BVD Flashcards
What type of virus is BVD
pestivirus
What are the 2 types of BVD and how prevalent is it
BVDv Type 1: prevalent
BVDv Type 2 rare
Describe what you see with type 1 BVDV
reduced repro performance
immunosuppression
mild systemic illness
When is mucosal disease seen
end stage of PI life
what is seen with type 2 BVDV
generally severe disease often fatal, usually adults
thrombocytopenia, diarrhoea, haemorrhagic disease
RARE in UK
How can BVDV virus increase resp disease in calves
Immunosupression
more likely for IBR +RSV and M. haemolytica infections
What happens if non-pregnant cow gets infected with BVDV
transient infection
When do antibodies show for non-pregnant cow gets infected with BVDV
from 2-4 weeks and persist for several years
what happens if <120 days gestation cow gets infected with BVDV
death and reabsorption, abortion, mummification or stillbirth; if the fetus survives, then PI
what happens if 120-190 days gestation cow gets infected with BVDV
stillbirth/abortion, abnormalities in calf
what happens if 190+ days gestation cow gets infected with BVDV
normal calf
List 5 possible outcomes of BVDV infection in pregnent animals
embryo loss
congenital defects
abortion
normal calf
PI calf
How id PI calf created
BVDV crosses placenta before immune system- calf recognises it as normal so never generates antibodies
T/F PI can only be caused by pregnant cow getting infected with BVD
False
All PI dam produce PI calves
T/F all PI calves go on to show mucosal disease
False
may show no signs at all
How long do PI calves shed BVDV for
their whole lives - and shed alot of virus
Describe the signs of mucosal disease
weight loss
bloody D+
dehydration
ulcerative lesions in mouth and interdigital space
Fatal condition
How does mucosal disease occur
Virus mutates from non-cytopathic to cytopathic form (ie cell killing form)- occurs in PI calves
Transmission of cp strain = potential for MD in other PIs
T/F bulls can spread BVDV
True
can be PI or acutely infected
How can a bull be blood Ab positive but antigen neg but still be PI
virus can ‘hide’ in testicles “immunological privileged site”
only identified by semen sample
What is a good screening test for BVDV in dairy cows
Viral Ag can be detected in bulk milk, from 1 PI in 300 cows
List 2 ways to look for BVDV in calves
blood Ag test pre-colostrum
ear tissue sample
Presence of virus in samples can mean….
Animal is PI
animal is acutely infected- Viraemia following acute infection lasts up to 2 weeks
Describe how to demonstrate a PI animal
2 positive antigen tests >3 weeks apart
Usually PIs have low/no antibody levels in both samples
What should you do if you find a PI
KILL IT- because shed virus alot and can’t treat
what do you need to consider when testing a high number of cows for BVDV
Sensitivity and specificity of both Ab and Ag test rel. good
BUT no test is perfect…
Describe the Blood sampling heifer cohort method of BVDV herd monitoring
Blood sample for Ab from ~ 8 months of age (maternal Ab)- sample 8-10 from group
should be Ab neg
at what level on bulk milk BVDV test shows recent or active exposure
> 0.7
Describe the basic approach to BVD control
Evaluate current herd status
Assess the routes by which virus could enter the herd and spread within the herd
Eradication by removal of PIs and preventing new cases
Describe how BVDV is spread
nose-to-nose contact main route
PIs most important sources
Faeces a poor source
When do you vaccinate for BVD
must ensure protection before first breeding
Lots of vaccines avaliable
What is the best way to eradicate BVD and prevent re-infections
Vaccination and monitor for PIs
When can do nothing approach to BVD work
If the herd only monitor through bulk milk Ab and are consistently low/medium positive, this is still a fairly common option
But probably lots of hidden coats
Is BVD zoonotic
No
What is the main clinical sign of Bovine viral diarrhoea virus ?
1 - Dyspnoea
2 - Abortion
3 - Diarrhoea
4 - Conjunctivitis
2- Abortion
Which of these is not a transmission route for BVD ?
1 - Feco-oral
2 - In-utero
3 - Milk
4 - Venereal
5 - Saliva
3- Milk
Which serotype of BVDV is most common in the UK ?
1 - BVDV type 1
2 - BVDV type 2
1- BVDV type 1
T/F The cytopathic form of BVDV can be transmitted to other cattle
False
limited to PI calves
Bulls can be PI animals and so can be a major spread for disease in BVDV. What is the rarer form that bulls can get in which they can transmit to the to the herd ?
Virus resides in
1 - Brain
2 - Lungs
3 - Testicles
4 - Lymph nodes
3
Which of these is an appropriate way of testing for BVDv on an individual basis ?
1 - Fecal PCR
2 - Blood ELISA
3 - Fecal ELISA
4 - Bulk milk tank ELISA
2
What can alter testing results sensitivity when testing for PI calves ?
colostrum
What is needed in order to diagnose a PI calf ?
1 - 1 x positive antigen and negative antibody test
2 - 2 x positive antigen and negative antibody tests (3 weeks apart)
3 - 2 x negative antibody tests (3 weeks apart)
4 - 2 x positive antigen tests (3 weeks apart)
2
In order to sample youngstock for presence of PI calves we need to do it before colostrum is given or after at what age ?
1 - >1 month
2 - >2 months
3 - >4 months
4 - >8 months
4- 8 months
