Department of Mathematics, University of Florida, Gainesville, FL 32611, USA; Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA; Center for African Studies, University of Florida, Gainesville, FL 32611, USA.
Math Biosci. 2023 Jan;355:108936. doi: 10.1016/j.mbs.2022.108936. Epub 2022 Nov 7.
Insecticide-treated nets (ITNs) have been useful and effective in mitigating the risk of malaria globally. However, due to misuse and normal/human-induced physical and chemical wear, the effectiveness of ITNs in combating malaria has been declining. Underlying heterogeneities in the nature of malaria, combined with environmental factors such as temperature lead to complex malaria transmission and control dynamics. In particular, temperature plays a significant role in determining the risk of malaria since it influences the growth and survival of mosquitoes and the malaria parasite. Here, a unifying mechanistic framework that integrates malaria dynamics with waning ITN-efficacy and temperature change is developed and used to assess the impact of interactions between significant sources of variation (e.g., temperature) and waning ITN-efficacy on the risk of malaria transmission and the success of ITN programs. The model exhibits a backward bifurcation when ITN-efficacy is constant implying that control efforts must be stepped up and sustained a bit longer even when the reproduction number is slightly less than one. The study shows that malaria is more effectively controlled with ITNs that have a longer lifespan and if ITNs are replaced before the end of their expiration period. Also, failing to account for waning ITN-efficacy leads to an underestimation of disease risk, burden, and effort level required to contain the disease. Local and global sensitivity analyses show that control and temperature-related parameters are primary drivers of the reproduction number and the human disease burden, highlighting the significance of temperature on malaria dynamics. Furthermore, the study shows that the human disease burden is optimal at a temperature of ≈28°C and that high seasonal variations can trigger major malaria outbreaks even in regions with low mean temperatures. Additionally, accounting for both seasonality and decay in ITN-efficacy leads to complex malaria patterns. To sum it up, insights into the sensitivity of malaria dynamics on temperature are useful in assessing the potential impact of changes in temperature on malaria risk. Also, a malaria control program, which ensures that ITNs are replaced regularly and early enough, and that educates at risk populations on proper use and care for ITNs is necessary for reducing the burden of malaria.
经杀虫剂处理的蚊帐（ITNs）在全球范围内减轻疟疾风险方面非常有用且有效。然而，由于误用以及正常/人为引起的物理和化学磨损，ITNs 在对抗疟疾方面的效果正在下降。疟疾的性质存在固有异质性，加上温度等环境因素，导致疟疾传播和控制的动态变得复杂。特别是，温度在确定疟疾风险方面起着重要作用，因为它会影响蚊子和疟原虫的生长和存活。在这里，开发并使用了一个统一的机制框架，将疟疾动态与 ITN 效果减弱和温度变化结合起来，以评估显著变化源（例如温度）与 ITN 效果减弱之间的相互作用对疟疾传播风险和 ITN 计划成功的影响。当 ITN 效果恒定时，模型表现出反向分岔，这意味着即使繁殖数略小于 1，也必须加强和持续更长时间的控制努力。研究表明，使用寿命更长的 ITN 可以更有效地控制疟疾，如果在 ITN 过期之前更换 ITN，则效果更佳。此外，未能考虑到 ITN 效果减弱会导致对疾病风险、负担和控制疾病所需的努力水平的低估。局部和全局敏感性分析表明，控制和与温度相关的参数是繁殖数和人类疾病负担的主要驱动因素，突出了温度对疟疾动态的重要性。此外，该研究表明，在 ≈28°C 的温度下，人类疾病负担最佳，季节性的高变化甚至在平均温度较低的地区也可能引发大规模的疟疾爆发。此外，同时考虑季节性和 ITN 效果减弱会导致复杂的疟疾模式。总之，了解疟疾动态对温度的敏感性有助于评估温度变化对疟疾风险的潜在影响。此外，为了降低疟疾负担，有必要实施一个疟疾控制计划，该计划应确保定期且尽早更换 ITN，并对高危人群进行正确使用和保养 ITN 的教育。
