Giardia
A protozoan parasite potentially found in water and other media. Giardia is defined in Method 1623 as an organism which exhibits brilliant apple green fluorescence under UV light, appropriate size (8 to 18 µm long by 5 to 15 µm wide), and shape (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.).