[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 8 The Nematodes
Ejaculatory duct
Testis
Curled tail
Esophagus
Vas deferens
Intestine
Cloaca
Mouth
Size range: 2.5-5 cm long
FIGURE 8-5 Trichuris trichiura, adult male.
prominent in infected samples processed using
the zinc sulfate flotation method (described in
more detail in Chapter 2). Adult worms may be
visible on macroscopic examination of the intestinal
mucosa. Adults may also be seen in areas
of the intestinal tract down to and including the
rectum in heavy infections. It is important to be
aware that samples examined from patients
treated for whipworm infection may reveal distorted
eggs, showing a variety of unusual shapes.
Life Cycle Notes
Ingestion of infective T. trichiura eggs containing
larvae initiates human infection. The larvae
emerge from the eggs in the small intestine.
Growth and development of the larvae occur as
they migrate within the intestinal villi. The larvae
return to the intestinal lumen and proceed to the
cecum, where they complete their maturation.
The resulting adults take up residence in the
colon, embedding in the mucosa. The life span
of the adult worms in untreated infections may
be from 4 to 8 years. Following copulation, the
adult female lays her undeveloped eggs. It is this
stage of egg that is passed into the outside environment
via the feces. Following approximately
1 month outside the human body, usually in the
soil, the eggs embryonate, become infective, and
are ready to initiate a new cycle.
Epidemiology
Considered as the third most common helminth,
T. trichiura is found primarily in warm climates
of the world where poor sanitation practices are
common, such as defecating directly into the
soil or using human feces as a fertilizer. Areas of
the United States that have been known to
harbor whipworm include the warm humid
South, particularly in rural settings. Persons
most at risk for contracting whipworm infections
include children as well as those in psychiatric
facilities.
Infections with both Trichuris and Ascaris,
another intestinal nematode (covered later in this
chapter), are known to occur. This is likely
caused at least in part because the human port
of entry, which serves as the mode of organism
transmission, is identical for both parasites.
Clinical Symptoms
Asymptomatic. Patients who suffer from a
slight whipworm infection often remain
asymptomatic.
Trichuriasis: Whipworm Infection: Heavy infections
of 500 to 5000 worms produce a wide
variety of symptoms. The conditions that a whipworm
infection may simulate vary with the age