Disease control and conservation: applying grazing pressure to solve ’The World’s Worst Wildlife Infectious Disease’

BACKGROUND & TIMELINESS: Infectious diseases threaten ecosystem function, biodiversity, and humans through zoonotic infections. Water-borne diseases, in particular, are predicted to increase through anthropogenic factors, including climate-change. Ecologically robust mitigation strategies are therefore needed to tackle this global issue. To date efforts have focused on the hosts (e.g. direct treatment), but this approach has had limited success and can damage ecosystem health. This study will evaluate a new approach.

NOVELTY: One promising, ecologically sustainable strategy is to target the disease’s infectious stages, preventing spread at its source. Many animal-diseases are spread by aquatic spores. These nutritious and vulnerable infective stages are potential prey for aquatic grazers. Enhancing grazing is anticipated to be a valuable means to mitigate such pathogens of wildlife, livestock, and humans. Understanding the role of grazers is, therefore, a new and exciting area of conservation biology.

OBJECTIVES: This PhD will focus on the “worst infectious disease ever recorded among vertebrates”: Batrachochytrium dendrobatidis (Bd). This devastating chytrid fungus has caused mass declines in amphibians worldwide. Bd infects via aquatic spores that can be consumed by invertebrates and protozoa. Our initial studies suggest that these small grazers may be manipulated to mitigate Bd infections, but the impact of the diverse grazer community and the extent to which fungal strains are susceptible to grazing remains unknown. To evaluate grazer control, the study will have five integrated components: 1) field work to survey and isolate grazers; 2) laboratory work to parameterize a host-parasite-grazer model; 3) ecosystem modelling to predict grazer impacts on Bd strains; 4) mesocosms to test model predictions; 5) conservation assessment (review), to evaluate impacts of mitigation strategies. The student will be supervised by a team of experts: Montagnes (grazer biology, experimental design); Fenton (parasite biology, modelling).