Individuals inevitably vary in both their susceptibility to disease and the severity of disease once an outbreak has occurred. My project is aimed at dissecting the genetic architecture underlying how a host defends against infectious disease and exploring the different strategies host can use to do this, such as resisting infection directly or minimising virulence once a pathogen has invaded. To do so I will combine both QTL mapping and modern quantitative genetic approaches to explore the nature of host-parasite interactions between the  crustacean Daphnia magna and it’s bacterial parasite Pasteuria ramosa. By extending the work of my previous fellowship and building on these findings with a series of new projects, I aim to identify regions of the host genome that influence the severity of disease, and then link these findings to the broad patterns of genetic variation within and between fitness related traits. This work will highlight how an understanding of both quantitative genetics and life-history trade-offs can generate new insights into the study of host-parasite intersections.