Transcript BVD – the disease, the veterinarian and the control strategies

BVD – the disease, the veterinarian and
the control strategies
Joe 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
Joe Brownlie © 2008 Royal Veterinary College
Veterinary motivation
The Vet was the main source of information on
infectious disease. The press was also a key source of
information
60%
Vet
28%
Farming press
DEFRA newsletters /
Internet
6%
6%
19%
27%
79%
55%
12%
Other farmers 3% 6%
Meetings 2%
Main
Own knowledge/experience 1%
Other
Markets 1%
Breed societies 1%
Other 1%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
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) Joe Brownlie © 2008 Royal Veterinary College
BVD was the main threat to herds – VETS
(especially according to vet assistants (87%) )
Vet
assistants:
BVD / Bovine Viral Diarrhoea
5%
Leptospirosis 2%
23%
14%
Johne's 2% 10%
RSV Pneumonia 3% 10%
TB
5% 3%3%
IBR 3% 10%
51%
16%
12%
9%
5%
10%
79% 87%
37%
34%
11%
17%
10% 3%
Mastitis 3%
1%
3%
Digital Dermititis 1%
1%
1%
4th
Salmonella 2%1%
3rd
2nd
1st
Other (<=2 mentions) 1%
2%5%
0%
10%
20%
30%
40%
50%
60%
70%
80%
Q11 Which infectious diseases OF CATTLE do you feel are the biggest threat to herds under your care. Lets take the main threa t first,
then the second etc.
Base All respondents (93)
Joe Brownlie © 2008 Royal Veterinary College
Pieces that need to be in place..
Motivation
Education
Joe Brownlie © 2008 Royal Veterinary College
Veterinary motivation
2/3 of VETS were actively promoting BVD
control; 1/3 were not!
I react to farmer
requests for advice
on BVD control
28%
I do not provide
advice on BVD
control
0%
Other
3%
I actively promote
BVD control to my
clients
69%
Vet partners more likely to actively promote
BVD control (74%) than assistants (63%)
Q24 Which of the following BEST reflects your approach to BVD?
Base All respondents (93)
Joe Brownlie © 2008 Royal Veterinary College
• 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
Joe Brownlie © 2008 Royal Veterinary College
Group 1
ACUTE INFECTION
- mild disease >90% UK herds
- virus clearance 10-14 days
BVDV nc
- antibody responses slow
plateau @ 10 – 12 weeks
- antibodies cross-protective to
other BVDV isolates
Joe Brownlie © 2008 Royal Veterinary College
Joe Brownlie © 2008 Royal Veterinary College
BVDV - immunosuppressive with mixed infections
Respiratory
infections
Worse with BVDV!
BVDV
+other viruses (IBR+RSV)
+bacteria (P. Haemolytica)
Worse with BVDV!
Enteric
infections
BVDV
+other viruses (corona & rota)
+bacteria (Salmonella etc)
Severe Haemorrhagic Syndrome
•Thrombocytopenia in acute infections
•field:(Perdrizet et al, 1987 Cornell Vet
Rebhun 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)
Joe Brownlie © 2008 Royal Veterinary College
Group 2
ACUTE INFECTION
- severe disease often fatal
- virus clearance 28 – 38 days
BVDV nc
- thrombocytopenia, diarrhoea, haemorrhagic
disease
- weak cross-protection to Group 1 BVDV
antibodies
- distinct 5’ UTR clustering
Joe Brownlie © 2008 Royal Veterinary College
Reproductive disease
Joe Brownlie © 2008 Royal Veterinary College
Infection of the pregnant dam
Early pregnancy (up to 110 days)
early foetal loss, congenital loss,
persistently infected animals
Joe Brownlie © 2008 Royal Veterinary College
BVDV reproductive disease
Stillbirths
Abortions/mummified
foetus
PI calves
BVD
Joe Brownlie © 2008 Royal Veterinary College
Birth of a PI calf
BVDV
in early
pregnancy
Cow and
calf
infected
Only dam
becomes
immune
Calf born
persistently
infected (PI)
Joe Brownlie © 2008 Royal Veterinary College
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)
Joe Brownlie © 2008 Royal Veterinary College
Transmission pathways
• PI dams to early
foetal calf
100%
• Acute infection to
PI calf
“the Holsteins go on Holiday”
?
