1. Digenea Trematoda - Flukes
Chapter 4

2. Learning Objectives Define terminology specific for Digenea.
State scientific and common names of flukes that parasitize humans.
Describe the general morphology of adult hermaphroditic trematodes.
Describe the general morphology of adult schistosomes.
Describe in graphic form the life cycle of adult trematodes.

3. Learning Objectives
State the methods of diagnosis used to identify fluke infections.
Differentiate adult trematodes using morphologic criteria.
Differentiate diagnostic stages of trematodes.
Classify the methods by which the flukes infect humans.
Compare and contrast the morphology of adult Cestoda and Digenea.

4. Learning Objectives
Given an illustration or photograph, identify diagnostic stages of trematodes and the body specimen of choice to be used for examination of each.
Discriminate among the trematodes on the basis of the required intermediate host(s).

5. Introduction Classification General body structure Life cycle
Hermaphroditic flukes
Schistosoma spp.
Life cycle

6. Trematode Life Cycle

7. Trematodes ( flukes) Fasciolopsis buski – Large intestinal fluke
Fasciola hepatica – Sheep liver fluke
Clonorchis sinensis – Chinese liver fluke
Paragonimus westermani – Oriental lung fluke
Schistosoma mansoni – Manson’s blood fluke
Schistosoma japonicum – Oriental blood fluke
Schistosoma haematobium – Bladder fluke
Heterophyes heterophyes – heterophyids ( intestine)
Metagonimus yokogawii – heterophyids (intestine)

8. Fasciolopsis buski (large intestinal fluke) and Fasciola hepatica (sheep liver fluke)
Method of diagnosis
Diagnostic stage
Disease names
Major pathology and symptoms
Treatment
Distribution

9. F. Hepatica & F. buski – Life cycle

10. F. hepatica & F. buski life cycle
F. hepatica – adults in liver (bile duct); F. buski – adults in small intestine
Fertilized eggs in feces ( DS )
Eggs hatch in fresh water – larva invade snail ( intermediate host #1)
Larva develop into cercaria – leave snail
Meta cercaria encyst on water plants
Human eats metacercaria on water plants ( IS )

11. Fasciola hepatica (Sheep Liver fluke) adult
Worldwide in sheep raising areas
Not common in U.S.
Sheep – natural host
Humans –accidental host
Snail – intermediate host
DS – eggs in feces
IS – metacercaria form cysts on aquatic vegetation
Eggs can’t be differentiated from F. buski eggs

12. F. Hepatica egg – Note size & operculum

13. F. hepatica egg Eggs cannot be differentiated from F. buski
Both eggs have an operculum and are large
Symptoms – diarrhea, bowel obstruction, malabsorption, even death

14. F.Buski (large intestinal fluke) adult
Adults are found in bile duct
Symptoms include
irritation, obstruction, enlarged liver, cirrhosis, anemia, diarrhea and cough

15. F. Buski egg
Operculum
Large size
Embryo is undifferentiated

16. F. buski egg
Eggs cannot be differentiated from those of F. hepatica

17. F. hepatica F. buski

18. F. hepatica F. buski

19. Clonorchis sinensis (Oriental or Chinese liver fluke; Opisthorchis)
Method of diagnosis
Diagnostic stage
Disease name
Major pathology and symptoms
Treatment
Distribution

20. Clonorchis sinensis – Chinese liver fluke

21. Clonorchis sinensis Adults – liver; bile ducts Eggs in feces (DS)
Eggs hatch in fresh water
Larva invade snail ( Intermediate host #1)
Develop into cercariae ; leave snail
Invade freshwater fish ( Intermediate host #2)
Metacercaria encyst in muscle of fish
Humans ingest metacercaria (IS) in undercooked fish
Migrates to liver

22. Clonorchis sinensis adult
Symptoms
Mild or no symptoms with light infection
Bile duct damage
Enlarged liver; jaundice
Abdominal pain; diarrhea; anorexia
Structures
Oral & ventral sucker
Uterus
Vitelline branches along uterus
testes

23. Clonorchis sinensis egg

24. Eggs can sometimes be recovered from bile ducts or drainage
Yellow-brown – stains from bile
Thick shell
Bell – shape
Operculum
Thickened opercular rim – “shoulders”
Polar knob opposite operculum

25. Heterophyes heterophyes and Metagonimus yokogawai (Heterophyids)
Method of diagnosis
Diagnostic stage
Disease names
Major pathology and symptoms
Treatment
Distribution

26. Heterophyes heterophyes and Metagonimus yokogawai (Heterophyids

27. Heterophyes heterophyes and Metagonimus yokogawai (Heterophyids

28. Paragonimus westermani (Oriental lung fluke)
Method of diagnosis
Diagnostic stage
Disease name
Major pathology and symptoms
Treatment
Distribution

29. Paragonimus westermani Adult

30. Paragonimus westermani egg

31. Paragonimus westermani

32. Schistosoma spp. (blood flukes)
Method of diagnosis
Diagnostic stages
Disease names
Major pathology and symptoms
Treatment
Distribution

33. Schistosome – Male & Female Adults Mating

34. S. Mansoni egg – Manson’s blood fluke Note the lateral spine

35. S. Mansoni eggs

36. S. japonicum egg – Oriental blood fluke very small lateral spine (knob) – may not be visible

37. S. japonicum egg

38. S. Haemotobium ( bladder fluke) Egg – note the terminal spine

39. S. Haemotobium egg Note the large terminal spine
eggs are usually found in urine, not feces
Can be associated with development of bladder cancer