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

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.

Aside from the international scientific community working on infectious diseases, and broader issues of population and community ecology, this project will be of considerable relevance for non-academic beneficiaries. In particular it will be directly relevant to those working in the areas of conservation policy and wildlife management, who are interested in the effect of environmental or species-level perturbations (in particular food supplementation) on species contact networks, wildlife management and disease spread. Given our tractable field system, we have the ability to conduct large-scale field treatment experiments, which are difficult or impossible to conduct in other mammal (including human) systems. We have specifically chosen to focus on 'exemplar' groups of parasites that have characteristics that are representative of many parasites found in many natural systems. Thus, this project has the potential to provide broadly applicable guidelines to public health and agricultural bodies into the likely effects of different forms of resource provisioning on a wide range of parasite types. As ever we will publicise our work to non-academic audiences through press releases, science festivals (e.g. Edinburgh International Science Festival and University of Edinburgh Research Open Days), public engagement (Soapbox Science events (http://soapboxscience.org) blogs and podcasts (e.g., planetearth.nerc.ac.uk/multimedia/story.aspx?id=1623, Naturally Speaking https://naturallyspeakingpodcast.wordpress.com) and specialist publications (e.g., Fenton & Pedersen. 'Parasite diversity among wood mice and bank voles in the North West of England'. Mammal News, 2014).

Finally, as detailed further in the 'Academic Beneficiaries' section, other key beneficiaries will be the undergraduates that help on our project; not only those that go on to become the scientists of the future, but also those that don't go into science, but have an enhanced understanding of the practicalities of science. Our previous undergraduate field assistants (>60) benefitted enormously from the experience, and many commented that it was the best thing they did at University. In many cases this experience directly inspired them to go on to further scientific education and research (e.g., postgraduate education and training). Even for those that don't become scientists, they still gain invaluable experience in the scientific method and the practicalities of science, making them better-informed and more scientifically-aware citizens. We will employ a further 10 undergraduate assistants (plus a number of volunteer helpers) throughout this project, and will aim to give them the same experience as those previous assistants.