1. Cestoda
Chapter 3

2. Learning Objectives
State the general characteristics of the phylum Platyhelminthes.
Describe the general morphology of an adult cestode.
State the methods of diagnosis used to identify cestode infections.
Compare and contrast the phylum Nemathelminthes with Platyhelminthes using morphologic criteria.

3. Learning Objectives
Define terminology specifically related to the Cestoda.
State the scientific and common names of cestodes that parasitize humans.
Describe in graphic form the general life cycle of a cestode.
Differentiate adult Cestoda using morphologic criteria.

4. Learning Objectives
Differentiate larval stages of Cestoda using morphologic criteria, the required intermediate host, or both.
Differentiate the diagnostic stages of the Cestoda.
Discuss the epidemiology and medical importance of cestode zoonoses.

5. Learning Objectives
Given illustrations or photographs, identify the diagnostic stages of Cestoda and the body specimen of choice to be used for examination of each.
Identify the stage in each life cycle for each cestode that can parasitize humans.

6. Introduction Classification General body structure
Platyhelminthes (flatworms )
Cestodes ( tapeworms)
General body structure
Scolex
Hooks
Suckers
Rostellum
Neck
Proglottids
Immature, mature, gravid (proglottids)
Reproduction - Hermaphroditic

7. Tapeworm body

8. Tapeworm body

9. Tapeworm body

10. Tapeworm body

11. Tapeworms infecting humans
Hymenolepsis nana -- dwarf tapeworm
Taenia saginata – beef tapeworm
Taenia solium – pork tapeworm
Diphyllobothrium latum – broad fish tapeworm
Echinococcus granulosis – hydatid tapeworm

12. Hymenolepis nana (dwarf tapeworm)
Method of diagnosis
Diagnostic stage
Disease name
Major pathology and symptoms
Treatment
Distribution

13. H. nana Tropics and sub tropics Children and institutionalized people
Most common tapeworm in U.S.
Requires no intermediate host
Autoinfection is common
Mice can be definitive host
Eggs in feces – infective stage
Fleas & beetles transport hosts
Cysticercoid larva – infective stage

14. Hymenolepis nana - (dwarf tapeworm)

15. H. Nana egg - Diagnostic Stage

16. H. Nana egg - Diagnostic Stage

19. H. nana
Small scolex
Rostellum with
1 row of
hooklets

20. Taenia saginata (beef tapeworm) and Taenia solium (pork tapeworm)
Method of diagnosis
Diagnostic stage
Disease names
Major pathology and symptoms
Treatment
Distribution

21. Taenia Life Cycle

22. Taenia eggs

23. Taenia saginatta (beef tapeworm) Life cycle

24. Taenia solium Lifecycle

27. T.Solium (pork tapeworm) “armed”-
4 suckers
Rostellum
20-30 large hooks set in 2 rows

28. T. Saginata (beef tapeworm) “Unarmed”- 4 large cup-shaped suckers

29. T. solium
Uterus
7-13 lateral branches
Eggs are infective

30. T. saginata
Uterus
15-30 lateral branches
Diagnostic - Identification

31. Diphyllobothrium latum (broadfish tapeworm)
Method of diagnosis
Diagnostic stage
Disease names
Major pathology and symptoms
Treatment
Distribution

32. D. latum

33. D. latum Worldwide – freshwater Florida, Great Lakes, Alaska
Often asymptomatic ; vague GI disturbance
Macrocytic, pernicious anemia
Competes with host for Vitamin B12

34. D. latum Scolex No Hooks or cup-shaped suckers
Bothria- 2 grooved suckers on either sideofscolex

35. D. latum Operculated egg with terminal knob

36. D. Latum egg

37. D. latum

38. D. latum proglottid Rosette shaped Uterus

39. Echinococcus granulosus (hydatid tapeworm) (dog tapeworm)
Method of diagnosis
Diagnostic stage
Disease names
Major pathology and symptoms
Treatment
Distribution

41. Echinococcus granulosus
Only found in canine host (DOG OR WOLF IS DEFINITIVE HOST)
Intermediate host – sheep or other ruminants
Human is accidental intermediate host
Eggs ingested
Contaminated food or water
Objects contaminated with dog feces
Dog becomes infected by eating raw meat containing hydatid cyst

42. E. Granulosus – hydatid cyst with 3 brood capsules

43. E. Granulosus – hydatid cyst
Each scolex has suckers and crown of hooks
Each scolex grows to adult tapeworm if ingested by dog

44. E. Granulosus – hydatid cysts from vertebral column (bone)
Humans – cysts in any tissue – most common
Liver
Lung
Central nervous system (CNS)
Bone – bone marrow
Disease varies with location of cysts - No symptoms or death
Disease may develop slowly
Slow-leaking cyst – allergic sensitization
Cyst rupture – anaphylaxis or dissemination

45. E. Granulosus Rare in Europe or U.S. except in sheep raising areas
Southwest ( Navajo) ; Utah
Common in Alaska and Canada
Diagnosis – history of exposure
Radiology – X-ray, ultrasound, CT
Immunodiagnostic skin testing
Serology – indirect hemagglutination, ELISA
Hooklets, scolices,, cyst membranes in histology tissue preps or body fluids
Hydatid sand- granular material found in older cysts; free scolices, daughter cysts ; hooklets
Biopsy dangerous – cyst leakage causes anaphyaxis

46. Zoonoses Cysticercosis Echinococcus granulosus
Dipylidium caninum (dog or cat tapeworm)
Human accidentally ingests larva from infected dog or cat flea (IH)
Mild infection – adults in intestine; egg packets or proglottids in feces
Hymenolepsis diminuta ( rat tapeworm)
Human accidentally ingests larva from infected flea or grain beetle (IH)
Mild symptoms; often resolves spontaneously; eggs in feces are diagnostic
Cysticercosis
Echinococcus granulosus

47. H. Diminuta vs H. nana

48. H. Diminuta vs H. nana

49. Zoonoses Dyphlobothrium spp. (dog or cat species)
Location of parasite in humans
How infection occurs
Disease symptoms
Diagnosis