecticide-treated nets (ITNs), ITNs with pyrethroids and the synergist piperonyl butoxide (PBO), and Interceptor ® G2 nets, a net treated with a combination of chlorfenapyr and alpha-cypermethrin, are believed to help in the control of pyrethroid-resistant mosquitoes.
Methods : The susceptibility of An. gambiae s.l. to pyrethroid insecticides with and without pre-exposure to PBO as well as to chlorfenapyr was investigated in fifteen sites across the country. Susceptibility tests were conducted on 2- to 4-day old adult female An. gambiae s.l. reared from larval collections. The resistance status, intensity, and effects of PBO on mortality after exposure to different concentrations of deltamethrin, permethrin and alpha-cypermethrin were determined using WHO susceptibility test kits. In the absence of a WHO-recommended standard protocol for chlorfenapyr, two interim doses (100 and 200 µg/bottle) were used to test the susceptibility of mosquitoes using the CDC bottle assay method.
Results : Pre-exposure to PBO did not result in full restoration of susceptibility to any of the three pyrethroids for the An. gambiae s.l. populations from any of the sites surveyed. However, PBO pre-exposure did increase mortality for all three pyrethroids, particularly deltamethrin (from 4.4% to 48.9%). Anopheles gambiae s.l. from only one site (Bettie) were susceptible to chlorfenapyr at the dose of 100 µg active ingredient (a.i.)/bottle. Even at the dose of 200 µg (a.i.)/bottle, susceptibility was only recorded in 10 of the 15 sites.
Conclusion : Low mosquito mortality was found for pyrethroids alone, and while PBO increased mortality, it did not restore full susceptibility. The vector was not fully susceptible to chlorfenapyr in one third of the sites tested. However, vector susceptibility to chlorfenapyr seems to be considerably higher than for pyrethroids alone or with PBO. These data should be used cautiously when making ITN procurement decisions, noting that bioassays are conducted in controlled conditions and may not fully represent field efficacy.
Keywords
Insecticide resistance, pyrethroids, piperonyl butoxide, chlorfenapyr, An. gambiae s.l., vector control, ITNs, Côte d’Ivoire.
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See the published version of this preprint at Malaria Journal.
This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research
Joseph Chabi
University of Ghana Noguchi Memorial Institute for Medical Research
Corresponding Author
ORCiD: https://orcid.org/0000-0003-1988-5403
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Published
View the published article at Malaria Journal.
No community comments so far
Editorial decision: Accept
On 23 Nov, 2020
Editor assigned
On 22 Nov, 2020
Submission checks complete
On 22 Nov, 2020
Editor invited
On 22 Nov, 2020
No comments provided
Editorial decision: Minor Revision
On 09 Nov, 2020
Editor assigned
On 08 Nov, 2020
Submission checks complete
On 08 Nov, 2020
Editor invited
On 08 Nov, 2020
No comments provided
Editor assigned
On 03 Nov, 2020
Submission checks complete
On 03 Nov, 2020
Editor invited
On 03 Nov, 2020
Version 1
Posted 06 Apr, 2020
No comments provided
Editorial decision: Major Revision
On 21 Oct, 2020
Reviewer #2 agreed
On 15 Oct, 2020
Review #2 received
Received 15 Oct, 2020
Review #1 received
Received 06 Oct, 2020
Reviewer #1 agreed
On 05 Oct, 2020
Reviewers invited
Invitations sent on 13 Apr, 2020
Editor assigned
On 03 Apr, 2020
First submitted
On 02 Apr, 2020
Submission checks complete
On 02 Apr, 2020
Editor invited
On 02 Apr, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Infectious Diseases
License:
This work is licensed under a CC BY 4.0 License. Read Full License
View the published article at Malaria Journal.
Background : Pyrethroid-treated mosquito nets are currently the mainstay of vector control in Côte d’Ivoire. However, resistance to pyrethroids has been reported across the country, limiting options for insecticide resistance management due to the paucity of alternative insecticides. Two types of insecticide-treated nets (ITNs), ITNs with pyrethroids and the synergist piperonyl butoxide (PBO), and Interceptor ® G2 nets, a net treated with a combination of chlorfenapyr and alpha-cypermethrin, are believed to help in the control of pyrethroid-resistant mosquitoes.
Methods : The susceptibility of An. gambiae s.l. to pyrethroid insecticides with and without pre-exposure to PBO as well as to chlorfenapyr was investigated in fifteen sites across the country. Susceptibility tests were conducted on 2- to 4-day old adult female An. gambiae s.l. reared from larval collections. The resistance status, intensity, and effects of PBO on mortality after exposure to different concentrations of deltamethrin, permethrin and alpha-cypermethrin were determined using WHO susceptibility test kits. In the absence of a WHO-recommended standard protocol for chlorfenapyr, two interim doses (100 and 200 µg/bottle) were used to test the susceptibility of mosquitoes using the CDC bottle assay method.
Results : Pre-exposure to PBO did not result in full restoration of susceptibility to any of the three pyrethroids for the An. gambiae s.l. populations from any of the sites surveyed. However, PBO pre-exposure did increase mortality for all three pyrethroids, particularly deltamethrin (from 4.4% to 48.9%). Anopheles gambiae s.l. from only one site (Bettie) were susceptible to chlorfenapyr at the dose of 100 µg active ingredient (a.i.)/bottle. Even at the dose of 200 µg (a.i.)/bottle, susceptibility was only recorded in 10 of the 15 sites.
Conclusion : Low mosquito mortality was found for pyrethroids alone, and while PBO increased mortality, it did not restore full susceptibility. The vector was not fully susceptible to chlorfenapyr in one third of the sites tested. However, vector susceptibility to chlorfenapyr seems to be considerably higher than for pyrethroids alone or with PBO. These data should be used cautiously when making ITN procurement decisions, noting that bioassays are conducted in controlled conditions and may not fully represent field efficacy.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
This is a list of supplementary files associated with this preprint. Click to download.
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