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Intestinal Nematodes 141

LIFE CYCLE of—

Ascaris lumbricoides

Trachea
Lungs Pharynx

Swallowed
Circulation

Larvae hatch
in intestine MAN

Adults in lumen
of small intestine
Ingested

Eggs in feces
Embryonated egg (diagnostic stage)
with 2nd stage larva
(infective stage)
Fertilized I cell
Unfertilized

Source: Centers for Disease Control and Prevention (CDC)
EXTERNAL ENVIRONMENT

Advanced cleavage
2-cell stage

FIGURE 6-4 Various stages in the life cycle of the intestinal roundworm nematode Ascaris lumbricoides

Treatment and Prevention A. lumbricoides includes the availability of sanitary
facilities for defecating and the proper hand washing
Treatment is available using a variety of antihelminthic and cleaning of food materials such as those grown in
drugs such as mebendazole and piperazine. Larvae may the soil. The use of human feces as fertilizer, a common
not be affected by this treatment so repeat treatments practice in some developing countries, should be
may be required. Prevention of the infection by avoided.