BVD – the disease, the veterinarian and the control strategies Joe Brownlie © 2008 Royal Veterinary College

BVD – the disease, the veterinarian and the control

strategiesJoe Brownlie © 2008 Royal Veterinary College

•BVD Disease…….and the Vet!

•European Dimension

•Control, Vaccination & Eradication

Joe Brownlie © 2008 Royal Veterinary College

Pieces that need to be in place..

Education

Veterinary motivationJoe Brownlie © 2008 Royal Veterinary College

The Vet was the main source of information on infectious disease. The press was also a key source of information

Q9 What are your sources of information on infectious diseases in cattle. Let's start with your main source? CODE ONE ONLY. And where else?

Base All respondents (679)

60%

28%

6%

3%

1%

19%

27%

6%

6%

2%

1%

1%

1%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

Vet

Farming press

DEFRA newsletters /Internet

Other farmers

Meetings

Own knowledge/experience

Markets

Breed societies

Other

Main

Other

79%

55%

12%


BVD was the main threat to herds – VETS (especially according to vet assistants (87%) )

Q11 Which infectious diseases OF CATTLE do you feel are the biggest threat to herds under your care. Lets take the main threat first, then the second etc.Base All respondents (93)

2%

2%

3%

3%

3%

1%

2%

1%

5%

14%

10%

10%

3%

10%

1%

1%

2%

23%

16%

12%

9%

3%

10%

1%

5%

51%

5%

10%

11%

17%

3%

5%

1%

3%

0% 10% 20% 30% 40% 50% 60% 70% 80%

BVD / Bovine Viral Diarrhoea

Leptospirosis

Johne's

RSV Pneumonia

TB

IBR

Mastitis

Digital Dermititis

Salmonella

Other (<=2 mentions)

4th 3rd 2nd 1st

79%

37%

34%

Vet assistants:

87%



Education

Motivation


2/3 of VETS were actively promoting BVD control; 1/3 were not!

I do not provide advice on BVD

control 0%

I actively promote BVD control to my

clients69%

I react to farmer requests for advice

on BVD control 28%

Other3%

Q24 Which of the following BEST reflects your approach to BVD?Base All respondents (93)

Vet partners more likely to actively promote BVD control (74%) than assistants (63%)


• Reproductive disease

Classical swine fever virus (Hog cholera virus)

Bovine virus diarrhoea virus

Border disease virus

non-cytopathogenic virus (except mucosal disease)

crosses placenta

foetal infection

congenital damage abortion


Group 1

BVDV nc

- mild disease >90% UK herds- virus clearance 10-14 days- antibody responses slow

plateau @ 10 – 12 weeks

- antibodies cross-protective to other BVDV isolates

ACUTE INFECTION



BVDV - immunosuppressive with mixed infections

Respiratory infections

Worse with BVDV!

BVDV +other viruses (IBR+RSV)

+bacteria (P. Haemolytica)

Enteric infections

Worse with BVDV!

BVDV +other viruses (corona & rota) +bacteria (Salmonella etc)

Severe Haemorrhagic Syndrome

•Thrombocytopenia in acute infections

•field:-(Perdrizet et al, 1987 Cornell VetRebhun et al, 1989 J Vet Int Med)

•experimental:-(Corapi et al, 1989 J Virology)

•Acute fatal diseases in adult cattle (Hibberd et al 1993 Vet Record

David et al 1993 Vet Record)


Group 2

BVDV nc

- severe disease often fatal

- virus clearance 28 – 38 days

- thrombocytopenia, diarrhoea, haemorrhagic disease

- weak cross-protection to Group 1 BVDV antibodies

- distinct 5’ UTR clustering

ACUTE INFECTION


Reproductive disease


Infection of the pregnant dam

Early pregnancy (up to 110 days)

early foetal loss, congenital loss,

persistently infected animalsJoe Brownlie © 2008 Royal Veterinary College

BVDV reproductive disease

BVD

Stillbirths

Abortions/mummified foetus

PI calves


BVDV

in early pregnancy

Cow and calf infected

Only dam becomes immune

Calf born persistently infected (PI)

Birth of a PI calf


PI animals

• Early pregnancy (up to 110 days)

early foetal loss,

persistently infected animals• 1-2% of national population are PI animals

• However may be much higher in foetal calves (up to 13%)

(Nettleton 1985)


“the Holsteins go on Holiday”

Transmission pathways

• PI dams to early foetal calf

100%

• Acute infection to PI calf

?


