Phylum
Sarcomastigophora: The amoebas and
flagellates
·
Amoebas:
o
Unicellular
o
Most are found in the GI tract
§
Commensals are harmless, but can be
easily confused with pathogenic Entamoeba
histolytica
§
Correct diagnosis is essential
o
Follow fecal-oral route
o
Sexual reproduction is unknown
o
Intestinal forms form metabolically
active trophozoites in the intestine, cyst forms for transmission in the
environment
·
Flagellates
o
Order Kinetoplastida
§
Although sexual reproduction has not
been observed under the microscope, there is genetic evidence of genetic
exchange
§
High morphological plasticity, depending
on whether it is in the invertebrate or vertebrate host
o
Other flagellates show no evidence of
genetic exchange
o
Unusual metabolic pathways, especially
in Giardia lamblia
o
Some intestinal forms form metabolically
active trophozoites in the intestine, cyst forms for transmission in the
environment
o
Trichomonas
vaginalis is one of several STD’s.
FIGURE
I. Comparative morphology of the amebas
of man and schematic representation of their nuclei. Adapted from Figure 3-1 and Table 3-1 of
Brown & Neva (1983), Basic Clinical Parasitology,
Appleton-Century-Crofts,
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