Giardia
A protozoan parasite potentially found in water and other media. Giardia is defined in Method 1623 as those organisms determined by brilliant apple green fluorescence under UV light, size (8 to 18 µm long by 5 to 15 µm wide), and shape (oval), excluding 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.).