Harmful Protists
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15% are parasites
A parasite is an organism that lives in a
close relationship with another organism
and causes it harm.
The harmful protists that we will view
are either flagellates or sporozoans.
Plasmodium
Phylum: Sporozoan
Causes malaria
300-500 million cases worldwide
yearly
more than 1 million deaths yearly
Mosquitos pick up the
parasite from the blood
of their
victims
They then pass the
parasite to their next
victim when they suck
that victims blood.
plasmodium
Red blood cell
Malarial parasites are visible within the red blood
cells.
They are stained a dark bluish color.
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Life cycle
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Female anopheles mosquito bites infected person
Plasmodium reproduces in mosquito for a week
Mosquito bites another person, carrying spores in its
saliva to deposit into blood of person
The parasite travels to liver, multiplies, and then
destroys red blood cells
Person has fever, chills, nausea, aches
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Treatment
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Quinine and other medicines are used
No vaccine is known
Anti-malarial drugs before you travel to
risky places. They disrupt the parasite
while it is in the liver.
Trypanosome
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Phylum: Flagellates
Causes African sleeping sickness
Red blood cell
trypanosome
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Life cycle
Tsetse fly bites an infected person and ingests trypanosome
Trypanosome reproduces in fly, passes into blood of next person who is
bitten.
Causes lesions, swollen lymph nodes, infected spleen. Meningitis,
encephalitis, weight loss and coma (sleeping sickness)
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Almost always fatal without treatment
Person given blood serum intravenously
No vaccine
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Giardia
Phylum: Flagellate
Causes giardiasis or
hiker’s disease
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flagellum
giardia
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Life cycle
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enters body when person drinks feces
contaminated food or water
multiplies in colon
causes diarrhea, weight loss and cramps
Cryptosporidium
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Phylum: Sporozoan
Cause cryptosporidiosis
Found throughout the world including USA
Life cycle
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Lives in intestine of infected humans or animals
Found in soil, food or water that has been
contaminated with feces
Symptoms include diarrhea, stomach cramps and
slight fever which last for two weeks.
In the background are the finger-like projections of the intestine. The
spore Is seen breaking open to release “newlyhatched” cryptosporidia.
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Cryptosporidium are hard to kill; they
are chlorine resistant, can live for days
in swimming pools
No treatment is known
Prevent by practicing good hygiene and
avoiding contaminated water.
Toxoplasmosis
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Phylum: Sporozoan
Carried by cats, can also be found in raw
meat
Life cycle
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Cats infected by eating rats or mice
Excreted in feces
Human eat sporozoan, perhaps after not washing
hands after handling kitty litter
Fever, liver and spleen enlarged
toxoplama
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Can infect unborn child, causes
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Retardation
Motor problems
Damage to brain
Progressive blindness
Also very dangerous to individuals with
AIDS
Other harmful protists
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Entamoeba - causes amebic dysentery which can
destroy intestines
Leishmania - causes tropical disease that can
harm spleen, liver, intestines
Trichomonas - causes sexually transmitted
disease. It resides in urethra of male and can be
transmitted to female during intercourse. It
causes pain, painful urination and vaginal
discharge
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Pneumocystisis carinii causes a lifethreatening pneumonia (PCP) for
people with AIDS