Word: protozoans
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Dates: during 1990-1999
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...cause of this destruction was kala-azar (scientifically known as visceral leishmaniasis), a deadly disease caused by a parasitic protozoan. The disease is transmitted by the bite of a sand fly that is about one-tenth of an inch long and is ubiquitous in certain woodlands. Once inside the body, the kala-azar protozoan invades and weakens the immune system, causing fever, weight loss, anemia and enlargement of the spleen. If the disease is untreated, a secondary infection, such as pneumonia or malaria, usually brings painful death...
...soon became apparent that the carrier was the female Phlebotomus orientalis sand fly, which passes the deadly protozoan to humans in an unusual manner (see box). The tiny insect, which cannot fly very high or far, inhabits the vast, red acacia forests, where it bites its victims in order to get protein-rich blood to develop its eggs. When female sand flies bit people driven by war or famine into the forests from areas where kala-azar was already endemic, the flies picked up the disease themselves, ready to be passed...
...next big epidemic in Sudan will probably be sleeping sickness. The African trypanosome parasite that causes it is a distant cousin of the kala-azar protozoan. Infection rates in some villages in Western Equatoria, just south of the western Upper Nile, are already running at 20%. Experts question whether the disease can be treated without hospitalization--an option that, because of the large numbers infected, is out of the question. It is the kind of impossible field-medical problem that is tailor-made for Jill Seaman, and she has already indicated that she would like to get involved...
This much is known: the disease is carried by a microscopic protozoan called Myxobolus cerebralis, whose spores are released when infected fish die. These spores are not in themselves harmful to trout. It is only after they have been ingested by inch-long Tubifex worms in the mud that the parasites become dangerous. In the worm's gut, the protozoan takes a new form: grappling-hook-shaped spore cases that when released from the worm, can invade the gills and skin of tiny rainbow fry. The infection eats away at the cartilage of young trout, leaving them deformed, discolored...
Plasmodium, a protozoan responsible for malaria, flourishes in the human body, growing inside red blood cells until the cells burst. And without enough red cells to carry oxygen through the body, humans become anemic and can die from renal failure or convulsions. Bacteria, which are considerably smaller than protozoans, generally do their damage indirectly, producing toxins that stimulate the body to mount an immune response. Ideally the immune cells kill the bacteria. But if the bacteria get out of control, their poisons can either kill cells or generate a huge immune reaction that is itself toxic...