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?