[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 7 Miscellaneous Protozoa
Quick Quiz! 7-8
Which genus of parasite is most similar to Sarcocystis
based on morphologic similarities? (Objective 7-11)
A. Isospora
B. Blastocystis
C. Entamoeba
D. Toxoplasma
Sporozoites
Dark granule
(may contain
1 to 6 granules)
Quick Quiz! 7-9
Average size: 4-6 m
FIGURE 7-9 Cryptosporidium parvum oocyst.
How do humans become infected with Sarcocystis?
(Objectives 7-5)
A. Ingestion of uncooked or undercooked beef or
pork
B. Inhalation of oocysts
C. Ingestion of animal fecal contaminated food
D. More than one of the above: ________________
(specify)
Quick Quiz! 7-10
In addition to oocysts, these Sarcocystis morphologic
forms may be seen in human samples: (Objective 7-5)
A. Packets of eggs
B. Single or double sporocysts
C. Clusters of cysts
D. Groups of sporoblasts
Cryptosporidium parvum
(krip”toe-spor-i’dee-um/par-voom)
Common associated disease and condition
names: Cryptosporidosis.
Morphology
Oocysts. Measuring only 4 to 6 µm, the
roundish Cryptosporidium oocysts are often
confused with yeast (Figs. 7-9 and 7-10; Table
7-5). Although not always visible, the mature
oocyst consists of four small sporozoites
FIGURE 7-10 Modified acid-fast stain, ×1000). Arrows
indicate Cryptosporidium oocysts, each containing four
undefined sporozoites. Note dark-staining granules.
TABLE 7-5
Cryptosporidium parvum
Oocyst: Typical
Characteristics at a Glance
Parameter
Description
Size 4-6 µm
Shape
Roundish
Number of sporocysts None
Number of sporozoites Four (small)
Other features
Thick cell wall
One to six dark granules
may be visible
surrounded by a thick cell wall. Contrary to
other members of the sporozoa, such as Isospora,
Cryptosporidium oocysts do not contain
sporocysts. One to six dark granules may also
be seen.