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Target product profiles for protecting against outdoor malaria transmission.

Killeen GF, Moore SJ - Malar. J. (2012)

Bottom Line: LLIN impact could be dramatically enhanced by high coverage with spatial repellents conferring near-complete personal protection, but only if combined indoor use of both measures can be avoided where vectors persist that prefer feeding indoors upon humans.While very high levels of coverage and efficacy will be required for spatial repellents to substantially augment the impact of LLINs or IRS, these ambitious targets may well be at least as practically achievable as the lower requirements for equivalent impact using contact insecticides.Vapour-phase repellents may be more acceptable, practical and effective than contact insecticides for preventing outdoor malaria transmission because they need not be applied to skin or clothing and may protect multiple occupants of spaces outside of treatable structures such as nets or houses.

View Article: PubMed Central - HTML - PubMed

Affiliation: Biomedical and Environmental Thematic Group, Ifakara Health Institute, PO Box 53, Ifakara, Morogoro, United Republic of Tanzania. gkilleen@ihi.or.tz

ABSTRACT

Background: Long-lasting insecticidal nets (LLINs) and indoor residual sprays (IRS) have decimated malaria transmission by killing indoor-feeding mosquitoes. However, complete elimination of malaria transmission with these proven methods is confounded by vectors that evade pesticide contact by feeding outdoors.

Methods: For any assumed level of indoor coverage and personal protective efficacy with insecticidal products, process-explicit malaria transmission models suggest that insecticides that repel mosquitoes will achieve less impact upon transmission than those that kill them outright. Here such models are extended to explore how outdoor use of products containing either contact toxins or spatial repellents might augment or attenuate impact of high indoor coverage of LLINs relying primarily upon contact toxicity.

Results: LLIN impact could be dramatically enhanced by high coverage with spatial repellents conferring near-complete personal protection, but only if combined indoor use of both measures can be avoided where vectors persist that prefer feeding indoors upon humans. While very high levels of coverage and efficacy will be required for spatial repellents to substantially augment the impact of LLINs or IRS, these ambitious targets may well be at least as practically achievable as the lower requirements for equivalent impact using contact insecticides.

Conclusions: Vapour-phase repellents may be more acceptable, practical and effective than contact insecticides for preventing outdoor malaria transmission because they need not be applied to skin or clothing and may protect multiple occupants of spaces outside of treatable structures such as nets or houses.

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Impact of products for outdoor malaria prevention expressed in terms of the mean relative risk of exposure experienced by the average community member (ψh,Ω). Scenarios are considered in which LLIN products that provide 50% personal protection (ρi = 0·5) by killing half of all mosquitoes that attack them (θμ,pre,i = 0·5) are complemented by use of additional products conferring equivalent personal protection (ρo or ρi+o = 0·5) with one of the three following profiles: Products for exclusively outdoor use that kill attacking mosquitoes before they feed (θμ,pre,o = 0·5) or products that deter mosquitoes from attacking that are used either outdoors only (θΔ,o = 0·5) or are used both indoors and outdoors (θΔ,i+o = 0·5). Further details of the model and symbol definitions are available online (See Additional file 4)
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Figure 1: Impact of products for outdoor malaria prevention expressed in terms of the mean relative risk of exposure experienced by the average community member (ψh,Ω). Scenarios are considered in which LLIN products that provide 50% personal protection (ρi = 0·5) by killing half of all mosquitoes that attack them (θμ,pre,i = 0·5) are complemented by use of additional products conferring equivalent personal protection (ρo or ρi+o = 0·5) with one of the three following profiles: Products for exclusively outdoor use that kill attacking mosquitoes before they feed (θμ,pre,o = 0·5) or products that deter mosquitoes from attacking that are used either outdoors only (θΔ,o = 0·5) or are used both indoors and outdoors (θΔ,i+o = 0·5). Further details of the model and symbol definitions are available online (See Additional file 4)

Mentions: This term was calculated for unprotected individuals lacking either of these measures (ψh,0,Ω) or as a community-wide average, reflecting the coverage-weighted mean of such non-users and users of one or both measures (ψh,Ω) [8]. For simplicity, only the community-wide average relative exposure and relative residual exposure for each scenario, reflecting combined community-level and personal protection effects, are presented in the main text in Figures 1, 2, 3). For comparison, equivalent plots of relative exposure and relative residual exposure of non-users, reflecting community-level protection effects only, are available online (See Additional file 1, Additional file 2, and Additional file 3).


