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Intestinal Cestodes 179

species of Taenia. In the 1600s it became apparent first descriptions of the disease. The first accurate
that there were two very different kinds of tapeworms description of the proglottids was by another Swiss
(broad and taeniid) in humans. Diphyllobothrium biologist, Charles Bonnet. By the mid-1700s, it was
was first recognized as being distinct from Taenia by apparent that infections with D. latum occurred in
a Swiss physician, Felix Plater, who contributed the humans whose diet was mainly fish.

CASE STUDIES

1. A tourist from the midwestern area of North America traveled to coastal Washington
State and in areas of western Canada. Taking advantage of the rich source of marine
foods, the main dishes at both lunch and dinner consisted of some type of fish. Upon
returning home, the traveler suffered from vague digestive upset along with consid-
erable abdominal pain. His physician requested a stool examination, which was nega-
tive for pathological bacterial but contained large operculated eggs. What would be
the probable causative organism that was the origin of these eggs?
2. An elderly Navaho Indian who raised sheep in northern Utah was forced to chase coyotes
and wild dogs from the land where his sheep typically grazed. He had always been in
good health but for the past year he had recurring bouts of pain in the stomach. When
he visited his physician, palpation of the liver revealed hardening and rounding of the
lobes of the liver. In addition, he complained of increased bouts of coughing, with chest
pain and sometimes small flecks of blood in the sputum. Given his vocation as a sheep
herder, and the fact that he spent a great deal of time outdoors and prepared his food
in the wild, what would be a likely parasite from which the man is suffering?

STUDY QUESTIONS

1. Name the two cestode groups that contribute most 8. What animal is affected by the Echinococcus
often to infection of humans. granulosus organism, and how does it manifest itself?
2. How do the eggs of the Taeniid species reach the 9. Why do Jewish and Muslim religions have cer-
intermediate host? tain prohibitions on the eating of certain meats,
3. Which of the tapeworms, T. saginata or T. solium, particularly pork? Why must some of these foods
be ritualistically prepared?
become the largest, and what are their approximate
lengths? 10. In your own thinking, how did observations of meat
4. Are both male and female organisms found in the conditions lead to official offices responsible for
food safety?
cestodes?
11. Dogs eating sheep meat led to the development of
5. What is a valuable characteristic used in differenti-
ating the eggs of pseudophyllidean tapeworms and hydatid cysts. Who determined this in 1853?
cyclophyllidean species? 12. What is the common name for Diphyllobothrium
latum, and how is it normally contracted?
6. With what animals are the cestodes called
T. saginata and T. solium associated?
7. How did Aristotle describe the appearance of the
cysticercus structure?