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Intestinal Nematodes 157

Treatment and Prevention is the same, but academic interest often requires the
differentiation between the two species of hookworms
Treatment for the hookworm may include treatment (Table 6-1).
with local cryotherapy (cold treatment) when it is still Prevention of hookworm infections and those of
in the skin and has not invaded the other organs and S. stercoralis are accomplished through proper sanita-
tissues. Medications are available that are effective tion, with effective sanitary facilities for disposal of hu-
both in the intestinal stage and during the migrating man wastes. Good and effective personal hygiene are
stage when the parasite is still under the skin. It is often essential for preventing and managing infections. The
necessary to treat the host for anemia when the disease medication of first choice is that of ivermectin, which has
is quite advanced by the administration of supplements fewer side effects than some of the other preparations.
to increase the red blood cell count. Other essential The second line medication is albendazole, but none of
supplements that may also be required to restore these are effective for autoinfective larvae that are migrat-
nutritive health include vitamins such as folic acid or ing through the body, so repeat administrations of medi-
vitamin B . The treatment for the two hookworms
12 cations is required to rid the body of the parasite.

SUMMARY

Besides the hookworms, Ancylostoma duodenale and in Europe during this early period in human history,
Necator americanus were briefly described in the pre- evidence has been destroyed by climactic and soil con-
vious chapter. Another roundworm called Ascaris lum- ditions, but eggs of A. lumbricoides have been found in
bricoides is of such epidemiological proportions that it casts of human feces from several regions in South Amer-
requires its own section. A. lumbricoides is a large round- ica that date to several thousand years ago. A. lumbri-
worm, one of six worms classified by Linnaeus who coides is a large worm that may reach up to 35 cm (almost
began a classification system for plants and animals. 14 inches) in length and may emerge from the anus even
Up to one billion people, or an estimated one- without defecation occurring.
seventh of the world population, are thought to now be Ancylostoma duodenale and Necator americanus
infected with a worm called A. lumbricoides. Soil con- range over broad areas of both the Old and the New
tamination by feces where food is grown causes most of World, are much smaller than A. lumbricoides, and are ca-
the infections by this parasite. The adult worm lives in the pable of passing into a human’s body tissues. Those two
intestine, but eggs pass out with fecal materials and eggs species are much smaller than the large roundworm called
develop in the soil where they mature and reach an infec- Ascaris lumbricoides, and include additional physical
tive stage. Foods contaminated by feces containing eggs complications through migration into the body’s tissues.
may directly transmit the eggs to humans, where the lar- Obstruction of the gastrointestinal tract, as is common with
vae hatch from the infective eggs that have been eaten. A. lumbricoides, seldom happens in hookworm infections.
Ascaris species that inhabit the human intestine Eosinophilia occurs in response to a number of
may grow to a length of more than 12 inches. A 2-week parasitic infections that include hookworm infections as
incubation period must occur before the eggs can cause an immune response to an invasion of the tissues them-
an infection. After eating these eggs, the eggs hatch in selves. Falling hemoglobin levels in the blood are often
the intestine and then enter the circulatory system (the found in cases of prolonged infections, as well as a gen-
veins), which takes the blood and the newly hatched eral appearance of illness along with sometimes a con-
larvae directly through the heart and into the lungs. In siderable loss of weight. Hookworm prevalence can be
the lungs, they are coughed up in sputum and then swal- higher among adult males due to plantation work and
lowed. Here the larvae enter the intestines (the jejunum) coalmining. Adult women have much higher physiologi-
where they continue infecting the body while developing cal needs for iron than men because of menstruation
into adult worms in the intestine. and repeated pregnancies, but in many endemic areas,
Ascariasis has been determined to have infected adequate nutrition is not available. As an additional risk,
humans prior to recorded history. If the disease occurred A. duodenale infections are also known to occur rarely