Maybe perhaps not a pathogen, maybe perhaps don't treat it. If you feel that you must, try. Usually treat the symptomatic pateint with lots of cysts and no other cause found, since co-infection is common with Giardia, Entamoeba histolytica, and D. fragilis.
Self limited most of the time maybe perhaps don't treat it. Metronidazole 750 or 500 tid x 10 days, iodoquinol, 650 tid for 10 to 20 days, TMP/Sulfa 2 DS qd for 7 days, nitazoxanide 500 bid for 3 days all inhibit in vitro. Review.
In most patients who have this in the stool and diarrhea, will, if you look hard enough, find another reason for the diarrhea.