[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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APPENDIX B Answers to Case Studies: Under the Microscope
3. Winterbottom’s sign and Kerandel’s sign.
4. Trypanosoma brucei gambiense.
5. West African sleeping sickness and Gambian
trypanosomiasis.
6. Humans become infected with T. brucei gambiense
following the injection of trypomastigotes
by the tsetse fly during its blood meal.
The entering trypomastigotes migrate through
the bloodstream and into the lymphatic
system, multiplying by binary fission. The
trypomastigotes are transmitted back to the
tsetse fly vector when it feeds on an infected
human. Once ingested by the tsetse fly, the
trypomastigotes continue to multiply and
eventually migrate back to the salivary gland,
converting into epimastigotes along the way.
Once in the salivary gland, the epimastigotes
transform back into trypomastigotes, thus
completing the cycle.
7. Treatments include melarsoprol, suramin,
pentamidine, and eflornithine. The treatment
of choice is situation-dependent and is dictated
by a number of factors, including patient
age and stage of disease. The toxicity level of
the chosen medication must be monitored to
ensure that the appropriate dose is used.
CHAPTER 6
Case Study 6-1: Under the Microscope
1. Plasmodium falciparum.
2. The presence of two rings in the red blood cell
and a double chromatin dot seen in form A;
the banana-shaped organism seen in forms B
and C.
3. Form A, ring form; form B, microgametocyte;
form C: macrogametocyte. The organization
of chromatin in the macrogametocyte is condensed
and centered in the cytoplasm, whereas
that of the microgametocyte shows a diffuse
pattern.
4. Only ring forms and gametocytes are typically
seen in the peripheral blood with this species.
Other species may show schizonts and
merozoites.
5. Black water fever.
6. Bite of a mosquito.
7. Maurer’s dots. Schüffner’s dots are often seen
with other species.
Case Study 6-2: Under the Microscope
1. Babesiosis.
2. Serologic or PCR techniques.
3. Ixodes dammini tick blood meal lasting 12
hours or longer.
4. Lyme disease, human granulocytic ehrlichiosis.
CHAPTER 7
Case Study 7-1: Under the Microscope
1. Blastocystis hominis, vacuolated form, The
parasite described exactly matches the features
of Blastocystis, which is characterized
by a center fluid-filled vacuole surrounded by
a cytoplasmic ring containing small nuclei.
2. False-negative results may appear if the
sample containing Blastocystis is only examined
using one or more saline wet preps.
Saline (as well as water) is known to lyse the
parasite, therefore making the sample appear
negative.
3. Blastocystis hominis reproduces by sporulation
or by binary fission.
4. Blastocystis hominis was initially considered
as a yeast most likely because of its size, shape
and minimal internal structures. It has since
been reclassified as a Protozoa.
5. Proper treatment of fecal material, thorough
hand washing, and subsequent proper handling
of food and water are critical to halt the
spread of Blastocystis hominis.
Case Study 7-2: Under the Microscope
1. Cryptosporidium parvum; the patient’s diagnosis
and the presence of oocysts that resemble
yeastlike cells in the wet preparations
indicate the presence of this parasite.
2. Modified acid-fast stain; these organisms are
acid-fast and stain red. Cryptosporidium
oocysts may display small, dark-staining
granules.
3. Yeast; yeast are not acid-fast and thus stain
blue after modified acid-fast staining.