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. 2023 Aug 28;16(1):300.
doi: 10.1186/s13071-023-05883-1.

Efficacy of a 'lethal house lure' against Culex quinquefasciatus from Bouaké city, Côte d'Ivoire

Innocent Z Tia  1   2   3   4 , Antoine M G Barreaux  5 , Welbeck A Oumbouke  6 , Alphonsine A Koffi  7   8 , Ludovic P Ahoua Alou  7   8 , Soromane Camara  7   8 , Rosine Z Wolie  7   8   9 , Eleanore D Sternberg  6 , Amal Dahounto  10 , Gregoire Y Yapi  11   12 , Matthew B Thomas  13 , Raphael N'Guessan  14   15   16
Affiliations

Efficacy of a 'lethal house lure' against Culex quinquefasciatus from Bouaké city, Côte d'Ivoire

Innocent Z Tia et al. Parasit Vectors. .

Abstract

Background: Eave tube technology is a novel method of insecticide application that uses an electrostatic coating system to boost insecticide efficacy against resistant mosquitoes. A series of previous experiments showed encouraging insecticidal effects against malaria vectors. This study was undertaken to assess the effects of the eave tube approach on other Culicidae, in particular Culex quinquefasciatus, under laboratory and semi-field conditions.

Methods: Larvae of Cx. quinquefasciatus from Bouaké were collected and reared to adult stage, and World Health Organization (WHO) cylinder tests were performed to determine their resistance status. WHO standard 3-min cone bioassays were conducted using PermaNet 2.0 netting versus eave tube-treated inserts. To assess the transient exposure effect on Cx. quinquefasciatus, eave tube assay utilizing smelly socks as attractant was performed with exposure time of 30 s, 1 min, and 2 min on 10% beta-cyfluthrin-treated inserts. Residual activity of these treated inserts was then monitored over 9 months. Field tests involving release-recapture of Cx. quinquefasciatus within enclosures around experimental huts fitted with windows and untreated or insecticide-treated eave tubes were conducted to determine house entry preference and the impact of tubes on the survival of this species.

Results: Bouaké Cx. quinquefasciatus displayed high resistance to three out of four classes of insecticides currently used in public health. After 3 min of exposure in cone tests, 10% beta-cyfluthrin-treated inserts induced 100% mortality in Cx. quinquefasciatus, whereas the long-lasting insecticidal net (LLIN) only killed 4.5%. With reduced exposure time on the eave tube insert, mortality was still 100% after 2 min, 88% after 1 min, and 44% after 30 s. Mortality following 1 h exposure on 10% beta-cyfluthrin-treated insert was > 80% continuously up to 7 months post-treatment. Data suggest that Cx. quinquefasciatus have a stronger preference for entering a house through the eaves than through windows. Beta-cyfluthrin-treated inserts were able to kill 51% of resistant Cx. quinquefasciatus released within the enclosure.

Conclusions: Eave tubes are a novel method for delivery of insecticide to the house. They attract nuisance host-seeking Cx. quinquefasciatus mosquitoes and are as effective in controlling them as they are against pyrethroid-resistant Anopheles gambiae, despite the high level of resistance Cx. quinquefasciatus have developed.

Keywords: Bouaké; Culex quinquefasciatus; Eave tubes; Insecticide resistance.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
The eave tube components and eave tube bioassay device. A Untreated eave tube insert. B Treated insert with visible 10% beta-cyfluthrin powder. C 20-cm tube of PVC. D Treated insert with WHO cone fixed with a rubber band to hold it in place and prevent mosquito escape. E Insert at the end of a dark pipe; the opposite side contains a clean plastic bottle filled with hot water with a smelly sock at the end to attract mosquitoes
Fig. 2
Fig. 2
Experimental hut with modifications. A Experimental hut fitted with eave tubes. B Experimental hut with enclosure and fitted with eave tubes
Fig. 3
Fig. 3
Percentage mortality in insecticide-resistant Cx. quinquefasciatus from Bouaké in WHO cylinder bioassays. Blue and red bars represent intensity and synergist assay, respectively. Error bars represent 95% confidence intervals
Fig. 4
Fig. 4
Percentage mortality from WHO cone assay with PermaNet 2.0 LLINs versus 10% beta-cyfluthrin-treated inserts of Cx. quinquefasciatus susceptible SLAB and resistant Bouaké strains. Error bars represent 95% confidence intervals
Fig. 5
Fig. 5
Residual activity of 10% beta-cyfluthrin-treated insert against insecticide-resistant Cx. quinquefasciatus from Bouaké. MAT months after treatment. Error bars represent 95% confidence intervals
Fig. 6
Fig. 6
Experimental hut evaluations. A Collection of Cx. quinquefasciatus from Bouaké to the hut via open windows or eave tubes within enclosure around huts. B Percentage mortality of insecticide-treated inserts against the proportion of resistant Cx. quinquefasciatus from Bouaké collecting in the hut within the enclosure. Error bars represent 95% confidence intervals
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