Truscott James, Hollingsworth T Déirdre, Anderson Roy
London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, St Marys Campus, Norfolk Place, London, United Kingdom.
Mathematics Institute, University of Warwick, Coventry, United Kingdom; School of Life Sciences, University of Warwick, Coventry, United Kingdom; Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
PLoS Negl Trop Dis. 2014 Dec 4;8(12):e3323. doi: 10.1371/journal.pntd.0003323. eCollection 2014 Dec.
The control or elimination of neglected tropical diseases has recently become the focus of increased interest and funding from international agencies through the donation of drugs. Resources are becoming available for the treatment of soil-transmitted helminth (STH) infection through school-based deworming strategies. However, little research has been conducted to assess the impact of STH treatment that could be used to guide the design of efficient elimination programs.
We construct and analyse an age-structured model of STH population dynamics under regular treatment. We investigate the potential for elimination with finite rounds of treatment, and how this depends on the value of the basic reproductive number R0 and treatment frequency.
Analysis of the model indicates that its behaviour is determined by key parameter groupings describing the basic reproduction number and the fraction of it attributable to the treated group, the timescale of material in the environment and the frequency and efficacy of treatment. Mechanisms of sexual reproduction and persistence of infectious material in the environment are found to be much more important in the context of elimination than in the undisturbed baseline scenario. For a given rate of drug use, sexual reproduction dictates that less frequent, higher coverage treatment is more effective. For a given treatment coverage level, the lifespan of infectious material in the environment places a limit on the effectiveness of increased treatment frequency.
Our work suggests that for models to capture the dynamics of parasite burdens in populations under regular treatment as elimination is approached, they need to include the effects of sexual reproduction among parasites and the dynamics infectious material in the reservoir. The interaction of these two mechanisms has a strong effect on optimum treatment strategies, both in terms of how frequently to treat and for how long.
通过捐赠药物，被忽视热带病的控制或消除最近已成为国际机构日益关注和资助的焦点。通过以学校为基础的驱虫策略，已有资源可用于治疗土壤传播的蠕虫（STH）感染。然而，很少有研究评估STH治疗的影响，而这可用于指导高效消除计划的设计。
我们构建并分析了在定期治疗下STH种群动态的年龄结构模型。我们研究了有限轮次治疗实现消除的潜力，以及这如何取决于基本繁殖数R0和治疗频率的值。
对模型的分析表明，其行为由关键参数分组决定，这些参数分组描述了基本繁殖数及其可归因于治疗组的部分、环境中物质的时间尺度以及治疗的频率和效果。发现在消除背景下，有性繁殖机制和感染性物质在环境中的持续存在比在未受干扰的基线情景中更为重要。对于给定的药物使用速率，有性繁殖表明较低频率、较高覆盖率的治疗更有效。对于给定的治疗覆盖率水平，环境中感染性物质的寿命对增加治疗频率的有效性设置了限制。
我们的工作表明，对于在接近消除时定期治疗人群中捕获寄生虫负担动态的模型，它们需要纳入寄生虫之间有性繁殖的影响以及宿主中感染性物质的动态。这两种机制的相互作用对最佳治疗策略有很大影响，无论是在治疗频率和治疗时长方面。
