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FCP > Bovine viral diarrhoea > Flashcards

Bovine viral diarrhoea Flashcards

1
Q

Cause of BVD

A
  • Bovine Viral Diarrhoea = pestivirus
  • Single stranded positive sense RNA virus
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2
Q

Effects of BVD infection

A
  • Abortion
  • Mucosal disease
  • Immunosuppression
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3
Q

What are the biotypes of BVD?

A
  • Non-cytopathic
  • Cytopathic (only in persistently infected animals)
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4
Q

What effect does BVD have if infection occurs early in gestation (<111 days)?

A
  • Abortion
  • Congenital damage
  • Persistently infected calves who do not recognise the virus as foreign
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5
Q

What effect does BVD have if infection occurs in mid-gestation (111-200 days)?

A
  • Congenital damage
  • Foetal loss
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6
Q

What effect does BVD have if infection occurs in late gestation (>200 days)?

A
  • No issues
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7
Q

What effect does BVD have on young stock?

A
  • Profound leukopenia
  • Increased disease susceptibility
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8
Q

What effect does BVD have on other cattle (non-cytopathic infection)?

A
  • Mild fever
  • ± transient leukopenia
  • ± diarrhoea
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9
Q

What effect does BVD have on bulls (non-cytopathic infection)?

A
  • Transient fever
  • Slight diarrhoea
  • Infected bulls transmit infection through their semen
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10
Q

What effect does a cytopathic BVD infection have on the animal?

A

Cytopathic infection = persistently infected animals only

  • Mucosal disease:
    • Acute diarrhoea with ulcers in the mouth
    • Pyrexia
    • Nasal discharge
  • These animals may not always show mucosal disease; other times they may appear normal but just a bit runty.
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11
Q

When and how do persistently infected animals present with mucosal disease?

A
  • Mucosal disease occurs when a PI animal is super-infected with a cytopathic virus which has a close antigenic relationship to the resident ncp-BVDV
  • This is usually rapid onset
  • Disease starts in the tonsils, lymph nodes, Peyer’s patches, and intestinal lymph nodes
  • There is diffuse distribution in the intestinal epithelium
  • Massive ulceration leads to death
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12
Q

Persistently infected animals don’t respond to ncp-BVD. Why?

A
  • Timing of the infection as calf = immune tolerance
  • These animals are viraemic: always shedding the virus
  • They never produce antibodies to BVD
  • The impact of being persistently infected = decreased DLWG, increased risk of disease
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13
Q

Persistently infected animals are ______ positive, _________ negative

A

Persistently infected animals are antigen positive, antibody negative

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14
Q

Relate this image to the clinical signs a calf infected with BVD would present with.

A
  • Cerebellar hypoplasia
  • Animal will shake and try to move but be unable
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15
Q

What are your differential diagnoses for congenital abnormalities/high empty scanning rates/abortion?

A
  • Blue tongue virus → bigger effect on sheep
  • Schmallenberg virus → leads to distinctive abnormalities (“spider calves”)
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16
Q

Questions to ask the farmer when BVD is a differential:

A
  • Has it happened before?
  • Have new bulls been brought onto the farm? Any new cows?
  • How many sick calves?
  • Any abortions and timing/high barren rate?
  • Biosecurity on the farm?
  • Visitors to the farm?
  • Do they have sheep?
  • Do they share borders with other farms?
17
Q

If dairy cows, how could you test for BVD?

A

Test the bulk milk tank for BVD antigen

18
Q

What are the benefits and drawbacks of doing antibody testing to detect BVD?

A

✅ Shows that there has been an infection

❌ Does not detect persistently infected animals

Don’t test calves. Cows are likely to test positive. Heifers, if positive, indicate recent exposure (perhaps BVD infection in the last year)

19
Q

What are the benefits and drawbacks of using antigen-testing to detect BVD?

A

✅ Shows either circulating virus or persistently infected animals

  • Perform the antibody test first.
  • Test calves for the antigen to identify persistently infected animals.
20
Q

What action should you take with a calf who tests positive on the antigen test?

A
  1. Isolate for a couple of weeks
  2. Retest
  3. If still positive = persistently infected. If negative = it was a transient infection
21
Q

What action should you take if the herd is infected with BVD?

A
  • Cull persistently infected calves
  • Trace persistently infected dams but antigen-testing the mothers of cull calves
  • Vaccinate cows prior to serving
  • Put up double fencing on borders
  • Introduce foot dips for visitors
  • Don’t share kit/muck between farms
  • Continue testing
22
Q

True/false: freezing semen kills BVD.

A

False.

Need to test the semen.

If the bull was infected as a certain point in gestation, he could be serum -ve, semen +ve (check this)

FCP (34 decks)

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