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BSC Zoology - Parasitology > 07. Lung and liver trematodes > Flashcards

07. Lung and liver trematodes Flashcards

1
Q

What kind of fluke is Paragonimus spp.?

A

Lung fluke

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2
Q

Where in the liver do liver flukes go to?

A

the bile ducts

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3
Q

What are the 3 large liver flukes?

A

Fasciola hepatica
Faciola gigantica
Fascioloides magna

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4
Q

Which is the most common and widely distributed of the species?

A

Paragonimus westermani

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5
Q

What is the zoonosis of Paragonimus

A

Paragonimiasis

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6
Q

What kind of host do humans serve as to Paragonimus

A

an exceptional host

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7
Q

How do humans get infected by lung flukes/Paragonimus?

A

by eating raw or undercooked freshwater crabs and river crayfish which contain the METACERCARIAE

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8
Q

Excystation occurs where? (Paragonimus)

A

in the duodenum - the larvae bore through the intestinal wall and migrate via the abdominal cavity to the lungs, there they develop into the adult worms

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9
Q

Who are the reservoirs of Paragonimus?

A

Several carnivores

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10
Q

Where do the adult worms of Paragonimus live in the host?

A

in the lungs

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11
Q

How are eggs passed in Paragonimus?

A

in the sputum

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12
Q

How else can the eggs be passed in Paragonimus?

A

if the sputum is swallowed and passed in the feces

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13
Q

What is the first larval stage of Paragonimus? What is their role in the life cycle?

A

miracidia - they hatch in the water and penetrate the snail

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14
Q

What part of the life cycle occurs in the crab in paragonimus?

A

cercariae develop into metacercariae (3rd larval stage)

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15
Q

What is the form of Paragonimus that infects the DH?

A

metacercariae, 3rd larval stage

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16
Q

What is the life cycle of Paragonimus?*

A

1- Unembryonated eggs
2- become embryonated in the water
3- The miracidia hatch in the water and penetrate the snail
4- In the snail there is further asexual development
a. Sporocysts
b. Rediae
c. Cercariae
5- Cercariae invade the crustacean and encyst into metacercariae
6- Humans ingest inadequately cooked or pickled crustaceans containing metacercariae
7- They excyst in the duodenum
8- Adults in cystic cavities in lungs lay eggs which are secreted in sputum. Alternatively eggs are swallowed and passed with stool

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17
Q

How do humans get infected with P. westermani

A

eating inadequately cooked or pickled crab or crayfish that harbour metacercariae of the parasite

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18
Q

What happens once the metacercariae are ingested in humans? (Paragonimus)

A
  • The metacercaria excyst in the duodenum, penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5 to 12 mm by 4 to 6 mm)
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19
Q

What other tissues can be reached by the parasite, and what is their fate there? (Paragonimus)

A

brain
striated muscles

However, when this takes place completion of the cycles is not achieved, because the eggs laid cannot exit these sites

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20
Q

What is the time from infection to oviposition for Paragonimus?

A

65-90 days, so you will not know you were infected until then

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21
Q

What are the clinical features of the acute phase of Paragonimiasis?

A

diarrhea, abdominal pain, fever, cough, urticarial, hepatosplenomegaly and manifestations include cough, expectoration of discolored sputum, and chest radiographic abnormalities

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22
Q

How is Paragonimiasis diagnosed?

A

o Based on microscopic demonstration of eggs in stool or sputum, but these are not present until 2 to 3 moths after infection. Biopsy may allow diagnostic confirmation and species identification when an adult or developing fluke is recovered

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23
Q

How do liver flukes benefit from the pathology that they cause in the liver?

A

they feed off cells that are dying around them

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24
Q

how are the eggs of liver flukes passed?

A

they deposit their eggs in the bile system, which is them flushed into the GI tract and they are passed into the environment

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25
Q

What do liver flukes do to the host?

A

Seldom kill the host but they do interfere with the health of the host

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26
Q

Where are liver flukes of concern?

A

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
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27
Q

What is the pathology caused by liver flukes?

A

fibrosis

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28
Q

What is fibrosis?

A

Mechanical damage: worms get numerous and clog up bile ducts

  • If bile can’t get out it will kill liver cells (necrosis of liver ducts)
  • Calcium deposits in bile ducts –> fibrosis, and lots of scar tissue eventually causing calcification of ducts, making them useless
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29
Q

What is a secondary pathology of liver flukes?