Joe Brownlie © 2008 Royal Veterinary College
Likely transmission
pathways to PI?
• PI dams to PI calf
7%
• Acute infection to
PI calf
“the Holsteins go on Holiday”
93%
Joe Brownlie © 2008 Royal Veterinary College
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 © 2008 Royal Veterinary College
Joe Brownlie © 2008 Royal Veterinary College
Joe Brownlie
Royal Veterinary College
The Bull
•Can be PI
•Can be acutely infected
•‘Cumulus’ bull
ALWAYS TEST THEM
Joe Brownlie © 2008 Royal Veterinary College
Pieces that need to be in place..
Motivation
Education
Good diagnostics
Joe Brownlie © 2008 Royal Veterinary College
Veterinary motivation
Mucosal Disease
A fatal disease of cattle, usually between 6 18 months, associated with BVDv (?)
Joe Brownlie © 2008 Royal Veterinary College
60% of these cattle were PI and all the PI animals died of Mucosal disease
Joe Brownlie © 2008 Royal Veterinary College
Normal bovine intestinal lymphoid
tissue
Discrete Peyer’s patch
Continuous Peyer’s patch
ileum
MD
Joe Brownlie © 2008 Royal Veterinary College
Intestinal lymphoid depletion
necrosis
MD
Joe Brownlie © 2008 Royal Veterinary College
BVDV
Two biotypes
NON-CYTOPATHOGENIC
CYTOPATHOGENIC
Joe Brownlie © 2008 Royal Veterinary College
VIRUS
-ve
-ve
+ve
nc
ANTIBODY
-ve
+ve
-ve
STATUS
naïve
immune
PI
+ve
nc+c
-ve
MD
Joe Brownlie © 2008 Royal Veterinary College
Mucosal Disease
BVDV
in early
pregnancy
Cow and
calf
infected
Only dam
becomes
immune
Superinfection with
second BVDV
‘biotype’
Calf born
persistently
infected (PI)
Fatal
Mucosal
disease
Joe Brownlie © 2008 Royal Veterinary College
What is happening in Europe?
Joe Brownlie © 2008 Royal Veterinary College
National
Regional
Joe Brownlie © 2008 Royal Veterinary College
Pieces that need to be in place..
Sufficient
resources
Motivation
Education
Good
diagnostics
Joe Brownlie © 2008 Royal Veterinary College
Veterinary motivation
Separation between non-infected- and
infected herds using herd level
diagnostics
BULK
MILK
BULK
MILK
Joe Brownlie © 2008 Royal Veterinary College
Strategy in non-infected herds
Screening/monitoring methods
1.
2.
3.
BULK
MILK
BULK
MILK
5-10
5-10
(7) 12
months
Joe Brownlie © 2008 Royal Veterinary College
BVD Virus
Measles
Joe Brownlie © 2008 Royal Veterinary College
Vaccination was a key factor in the control
& prevention of infectious disease - VETS
77%
Vaccination
Biosecurity advice
45%
37%
Testing
Blood Testing
Vaccination
more likely in
South 86%
(North 68%)
26%
Monitor performance characteristics
12%
Diagnosis
11%
Herd Health Plan
10%
10%
Milk Testing
Isolation
6%
Cull infected animals
5%
Promote routine herd visits by the vet
5%
Stock purchase control/close herd
5%
Herd health
3%
Other (<=2 mentions)
9%
0%
10%
20%
30%
40%
50%
60%
70%
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
80%
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.
Although applied almost world-wide, just unsystematically
vaccinating cattle does not even influence the high
incidence of BVDV infections
* in the USA
** J. Ridpath, 2002: http://www.avma.org/onlnews/javma
Joe Brownlie © 2008 Royal Veterinary College
Pieces that need to be in place..
Sufficient
resources
Motivation
Education
Good
diagnostics
Ownership
strategy
Joe Brownlie © 2008 Royal Veterinary College
Veterinary motivation
Is there a UK national strategy?
Joe Brownlie © 2008 Royal Veterinary College
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
Joe Brownlie © 2008 Royal Veterinary College
BVD Control Options GB
• Do Nothing
• Vaccinate
• Control PI calves
• Control PI calves & Vaccinate
Joe Brownlie © 2008 Royal Veterinary College