Modeling Vector-Borne Disease Risk In Migratory Animals Under Climate Change

Recent theory suggests that animals that migrate to breed at higher latitudes may benefit from reduced pressure from natural enemies, including pathogens ("migratory escape''), and that migration itself weeds out infected individuals and lowers infection prevalence ("migratory culling''). The distribution and activity period of arthropod disease vectors in temperate regions is expected to respond rapidly to climate change, which could reduce the potential for migratory escape. However, climate change could have the opposite effect of reducing transmission if differential responses in the phenology and distribution of migrants and disease vectors reduce their overlap in space and time. Here we outline a simple modeling framework for exploring the influence of climate change on vector-borne disease dynamics in a migratory host. We investigate two scenarios under which pathogen transmission dynamics might be mediated by climate change: (1) vectors respond more rapidly than migrants to advancing phenology at temperate breeding sites, causing peak susceptible host density and vector emergence to diverge ("migratory mismatch'') and (2) reduced migratory propensity allows increased nonbreeding survival of infected hosts and larger breeding-site epidemics (loss of migratory culling, here referred to as "sedentary amplification''). Our results highlight the need for continued surveillance of climate-induced changes to migratory behavior and vector activity to predict pathogen prevalence and its impacts on migratory animals.