“the Holsteins go on Holiday”

Likely transmission pathways to PI?

• PI dams to PI calf

7 %

• Acute infection to PI calf

93%


BVDV: Effects on Reproduction Infection during early pregnancy (Day 1-24)

Embryonic Mortality

Expt 1• 22% conception in infected heifer

79% conception in uninfected heifers (Virakul 1988)

Expt 2• 33% pregnancy rate in infected cattle

79% pregnancy rate in un-infected cattle

(McGowan 1993)



Joe Brownlie Royal Veterinary College

The Bull

•Can be PI

•Can be acutely infected

•‘Cumulus’ bull

ALWAYS TEST THEM



Education

Good diagnostics

Motivation


Mucosal Disease

A fatal disease of cattle, usually between 6 -

18 months, associated with BVDv (?)


60% of these cattle were PI and all the PI animals died of Mucosal diseaseJoe Brownlie © 2008 Royal Veterinary College

Normal bovine intestinal lymphoid tissue

MD

Discrete Peyer’s patch

Continuous Peyer’s patchileum


Intestinal lymphoid depletion

MD

necrosis


BVDV

NON-CYTOPATHOGENIC CYTOPATHOGENIC

Two biotypes


VIRUS -ve -ve+venc

+venc+c

ANTIBODY -ve +ve -ve-ve

STATUS naïve immune PIMD


BVDVin early pregnancy

Cow and calf infected

Only dam becomes immune

Calf born persistently infected (PI)

Fatal Mucosaldisease

Mucosal Disease

Superinfection with second BVDV ‘biotype’ Joe Brownlie © 2008 Royal Veterinary

College

What is happening in Europe?


National Regional Joe Brownlie © 2008 Royal Veterinary College

Sufficient resources


Education

Good diagnostics

Motivation

Veterinary motivation


Separation between non-infected- and infected herds using herd level diagnostics

BULK MILK

BULK MILK


Screening/monitoring methods

BULK MILK

BULK MILK

5-10

5-10

1.

2.

3.

(7) 12 months

Strategy in non-infected herds


BVD VirusBVD Virus

VACCINE

Measles Joe Brownlie © 2008 Royal Veterinary College

Vaccination was a key factor in the control & prevention of infectious disease - VETS

Q15 What if any steps do you take to control and prevent infectious diseases on farms under your care?Base All respondents (93) South (49) = SE, SW, Wales, W Mids, E Mids, Eastern; North (44) = Scotland, NE, NW, Yorks

77%

45%

37%

26%

12%

11%

10%

10%

6%

5%

5%

5%

3%

9%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Vaccination

Biosecurity advice

Testing

Blood Testing

Monitor performance characteristics

Diagnosis

Herd Health Plan

Milk Testing

Isolation

Cull infected animals

Promote routine herd visits by the vet

Stock purchase control/close herd

Herd health

Other (<=2 mentions)

Vaccination more likely in South 86% (North 68%)

Non-Systematic Approach Involving Vaccination

What can 40 years of vaccination and 160 currently licensed vaccines* do to eradicate a disease? When you are talking about bovine viral diarrhea virus, apparently not much — it is still thriving.

* in the USA** J. Ridpath, 2002: http://www.avma.org/onlnews/javma

Although applied almost world-wide, just unsystematically vaccinating cattle does not even influence the high incidence of BVDV infections


Sufficient resources


Education

Good diagnostics

Ownership

strategy

Motivation

Veterinary motivation


Is there a UK national strategy?


Is there a UK national strategy?

• National initiative to prepare a National Strategy

•BVD Control Strategy Group

• Wide representation from industry, veterinary profession (BCVA), academia & government

• Pilot BVD Eradication programmes underway


BVD Control Options GB

• Do Nothing • Vaccinate• Control PI calves

• Control PI calves & Vaccinate


Documents

BVD – the disease, the veterinarian and the control strategies Joe Brownlie © 2008 Royal Veterinary College