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Parasitology and entomology > Trematodes (intestinal, lung and liver) > Flashcards

Trematodes (intestinal, lung and liver) Flashcards

1
Q

Where does the asexual reproductive stage occur in trematodes?

A

In a mollusc (freshwater).

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2
Q

Describe the general trematode lifecycle.

A

Adults produce eggs –> miracidia infect stains –> asexual reproduction within the snail –> cercariae are released from the snail –> penetrate host (schisto) OR have a second cyst stage called metacercariae –> metacercariae encyst on plants or fish –> oral ingestion of metacercariae cause infection.

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3
Q

What are metacercariae? What is their lifespan?

A

Round cysts with dormant cercariae inside. Can live for several years like this.

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4
Q

Where are the metacercariae in clenorchis and fasciola?

A

Clenorchis: aquatic plants
Fasciola: fish

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5
Q

What are the infective agents for fluke infection in the -lungs, - intestinal, -liver?

A

Lungs: Paragonimus
Intestinal: fasciolopsis buski
Liver: fasciola, opistorchis, clenorchis

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6
Q

Where do most of the liver/lung/intestinal flukes occur?

A

Mainly in Asia (particularly SE Asia), infection is close to 100% in SW China

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7
Q

What is the most common species of paragonimus?

A

Westermanii

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8
Q

Which paragonimus is very common in the US where lots of crayfish is eaten?

A

Paragonamus kellicotti

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9
Q

Where does paragonimus infect?

A

Lung

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10
Q

What is the lifecycle of paragonimus?

A

Ingestion of metacercariae by eating undercooked or raw crab/crayfish –> juvenile worm excysts in the small intestine (duodenum) –> migration through the pleural cavity to the lungs, 3 months –> form a cyst in the lungs/ encapsulate and form adults –> eggs are produced –> eggs are transported up and leave through sputum or are swallowed (=eggs in stool) –> eggs embryonate in water –> miracidia hatch from eggs and infect snails –> cercariae are released from snails and form metacercariae in fish.

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11
Q

As well as Asia, where else is paragonimus found?

A

The pacific coast of S America.

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12
Q

What are the possible locations of ectopic paragonimus?

A

Spleen, brain, abdominal cavity etc.

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13
Q

What can be infected by paragonimus?

A

Anything that eats crabs: dogs, cats, pigs etc.

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14
Q

Describe the morphology of adult paragonimus worms.

A

In lungs, oral and ventral suckers, branched gut, male and female sex organs (hermaphroditic), live around 5 years.

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15
Q

Although being hermaphrodites, what is unusual about the behaviour of paragonimus?

A

They lay more eggs when they are in pairs.

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16
Q

How do adult paragonimus worms present in the lungs?

A

Inside cysts/ bubbles, often found in pairs. Eggs can get stuck in the lungs and cause granuloma.

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17
Q

What do the eggs of paragonimus look like

A
  • Operculated
  • No button on the other end
  • Around 90µm
  • Look a bit like diphyllobothrium but with no knob (diphyl is also smaller at around 70 µm).
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18
Q

How do we diagnose paragonimus?

A
  • Typical cough with brown sputum (sometimes with blood)
  • X ray shows bunches of grapes or singular grapes
  • Gold standard= microscopy, eggs seen in sputum or faeces
  • Skin test to test for hypersensitivity- inject into skin and look for a flare reaction.
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19
Q

How do we treat paragonimus?

A

Praziquantel or triclabendazole.

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20
Q

How do we control for paragonimus?

A

Cook crabs and crawfish. Improve sanitation especially in aquatic farms.

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21
Q

What are the three major liver flukes?

A

Fasciola, clonorchis, opistorchis.

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22
Q

What is the infective source for chlonorchis opistorchis?

A

Infected freshwater fish consumption.

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23
Q

What are the zoonotic hosts for clonorchis opistorchis?

A

Highly zoonotic, cats, dogs, pigs.

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24
Q

Where do adult worms of clonorchis opistorchis reside?

A

In the gall bladder, and the bile and pancreatic ducts.

25
Q

What is the lifecycle of clonorchis opistorchis?

A

Embryonated eggs pass in faeces –> eggs ingested by an intermediate host (snail) –> cercariae are released and encyst in the skin or flesh of freshwater fish –> metacercariae in fish are ingested by the definitive host –> excyst in the duodenum –> ascend the biliary tract through the ampulla of Vater –> reside in small and medium sized biliary ducts.

26
Q

What is the species of clonorchis that we learn about the most?

A

Clonorchis sinensis.

27
Q

How long do chlonorchis adults live for?

A

Long lived, around 30 years.

28
Q

Describe the morphology of chlonorchis adults.

A
  • Around 1- 1.25cm.
  • Oral and ventral suckers
  • Hermaphrodites
  • > 30 year lifespan
29
Q

How long does it take chlonorchis to mature in the human?

A

3 months.

30
Q

How do we differentiate between clonorchis and opistorchis?

A

Clonorchis has branched testes
Opistorchis has ovular testes
Eggs cannot be told apart

31
Q

What do the eggs of clonorchis opistorchis look like?

A

30µm, operculum and knob.

32
Q

What do the cercariae of clonorchis opistorchis look like?

A

Unforked tail. Unlike Schistosoma which has a branched tail in the cercariae.

