ENVIRONMENTAL ECOLOGY OF CRYPTOSPORIDIUM AND PUBLIC-HEALTH IMPLICATIONS

Cryptosporidium has become the most important contaminant found in dri nking water and is associated with a high risk of waterborne disease p articularly for the immunocompromised. There have been 12 documented w aterborne outbreaks in North America since 1985; in two of these (Milw aukee and Las Vegas) mortality rates in the immuno-compromised ranged from 52% to 68%. The immunofluorescence antibody assay (IFA) using epi fluorescence microscopy has been used to examine the occurrence of Cry ptosporidium in sewage (1 to 120 oocysts/liter), filtered secondary tr eated wastewater (0.01 to 0.13 oocysts/liter), surface waters (0.001 t o 107 oocysts/liter), groundwater (0.004 to 0.922 oocysts/liter) and t reated drinking water (0.001 to 0.72 oocysts/liter). New rules are bei ng developed (Information Collection Rule and Enhanced Surface Water T reatment Rule) to obtain more occurrence data for drinking water syste ms for use with new risk assessment models. Public health officials sh ould consider a communication program to physicians treating the immun ocompromised, nursing homes, develop a plan to evaluate cases of crypt osporidiosis in the community, and contribute to the development of pu blic policies that limit contamination of source waters, improve water treatment, and protect public health.