Long-lasting insecticidal nets and the quest for malaria eradication: a mathematical modeling approach
Long-lasting insecticidal nets and the quest for malaria eradication: a mathematical modeling approach
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DOI：
10.1007/s00285-020-01503-z
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发表时间：
2020-05-23
影响因子：
1.9
通讯作者：
Paaijmans, Krijn
中科院分区：
文献类型：
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作者：
Enahoro, Iboi;Eikenberry, Steffen;Paaijmans, Krijn
全球疟疾负担和死亡率近期的大幅下降在很大程度上可归因于以杀虫剂为基础的措施的大规模应用，即长效驱虫蚊帐（LLINs）和室内滞留喷洒。然而，这些成果的可持续性以及到2040年全球根除疟疾的可行性，可能会受到按蚊疟疾传播媒介中杀虫剂抗性不断增强的影响。我们采用了一种基于新的微分方程的数学模型，该模型纳入了完整的、依赖天气的蚊子生命周期，以评估在按蚊对拟除虫菊酯杀虫剂具有不同抗性水平的情况下，大规模使用长效驱虫蚊帐对一个社区的疟疾传播动态和控制在种群层面的影响。此外，我们使用可从不同有效拟除虫菊酯抗性水平下的大型实验小屋试验文献中估计的参数来描述蚊帐 - 蚊子的相互作用。推导出了基本繁殖数\(R_0\)作为种群层面蚊帐覆盖率函数的表达式。由于后向分支现象，结果表明，必须将\(R_0\)显著降低到1以下才能在流行地区消除疟疾，这可能会使根除工作变得复杂。该模型的数值模拟表明，当基线\(R_0\)较高（大致对应于高度地方性疟疾）时，需要非常高的高效蚊帐覆盖率才能接近消除疟疾的条件。此外，虽然>50%的蚊帐覆盖率可能足以从具有中度地方性疟疾基线的地区有力地控制或消除疟疾，但拟除虫菊酯抗性即使在这种情况下也可能破坏控制和消除工作。我们的模拟表明，蚊子的拟除虫菊酯抗性在参数空间内显著降低了蚊帐的有效性。这项建模研究还表明，增加蚊子吸血前的驱避作用（阻止它们进入受保护的房屋）实际上会阻碍消除工作，因为这可能会使蚊子叮咬集中在较小的未受保护的宿主亚群上。最后，我们观察到温度独立于蚊帐覆盖率和拟除虫菊酯抗性水平影响疟疾发生的可能性，气候变化和拟除虫菊酯抗性都对疟疾控制构成未来的威胁。
Recent dramatic declines in global malaria burden and mortality can be largely attributed to the large-scale deployment of insecticidal-based measures, namely long-lasting insecticidal nets (LLINs) and indoor residual spraying. However, the sustainability of these gains, and the feasibility of global malaria eradication by 2040, may be affected by increasing insecticide resistance among the Anopheles malaria vector. We employ a new differential-equations based mathematical model, which incorporates the full, weather-dependent mosquito lifecycle, to assess the population-level impact of the large-scale use of LLINs, under different levels of Anopheles pyrethroid insecticide resistance, on malaria transmission dynamics and control in a community. Moreover, we describe the bednet-mosquito interaction using parameters that can be estimated from the large experimental hut trial literature under varying levels of effective pyrethroid resistance. An expression for the basic reproduction number, R-0, as a function of population-level bednet coverage, is derived. It is shown, owing to the phenomenon of backward bifurcation, that R-0 must be pushed appreciably below 1 to eliminate malaria in endemic areas, potentially complicating eradication efforts. Numerical simulations of the model suggest that, when the baseline R-0 is high (corresponding roughly to holoendemic malaria), very high bednet coverage with highly effective nets is necessary to approach conditions for malaria elimination. Further, while >50% bednet coverage is likely sufficient to strongly control or eliminate malaria from areas with a mesoendemic malaria baseline, pyrethroid resistance could undermine control and elimination efforts even in this setting. Our simulations show that pyrethroid resistance in mosquitoes appreciably reduces bednet effectiveness across parameter space. This modeling study also suggests that increasing pre-bloodmeal deterrence of mosquitoes (deterring them from entry into protected homes) actually hampers elimination efforts, as it may focus mosquito biting onto a smaller unprotected host subpopulation. Finally, we observe that temperature affects malaria potential independently of bednet coverage and pyrethroid-resistance levels, with both climate change and pyrethroid resistance posing future threats to malaria control.