Target product profiles for protecting against outdoor malaria transmission.

Killeen GF, Moore SJ - Malar. J. (2012)

Impact of products for outdoor malaria prevention expressed in terms of the mean relative risk of exposure experienced by the average community member (ψh,Ω). Scenarios are considered in which LLIN products that provide 50% personal protection (ρi = 0·5) by killing half of all mosquitoes that attack them (θμ,pre,i = 0·5) are complemented by use of additional products conferring equivalent personal protection (ρo or ρi+o = 0·5) with one of the three following profiles: Products for exclusively outdoor use that kill attacking mosquitoes before they feed (θμ,pre,o = 0·5) or products that deter mosquitoes from attacking that are used either outdoors only (θΔ,o = 0·5) or are used both indoors and outdoors (θΔ,i+o = 0·5). Further details of the model and symbol definitions are available online (See Additional file 4)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3298720&req=5

Figure 1: Impact of products for outdoor malaria prevention expressed in terms of the mean relative risk of exposure experienced by the average community member (ψh,Ω). Scenarios are considered in which LLIN products that provide 50% personal protection (ρi = 0·5) by killing half of all mosquitoes that attack them (θμ,pre,i = 0·5) are complemented by use of additional products conferring equivalent personal protection (ρo or ρi+o = 0·5) with one of the three following profiles: Products for exclusively outdoor use that kill attacking mosquitoes before they feed (θμ,pre,o = 0·5) or products that deter mosquitoes from attacking that are used either outdoors only (θΔ,o = 0·5) or are used both indoors and outdoors (θΔ,i+o = 0·5). Further details of the model and symbol definitions are available online (See Additional file 4)
Mentions: This term was calculated for unprotected individuals lacking either of these measures (ψh,0,Ω) or as a community-wide average, reflecting the coverage-weighted mean of such non-users and users of one or both measures (ψh,Ω) [8]. For simplicity, only the community-wide average relative exposure and relative residual exposure for each scenario, reflecting combined community-level and personal protection effects, are presented in the main text in Figures 1, 2, 3). For comparison, equivalent plots of relative exposure and relative residual exposure of non-users, reflecting community-level protection effects only, are available online (See Additional file 1, Additional file 2, and Additional file 3).

Bottom Line: LLIN impact could be dramatically enhanced by high coverage with spatial repellents conferring near-complete personal protection, but only if combined indoor use of both measures can be avoided where vectors persist that prefer feeding indoors upon humans.While very high levels of coverage and efficacy will be required for spatial repellents to substantially augment the impact of LLINs or IRS, these ambitious targets may well be at least as practically achievable as the lower requirements for equivalent impact using contact insecticides.Vapour-phase repellents may be more acceptable, practical and effective than contact insecticides for preventing outdoor malaria transmission because they need not be applied to skin or clothing and may protect multiple occupants of spaces outside of treatable structures such as nets or houses.

View Article: PubMed Central - HTML - PubMed

Affiliation: Biomedical and Environmental Thematic Group, Ifakara Health Institute, PO Box 53, Ifakara, Morogoro, United Republic of Tanzania. gkilleen@ihi.or.tz

ABSTRACT

Background: Long-lasting insecticidal nets (LLINs) and indoor residual sprays (IRS) have decimated malaria transmission by killing indoor-feeding mosquitoes. However, complete elimination of malaria transmission with these proven methods is confounded by vectors that evade pesticide contact by feeding outdoors.

Methods: For any assumed level of indoor coverage and personal protective efficacy with insecticidal products, process-explicit malaria transmission models suggest that insecticides that repel mosquitoes will achieve less impact upon transmission than those that kill them outright. Here such models are extended to explore how outdoor use of products containing either contact toxins or spatial repellents might augment or attenuate impact of high indoor coverage of LLINs relying primarily upon contact toxicity.

Results: LLIN impact could be dramatically enhanced by high coverage with spatial repellents conferring near-complete personal protection, but only if combined indoor use of both measures can be avoided where vectors persist that prefer feeding indoors upon humans. While very high levels of coverage and efficacy will be required for spatial repellents to substantially augment the impact of LLINs or IRS, these ambitious targets may well be at least as practically achievable as the lower requirements for equivalent impact using contact insecticides.

Conclusions: Vapour-phase repellents may be more acceptable, practical and effective than contact insecticides for preventing outdoor malaria transmission because they need not be applied to skin or clothing and may protect multiple occupants of spaces outside of treatable structures such as nets or houses.

Show MeSH
Related in: MedlinePlus