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Quantifying late-stage host-seeking behaviour of Anopheles gambiae at the insecticidal net interface using a baited-box bioassay

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Hughes, Angela, Foster, Geraldine ORCID: https://orcid.org/0000-0002-9769-4349, Guy, Amy, Matope, Agnes, Abe, Mayumi, Towers, David and McCall, Philip ORCID: https://orcid.org/0000-0002-0007-3985 (2020) 'Quantifying late-stage host-seeking behaviour of Anopheles gambiae at the insecticidal net interface using a baited-box bioassay'. Malaria Journal, Vol 19, Issue 140.

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Abstract

Background
Insecticide-treated nets (ITNs) are losing efficacy against pyrethroid-resistant malaria vector populations throughout Africa. Safeguarding bed net efficacy, vital for effective malaria control, requires greater knowledge of mosquito–ITN interactions and how this impacts on the mosquito.

Methods
A purpose-built benchtop apparatus with a closed 10 cm cubic chamber (the ‘Baited-box’) was used to video record behaviour of individual free-flying female Anopheles gambiae during approach and blood-feeding on a human hand through untreated nets and ITNs at close range. Time and duration of defined behavioural events, and knockdown and mortality at 1- and 24-h post-exposure respectively, were recorded for pyrethroid susceptible and resistant mosquitoes.

Results
Using three human volunteers differing in relative attractiveness to mosquitoes, 328 mosquitoes were individually tested. There were no significant differences between response rates to ITNs and untreated nets (P > 0.1) or between resistant (Tiassalé) and susceptible (Kisumu) mosquito strains, at untreated nets (P = 0.39) or PermaNet 2.0 (P = 1). The sequence of behavioural events from host-seeking to completion of blood-feeding was consistent in all tests but duration and start time of events involving net contact were reduced or delayed respectively with ITNs. Blood-feeding durations at untreated nets (means from 4.25 to 8.47 min (95% confidence interval (CI) = 3.39–9.89) at 3 human volunteers) were reduced by 37–50% at PermaNet 2.0, in susceptible (mean 2.59–4.72 min, 95% CI = 1.54–5.5, P = < 0.05) and resistant (mean 4.20 min, 95% CI = 3.42–4.97, P = 0.01) strains. Total accumulated net contact was approximately 50% lower at PermaNet and Olyset ITNs (P < 0.0001) in susceptible (two of the three volunteers) and resistant mosquitoes. Times prior to first net contact were similar at untreated nets and ITNs (P > 0.2), and neither ITN type showed detectable spatial repellency. After initial contact, blood-feeding commenced later at Olyset (mean 2.76 min, 95% CI = 1.74–3.76, P = 0.0009) and PermaNet (mean 2.4 min, 95% CI = 1.52–3.33, P = 0.0058) than untreated netting (mean 0.68 min, 95% CI = 0.42–0.94).

Conclusions
The baited box offers a simple method for detailed characterization of mosquito behavioural responses to insecticidal nets, for comparing entomological modes of action between nets and for defining the behavioural responses of particular mosquito strains or populations. The device has potential as a screening assay in the search for novel net treatments and for investigations into behavioural resistance mechanisms.

Item Type: Article
Subjects: QV Pharmacology > Drug Standardization. Pharmacognosy. Medicinal Plants > QV 771 Standardization and evaluation of drugs
QX Parasitology > Insects. Other Parasites > QX 510 Mosquitoes
QX Parasitology > Insects. Other Parasites > QX 515 Anopheles
WA Public Health > Preventive Medicine > WA 240 Disinfection. Disinfestation. Pesticides (including diseases caused by)
Faculty: Department: Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI): https://doi.org/10.1186/s12936-020-03213-9
Depositing User: Mel Finley
Date Deposited: 16 Apr 2020 10:11
Last Modified: 16 Apr 2020 10:11
URI: https://archive.lstmed.ac.uk/id/eprint/14197

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