[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 11 The Trematodes
Epidemiology
Shoulder
Average size: 3 cm by 1 cm
FIGURE 11-4 Fasciola hepatica adult.
The adult F. hepatica (Fig. 11-4) is comparable
in size to F. buski, measuring approximately 3 by
1 cm. Unlike F. buski, F. hepatica is equipped
with so-called shoulders (see Fig. 11-4).
Laboratory Diagnosis
The specimen choice for recovery of the eggs of
F. buski and F. hepatica is stool. Because the eggs
are indistinguishable, information regarding
patient symptoms and travel history is necessary
to diagnose the causative species. Speciation may
also be accomplished by recovery of the adult
Fasciolopsis worm. Other methodologies available
for the detection of Fasciola include the
Enterotest, ELISA, and gel diffusion.
Life Cycle Notes
The primary difference in the life cycles of F.
buski and F. hepatica is where the adult worms
reside in the human host. F. buski adults live in
the small intestine—thus, the common name
intestinal fluke. The adults of F. hepatica take up
residence in the bile ducts—hence, the common
name liver fluke.
Although the transmission of infection to humans
is the same, through ingestion of raw infected
water plants, the geographic distribution of these
two parasites, F. buski and F. hepatica, varies. F.
buski is limited to areas of the Far East, including
parts of China, Thailand, Taiwan, and Vietnam,
as well as regions in India and Indonesia. Several
animals, including rabbits, pigs, and dogs, may
serve as reservoir hosts. The water chestnut, lotus,
and water caltrop are common food sources.
F. hepatica is found worldwide, particularly in
areas in which sheep and cattle are raised. The
natural host for the completion of the F. hepatica
life cycle is the sheep. Humans serve as accidental
hosts.
Clinical Symptoms
Fasciolopsiasis. Patients suffering from F.
buski infection usually develop abdominal discomfort
because of irritation at the site of worm
attachment in the small intestine. This is often
accompanied by inflammation and bleeding of
the affected area, jaundice, diarrhea, gastric
discomfort, and edema. These symptoms often
mimic those of a person suffering from a duodenal
ulcer. Patients may also suffer from malabsorption
syndrome, similar to that seen in patients
with giardiasis. Intestinal obstruction, and even
death, although rare, may result.
Fascioliasis: Sheep Liver Rot. Persons infected
with F. hepatica experience symptoms caused by
the presence and attachment of the adult worm
to the biliary tract. These include headache,
fever, and chills, and pains in the liver area of the
body (because of tissue damage), some of which
may extend to the shoulders and back. Eosinophilia,
jaundice, liver tenderness, anemia, diarrhea,
and digestive discomfort are sometimes
seen. Biliary obstruction may also result.
Treatment
Infections with F. buski may be treated with praziquantel.
Patients suffering from F. hepatica