1. Phylum Platyhelminthes

2. Overview Readings Platyhelminthes
Chapter 13 Introduction (skim to appreciate diversity and morphology)
Chapter 14 Aspidobothrea (skim to appreciate diversity)
Chapter 15 Trematoda Introduction
Chapter 18 Plagiorchiformes
Chapter 17 Echinostomatiformes
Chapter 16 Strigeiformes

3. Phylum Platyhelminthes
Class Monogenea
Class Cestoidea
Class Trematoda
Subclass Digenea

4. Class Monogenea: Most ecto-parasites of fish.
Some endo-parasites of urinary bladder and mouth of amphibians and reptiles.
Body covered by tegument.
Posterior hooks with opisthaptor (haptor).
Direct life cycle with single host.

5. Opisthaptor (Haptor)
Ciliated larva

8. Life cycle of Ecto parasitic monogenean

9. Class Trematoda Digenetic and aspidogastrean flukes: all parasitic.
Body covered by tegument.
Most have complicated life cycles with 2-3 hosts (alternation of generations)

10. Aspidogastrean flukes
Alveoli

14. Digenetic Trematodes

15. Host Definitions
Definitive Host: Host in which the parasite reproduces sexually.
Intermediate Host: Host in which the parasite develops, but does not become sexually mature.
multiple intermediate hosts.
First Intermediate Host
Second Intermediate Host

16. Life Cycle

17. Life Cycle
First Intermediate Host
Mollusk-snail

18. Life Cycle First Intermediate Host
Mollusk-snail
Second Intermediate Host (wide range of animals, including mollusks, arthropods, and vertebrates!

19. Life Cycle First Intermediate Host
Mollusk-snail
Second Intermediate Host (wide range of animals, including mollusks, arthropods, and vertebrates!
Definitive Host (in most cases vertebrates)
Reservoir hosts can be both an intermediate host and/or definitive host!

20. Life Cycle
Egg
Miracidium
Adult
Sporocyst
Cercaria
Metacercaria
Redia

21. Polyembryony Egg Miracidium Adult Sporocyst Cercaria Metacercaria
Redia

22. Multiple Sporocyst/Redia Generations
Egg
Miracidium
Adult
Sporocyst
Daughter Sporocyst
Cercaria
Metacercaria
Daughter Redia
Redia

23. Egg
Miracidium
Sporocyst
Sporocyst
Redia
Redia
Cercaria
Many Metacercaria
Many Adults

24. Life Cycles
Basic Pathway
Lots of variation

25. Liver Flukes Fasciola hepatica Fasciola gigantica Fascioloides magna
Dicrocoelium dendriticum
Clonorchis sinensis

27. Habitat: live in the duct system of the liver!

28. Between any three liver cells there is a bile capillary (Bile Canaliculus)
Flukes feed on epithelial cells, blood, and mucous caused by destruction of these cells!

29. Fasciola hepatica “The Sheep Liver Fluke”
Because sheep are the normal definitive host.
In places where sheep are not raised can be found in cattle.
Humans can become infected!
30 mm long

30. Fasciola hepatica “The Sheep Liver Fluke”
Distribution is cosmopolitan, and they are found primarily in agricultural animals.
In US and S. America commonly found in sheep and cattle.

32. Fasciola gigantica
Equivalent of F. hepatica in Southeast Asia, Hawaii, and Africa.
Basically big species of F. hepatica.
75 mm long mm long

33. Fascioloides magna “Giant Deer Fluke or Giant Liver Fluke”
Found in deer, moose, and elk.
Sometimes in cattle, bison, sheep, goats, llamas, and pigs.
Never found in people!
100 mm long!

34. Fascioloides magna “Giant Deer Fluke or Giant Liver Fluke”
Domestic ruminants are aberrant hosts.
Common parasite in N. America especially in the Gulf coast, N.W., and Great Lakes area!

35. Dicrocoelium dendriticum The Lancet Fluke
Sheep, goats, deer, cattle, rabbits, and woodchucks.
Occasionally found in people.
10 mm long

36. Dicrocoelium dendriticum The Lancet Fluke
Cosmopolitan distribution but predominantly found in Eastern Europe.

37. Clonorchis sinensis “Chinese Liver Fluke or Oriental Liver Fluke”
Carnivorous animals are definitive hosts.
Dogs and cats (animals that eat fish-2nd IH) also occurs in people.
Also found in pigs, rats and camels (?)!
8-25 mm long

38. Clonorchis sinensis “Chinese Liver Fluke or Oriental Liver Fluke”
Korea
Thailand
Vietnam
Japan
China

39. Life Cycles!
Liver fluke of ruminants and man: Fasiola hepatica, Fasciola gigantica and Fascioloides magna!

40. Life Cycles of Ruminant Liver Flukes
First intermediate hosts are snails in the family Lymnaeidae (pond snails): these are aquatic and semi-aquatic snails.