33
Q

What is the pathology of clonorchis opistorchis?

A

After travelling to the bile duct, over time they cause inflammation, hyperplasia, oedema, and bile duct carcinoma.

34
Q

What is the clinical presentation of clonorchis opistorchis?

A

Light infections are usually asymptomatic. Heavy burdens show inflammation, chronic bile duct symptoms, fibrosis of bile duct and wall, liver problems, pancreatic inflammatory symptoms caused by migration.

35
Q

Why is clonorchis opistorchis a group 1 biological carcinogen?

A

Because it gives a 40x higher risk of bile duct carcinoma and decreases the average age of onset (to about 54 years old in areas endemic for disease).

36
Q

How do we diagnose clonorchis opistorchis?

A
  • Eggs in faeces
  • Ultrasound of gall bladder to visualise
  • Serology
37
Q

How does transmission of clonorchis opistorchis occur? i.e. what might be contaminated and how?

A
  • Night soul fertilisation in fish ponds
  • RIce paddies double as fish farms
  • Fish toilets
  • Animal reservoirs e.g. pigs- their faeces used for fish pond fertilisation
38
Q

How is clonorchis opistorchis treated?

A

Single dose of praziquantel.

39
Q

How do we control for clonorchis opistorchis?

A
  • Cooking fish
  • Sanitation, do not shit in the fish ponds
  • Control animal access to fish ponds.
  • Annual MDA with PZQ where prevalence >50%
40
Q

What are the two main fasciolas?

A

Hepatica and gigantica.

Hepatica is more common but we are now starting to see hybrid species.

41
Q

What is fasciola hepatica associated with? (i.e. zoonosis) How do humans become infected?

A

Associated with sheep and cattle farming (ruminants).
Humans infected from ingesting contaminated water plants e.g. watercress in the UK or water spinach in Asia or drinking cercariae in water.

42
Q

What is the dsitrubition of fasciola/ where is it found?

A

All continents bar Antarctica.

43
Q

Describe the transmission cycle for fasciola.

How long does maturation to adult take? How long is their lifespan?

A

Metacercariae encyst on aquatic plants –> consumed and excyst in small intestine –> migrate directly through intestine wall straight to the liver –> eventaully end uo in the bile duct –> eggs excreted in faeces –> infect snails –> cercariae released from snails –> excyst as metacercariae on aquatic plants.

Mature to adult stage in 3-4 months. Live 15 years.

44
Q

How are fasciola eggs deposited in the environment?

A

Excreted in faeces

Shat out!!

45
Q

What are the symptoms of fasciola infection?

A

Liver damage and inflammation (from juveniles migrating through the liver). This causes fever and abdominal pain about 2-3 months after infection.
We also get chronic bile duct fibrosis.

46
Q

How do we diagnose fasciola infection?

A
  • Measure eosinophilia
  • Serology
  • Eggs in stool (may get false positive from eating infected liver which contains eggs).
  • History of eating water plants.
47
Q

What is pharangyeal fasciolitis?

A

Where they attach to the respiratory tract and sufferer’s suffocate.

48
Q

How is fasciola treated?

A

PZQ is NOT effective, use triclabendazole instead.

PZQ resistance is particularly prevalent in farm animals.

49
Q

How do we control for fasciola?

A
  • Cook plants
  • Exclude livestock from aquatic plant environments
  • Education and sanitation
  • MDA in some areas
50
Q

How do we differentiate clonorchis opistorchis and fasciola in bile duct histology slide?

A

Clonorchis opistorchis: smooth tegument, two gut branches.

Fasciola: Rough teguement, multiple gut branches.

51
Q

What is the source of infection of Fasciolopsis buski?

A

Aquatic plants: lotus, water chestnut.

52
Q

What animal is fasciolopsis associated with?

A

Pigs, is strongly zoonotic!

53
Q

How big are adults of fasciolopsis and where do they reside?

A

In the small intestine, around 7cm long.

54
Q

What is the lifecycle for fasciolopsis?

A

Immature eggs are discharged into the intestine and stool . Eggs become embryonated in water , eggs release miracidia , which invade a suitable snail intermediate host . In the snail the parasites undergo several developmental stages (sporocysts , rediae , and cercariae ). The cercariae are released from the snail and encyst as metacercariae on aquatic plants . The mammalian hosts become infected by ingesting metacercariae on the aquatic plants. After ingestion, the metacercariae excyst in the duodenum and attach to the intestinal wall. There they develop into adult flukes (20 to 75 mm by 8 to 20 mm) in approximately 3 months, attached to the intestinal wall of the mammalian hosts (humans and pigs) . The adults have a life span of about one year.

55
Q

How big are fasciolopsis eggs?

A

HUGE 130/140/150µm.

56
Q

Which egg can we not distinguish from fasciolopsis?

A

Fasciola. Both have an operculum and knob.

57
Q

How do we treat fascolopsis?

A

Treat with PZQ (however, cannot be used for fasciola, must use triclabendazole instead).

58
Q

How do we control for fasciolopsis?

A

Peel and wash veg appropriately.

Minimise access of animals to aquatic veg crops.

59
Q

What are the symptoms of fasciolopsis?

A

Symptoms according to burden: low (< 20) asymptomatic

high (>100) diarrhoea, malabsorption, intestinal obstruction

Parasitology and entomology (26 decks)

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