Disease burden from simultaneous exposure of Cryptosporidium sp. and Giardia sp. and land use vulnerability assessment in a Costa Rican drinking water system

•Microbial pollution vulnerability was analyzed using GIS and machine learning.•Cryptosporidium and Giardia risk was higher than US EPA standards.•DALY's of Cryptosporidium and Giardia were higher than WHO recommendations. Human and animal feces are one of the main pollutants in drinking water systems (DWS). Both sources of fecal pollution are related to environmental conditions, such as poor land use management and little micro-basin protection. Cryptosporidium sp. and Giardia sp. are zoonotic protozoan water and foodborne transmitted parasitic pathogens and a frequent cause of diarrhea in children in low- and middle-income countries. In Latin America, DWS microbial risk assessment of these parasites is scarce. The aim of this study was to apply land use analysis, quantitative microbial risk assessment (QMRA), and disease burden (DALY; disability-adjusted life years) estimation of Cryptosporidium sp. and Giardia sp. for DWS that supplies 1.4% of the Costa Rican population. Land use analysis showed pollution sources and urban activities at the catchment area of all micro-basins, demonstrating the pollution's vulnerability, especially near to catchment sites of the DWS. The risk of infection by Cryptosporidium sp. and Giardia sp. was higher than US EPA standards, and the health burdens were above WHO recommendations. The higher risk of infection was observed in the micro-basins with the higher area of urban use, mainly in the buffer zones. QMRA and land use analysis are useful tools for the characterization of possible pollution foci in hazard identification.