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Y3 Parasitology > Dictyocaulus viviparus - Cattle lungworm > Flashcards

Dictyocaulus viviparus - Cattle lungworm Flashcards

1
Q

Give the name of the cattle lungworm

A

Dictyocaulus viviparous

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2
Q

What condition is caused by Dictyocaulus viviparus?

A

Parasitic bronchitis

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3
Q

Describe the morphology of adult Dictyocaulus worms

A
  • 4-8cm long
  • Slender, white
  • Male has a reduced bursa at the tail end (not as obvious as GI worms)
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4
Q

Define the term ovo-viviparous

A

Producing young by means of eggs which are hatched within the body of the parent

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5
Q

Describe life cycle 1 of Dictyocaulus

A
  • direct
  • female worms are ovoviviparous and lay larvated eggs which hatch immediately (L1 is already developed)
  • L1 in lungs are coughed up and swallowed
  • L1 is passed out in faeces
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6
Q

When doing a faecal sample for Dictyocaulus what are you looking for?

A

L1

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7
Q

Describe life cycle 2 of Dictyocaulus

A
  • L1 in faeces
  • L1 => L2 => L3
    All ensheathed - retains the sheath from each moult giving it protection
  • Larvae contain food granules which when used up cause it to die
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8
Q

How many days does it take for an L1 to moult to L3?

A

5-7 in optimum conditions

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9
Q

What is the infective stage of Dictyocaulus?

A

L3

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10
Q

Which 4 stages make up the 3rd life cycle of Dictyocaulus?

A
  • Penetration phase
  • Pre-patent phase
  • Patent phase
  • Post-patent phase
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11
Q

Describe the penetration phase

A
  • occurs 0-7 days after infection
  • L3 are ingested
  • Lympho-tracheal migration
  • moult to L4 in lymph nodes
  • L4 reach lungs
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12
Q

Describe the pre-patent phase

A
  • 8-25 days after infection
  • L4-L5 in lungs
  • L5 migrate up bronchial tree
  • Adults in the bronchi and trachea
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13
Q

Describe the patent phase

A
  • 26-55 days after infection
  • Adult worms in the upper respiratory tract
  • Eggs and L1
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14
Q

Describe the post-patent stage

A
  • 55+ days after infection
  • Immune expulsion of adults
  • Protective immunity
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15
Q

Which stages of the 3rd life cycle are the most pathogenic?

A

Pre-patent and patent

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16
Q

After how many days on infection can Dictyocaulus adults be seen?

A

25

17
Q

Which calves are most affected by Dictyocaulus?

A

Smallest and weakest

18
Q

Describe the pre-patent phase pathological response

A
  • intense inflammatory response
  • alveolitis, bronchitis
  • interstitial emphysema (alveoli breakdown)
  • pulmonary oedema
19
Q

Describe the pre-patent phase clinical signs

A
  • Coughing
  • Respiratory distress
  • Tachypnoea
  • Weight loss
  • Calves have their neck stretched out trying to breathe
20
Q

Describe the patent phase pathological response

A
  • Mature adults in bronchi and trachea
  • Eggs and L1 swept into alveoli
  • Emphysema, hypoxia
21
Q

Describe the patent phase clinical signs

A
  • Gasping
  • Coughing
  • Death
  • Frothy, white mucus
22
Q

Describe the post-patent phase pathological response and clinical signs

A
  • Resolution of clinical signs
  • In some animals, epithelialisation of lung tissue never completely recovers
  • Lung function is compromised throughout their lives
23
Q

Which factors affect the parasitic stages of Dictyocaulus?

A
  • temperature and moisture
  • dispersal of L3 by fungi on faecal pats
  • L3 overwinter on pasture
24
Q

When does disease with Dictyocaulus occur?

A

August-September

25
Q

How many Dictyocaulus worms are needed to cause disease?

A

800-1000

26
Q

Is Dictyocaulus immunity long lasting?

A

No, needs continual boosting

27
Q

How can Dictyocaulus be diagnosed?

A

L1 identification in faeces using a Baermann

28
Q

How can Dictyocaulus infection be treated?

A
  • Anthelmintics
  • NSAIDs, antibiotic
  • House severely affected calves
29
Q

Describe the Dictyocaulus vaccine

A

Huskvac

  • Live, attenuated
  • oral
  • two doses, four weeks apart
  • give before turnout
30
Q

To control Dictyocaulus arnfieldi in horses, why are owners advised to graze donkeys separately?

A

Because donkeys can be asymptomatic carriers of D. arnfieldi, pass L1 in faeces that develop to L3 and are a source of infection for horses.

31
Q

How would you isolate and identify L1 of D. viviparus in cattle?

A

Use a Baermann apparatus to isolate the larvae, they are the only L1 found in the faeces of cattle in the UK.

32
Q

What is the infective stage and what is the prepatent period (PPP) of D. viviparus?

A

Infective stage is the L3 and PPP is around 25 days

33
Q

How would you diagnose dictyocauliosis in (a) FSG calves and (b) adult milking cows?

A

(a) Calves would show clinical signs of coughing, dyspnea and weight loss, confirm by detecting L1 in faeces using the Baermann method
(b) adult milking cows usually show drop in milk yield first, then may show coughing and dyspnea. Confirm with Baermann as for (a).

34
Q

Explain why dictyocauliosis is an unpredictable disease.

A

Fewer larvae required to cause disease, so don’t need the same build up of L3 on pasture compared to Ostertagia. L3 can survive on pasture for more than a year, and L3 can be blown onto clean pasture on spores of Pilobolus. Cannot predict pasture larval burden, immunity plays an important role, very strong immunity develops following exposure.

Y3 Parasitology (13 decks)

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