Organisms across a wide range of taxa use migration as a strategy to avoid, reduce or recover from parasitic infection. Previous work has identified three different processes by which migration can help reduce infection risk and/or costs: migratory escape from infection, migratory culling of infected individuals and migratory recovery from infection. However, most theoretical modelling of host migration in response to infection assumes that individuals have a single strategy during both infected and susceptible states, meaning an individual's state (susceptible or infected) is irrelevant to its decision to migrate. Here, we construct a model with two independent strategies of migration for an individual based on whether they are infected or susceptible, to study when the decision to migrate is favourable. We show that the best strategy for individuals of a given infection state is to either always migrate or never migrate. When infected and susceptible individuals differ in their migration strategy, this leads to partial migration at the population level (only some individuals migrate). Whereas previous theory showed that partial migration can be optimal in the face of infection, our work further parses out the contributors to partial or complete migration by determining which individuals in the population are involved in migration for different sets of conditions.

中文翻译：

---

感染状态会影响宿主的迁徙决定

各种分类单元中的生物都采用迁移作为避免，减少或从寄生虫感染中恢复的策略。先前的工作已经确定了迁移可以帮助降低感染风险和/或成本的三个不同过程：从感染中迁徙逃逸，被感染个体的迁徙淘汰和从感染中迁徙恢复。但是，大多数针对感染的宿主迁移的理论模型都假设个体在感染和易感状态下都有单一策略，这意味着个体的状态（易感或感染）与其迁移决定无关。在此，我们基于个体是被感染还是易感染的情况，构建了一个具有两种独立迁移策略的模型，以研究何时做出有利于迁移的决定。我们表明，对于给定感染状态的个体，最佳策略是始终迁移或永不迁移。当受感染和易感的个体的迁移策略不同时，这将导致在人口级别上部分迁移（只有一些个体迁移）。先前的理论表明，面对感染，部分迁移可能是最佳选择，但我们的工作通过确定人口中哪些人参与不同条件的迁移，进一步解析了部分或完全迁移的原因。