This report provides a review of the literature on Cryptosporidium and helps to identify the findings and formulates the key research questions. It covers these central questions: What are the sources/carriers of human pathogenic strains and what are the key species for a range of catchments? What is the contribution of pre and post weaned cattle and sheep to catchment contamination? What data on animal management practices (including vegetation management of riparian zones) is available?What are the different climatic zones across catchments and how will this impact on the survival and transmission of Cryptosporidium? Co-published with WaterRA.