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Intestinal Nematodes 143

whip with a long and slender thread-like anterior portion by a second parasite such as A. lumbricoides, and per-
and with thicker, wider “handles” at the posterior end haps along with other common intestinal parasites.
that is long and slender, described as a threadlike caudal Whipworm organisms are spread to humans
portion. The male is characterized by a slightly coiled through a fecal-oral transmission when contact with soil
tail, whereas the female has a rounded and somewhat containing whipworm eggs occurs. Whipworm infections
blunt posterior that is not coiled. are more common in children through playing outside
The adult worm ranges from 30 to 50 mm with a and introducing focally contaminated dirt containing
range of 35 to 50 mm for the female. The male is slightly whipworm eggs into the mouth. Although whipworms
smaller than the female, ranging from 30 to 45 mm in length. are distributed on a worldwide basis, they survive best in
The eggs have a mucogelatinous plug at each terminal end tropical or semitropical climates including the southeast-
of the elongated egg that is bile-stained and barrel-shaped. ern United States where the weather is warm and humid
A smooth but thick shell covers the egg, which is from and plentiful rainfall is present. In addition, recent stud-
45 to 55 μm in length and 20 to 23 μm in width. ies have shown a possible genetic predisposition to infec-
tion with the whipworm.
Symptoms
Disease Transmission
Whipworm infections in humans can cause a range
of symptoms, by presenting no symptoms at all to only Ingestion of embryonated eggs from both contami-
mild symptoms that may progress to somewhat severe nated water and food is the most common route leading
symptoms. As in the case with hookworm infections, to a whipworm infection. But direct infection from the
severely heavy numbers of whipworms in humans can soil contaminated with feces and close contact during
cause stomach pain with loss of appetite and iron de- activities such as gardening and farming also provides
ficiency, bloody diarrhea, weight loss, rectal prolapse for a major portion of the cases of trichiuris. In addition
(detached rectum), and fecal incontinence. to placing dirty fingers into the mouth, another common
way of becoming infected is the ingestion of T. trichiura
Life Cycle eggs due to poor preparation of foods (e.g., eating un-
washed vegetables from soil that is contaminated).
A simple and direct life cycle for T. trichiuria involves Following ingestion, the eggs then hatch in the
the passage of feces containing eggs that mature in about small intestine where the resultant larvae grow and molt
2 weeks and become infective. Embryonated eggs with (shed their skin periodically as they grow). These larvae
first-stage larvae are ingested from contaminated and then penetrate the villi of the small intestine and continue
packed clay soil that clings to root vegetables and leaves developing into young worms. The young worms then
of other vegetables in many areas of the world where move to the cecum (first portion of the large intestine)
environmental conditions suitable for the propagation and the duodenum where they penetrate the mucosa
of whipworms are present. Development of the larvae and complete their development to adult worms in the
occurs in the duodenum and cecum, where the worm large intestine. The life cycle from time of ingestion of
attaches to the mucosa of the intestine by its anterior eggs to development of mature worms is approximately
mouthparts. In about 3 months, the adult is able to lay 3 months, at which time the female T. trichiura is capa-
eggs. A female may produce 2,000 to 20,000 unem- ble of laying eggs. Adult worms can live up to 5 years and
bryonated eggs per day, which may be deposited in the the female worm can lay up to 20,000 eggs per day for an
human feces and into the soil. entire lifetime. When these eggs from the feces are used
These unembryonated eggs from the stool of the as fertilizer or if an infected individual has defecated on
infected individual incubate in the soil and reach an in- the ground, the eggs incubate in the soil and become
fective capability when they achieve an embryonated infective when they reach an embryonated stage after a
stage after 2 to 3 weeks. The embryonated eggs contain period of 2 to 3 weeks. As with a number of parasitic in-
the first stage of larval development and are contracted fections, whipworms are frequently transmitted to a host
primarily from hard clay soil, where heavy rain fall may either through eating vegetables grown in contaminated
leach other organic nutrients from the soil. It is not soil or by direct contact by an individual with the soil
uncommon to find a T. trichiura infection accompanied where infective eggs are introduced to the mouth. It is