Y3 Parasitology > Flukes > Flashcards

Flukes Flashcards

(50 cards)

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1
Q

Name the two most common fluke species

A
  • Fasciola hepatica

- Fasciola gigantica

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2
Q

Give examples of typical fluke characteristics

A
  • Indirect lifestyle
  • Dorso-ventrally flattened
  • Hermaphrodite
  • No body cavity
  • Branches of the gut are visible
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3
Q

What are the major impacts of fluke on animal production?

A
  • Growth rate
  • Milk yield
  • Wool and fibre
  • Liver condemnation
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4
Q

How can you tell apart the eggs of Fasciola hepatic and Fasciola gigantics?

A

Fasciola gigantica eggs are larger and paler in colour

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5
Q

Describe the host cycle of Fasciola hepatica

A
  • Indirect (includes more than one host)
  • Definitive mammalian host where sexual reproduction occurs – where the adults reside
  • Snail intermediate host is where asexual reproduction occurs
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6
Q

Give examples of the definitive mammalian host of Fasciola hepatica

A
  • Ruminants
  • Camelids
  • Horses
  • Humans (zoonosis)
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7
Q

Name and describe the intermediate host of Fasciola hepatica in the UK

A

Mud snail - Galba truncatula

- 5mm in size, burrow in mud so hard to find

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8
Q

Describe the eggs of F.hepatica when they are passed in the faeces

A

Undifferentiated so have a golden appearance with a very thin egg shell

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9
Q

Over how many weeks does the F.hepatica develop in the eggs on pasture?

A

2-4

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10
Q

When the F.hepatica eggs hatch, what happens, and how does it reach the snail?

A

The operculum on the egg opens up and the miracidium is released and it is covered in a ciliated outer surface, these cilia help it swim to come into contact with the snail

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11
Q

Describe how the miracidium are adapted to reach and infect the snail?

A
  • Miracidium are motile, photosensitive and they can detect the chemical signature of the snail
  • The miracidium are short lived (24hrs) so they have to rapidly swim to the snails to infect them
  • They burrow into the foot of the snail to gain access to the body cavity
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12
Q

What happens to the miracidium when they have infected the snail?

A

They lose the outer ciliated surface – they are now called sporocysts

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13
Q

Describe the reproduction of sporocysts

A

From one sporocyst we can get multiple rediae (asexual reproduction, clonal expansion), which are genetically identical

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14
Q

Further asexual reproduction of the rediae produces?

A

Cercariae

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15
Q

How do cercariae continue the life cycle?

A
  • This stage burrows out of the snail

- When they come into contact with a solid surface e.g. vegetation, they encyst

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16
Q

What is involved in the encystation of a cercariae?

A

Lose their tail, surround themselves with a carbohydrate and protein rich coating which protects the parasite when its out on pasture – now named a metacecariae

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17
Q

Name the stage of the F.hepatica that is infective to the mammalian host

A

Metacecariae

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18
Q

How do metacecariae infect the mammalian host, and which tissues do they migrate to?

A
  • ingested with vegetation
  • exist as juveniles in the gut
  • there is a cap on the metacecariae that opens up and releases the parasite – they exist within the intestine in the duodenum, they pass through the peritoneal cavity in search of the liver, where they migrate
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19
Q

How long does it take the metacecariae to migrate to the liver?

A

6-8 days

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20
Q

Once the metacecariae have reached the liver, what happens next?

A
  • By secreting proteolytic enzymes they make holes in and migrate through the liver
  • After 10-12 weeks the parasites are continuing to grow in size, once they are adults they migrate into the bile ducts- they are sexually mature adults producing eggs at this point
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21
Q

What is the name of the diseases caused by migrating fluke?

22
Q

What are the two forms of Fasciolosis?

23
Q

The type of Fasciolosis disease is determined by?

