Mechanistic models of host movement to understand disease dynamics in variable environments

在加拿大，在过去20年里，出现了新的野生动物疾病，现有疾病的模式发生了重大变化。这些变化突显了研究疾病动力学的必要性。当易感宿主接触感染宿主或寄生虫时，疾病就会传播。这些相遇的比率很大程度上取决于宿主如何移动，然而，大多数疾病传播的数学模型并没有明确地考虑宿主的移动。此外，温度、湿度等非生物因素既影响寄生虫的感染性，又影响寄生虫整个生活期的成熟率。季节性的强度和机制都会影响疾病的动态。寄生虫影响宿主的移动方式，从而影响寄生虫的传播和寄生虫毒力等特征的进化。我的研究小组将调查宿主移动如何影响由此导致的流行病类型。我们将考虑不同类型的运动模型，包括相关和有偏的随机行走和状态空间模型。我们将调查环境条件变化对自由生活寄生虫传播的影响。我们还将通过推导和分析寄主移动速率和/或寄生虫传染性、寄生虫脱落率和疾病引起的死亡率之间的权衡数学模型来研究寄生虫毒力的进化。在所有情况下，模型都将使用数学和计算技术进行分析。 这项研究将利用动物运动机制模型的最新进展，并将为传染病传播的研究贡献新的概念、定量和计算工具。我们将得出的模型改进了现有理论的生物学现实主义，并可能导致对疾病动力学的更好理解。对于一个具体的案例研究，我们将应用我们开发的理论来了解脑蠕虫在纽芬兰日益衰落的驯鹿群中的传播。该研究项目将支持培养1名博士生、4名硕士研究生和4名本科生。这些学生将接受数学建模和理论生物学方面的培训，并将在跨学科研究方面获得宝贵的经验。

In Canada, over the last two decades new wildlife diseases have emerged and patterns of existing diseases have changed substantially. These changes highlight the need for research that investigates disease dynamics. Diseases are spread when a susceptible host contacts an infectious host or a parasite. These rates of encounter depend strongly on how hosts move, and yet, most mathematical models of disease spread do not explicitly consider host movement. In addition, temperature, humidity and other abiotic factors affect both the infectivity of parasites and the rate of maturation through parasite life stages. Both the strength and mechanisms of seasonality will affect disease dynamics. Parasites affect how hosts move and this affects parasite spread and the evolution of characteristics such as parasite virulence. My research group will investigate how host movement affects the types of epidemics that result. We will consider different types of movement models including correlated and biased random walks and state-space models. We will investigate the effect of fluctuating environmental conditions on the spread of free-living parasites. We will also investigate the evolution of parasite virulence by deriving and analyzing mathematical models where a trade-off exists between the rate of host movement and/or parasite infectivity, the parasite shedding rate, and the disease-induced death rate. In all cases, the models will be analyzed using mathematical and computational techniques. This research will capitalize on recent progress in developing mechanistic models of animal movement and will contribute new conceptual, quantitative, and computational tools to the study of infectious disease spread. The models that we will derive improve the biological realism of existing theory and are likely to lead to a better understanding of disease dynamics. For a specific case study, we will apply the theory we develop to understand the spread of brain worm in declining herds of caribou in Newfoundland. This research program will support the training of 1 PhD student, 4 MSc students and 4 undergraduate researchers. These students will be trained in mathematical modelling and theoretical biology and will gain valuable experience in interdisciplinary research.