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Protists and Disease

• Protists have significant effects on humans and other organisms.

• They can cause disease and alter ecosystems, and they are useful in industry and research.

• Protists cause a number of human diseases, including giardiasis, amebiasis, toxoplasmosis, trichomoniasis, cryptosporidiosis, Chagas disease, and malaria.

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Most common human parasites

• Protists– Single-celled microbes– Can live on its own, or as a

parasite– Can live in intestines

without problems– Dangerous if in blood or

body tissue– Transmitted fecal-mouth, or

through a invertebrate vector (mosquito, tick)

Entamoeba histolytica casues amebic dysentery

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Diseases Caused by Protists

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Most common human parasites

• Helminths (worms)– Flatworms (tapeworms),

Thorny-headed worms, Round worms

– Only larvae reproduce in humans, not adult worms

– Often passed between animals and humans (eggs, not worms!)

25-foot tapeworm on display at the Tokyo Parasite Museum.

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Ectoparasites

• Attach to skin for long periods of time

• Often vectors (carriers) of other pathogens

An adult louse; actual size is about as big as a sesame seed.

The “kissing bug” is a vector for Trypanosoma cruzi, a protist that causes Chagas disease.

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Protists and Disease, continuedMalaria

• Treatment for malaria is inexpensive, but not always available.

• Plasmodium is developing resistance to many drugs, so treatment is becoming more difficult.

• Efforts to control malaria include distribution of insecticide treated mosquito nets and fumigation to kill mosquitoes.

• Research is also underway to develop a malaria vaccine.

• Learn more on p. 509

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Life Cycle of Malaria