A nematode, aka whipworm. It is a round worm.
Part of the human colon if you are from a third world county like, say, the US South.
Usually asymptomatic, it can cause bloody diarrhea, anemia, and people to freak when they pass a worm.
Mebendazole 100 mg bid x 3 days.
Combining either mebendazole (500 mg) or albendazole (400 mg) with ivermectin (200 mg/kg) all x 1 given better results in African children (PubMed), although in areas with high drug use, albendazole is of low effiacy (PubMed).
Trichuris trichuria 127.3.