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.
In children in a NEJM study, oxantel pamoate (20 mg per kilogram) plus of albendazole(400 mg) resulted in higher cure and egg- reduction than albendazole, mebendazole or oxantel pamoate (PubMed).
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).