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Protozoal Microorganisms as Intestinal Parasites 75

CASE STUDIES

1. A 25-year-old male graduate student from a local university arrived at the emergency de-
0
partment with a sudden onset of fever. Upon arrival, his temperature was 101 F when
measured orally and he reported feeling a need to defecate almost constantly. The
student most often prepared his own meals or ate at local restaurants and occasionally
traveled to a number of Asian countries for research toward his degree. He appeared
somewhat thin and pale and somewhat dehydrated. What should the physician con-
sider as the probable type of infection from which the patient is suffering?
2. An anthropology student from a U.S. college was performing field studies of the
Mayan ruins in Guatemala, eating and drinking food and beverages from the local
farmers and merchants. Shortly before returning from South America, he began to
suffer from cramping abdominal pain that worsened during the flight home. Soon
after arriving at the campus, the diarrhea showed small amounts of blood and he felt
weak and suffered from malaise. At the student health center, the physician ordered
a stool culture which revealed no pathogenic bacterial organisms. The laboratory
technologist examined a wet mount from a new stool sample and noted round pro-
tozoal cysts with finely granular cytoplasm that measured 10 to 20 μm and most of
which showed four nuclei with cigar-shaped chromatoidal bars with blunt, rounded,
and smooth ends.
3. After summer camp in a rural and wooded area, a group of adolescent students
returned home following this two-week trek into the wilderness. On the way home,
the driver of the van in which the close friends were riding decided to treat the stu-
dents to a buffet-type meal at a chain restaurant. All of the children ate a meal similar
to each other that included a few items from the same prepared container on the
steam table. One day after reaching home, all of the children suffered from camp-
ing diarrhea and nausea, accompanied by a moderately elevated temperature. The
pediatrician who treated the children considered parasitic involvement, because the
children had been to camp and swam in the lake together. Stool examinations were
ordered and the microscopic findings reported trophozoites of 30 to 40 μm and cyst
forms of approximately 25 μm. The cysts revealed eight nuclei and chromatoidal bars
with splintered ends in most of the organisms.
4. A computer software salesperson travels extensively in Asia and parts of Europe.
Recently when he returned home from a month of business activities in Southeast Asia,
he quickly developed severe diarrhea and intestinal discomfort that worsened over a
period of several weeks. His family physician suspected either a bacterial or a parasitic
infection, but leaned toward a diagnosis of a parasitic infection because the patient’s
temperature was not extremely abnormal. A stool specimen sent to the laboratory of
the local hospital was negative for the presence of bacterial pathogens but revealed a
large protozoan which contained cilia around the entire periphery of each organism.
What was the most likely diagnosis for this parasite, and is it nonpathogenic?
5. A 23-year-old sexually active male reported to his physician that he had recently
noticed a urethral irritation with slight burning after urination and ejaculation.
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