[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 3 The Amebas
Cytoplasm
Eccentric
karyosome
Cyst wall
Achromatic
granules
Large
glycogen
vacuole
No peripheral
chromatin
A
Size range: 5-22 m
B
Average size: 8-12 m
FIGURE 3-17 A, Iodamoeba bütschlii cyst. B, Iodamoeba bütschlii cyst. (B from Forbes BA, Sahm DF, Weissfeld AS:
Bailey & Scott’s diagnostic microbiology, ed 12, St Louis, 2007, Mosby.)
choice for laboratory diagnosis. Iodine wet preps
often prove to be of benefit, particularly in the
identification of I. bütschlii cysts. The glycogen
mass typically picks up the iodine stain and is
thus characteristically recognizable. It is important
to point out that the glycogen mass remains
unstained following trichrome staining, another
feature that aids in the identification of I. bütschlii
cysts.
Epidemiology
I. bütschlii is found worldwide and has a higher
prevalence in tropical regions than in temperate
regions. The frequency of I. bütschlii infection
appears to be much less than that of E. coli and
E. nana. Transmission of I. bütschlii occurs when
the infective cysts are ingested in contaminated
food or drink. Hand-to-mouth transmission may
also occur.
Prevention and Control
Upgrading the personal hygiene and sanitation
practices in substandard areas, particularly in
regions of high prevalence, is critical for the prevention
of I. bütschlii infections.
Notes of Interest and New Trends
The term Iodamoeba was coined to describe an
ameba that stains well with iodine. Unlike the
other intestinal ameba, the nucleus of I. bütschlii
does not undergo typical division. The nucleus
of the I. bütschlii cyst is often described as resembling
a basket of flowers in shape. Contaminated
hog feces have been implicated as the source of
some infections with I. bütschlii.
Clinical Symptoms
I. bütschlii is a nonpathogenic intestinal ameba
that usually does not produce clinical symptoms.
Treatment
Because I. bütschlii is considered to be a nonpathogen,
treatment is usually not indicated.
Quick Quiz! 3-17
Iodamoeba bütschlii cysts typically: (Objective 3-9A)
A. Contain four nuclei
B. Have a small karyosome in a central position
C. Lack chromatoid bars
D. Lack a glycogen mass