Cryptosporidium movement in water - impact of eutrophication and climate change on the zoonotic disease agent

Cryptosporidium is a human pathogen unknown until the mid-1970s; in 1993 0.4 million people were infected in Milwaukee following a water treatment failure, and since then, large outbreaks throughout the developed world (most recently Sweden, 2010) have kept the parasite in the public eye. Infected hosts release up to 109 oocysts per day, and the discovery of a single oocyst forces closure and loss of drinking water supplies (e.g. NW England 2015, 0.3 million homes affected). In rural Wales, the different sources of contamination are unknown, but are likely to arise from sheep farming in rural communities. These multiple sources of contamination are difficult to diagnose and monitor, and almost impossible to eliminate due to costs of complex methodologies. The huge excess production of oocysts compared to the infective dose (only 10 oocysts can start an infection) suggests that in the natural environment, most oocysts are removed biotically, probably by grazing and suspension feeding invertebrates and protists. These interactions may be adversely affected by eutrophication (connected with land use and climate change), increasing the importance of Cryptosporidium in both the developing world and in 'Blue Marble' situations within the developed world. This project will test these hypotheses using a combination of Next Generation Sequencing to identify Cryptosporidium oocysts within communities of invertebrate grazing organisms in response to water eutrophication and laboratory experiments to directly establish the link between Cryptosporidium clearance and grazer community structure, linked by agent-based simulation modelling to predict the impact of eutrophication on Cryptosporidium clearance from freshwater. Laboratory experiments with oocysts grown in vitro in the Cardiff Cryptosporidium Bioreactor will establish the potential of relevant invertebrates to ingest, digest or transport oocysts. Immunofluorescence staining, qPCR and infectivity assays will be used to assess the potential of invertebrates for oocyst clearance. Functional responses, and the impact of nitrogen eutrophication and turbidity on clearance by important grazers will be established. Field studies will utilise sites in Wales (identified through Welsh Water and the Water Research Centre at Cardiff) along gradients of nitrogen eutrophication (due to e.g. different land use) established using standard techniques. NGS with environmental metabarcoding, and conventional screening of the biota samples into biologically relevant categories, will be used to establish the response of the aquatic community to eutrophication, while the environmental abundance of Cryptosporidium oocysts in these samples will be estimated from NGS data. The infectivity of Cryptosporidium oocysts from Welsh study sites will be established, and the faith of the oocysts under different environmental conditions (e.g. flooding, climate change) will be experimentally assessed.