Anticipating infection: How parasitism risk changes animal physiology

Uninfected animals can attempt to prevent parasitism in many ways. Behavioural avoidance of parasitized conspecifics, for instance, is documented in several species. Interactions with parasitized conspecifics can also, however, lead to physiological changes in uninfected animals, an effect that is much less well studied, and consequently, less well understood. The way in which exposure to parasitism risk changes the physiology of uninfected animals and the impacts of those changes on animal fitness remain a significant gap in knowledge. Determining how the disease environment experienced by animals impacts their physiology, survival and reproduction has major implications for our knowledge of how parasites affect populations beyond their consumptive effects. If the physiological changes triggered in uninfected animals help reduce disease burden or speed up recovery from disease, they can have cascading effects on disease dynamics; therefore, they are important to study and understand. In this perspective, I highlight studies in vertebrates and invertebrates that demonstrate the existence of these responses. I also consider how these responses may be adaptive and instances when they should occur. Finally, I briefly discuss the importance of studying these responses in relation to animal welfare, human health, disease dynamics and experimental design. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog.