PROTOZOA
While still microscopic in size, protozoa are much
larger than bacteria. Protozoan diseases occur in this country, but they are
much more prevalent in the tropics. An amoeba, a particularly dangerous
protozoan, causes a severe form of dysentery. Another protozoan causes malaria.
The dreaded African sleeping sickness is caused by a protozoan carried by the
tsetse fly.
PARASITIC WORMS
Some of these can be seen by the unaided
eye, but others can be identified only with a microscope. The smallest are
roughly the size of pin- heads, while a tapeworm can grow to a 30-foot length.
Many parasites, including the flukes (one of the two types of flat- worms), are
more prevalent in the tropics than here. The other type of flatworm, the
tapeworm, is found in this country and is acquired by eating beef, pork, or
fish containing the parasite. Inside the intestine, the tapeworm attaches
itself to the intestinal wall and proceeds to grow.
Some roundworms are also
common in this country, especially in the South. They include the pinworm,
intestinal roundworm, and hookworm. Another roundworm, found in pork, causes
trichinosis, a disease in which the parasites eventually get into muscles.
FUNGI Related to mushrooms, fungi are smaller growths. It is a tiny fungus that
produces the green or white mold on stale bread; another causes athlete's foot;
others are responsible for various skin disorders; still others pro- duce
internal infections. There are many fungal diseases. Fortunately, most are rare
in this country.
