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Balantidiasis, infection by the protozoan Balantidium
coli, is encountered worldwide, but infections are more common in
tropical and subtropical regions.
B. coli infects many animals but pigs
and rats are the most important reservoirs.
B. coli
is a ciliated protozoan with two stages - cyst and trophozoites. In
tissue sections, the trophozoites usually measures 25-40x 40-80 micrometer.
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The trophozoites are oval, with a
slightly pointed anterior end and a rounded posterior end. The thin
cell membrane is ciliated.
The foamy cytoplasm contains vacuoles, a large macronucleus and a
small micronucleus.
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Cysts are round or oval, 40 to 65
micrometer across, and have both a micro and a macronucleus.
Visit:
Giardiasis
;
Amoebiasis
Trophozoites of B. coli live in the large intestine
and are concentrated in the caecal and sigmoidorectal regions.
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They
multiply by transverse biniary fission and under some conditions
transform into cysts that are passed in the stool.
Humans become
infected by ingesting cysts in water or food. After ingestion, the
cyst wall dissolves and liberates trophozoites that invade the mucosa
of the large intestine.
Most balantidial infections are
asymptomatic or characterized by intermittent diarrhea or
constipation.
Severe infections may cause
abdominal pain, colonic tenderness, fever, anorexia, and severe
diarrhea.
Other symptoms are headache, insomnia,
nausea, vomiting, cachexia, pallor, weakness, anemia, dehydration, malaise,
and distention.
Stool specimens may be watery and
contain blood, mucus, and pus.
Balantidia invade the bowel wall and cause ulcers
that resemble amebic ulcers.
The ulcers are flask-shaped with
undermined edges and may involve the entire thickness of the
intestine.
The base of the ulcer is formed by a zone of coagulative
necrosis that contains balantidial trophozoites.
Beyond the necrotic bed the tissues are
edematous and contain chronic inflammatory cells, mostly lymphocytes
and plasma cells.
Rarely, an ulcer may perforate the
bowel wall.
Diagnosis is usually made by identifying trophozoites or cysts of B. coli in the stool or in a biopsy specimen
taken through a sigmoidoscope, or by finding trophozoites in the ulcer
at autopsy.
Tetracycline or iodoquinal are treatment of choice.
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