1. Class Cestoda: The tapeworms
Exclusively endoparasites
Body covered by a tegument
Body consists of an anterior scolex, followed by a short neck and then a strobila composed of a series of “segments” or proglottids.
Digestive track absent.

2. Scolex, anterior holdfast organ
Neck, region of growth
Strobila made up of individual proglottids.
Three types of proglottids: immature, mature and gravid.

3. SEM of a Scolex

4. Diversity of scolexes.

5. Adult Tapeworms

8. You will be responsible for 2 orders of tapeworms!
Phylum Platyhelminthes
Class: Cestoidea
Subclass Eucestoda
Order Pseudophyllidea
Order Cyclophyllidea

9. Life Cycles
Adult tapeworms live in the intestine of vertebrates specifically the small intestine.
Eggs pass in the feces of vertebrate host.
Larval stage in egg = onchosphere.
It is spherical and has 6 hooks (hexacanth).

10. Generalized Pseudophyllidean Life Cycle Aquatic Life Cycle

11. Adult in Vertebrate Small Intestine
Uterine pore
Eggs released; later chains of spent proglottids

12. Eggs are usually operculated and unembryonated when laid.

13. The first larval stage the Coracidium
The oncosphere develops in the egg and a free swimming larva the Coracidium hatches.
The first larval stage the Coracidium

14. Coracidium

16. The free swimming coracidium is eaten by 1st intermediate host usually an aquatic arthropod!
Copepod

17. In the copepod the second larval stage (PROCERCOID)
Frontal glands
Cercomer posterior end

18. 2nd IH is a vertebrate of some kind (usually cold blooded)

19. The 3rd type of larva that develops in the 2nd IH is the PLEROCERCOID
The cercomere is lost and a scolex develops (no proglottids)!

22. Life cycle of Ligula intestinalis

23. Generalized Cyclophyllidean Life Cycle Terrestrial Life Cycle

24. Adults live in the small intestine of vertebrates.

25. Eggs passed not by uterine pore but instead by short chains or terminal proglottids that split open to release eggs!

26. Only one IH can be vertebrate or invertebrate depending on species of tapeworm!
The type of larval stage that develops varies depending on species of tapeworm!
Cysticercoid
Cysticercus
Strobilocercus
Coenurus
Hydatid
Alveolar hydatid

27. Cysticercoid
Anterior vesicle with scolex invaginated; solid posterior with tail-like region; in arthropods!

28. Cysticercus
Central cavity; fluid-filled; invaginated scolex; in reptiles or mammals, rarely birds!

29. Cysticercus

30. Strobilocercus
Strobiloceroid-a simple cysticercus in which some strobilation occurs in the cyst.

31. Coenurus
Bladder with multiple scolices; in mammals; hydatid cyst a special case!

32. Hydatid Cysts
Secondary brood cysts

33. Hydatid Cysts

34. Alveolar Hydatid Cysts
Alveolar hydatid cyst in a mouse - cyst metastasizes from the liver to fill the body cavity

35. Pseudophyllidea

36. Diphyllobothrium latum
Broad fish tapeworm
Fish eating mammals
Scandinavia, Baltic States, Russia, Great Lakes, West coast of N. America
unusual
9 million people infected
10 meters long
1 million eggs per day

37. The broad fish tapeworm Life cycle of Diphyllobothrium latum
Plerocercoid
Coracidium
Procercoid

38. Pike and salmon common hosts
Paratenic host

39. Pathology and Symptoms
Attaches to small intestine
Pathogenicity varies
Asymtomatic
Abdominal discomfort, diarrhea, nausea
Megaloblastic Anemia (caused by loss of vitamin B12)
Worms absorb vitamin B12
Disrupt host ability to absorb B12
Finland

40. Diagnosis and Treatment
Look for ___________________in feces.
Praziquantel

41. Epidemiology How do you get infected with Diphyllobothrium latum?
What else should we be concerned about?
Fish ponds

42. Life Cycle of Spirometra (Diphyllobothrium) mansonoides
Adult tapeworm occurs in the small intestine of a cat the definitive host.

43. Frog second intermediate host containing the plerocercoid

44. Spirometra (Diphyllobothrium) mansonoides
Unusual causes a great increase in size of a mammalian second intermediate host (mice).

45. Sparganosis

46. Human Infections of Spirometra (Diphyllobothrium) mansonoides
A few cases in the US have involved finding plerocercoids in the eyes.

47. Human Infections of Spirometra (Diphyllobothrium) mansonoides
Parasite is rare - only about 40 cases of human sparganosis have been reported in the U.S.

48. Sparganosis Disease Humans infected with plerocercoid Ingest copepod
Eating raw meat with plerocercoids
Plerocercoid transfers to human
Frog or snake flesh poultice
Pluerocercoid moves into human tissue

49. Sparganosis Seriousness depends on Removed by surgery
Where plerocercoid establishes
Number
If reproduction occurs
Removed by surgery