An intestinal parasite is an organism that lives in the intestines of a host organism and obtains nutrients from it. Two common examples of intestinal parasites are tapeworms and trichinae. Tapeworms are flat, segmented worms that can grow up to several meters in length and live in the intestines of humans and other animals. Trichinae are microscopic roundworms that can cause trichinosis, a disease that affects the muscles and nervous system.