Study These Flashcards
A

The number of metacercariae ingested and the time period over which they are ingested

24
Q

Describe the pathogenesis of Acute fasciolosis

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A
  • Large numbers of immature flukes migrating through the liver, cause lots of damage
  • Multifocal necrotic or haemorrhagic tracts throughout the liver
  • Inflammation, liver enlargement, fibrosis
25
At what time of the year would you see acute fasciolosis?
October - December
26
What are the clinical signs of acute fasciolosis?
- Occurs in sheep most commonly - Sudden death - Weakness/dull - Abdominal pain - Anaemia
27
Describe the pathogenesis of chronic fasciolosis
- Sheep and cattle - Low numbers of metacercariae ingested over longer period of time - Adult flukes in bile ducts feed on blood - Spines on the tegument irritate bile duct walls - Hyperplasia of the bile ducts to accommodate the number of parasites - Inflammation of the bile duct system
28
At what time of the year would you see chronic fasciolosis?
late winter/early spring – January-March
29
What are the clinical signs of chronic fasciolosis?
- progressive weight loss - anaemia - sub-mandibular oedema - ascites
30
Describe spring in a year in the life of a British fluke
- low snail population - eggs on pasture - eggs develop following an increase in temperature - miracidia infect snails
31
Describe summer in a year in the life of a British fluke
- Summer infection of snails - Asexual reproduction - sporocyst – rediae - cercariae
32
How can the weather in summer cause acute disease?
Three warm, wet months cause large numbers of cercariae released on pasture in September - Large numbers of metacercariae on pasture, ingested by sheep - Acute disease 2-6 weeks later
33
How can the weather in summer cause chronic disease?
A cool dry summer: - Fewer metacercariae produced – cause chronic disease - Released gradually from snails between September and November - Chronic disease in winter and early spring the following year
34
How can fluke be diagnosed at an individual level?
- Clinical signs (sudden death, weight loss, anaemia) - Season (autumn & winter) - Farm history - Post-mortem exam
35
How can fluke be diagnosed at a farm level?
- Composite faecal egg counts (10 animals/group) - Bulk tank milk ELISA - Abattoir returns
36
Describe some fluke control methods
- Disease forecasting: used to predict the levels of disease at different times of the year based on the weather previously had - Grazing management - Elimination of snail habitat - Drug prophylaxis
37
Which drug can be used in the prophylaxis of fluke?
Triclabendazole - effective against all stages of fluke | - resistance in the UK
38
Which 2 drugs can be used to treat fluke in dairy herd and why?
Albendazole Oxyclozanide - Short withdrawal periods
39
What are paramphistomes?
Rumen fluke
40
Name the predominant species of rumen fluke in the UK
Calcicophoron daubneyi
41
Describe clinical disease of Calcicophoron daubneyi
Acute infection when large numbers of metacercariae excyst en masse in the duodenum - stay within the rumen and intestine
42
How can Calcicophoron daubneyi be treated?
- Cloantel: affective but only as an oral drench | - Oxyclozanide
43
The life cycle of Dicrocoelium dendriticum involves which two intermediate hosts?
Garden land snails | Brown ants
44
How does Dicrocoelium dendriticum go from the snail to the ant?
Released from the respiratory pore of the snail in a slime ball which is ingested by the ant
45
Name the blood fluke spp
Schistosoma spp
46
state three characteristics of trematodes
- Dorsoventrally flattened - Solid parenchyma body (no body cavity) - Hermaphrodite - Indirect life cycles.
47
How long does it take for the development of (a) the egg and (b) the stages in the snail of F. hepatica during a typical UK summer?
(a) 2-4 weeks. (b) 6-8 weeks. Development only occurs if temps above 10oC, warmer the temperature, the more rapid the development
48
What is the PPP for F. hepatica?
10-12 weeks
49
What drug(s) could you use to treat acute fasciolosis?
Triclabendazole but check for resistance, or closantel
50
What drug(s) could you use to treat chronic fasciolosis?
Ideally not triclabendazole or closantel to reduce selection pressure on fluke populations, so use nitroxynil, clorsulon, albendazole (increased dose cf nematode dose) or oxyclozanide.
Y3 Parasitology
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