Mohammed-Awel Jemal, Agusto Folashade, Mickens Ronald E, Gumel Abba B
Department of Mathematics, Valdosta State University, Valdosta, GA 31698, USA.
Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS USA.
Infect Dis Model. 2018 Nov 2;3:301-321. doi: 10.1016/j.idm.2018.10.003. eCollection 2018.
The large-scale use of insecticide-treated bednets (ITNs) and indoor residual spraying (IRS), over the last two decades, has resulted in a dramatic reduction of malaria incidence globally. However, the effectiveness of these interventions is now being threatened by numerous factors, such as resistance to insecticide in the mosquito vector and their preference to feed and rest outdoors or early in the evening (when humans are not protected by the bednets). This study presents a new deterministic model for assessing the population-level impact of mosquito insecticide resistance on malaria transmission dynamics. A notable feature of the model is that it stratifies the mosquito population in terms of type (wild or resistant to insecticides) and feeding preference (indoor or outdoor). The model is rigorously analysed to gain insight into the existence and asymptotic stability properties of the various disease-free equilibria of the model namely the trivial disease-free equilibrium, the non-trivial resistant-only boundary disease-free equilibrium and a non-trivial disease-free equlibrium where both the wild and resistant mosquito geneotypes co-exist). Simulations of the model, using data relevant to malaria transmission dynamics in Ethiopia (a malaria-endemic nation), show that the use of optimal ITNs alone, or in combination with optimal IRS, is more effective than the singular implementation of an optimal IRS-only strategy. Further, when the effect of the fitness cost of insecticide resistance with respect to fecundity (i.e., assuming a decrease in the baseline birth rate of new resistant-type adult female mosquitoes) is accounted for, numerical simulations of the model show that the combined optimal ITNs-IRS strategy could lead to the effective control of the disease, and insecticide resistance effectively managed during the first 8 years of the 15-year implementation period of the insecticides-based anti-malaria control measures in the community.
在过去二十年中，大规模使用经杀虫剂处理的蚊帐（ITNs）和室内滞留喷洒（IRS）已使全球疟疾发病率大幅降低。然而，这些干预措施的有效性目前正受到多种因素的威胁，例如病媒蚊子对杀虫剂产生抗药性，以及它们偏好户外觅食和休息或在傍晚早期（此时人类未受到蚊帐保护）活动。本研究提出了一种新的确定性模型，用于评估蚊子抗药性对疟疾传播动态的群体水平影响。该模型的一个显著特点是，它根据类型（野生型或对杀虫剂有抗性）和觅食偏好（室内或室外）对蚊子种群进行分层。对该模型进行了严格分析，以深入了解模型各种无病平衡点的存在性和渐近稳定性特性，即平凡无病平衡点、仅抗性边界无病平衡点以及野生型和抗性蚊子基因型共存的非平凡无病平衡点。使用与埃塞俄比亚（一个疟疾流行国家）疟疾传播动态相关的数据对该模型进行模拟，结果表明，单独使用最优ITNs或与最优IRS联合使用，比单纯实施最优IRS策略更有效。此外，当考虑到杀虫剂抗性对繁殖力的适合度成本效应（即假设新的抗性型成年雌性蚊子的基线出生率下降）时，该模型的数值模拟表明，最优ITNs - IRS联合策略可有效控制疾病，并且在基于杀虫剂的社区抗疟疾控制措施15年实施期的前8年中可有效管理杀虫剂抗性。
