The brushtail possum is the key wildlife maintenance host of bovine tuberculosis (TB) in New Zealand. However, possums are perceived as solitary animals. With TB being rapidly killed in the environment, this raises questions about how the disease persists. We demonstrate far greater than expected sociality among over 150 contact-logging collared wild free-living individuals, relating patterns observed to TB incidence.

Co-infections affect parasite transmission but how this happens is unclear. We used an experimental approach and examined the dynamics of shedding of a respiratory bacterium and two gastrointestinal nematodes, common infections of the European rabbit. We showed that co-infection significantly enhanced the amount of bacteria and helminths shed although large variability was observed within and between hosts.  

Using a well characterised water vole (Arvicola amphibius) metapopulation, this research project explores the extent to which endemic parasite dynamics are influenced by host metapopulation structure.  Specifically, I will be using examples of microparasites and macroparasites with differing life histories to discuss how population size, connectivity, and transmission from alternative hosts can influence the distribution and prevalence of infected hosts.

Treating a person for one infection could affect other infections. Many parasites co-occur in human communities and infect millions of people, but interactions among coinfecting parasites are rarely considered when planning or evaluating treatment programs. I present a model where either “top-down” (immune-mediated) or “bottom-up” (resource-mediated) parasite interactions modify health outcomes, in order to identify scenarios for successful treatment programs.

Like most habitats, individual hosts can potentially support large communities of a diverse array of species (parasites and pathogens), exploiting a variety of niches, feeding on various resources, and faced with a range of natural enemies (immune components).  Using data from a natural host parasite community we ask, what factors (habitat, resources or ‘enemies’) drive patterns of parasite species associations?

Disease resistance is nutrition-dependent, which may be a result of the acquisition and allocation of resources by the host, or resource availability to the parasite. Using the geometric framework, we examined trait-specific nutritional requirements for an insect host and a bacterial parasite, in order to identify the role of macronutrients in determining the outcome of infection. 

 Root-hemiparasites represent a special functional group of temperate grasslands. Based on a mesocosm experiment with Rhinanthus alectorolophus, we demonstrate that the nature of their interaction with hosts substantially changes along the environmental gradients of humidity and nutrient availability. We also reveal underlying physiological mechanisms using a carbon stable isotope analysis and chlorophyll fluorescence.

Parasitic infection during development has the potential to shape the rest of an organism's life. We experimentally reduced the parasite load of nestling European shags across four years, and show that last-hatched brood members are most heavily impacted by parasitism. This effect is stronger in years of low breeding success. These patterns are mediated by behavioural interactions within the brood.

We used an eight year population wide survey of M.bovis genotypes isolated from cattle in Northern Ireland, investigating the influence of pathogen genotype on host response. Lesion distribution varied subtly with genotype but genotype does not appear to influence outbreak size or detectability of cases to the skin test, the primary means of bovine TB screening in the UK.

Many studies have tried identifying what causes stable polymorphisms in gene-for-gene systems by testing various specific and complex factors. We tested whether they can be caused by simple epidemiology alone and found that density-dependence can cause stable polymorphisms and that the mode of coinfection can greatly affect the evolutionary outcome. 

Theories suggest parasites can regulate host populations but few have quantified the impact of parasites in wild animals. A novel delayed-release intra-ruminal bolus was developed to remove nematode parasites from Svalbard reindeer during early winter. By measuring body-mass and pregnancy of animals re-caught in February and April, we were able to quantify the effects of over-winter parasitism on reindeer fitness.

The Tasmanian devil Sarcophilus harrisii is threatened by a unique infectious cancer, Devil Facial Tumour Disease (DFTD). Using modelling, we examine management strategies such as selective culling, and attempt to shed some light on relevant problems such as mapping its pre-DFTD abundance, estimating the disease's infectiousness and latency, and modelling its spatial progression.

The presence of higher trophic predators may alter an exotic species’ predatory function as a result of the exotic species’ own predation risk and behaviour modifications induced by parasites. Our results suggest that native and exotic amphipods make different foraging choices dependent on the combined influences of predation risk and parasitism, and that this behaviour is community context dependent.