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Personal Protection with PBO-Pyrethroid Synergist Treated Nets After Two Years of Household Use Against Pyrethroid-Resistant Anopheles in Tanzania

Article scientifique 2020 Anglais

Résumé

Abstract Background: The spread of pyrethroid resistance in malaria vectors threatens the effectiveness of standard long-lasting insecticidal nets (LLIN). Synergist nets combine pyrethroid (Py) and piperonyl-butoxide (PBO) to enhance potency against resistance mediated by mono-oxygenase mechanisms. Our project assessed personal protection of WHO first-in-class PBO-Py treated nets (Olyset Plus) versus standard LLIN (Olyset net) against pyrethroid resistant Anopheles gambiae and An. funestus in North West Tanzania after 20 months of household use.Methods: From household survey, 39 standard Olyset net and 39 Olyset Plus houses were selected, physical integrity and hole index (HI) of nets assessed, resting mosquitoes collected from inside nets and from room walls, indoor abundance estimated using CDC light traps and species identified using PCR. Residual bio-efficacy of PBO and standard LLINs was assessed using 30 min cylinder bioassays.Results: Of 2397 Anopheles collected, 8.9% (n=213) were resting inside standard Olyset nets while none were found inside Olyset Plus PBO-Py nets of any HI category. Resting density of blood fed mosquitoes was higher on walls of sleeping rooms with Olyset net compared to Olyset Plus (0.62 vs 0.10, density ratio: 0.03, 95% CI: 0.01-0.13, p<0.001). Mosquitoes were found inside Olyset nets of all WHO HI categories but more were collected inside the more damaged (HI≥ 643) nets than in less damaged (HI 0-64) nets (DR: 6.4, 95% CI: 1.1-36.0, p=0.037). In residual bioassay, mortality of An. gambiae s.l was higher with Olyset Plus than with Olyset net for new nets (76.8% vs 27.5%) and 20 months’ nets (56.8% vs 12.8%); similar trends were observed with An. funestus. Conclusion: The PBO-Py treated net provided improved protection after 20 months of household use, as demonstrated by the higher bioassay mortality and absence of pyrethroid resistant An. gambiae s.s. and An. funestus collected from inside Olyset Plus, irrespective of hole index category, as compared to Olyset nets.

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Martin, J., Mosha, F., Lukole, E., Rowland, M., Todd, J., Charlwood, J., Mosha, J., Protopopoff, N. (2020). Personal Protection with PBO-Pyrethroid Synergist Treated Nets After Two Years of Household Use Against Pyrethroid-Resistant Anopheles in Tanzania. https://doi.org/10.21203/rs.3.rs-57340/v1

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Auteur(s)

Jackline Martin Franklin W. Mosha Eliud Lukole Mark Rowland Jim Todd J. D. Charlwood Jacklin F Mosha Natacha Protopopoff

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