My current and recent research deals primary in two systems: Soay Sheep (Ovis aries) and wood mice (Apodemus sylvaticus). I deal heavily with samples and data collected from wild populations in the field, and increasingly with statistical approaches & bioinformatics to make sense of the complicated relationships between hosts and their parasites. Some more information on my main projects can be found below.
The Ecology Within Project is a funded by a large NERC grant. This project, which kicked off in March 2019, combines the unique long-term monitoring of the Soay Sheep population of St. Kilda with next-generation sequencing methods to investigate the drivers of gut community dynamics from the host and environment, relationships among microbiota and other parasitic gut residents. By sampling longitudinally, the project will be able to study changes within individuals due to diet and environmental changes, and explore fitness consequences of gut community composition in the wild. Find out more about this collaborative project here, or learn more about the long-term Soay Sheep Project here.
As a Postdoctoral Research Associate with the Ecology Within Project, I work with Luke McNally and Dan Nussey. I work with both field and lab teams to coordinate data pipelines for the broader project and am currently working with Luke to develop novel statistical methods to integrate gut community data into our understanding of the ecology and fitness of this well-studied population. I am also interested in the relationships between the gut microbiota and the diverse gastrointestinal parasites harboured by Soay Sheep.
A GLMM approach to microbiota analysis in the wild
We use a generalised linear mixed-effects model approach to estimate relative contributions of multiple factors to gut microbiota community composition from multiple complex factors. We also use this approach to estimate differential abundances at multiple taxonomic levels across groups of interest within the population. You can read the preprint dealing this approach and its applications here.
Additionally, I am investigating the effects of nutrition supplementation and parasite community perturbations on the gut microbiota. I am doing so in a natural host-helminth system using samples collected from wild and laboratory studies in my PhD study system, Apodemus sylvaticus.
Research efforts are rapidly increasing for characterising microbiomes of wild animals. However, there remain many gaps in our understanding of how results generalise across systems and the broader role of host-associated microbial communities for host fitness and phenotypes in the wild. To address the many pressing questions surrounding this area of research, bringing together international and interdisciplinary researchers with complementary insights and interests can facilitate discussion and advancement of the field. I am a co-organiser of two such networks which bring together a broad range of microbiome scientists. ‘Wild Animal Microbiome Evolution’ is a special topic network funded by the European Society for Evolutionary Biology offering events and resources and ‘Animal Microbiome Research Group’ is an early career researcher-led group offering free annual meetings and a year-round Slack workspace. Find out more for either group by clicking below or follow us on twitter.
Ecologists increasingly recognise coinfection as an important component of emergent epidemiological patterns, connecting aspects of ecoimmunology, behaviour, ecosystem function and even extinction risk. Building on syndemic theory in medical anthropology, we propose the term ‘synzootics’ to describe co-occurring enzootic or epizootic processes that produce worse health outcomes in wild animals. Using framing from syndemic theory, we describe how the synzootic concept offers new insights into the ecology and evolution of infectious diseases. We then recommend a set of empirical criteria and lines of evidence that can be used to identify synzootics in nature. We conclude by exploring how synzootics could indirectly drive the emergence of novel pathogens in human populations.
Within-year variation in infection is a ubiquitous feature of natural populations, but is determined by a complex interplay of environmental, parasitological and host factors. At the same time, co-infection is the norm in the wild. Longitudinal dynamics of co-infecting parasites may therefore be further complicated by covariation across multiple parasites. Here, we used faecal parasite egg & oocyst counts collected repeatedly from individually marked wild Soay sheep to investigate seasonal dynamics of six gastrointestinal parasite groups. Prevalence and abundance tended to be higher in spring and summer, and abundance was higher in lambs than adults. We found within-year variation in highly prevalent strongyle nematode counts was dependent on adult reproductive status, where reproductive ewes had distinct dynamics compared to males and barren ewes. For similarly prevalent coccidia we found an overall peak in oocyst counts in spring but no differences among males, barren and pregnant ewes. Using multivariate mixed-effects models, we further show that apparent positive correlation between strongyle and coccidia counts was driven by short-term within-individual changes in both counts rather than long-term among-individual covariation. Overall, these results demonstrate that seasonality varies across demographic and parasite groups and highlight the value of investigating co-infection dynamics over time.
Individuals are often coinfected with several parasite species, yet measuring within-host interactions remains difficult in the wild. Consequences of such interactions on host health and epidemiology are therefore often unknown. We experimentally reduced common nematode infections and found a subsequent increase prevalence of an important zoonotic pathogen, Sin Nombre virus (SNV), in its primary wild rodent reservoir. Furthermore, we found that nematode – SNV coinfected mice were in better condition and survived longer than uninfected or singly infected mice. Our results suggest that parasite community interactions may play a key role in epidemiology and transmission of zoonotic pathogens
Wood mice (Apodemus sylvaticus) are a common ecological study system given their tractable populations and diverse natural parasite communities. For my PhD, I carried out paired experiments in wild and captive wood mouse populations, which are host to the well-studied nematode Heligmosomoides polygyrus. We found that a supplemented diet in both settings controlled infection, and improved anthelminthic efficacy, host condition, and immunity.
Poster Presentation. EEID 2018. Glasgow, UK.
Graphical abstract of my first thesis chapter used for the University of Edinburgh Three Minute Thesis Competition. Map source: who.int; H. polygyrus image credit: Constance Finney.
Changes to resource availability and quality can drastically affect parasite infection in wild animals. Increasingly, anthropogenic change alters food sources available to wildlife, which has important consequences for wildlife health. However, it is difficult to predict the effects of these changes, as they can happen on multiple scales and that co-infection with multiple parasites is the norm in the wild. I use experimental resource supplementation and parasite community perturbation in a naturally co-infected wild wood mouse population and find that effects of resource changes are dependent on parasite biology and within-host parasite interactions.
Viva card courtesy of Greg Albery, adapted from work of https://webcomicname.com/
Poster Presentation. Jacques Monod 2017 ‘Open Question is Disease Ecology.’ Roscoff, France.
Factors from the environment, host, and within-host levels can influence parasitism in wild populations. Despite substantial spatial and temporal variation in these ecological factors, disease ecology studies are often limited practically in spatiotemporal sampling replicates. We used data from six years of wild wood mouse trapping to ask “how variable are the key factors driving parasitism?” - turns out, highly variable!
Poster Presentation. EEID 2019. Princeton, USA. Princeton University Press Book Prize Winner, Environment Session.