41. Liver flukes of ruminants (aquatic life cycle).

42. Eggs of Fasciola hepatica
Eggs are X μm; golden brown, indistinct operculum, and unembryonated.

43. Miricidia develop in the egg (9-10 days) in the external environment, hatch and infect snail 1st IH

44. In the snail they develop sporocysts, 2 redia generations which release cercariae into the external aquatic environment! (five to seven weeks)

45. Cercariae encyst as metacercariae on aquatic vegetation!
Grass and water cress are typical 2nd IH

46. What happens in the DH

47. What happens in the DH
Juvenile worms penetrate the small intestine: enter the coelom and creep over the viscera until contacting the liver capsule!

48. What happens in the DH
Juvenile worms penetrate the small intestine: enter the coelom and creep over the viscera until contacting the liver capsule!
They then burrow into the liver parenchyma: wander about for almost two months feeding and growing.

49. What happens in the DH
Juvenile worms penetrate the small intestine: enter the coelom and creep over the viscera until contacting the liver capsule!
They then burrow into the liver parenchyma: wander about for almost two months feeding and growing.
Finally they enter the bile ducts: worms become sexually mature in another month and begin producing eggs. PPP wk. Live for 11 years!

50. Habitat Found In
Flooded Pastures!

52. Life cycle of Dicrocoelium dendriticum The Lancet Fluke
Terrestrial life cycle!

53. Terrestrial land snails 1st IH

54. Terrestrial land snails 1st IH
Ants 2nd IH
Terrestrial land snails 1st IH

55. Terrestrial land snails 1st IH
Up to 50,000 worms in 1 DH!
Ants 2nd IH
Terrestrial land snails 1st IH

56. Life Cycle of Clonorchis sinensis “Chinese Liver Fluke”
Aquatic life cycle!

57. Snails 1st IH ingest eggs
Miracidium
Sporocyst
Rediae

58. Snails 1st IH ingest eggs
Miracidium
Sporocyst
Rediae
Cercariae
Encyst under scale or in muscle of freshwater fish 2nd IH
Metacercariae

59. Snails 1st IH ingest eggs
Miracidium
Sporocyst
Rediae
Cercariae
Encyst under scale or in muscle of freshwater fish 2nd IH
Metacercariae
Adult DH
Egg production 1 month
3 months total
Adults live 8 years

60. Eggs of Clinorchis sinensis
Vase shaped, X µm long, golden brown with a distinct operculum and abopercular knob.

61. Commercial Fish Ponds

62. What do liver flukes do to the host?
Seldom kill host; but do interfere with health of the host.
More significant to us because of agriculture.
If animals are infected, they are sick and don’t gain weight, won’t produce milk, etc.
In Gulf coast states up to 23% of meat is lost due to liver flukes!

65. Pathological Damage
Mechanical Damage: Worms get numerous and clog up bile ducts.

66. Pathological Damage
Mechanical Damage: Worms get numerous and clog up bile ducts.
Hard to digest.
If bile can’t get out it will kill liver cells (necrosis of liver cells).
Calcium deposits in bile ducts fibrosis, and lots of scar tissue eventually causing calcification of ducts, making them useless.

67. Fasciola hepatica
Pipestem fibrosis

68. Fasciola hepatica

69. White areas show cirrhosis in infected liver!

70. Big Picture for Major Pathology
FIBROSIS!

71. 2ndary Pathology
Metacercariae penetrate intestine and migrate through body cavity (they don’t have a map!) through diaphragm and enter liver from outside.
Most make it but some become lost and become ECTOPIC INFECTIONS!
If encapsulated in wrong place can cause seizures!

72. Symptoms
Adult liver flukes feed on bile duct epithelium and suck blood, so symptoms are anemia, hypoalbuminemia, hypoproteinemia.

73. Bottle Jaw

74. Symptoms Diarrhea, edema, and enlarged liver.
Lower abdominal pain and discomfort (can last for up to 10 yrs after treatment and no probability of getting re-infected!