PARASITIC WORM INFESTATIONS
a. Roundworms (Ascariasis).
(1) Identification. The most common parasitic infestation in the world is
ascariasis, or infestation with the nematode (roundworm) Ascaris Iumbricoides, the
large roundworm of man.
(2) Location. It is estimated that about one billion people throughout the
world are infested with the worm. Occurrence is greatest in moist, tropical countries,
where half the population may be affected. In the United States, the disease is most
prevalent in the South.
(3) Signs/symptoms. The adult roundworm usually lives within the
gastrointestinal tract of the human host. The disease is usually mild; however, heavy
infestations may cause digestive disturbances, abdominal pain, vomiting, restlessness,
and disturbed sleep. Complications occur when the adult worm migrates into and
obstructs the bile duct or the pancreatic duct of the host.
(4) Reservoir. The reservoir of the disease is the infected human, who
passes the eggs in his feces.
Under favorable conditions, the eggs may live in soil for months or
Infection occurs when a person eats food contaminated with soil or
other infective material containing Ascaris eggs.
The eggs hatch in the intestine, after which the larvae penetrate the
intestinal wall and travel, via the lymphatic and circulatory systems, to the liver and
From the lungs, larvae pass into air passages, ascend the bronchi,
and are swallowed, eventually reaching the small intestine, where they mature and
The female worm produces about 200,000 eggs a day over her life
span of less than a year (most live less than 6 months).
(5) Treatment. Drug therapy is effective in removing the adult stage of the
worm; however, surgery may be required to remove obstruction caused by abnormal
(6) Control measures. Control measures consist primarily in:
Educating persons in proper hygienic habits