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FARM ANIMAL > 11.3.3: BVD > Flashcards

11.3.3: BVD Flashcards

1
Q

What is the causative agent of BVD? What types of BVD are there?

A
  • BVD is caused by a pestivirus
  • There is antigenic variation of the viral surface protein, producing 2 types.
  • Majority of UK cases: Type 1
  • Type 2 seen in Europe and US.
  • Both forms can by cytopathic or non-cytopathic.
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2
Q

What are clinical signs of Type 1 BVD?

A
  • Acute infection -> mild systemic illness, immunosuppression, reduced reproductive performance
  • Persistently infected animals show mucosal disease
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3
Q

What the clinical signs of Type 2 BVDv?

A
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4
Q

True/false: transient infection with BVD can lead to immunosuppresion.

A

True
This is why have a PI calf, who is constantly shedding BVDv, can make other non PI calves more vulnerable to respiratory and enteric infections.

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5
Q

What is the effect of BVD infection in the non-pregnant animal?

A
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6
Q

What is the effect of BVD in the pregnant animal?

A
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7
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1

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8
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2

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10
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11
Q

If a persistently infected animal has a calf, this calf will be:
a) normal
b) a PI animal

A

b) Persistently infected mothers produce persistently infected calves

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12
Q

True/false: if a persistently infected calf is identified, the calf’s mother must also be culled as she is a PI animal too.

A

False
She might be, but we need to check. She may just have been transiently infected during pregnancy and hence produced a PI calf.

Most PI calves come from transiently infected mothers, rather than PI dams.

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13
Q

Clinical signs of a persistently infected animal

A

They may be clinically normal!

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14
Q

What are the clinical signs of an animal with mucosal disease caused by BVD? How might you differentiate this from FMD?

A
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15
Q

What happens if a bull is transiently infected with BVD?

A
  • The virus may induce temporary infertility
  • During this time the virus may be detected in semen
  • This is a transmission risk to cows
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16
Q

Describe how a bull could be antibody positive, antigen negative on bloods and yet be shedding BVD

A

Bull can be persistently infected but virus hides in testes (immune priviledged site). This is rare. (These are ‘Trojan horse’ bulls).
* Bull is infected in-utero (even after calf immune system has formed) and virus infected testis
* Therefore the bull will be born antibody positive and antigen negative on bloods
* BVD can be detected and spread in semen

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17
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1

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2

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24
Q

What happens if a pregnant cow becomes infected with a cytopathic BVD?

A
25
Q

True/false: once a PI animal has the cytopathic strain, they will then shed this strain and are at risk of kicking off other PIs.

A

True

26
Q

How could you demonstrate an animal is a PI? What should you do with this animal?

A
  • 2 positive antigen tests >3 weeks apart
  • Usually PIs have no (or rarely low) antibodies in both samples
  • PI animals represent a major reservoir of infection so should cull this animal
27
Q

True/false: you can test for BVD antigen in the bulk milk tank.

A

True
This is detectable at a level of 1 PI in 300 cows.
If more than 300 cows may need to split them to sample.

28
Q

How can we identify BVD antibody in an individual animal?

A
  • Blood
  • Milk
29
Q

How can we test for BVD antigen in an individual animal?

A
  • Blood
  • Milk
  • Semen
  • Skin
  • Hair
30
Q

True/false: BVD is species-specific.

A

False
It can affect other species e.g. pigs and is close to Border Disease virus in sheep

31
Q

BVD is
a) reportable
b) notifiable
c) neither

A

c) neither

32
Q

When is a persistently infected animal created?
a) During pregnancy at any time
b) During first trimester
c) During second trimester
d) During third trimester

A

b) During first trimester

33
Q

What method could you suggest to a farmer who is keen to identify and eradicate PI calves as soon as possible?

A
  • Ear tag and test
  • Special ear tag applicators take a sample at the same time as putting the tag in
  • Put the sample in a sealed tissue pot and send to lab
  • This is feasible to do immediately after the calf is born
34
Q

True/false: some PI animals can make antibodies.

A

True but this is rare

35
Q

True/false: paired serology to demonstrate rising titre is a good way to asses acute BVD infection in a herd.

A

False
Paired serology won’t necessarily show rising titre even in transient infection - response to BVD infection can be slow especially in cattle where it has caused abortion.

36
Q

What is a useful way of monitoring if there is BVD actively circulating in a herd?

A
  • Blood sample the heifer cohort from ~8 months old
  • Sample 8-12 animals from the group
  • These animals should be antibody (and antigen) negative if the herd considers itself free of BVD
  • If these animals are antibody positive, they must have been exposed to a PI calf OR had contact with a transiently infected or PI adult
37
Q

A calf has been aborted and you suspect BVD. Which sample will you send to the lab?

A

Send the calf spleen for PCR

38
Q

True/false: there is a BVD vaccine but you should not use it because it interferes with testing of PIs.

A

False
There is a vaccine.
It does not affect your ability to test for PIs (because PIs will be consistently antigen positive)
It will lead to antibodies and these cannot be differentiated from those produced by a transient infection.

39
Q

If you want to vaccinate cattle against BVD, when should you do it?

A
  • Vaccinate prior to first breeding (maiden heifers around 10 months old)
  • Continue to monitor BVD status of the herd
  • Eventually PI animals should be culled and no more should be produced as long as the vaccination protocol is kept up
40
Q

If you want to vaccinate cattle against BVD, when should you do it?

A
  • Vaccinate prior to first breeding (maiden heifers around 10 months old)
  • Continue to monitor BVD status of the herd
  • Eventually PI animals should be culled and no more should be produced as long as the vaccination protocol is kept up

FARM ANIMAL (56 decks)

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