[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 11 The Trematodes
and monkeys serve as reservoir hosts, as well as
other animals whose diet includes crayfish and
crabs. A number of related species of Paragonimus
have also been known to cause human
disease, not only in Central and South America
but also in portions of the United States.
Clinical Symptoms
Average size: 1 cm by 0.7 cm
FIGURE 11-8 Paragonimus westermani adult.
Laboratory Diagnosis
Diagnosis of P. westermani is accomplished by
the recovery of eggs in sputum specimens.
These eggs are commonly found in bloody
samples. Occasionally, the eggs may be seen in
stool samples when sputum is swallowed. Serologic
tests have also been developed.
Life Cycle Notes
P. westermani is transmitted in undercooked
crayfish or crabs. On ingestion of such freshwater
products, the immature flukes (often occurring
in pairs) are released into the body, where
they migrate through the intestinal wall, through
the peritoneal cavity, into the diaphragm, and
finally into lung tissue, where encystation occurs.
Migration of immature flukes to other areas of
the body, such as the brain or liver, has been
known to take place.
Epidemiology
Infections caused by P. westermani occur in
several areas of the world, including portions of
Asia and Africa, India, and South America. Pigs
Paragonimiasis: Pulmonary Distomiasis. As
the common name oriental lung fluke suggests,
patients infected with Paragonimus typically
experience symptoms associated with pulmonary
discomfort—cough, fever, chest pain, and
increased production of blood-tinged sputum.
Individuals infected with this parasite (the corresponding
condition is known at paragonimiasis
and as pulmonary distomiasis) may also
experience chronic bronchitis, eosinophilia, and
the production of fibrous tissue. These symptoms
often mimic those seen in persons infected
with tuberculosis.
Patients who develop infections in areas other
than the lung experience symptoms corresponding
to the affected organ or tissue. One area is
the brain, as described in the next section.
Cerebral Paragonimiasis. Migration of immature
P. westermani organisms to the brain may
result in the development of a serious neurologic
condition. Patients experience seizures, visual
difficulties, and decreased precision of motor
skills.
Treatment
Praziquantel is the medication of choice for the
treatment of Paragonimus. An acceptable alternative
drug is bithionol.
Prevention and Control
As for other trematodes discussed in this chapter,
the primary prevention and control measures for
the eradication of Paragonimus include avoiding
human ingestion of undercooked crayfish and
crabs and exercising proper disposal of human
waste products.