Some parasites that attack humans include Entamoeba histolytica, Trypanosoma brucei, Plasmodium falciparum and Enterobius vermicularis, according to the Des Moines Area Community College. Many of these parasites affect people living in the tropics or subtropics, states the U.S. Centers for Disease Control and Prevention.
The microscopic E. histolytica is dangerous to humans because it causes amoebic dysentery, the DMACC asserts. Many infected people have abdominal pain, diarrhea and bloody stools, although some individuals display no symptoms. These parasites are typically picked up through food or water contaminated by untreated sewage.
T. brucei is passed along by the bite of a tsetse fly, says the DMACC. Typically, the flies picks up parasites from animals such as a cows and then transfer the protozoa to humans. These parasites cause sleeping sickness, which is widespread throughout Africa. Symptoms include daytime sleepiness, swollen lymph nodes, fever and sweating, MedlinePlus lists.
P. falciparum is one of the carriers of malaria, reports the DMACC. Mosquitoes harboring the parasites bite and then infect humans. Although malaria is uncommon in the United States, the disease is a major cause of death in other parts of the world, MedlinePlus declares.
E. vermicularis, or pin worms, are most common in children, observes the DMACC. Humans ingest the parasites through food or other substances contaminated with eggs. The adult parasites reproduce in the intestines. However, the female typically deposits eggs in the anus, which causes severe itching.