[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

APPENDIX B Answers to Case Studies: Under the Microscope
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fluid. Further specificity for diagnosis can
be achieved through molecular and immunologic
methods (e.g., polymerase chain
reaction [PCR], restriction fragment length
polymorphism, isoelectric focusing, monoclonal
antibody testing).
Case Study 3-2: Under the Microscope
1. Protozoa and, in particular, the amebas.
2. Size, position of the karyosome, arrangement
of peripheral chromatin, and cytoplasmic
inclusions; specific to trophozoites, the presence
of pseudopods, specific to cysts, the
number of nuclei.
3. Trophozoite, yes.
4. Red blood cells.
5. Entamoeba histolytica trophozoite. Features
that substantiate this identification are size
(13 µm), with a single nucleus that contains a
central karyosome and evenly distributed
peripheral chromatin, and the presence of
RBCs (diagnostic for this organism).
6. Yes, this organism is pathogenic in the human
host and is known to cause the patient’s
symptoms.
7. Yes, Entamoeba histolytica cysts (Fig. 2-2A)
may also be present in a fresh stool sample.
The typical cyst measures 12 to 18 µm and
contains one to four nuclei. The appearance
of the nuclei is identical to that in the trophozoite
form, a centrally located karyosome surrounded
by evenly distributed peripheral
chromatin. The cytoplasm resembles ground
glass and may contain chromatin bars with
large blunt ends as well as a glycogen mass.
CHAPTER 4
Case Study 4-1: Under the Microscope
1. The most likely identification of the organism
is Giardia intestinalis. G. intestinalis cysts are
ovoid in shape, ranging in size from 8 to 17
µm long by 6 to 10 µm wide. Immature cysts
contain two nuclei and two median bodies.
Mature cysts can have four nuclei.
2. Bryan most likely contracted his illness by
drinking unfiltered water while hiking. G.
intestinalis can be found in the environment,
commonly in stagnant or slowly moving
water such as streams, marshes, and lake
shores. Campers and hikers should always
carry bottled water or use a water purification
method such as filtering or chemical
treatment.
3. If a G. intestinalis infection is suspected, multiple
stool samples collected on subsequent
days should be submitted for routine O&P
analysis.
Case Study 4-2: Under the Microscope
1. Dientamoeba fragilis.
2. Trichrome.
3. Chromatin granules.
4. Pseudopods.
5. None, the trophozoite is the only known form
in the Dientamoeba fragilis life cycle.
6. The exact mode of transmission is not clear.
One theory suggests that transmission of
Dientamoeba trophozoites occurs via the eggs
of select helminth parasite eggs such as those
of Enterobius vermicularis and Ascaris lumbricoides
(see Chapter 8).
CHAPTER 5
Case Study 5-1: Under the Microscope
1. Leishmania donovani.
2. Amastigote (Fig. 5-1).
3. Playing outdoors in Kenya with dogs and
other animals known to be reservoir hosts for
Leishmania species and increased potential of
coming into contact with the sandfly vectors.
4. India, Thailand, Peoples Republic of China,
Burma, East Pakistan.
5. Weight loss, anemia, emaciation, darkening of
the skin.
6. Venous blood may sometimes reveal the
parasites.
Case Study 5-2: Under the Microscope
1. Lymph node aspirations and peripheral blood;
Giemsa staining of the preparations.
2. Trypomastigotes.