The impact of resource availability on parasite transmission: insights from a natural multi-parasite community

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Understanding the relationship between resource availability and parasitic infection in wildlife is of increasing importance given rising rates of habitat modification and anthropogenic change. These changes can alter the distribution, quality and availability of resources, either accidentally or deliberately. However, understanding how different resource availability scenarios, either natural or anthropogenic, affect infection levels in wildlife is a major conservation challenge due the myriad of ways in which resources affect hosts, both at the individual and population scales. Most studies into the relationship between resources and infectious disease focus only on specific aspects (e.g. how food quality affects host physiology, or how food levels affect host population size). In reality the impact of resources on the risk and burden of disease can be complex, affecting various aspects at both the individual and population levels. For example, high quality resources may significantly improve individual health and condition, resulting in reduced susceptibility to disease. However, aggregated food patches that attract groups of animals can lead to increased opportunities for parasite transmission. Importantly, the relative sizes of these effects are likely to differ for parasites with different transmission modes or lifecycles. Given these diverse effects, it can be highly challenging to understand and predict the impact of different resource availability scenarios in natural wildlife systems. This knowledge gap forms a major barrier to understanding how resources affect wildlife conservation and, for some diseases, human and domestic animal health.To help understand the relationship between resource availability and wildlife disease we need to assess (1) different types of resource availability (e.g. aggregated v. evenly distributed, high v. low quality food), (2) the effects on different types of parasites (e.g. direct v. environmentally transmitted, chronic v. acute infections) and (3) whether those effects are due to changes in host physiology, behaviour, demography, or other parasites. To our knowledge, no studies have addressed all these aspects in the same study. However we have developed an ideal natural system: wild wood mice and their diverse parasite community. Not only have we optimised the methods for studying this host-parasite community in its natural setting, we have also recently developed a lab colony of formerly wild wood mice and some of their key natural parasite species, which provides unprecedented ability to combine intensive lab experiments with extensive field studies, using the same host-parasite community.Here we will combine (1) lab studies of host and parasite responses to a range of infections/coinfections and resource availabilities, with (2) large-scale perturbation experiments using alternative resource provisioning scenarios in the wild to measure how different forms of resource availability affect transmission of a broad range of parasite types in their natural host. Furthermore, we will combine these results with general mathematical models of alternative resource scenarios to develop a broad understanding of how different resource-transmission relationships affect disease spread. Together, these approaches will allow us to: (1) assess how host physiology and behaviour change following alternative resource availability scenarios, (2) test whether we can make generalised predictions about how different parasites will respond to different types of resources, and (3) provide insight into how other wildlife systems are likely to respond to changes in resource availability scenarios in the future. Given increasing concerns over how anthropogenic activities impact wildlife, this project is highly timely, and will provide much-needed experimental data, and general insight, into how shifts in resource availability and distribution drive parasite dynamics in natural wildlife communities.