Title Global Climate Change Effects on the Transmission of Waterborne Cryptosporidiosis
 Collaborators Elizabeth Casman (CMU)
 Keywords climate change, health, Cryptosporidium, cryptosporidiosis, drinking water, diarrhoea, mental model, expert elicitation, risk analysis

It has been suggested that the occurrence of outbreaks of the diarrhoeal disease, cryptosporidiosis, might increase as a result of global climate change. The expected positive relationship between rainfall and the concentration of Cryptosporidium oocysts (this parasite's environmental form) in surface water has been documented a number of times in a variety of locations, and some, but by no means all, outbreaks of cryptosporidiosis have been associated with rainfall events. Clearly climate can play a role in the waterborne transmission of this disease. The question is what factors control the current incidence of cryptosporidiosis throughout the world and which factors will change under various projected climate scenarios.

Factors such as water treatment system technology, water distribution system quality, efficacy and availability of point-of-use water purification options, public health services access, disease endemicity level, HIV infection rate, secondary transmission, foodborne transmission, population age structure, and herd immunity, are not usually included in the analysis of the effects of climate change on disease transmission, though combinations of these factors may dominate the climate-mediated effects.

This project utilizes the mental model methodology developed at Carnegie Mellon University. Mental models which include the major factors controlling the transmission of cryptosporidiosis in various industrialized and industrializing countries are being developed and parameterized. Judgments of how different climate change scenarios would impact the parameterization of these models will be elicited from prominent experts in the field. Updating the mental models to include the climate scenarios will permit the calculation of the expected impact of changes in climate on the incidence of cryptosporidiosis within the context of site-specific socio-economic, infrastructural, and demographic influences. The uncertainty in predicted climate scenarios is also incorporated in the analysis. An array of climate change scenarios will be evaluated for their potential effect on transmission and the results will be presented in a risk analytic framework.