Cryptosporidium
A protozoan parasite potentially found in water and other media. Cryptosporidium is defined in Method 1622/1623 as an organism which exhibits brilliant apple green fluorescence under UV light, appropriate size (4 to 6 µm), and shape (round to oval), and excludes atypical organisms specifically identified as other microbial organisms by FITC and DIC (for example, those possessing spikes, stalks, appendages, pores, one or two large nuclei filling the cell, red fluorescing chloroplasts, crystals, spores, etc.).