The online version of this article (doi:10.1186/1475-2875-11-17) contains supplementary material, which is available to authorized users.
While this study was independently funded by the Bill & Melinda Gates Foundation, both authors have received funding support for other research projects from manufactures of insecticidal public health products: Vestergaard Frandsen SA (GFK), Syngenta (SJM), Pinnacle Development (SJM) and SC Johnson (SJM).
Both authors formulated the research questions and developed the conceptual basis of the model. GFK drafted the model formulation and manuscript, which was then critiqued and edited by SJM. All authors have read and approved the final version of the manuscript.
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.
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.
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.
Additional file 1: Figure S1. Purely community-level impact of products for outdoor malaria prevention expressed in terms of the mean relative risk of exposure experienced by non-users of any protective measure. (PDF 76 KB)12936_2011_2012_MOESM1_ESM.PDF
Additional file 2: Figure S2. Additional incremental community-level impact of outdoor contact toxins or repellents that are exclusively used outdoors or used both indoors and outdoors when combined with indoor LLINs with contact toxins, compared with their direct impact as stand-alone intervention strategies. (PDF 77 KB)12936_2011_2012_MOESM2_ESM.PDF
Additional file 3: Figure S3. Progressive community-level impact upon a completely outdoor transmission system of products with increasing efficacy of personal protection achieved by either repelling or killing attacking mosquitoes before they feed upon human users. (PDF 76 KB)12936_2011_2012_MOESM3_ESM.PDF
Additional file 4: Supplemental methods S4. Detailed model description. (PDF 223 KB)12936_2011_2012_MOESM4_ESM.PDF
Authors’ original file for figure 112936_2011_2012_MOESM5_ESM.pdf
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Authors’ original file for figure 312936_2011_2012_MOESM7_ESM.pdf
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- Target product profiles for protecting against outdoor malaria transmission
Gerry F Killeen
Sarah J Moore
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