A
  • Metacercariae penetrate intestine and migrate through body cavity through diaphragm and enter liver from outside
  • Most make it but some become lost and become ectopic infections
  • If encapsulated in wrong place (i.e. brain) can cause seizures
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30
Q

What is bottle jaw? Who is likely to get this phenotye?

A

A soft swelling beneath the jaw resulting from hyproteinemia and is most often caused by liver flukes - farm animals; sheep, cows

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31
Q

What is the sheep liver fluke?

A

Fasciola hepatica

32
Q

Who is the normal DH of Fasciola hepatica? what if they are not around?

A

Sheep; otherwise cattle, humans can become infected

33
Q

In which host is F. magna found?

A

deer, moose and elk

can be found in cattle, sheep, goats, llamas and pigs

34
Q

Is F. magna found in humans?

A

NO

35
Q

Who is the abbrant host of F. magna?

A

domestic ruminants

36
Q

What is the first IH if ruminant liver flukes?

A

snails

37
Q

Where are the cercariae found of ruminant liver flukes?

A

they are found encysted on plants (vegetation; food of ruminants)

38
Q

What is the DH of a ruminant liver fluke?

A

a herbivore - eat plant tissue containing encysted cercariar

39
Q

What is the morphology of the eggs of F. hepatica?

A

golden brown
indistinct operculum
non-embryonated

40
Q

What develops in the egg of Fasciola? How long does it take? Where?

A

the miracidia
9-10 days
in the external environment

41
Q

What develops in the snail?

A

sporocysts, 2 redia generation which release cercariae into the external aquatic environment

42
Q

What are common plants for the encystment of metacercariae?

A

grass and water cress

43
Q

What kind of host is the plant for metacercariae?

A

second IH

44
Q

What are the small liver flukes?

A
  • Clonorchis sinensis

- Dicrocoelium dendriticum

45
Q

What is the chinese liver fluke?

A

Clonorchis sinensis

46
Q

Who is the DH of the chinese liver fluke?

A

carnivorous animals including humans

47
Q

where else can the chinese liver fluke be found?

A

in pigs rats, and camels

48
Q

what is the first IH or the chinese liver fluke, Clonorchis sinensis?

A

snails

49
Q

what is the second IH or the chinese liver fluke, Clonorchis sinensis?

A

fish (an animal rather than a plant) like ruminant liver flukes

50
Q

What length is Clonorchis sinensis comparably to other liver flukes?

A

much smaller than the other liver flukes

51
Q

Which people are often exposed to Clonorchis sinensis?

A

The workers working with commercial fish ponds - because the habitat is in commercial fish ponds

52
Q

What is the lancet fluke?

A

Dicrocoelium dendriticum

53
Q

Is the lancet fluke big or small?

A

small

54
Q

What is the DH of the lancet fluke/Dicrocoelium dendriticum?

A

Definitive hosts are sheep, goats, cattle, deer, rabbits, and groundhogs

DH is any kind of mammal, we rarely become infected but it is possible to be the DH

55
Q

What is special about Dicrocoelium dendriticum that we have not seen in other trematodes?

A

the life cycle is entirely terrestrial

56
Q

what is the first IH of Dicrocoelium dendriticum?

A

terrestrial land snail

57
Q

what is the second IH of Dicrocoelium dendriticum?

A

an ant

58
Q

Which parasites are capable of host manipulation?

A 
Dicrocoelium dendriticum (small liver fluke) 
Euhaplorchis californiensis (GI tract fluke)
59
Q

What does Dicrocoelium dendriticum do to the 2nd IH, the ant, in order to increase its chances of continuing its life cycle?

A
  • The second intermediate host, an ant, uses the trail of slime as a source of moisture. The ant then swallows a cyst loaded with hundreds of juvenile lancet flukes
  • The parasites enter the gut and then drift through its body. Most of the cercariae encyst in the hemocoel of the ant and mature into metacercariae, but one moves to the sub-esophageal ganglion (a cluster of nerve cells underneath the esophagus). There, the fluke takes control of the ant’s actions by manipulating these nerves
60
Q

Where does Dicrocoelium dendriticum spend all of its adult life?

