Authors

J Fenn¹; S Young¹; S Goertz¹; A MacColl¹; J Bradley¹;  ¹ University of Nottingham

Discussion

Parasitology of non-human species is typically studied in one of two ways; ecologically, whereby the life cycle of both host and parasite are examined in their environmental context, and through utilising infections in lab models, allowing for mechanistic studies of the interface between a parasite and the hosts’ immune system. Traditional laboratory-based immunological studies tend to measure the immunophenotype of the host, and any defensive adaptations on the part of the parasite. Although much has been learnt about parasite biology from such studies, by combining ecology with lab immunology, we can learn more about how parasites interact with wild populations on a more detailed level, and study host and parasite adaptations in the context in which they evolved. Lab-based studies have shown us a great deal about the fundamentals of parasite immunology, but are limited in that they typically require an unnaturally sterile environment, with animals of limited genetic diversity, which are identically housed and fed. This is of course, a necessity of experimental design, but limits what such studies can tell us about ‘natural’ populations. Similarly, attempting to assess immune function of wild animals has been hindered for many years by lack of suitably sophisticated assays.

We have studied a population of feral mice on the Isle of May, Scotland, which, being the same species as the lab model mouse (Mus musculus), means that sophisticated immunophenotyping techniques could be transferred directly to the wild animals. We have applied lab-developed assays to assess the immune function of naturally infected individuals in the wild, where factors including genetic diversity, food supply, climatic variation, competition and coinfection are all likely to have some impact on the level and nature of any induced immune response. We have discovered that these mice are naturally infected with a variety of parasites, including two regularly-occurring helminths, Trichuris muris and Syphacia obveolata, and at least two blood-borne microparasites, Bartonella sp. and Babesia sp. Cross-sectional assessment of parasite prevalence and burden was compared with immune gene expression levels measured through qPCR and bioplex assays. Although observed immune responses are in part in agreement with theory developed through lab assays, there is predictably a much greater degree of variation, involving a complex network of interactions between dynamic environmental factors. Assessment of the precise mechanisms and costs of parasitic infection in wild populations is crucial when considering questions of conservation and public health.