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What Parasites Can Kill a Human?

Parasites, organisms that invade and feed off a host, range in size from single-cell protozoan microparasites to helminths, parasitic worms that can grow up to 25 feet long. The Centers for Disease Control lists more than 100 parasitic diseases that can affect humans. Some parasites, such as Pediculus humanus capitis, commonly known as head lice, causes minor symptoms and are easily treated. Others cause potentially fatal diseases.

  1. Plasmodium falciparum

    • Plasmodium falciparum protozoan parasites cause the most deadly strain of malaria, which is spread by female Anopheles mosquitoes. More than a million people die each year from malaria, many of them infants, children and pregnant women in Africa, according to the Centers for Disease Control. Avoiding serious and potentially fatal complications requires prompt treatment with anti-malarial prescription drugs.

    Schistosoma mansoni, S. haematobium and S. japonicum

    • Several species of Schistosoma flatworms cause schistosomiasis, a disease acquired by drinking or swimming in waters infested by freshwater snails. Worms live in the human bladder or intestines, laying eggs that travel through the body and damage the liver and kidneys. According to epidemiologists at Brown University, Schistosomiasis causes 800,000 deaths annually in developing countries. Chemotherapy is the primary means of treatment.

    Entamoeba histolytica

    • Amebic dysentery, also called amebiasis, infects 50 million people per year and kills up to 100,000, according to researchers at Tulane University. Entamoeba histolytica, protozoan parasites spread by fecal-contaminated food and water, usually infect the intestine causing severe diarrhea but can migrate to the liver, heart, brain and other organs and cause fatal complications. The disease responds to several prescription drugs.

    Leishmania

    • Sandflies bite humans and spread the protozoan parasite Leishmania. Visceral leishmaniasis, also called kala-azar or black fever, is almost always fatal, if not treated with a long course of medication, according to the parasitologist Dr. Robert Killick-Kendrick of Imperial College, London. The disease compromises the immune system and causes fever, abdominal swelling, spleen enlargement, diarrhea, coughing and bleeding, resulting in more than 50,000 deaths annually.

    Trypanosoma

    • Transmitted by the bite of the tsetse fly, the protozoan parasite Trypanosoma brucei causes human African trypanosomiasis, also known as HAT disease or sleeping sickness. According to U.S. Senate testimony by a director of Doctors Without Borders, 100 percent of patients with HAT disease will descend into a coma and die within two years without treatment. New pharmaceutical treatments can reverse the disease and prevent relapse but are difficult to administer in rural areas. American trypanosomiasis, or Chagas disease, kills 14,000 people annually in Central and South America. Primarily transmitted by the bite of a triatome bug infected with Trypanosoma cruzi, the disease affects the heart and digestive system and is fatal about 30 percent of the time. Medications used to treat it can cause dangerous side effects in the elderly, and there is no test to show whether the disease has been cured.

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