A

inside the liver of the host, after mating the eggs are excreted in the feces

61
Q

How does the first IH, the snail, become infected with Dicrocoelium dendriticum and what stage infects it?

A

it becomes infected with the eggs by eating the feces of the DH containing the eggs

62
Q

What happens to the snail after ingestion of the eggs of Dicrocoelium dendriticum?

A
  • the larvae drill through the wall of the gut and settle in its digestive tract, where they develop into juvenile stage
  • The snail tries to defend itself by shedding the parasites in slime balls, which it excretes and leaves behind in the grass
63
Q

What purpose does the snail’s slime serve to the ant?

A

the ant, 2nd IH, uses the slime from the snail, 1st IH, ad a source of moisture

64
Q

What is the slime ball? Which parasite is this?

A

the excretion of the parasites in the juvenile stage (of Dicrocoelium dendriticum) out of the snail that is picked up by the ant, 2nd IH, because the ant uses it for moisture

65
Q

How does Dicrocoelium go from the 1st IH to the 2nd IH?

A

The second intermediate host, an ant, uses the trail of slime created by the slime (which includes the slime balls, containing the juvenile stage of the parasite) as a source of moisture. The ant then swallows a cyst loaded with hundreds of juvenile lancet flukes

66
Q

What happens with Dicrocoelium dendriticum within the 2nd IH, the ant?

A

The parasites enter the gut and then drift through its body. Most of the cercariae encyst in the hemocoel of the ant and mature into metacercariae,

but one moves to the sub-esophageal ganglion (a cluster of nerve cells underneath the esophagus). There, the fluke takes control of the ant’s actions by manipulating these nerves

67
Q

What is the result of the manipulation of the ant by Dicrocoelium dendriticum?

A
  • As evening approaches and the air cools, the infested ant is drawn away from other members of the colony and upward to the top of a blade of grass. Once there, it clamps its mandibles onto the top of the blade and stays there until dawn
  • Afterward, it goes back to its normal activity at the ant colony. If the host ant were to be subjected to the heat of the direct sun, it would die along with the parasite
  • Night after night, the ant goes back to the top of the blade of grass until a grazing animal comes along and eats the blade, ingesting the ant along with it, thus putting the lancet flukes back inside their preferred host.
68
Q

Where does the fluke Euhaplorchis californiesis live?

A

In the Carpentaria Salt Marshes in southern California

69
Q

Describe, briefly, the life cycle of Euhaplorchis californiesis

A

It has a like cycle that includes two intermediate hosts, first the California Horn Snail and then the California killifish (Fundulus parvipennis) and a final host which can be any of a variety of fish eating shorebirds

70
Q

How does the fluke Euhaplorchis californiensis leave the DH? what is its DH?

A

The fluke leaves its definitive host as an egg in bird droppings which are eaten by the fluke’s intermediate host, the snail

71
Q

What kind of reproduction does Euhaplorchis californiesis use and where? what is shed as a result?

A

The fluke then reproduces asexually in the snail and sheds cercariae into the water

72
Q

What is the role of the cercariae of Euhaplorchis californiesis after being shed into the water by the snail?

A

The cercariae seek out the next intermediate host the killifish and latch onto the fish’s gills

73
Q

What happens once the cercariae of Euhaplorchis californiesis is inside the fish?

A
  • Each cercariae works its way into a blood vessel and explores until it finds a nerve which it then follows until it reaches the fish’s brain
  • The cercariae don’t penetrate the brain but sit on top of it. Then they wait for the fish to be eaten by a bird
74
Q

How does the cercariae of Euhaplorchis californiesis get from the fish to the bird?

A

the bird eats the fish containing the cercaria

75
Q

What happens yo Euhaplorchis californiesis within the bird?

A

Once eaten by a bird they break out of the fish’s head and move into the bird’s gut (GI tract) where they produce eggs that continue the cycle

76
Q

What happens to the fish when infected with the cercariae of Euhaplorchis californiesis?

A
  • Killifish – when swimming – occasionally shimmy and jerk around, flashing their bellies. Those infected with cercariae are more likely to do this than non-infected fish
  • Infected killifish come up to the water surface more frequently than normal, which in turn makes them more conspicuous to predatory birds
  • Infected killifish are 30 times more likely to be consumed by water-birds than the uninfected fish

BSC Zoology - Parasitology (27 decks)

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