Lecture 10: Bovine Viruses 1 Flashcards
What are examples of diseases in the Genus Pestivirus
- Genus: Pestivirus (NADL/Singer strains are most common in vx)
o Border disease virus
o Classical swine fever
o BVD1
o BVD2
What is the taxonomy of BVDV
Pestivirus
o 1a and 2a in vx – 2b not in vaccine but is more prevalent
o Enveloped
What are is the target(s) species for BVDV
- Target: bovine, wildlife (pig/deer/goat/rabbit)
o Wildlife reservoir: must be susceptible, shed, and maintain BVDV + contact with cattle to allow spill back
How is BVDV transmitted in 3 main affected species
- Transmit (pigs): raw milk
- Transmit (sheep): trans-placental
- Transmit (cow): oronasal
How is BVDV clinically affecting pigs
- Clinically (pigs): poor conception/abortion/stillborn – subclinical
How is BVDV clinically affecting to sheep
- Clinically (sheep): hairy shakers (kids)
How is BVDV clinically affecting to cows
- Clinically (cow):
o Infected 1 mo in utero: embryonic death
o Infected 2-4 mo in utero: persistent infected calf (Ig negative) or abortion or malformation
o Infected 5-9 mo in utero: normal (Ig positive) or abortion or malformation
Why is there different outcomes for BVDV infection at 2-4 mo vs 5-9 mo
o Infected 2-4 mo in utero: persistent infected calf (Ig negative) or abortion or malformation
Will shed disease in high quantities
Immune system is not developed – virus is recognized as self
look like malignant catarrhal fever – deterioration of mucosal surface
* mucosal disease: mutated persistently infecting virus (converts from non-cytopathic to cytopathic)
o Infected 5-9 mo in utero: normal (Ig positive) or abortion or malformation
Immune system is more developed – recognize as non-self
What is mucosal dz? Who does it infect
Persistently infected calves with BVDV
- mucosal disease: mutated persistently infecting virus (converts from non-cytopathic to cytopathic)
o ulcers on mucosal surfaces
o NS2 and NS3 genes – non structural viral proteins that split in genome
o Cannot transmit cytopathic form between calves
o Not recoverable – euthanasia indicated
What is the pathogenesis of BVDV?
- Path: lymphatic spread from tonsil to regional LN to blood
o Found in lymphoid tissue in GI/lung (thymus/bone marrow/spleen)
o All organs are BVDV positive
o Result in immunosuppression
How is BVDV controlled in NA and Europe
o CA: BVDV screening/ProAction/vx
o Europe: kill the persistently infected (legislative change)
What methods are used to screen for BVDV
o Serology (ELISA antigen and/or antibody)/bulk tank PCR (only target milk producing animals) test calves
Target: unvaccinated and low maternal Ig levels – find PI’s
Test whole herd serology: if whole herd is negative = no BVDV
* If some +/- = there are persistently infected + generally infected animals
o Individual sample (blood/ear notch/milk)
Ear notch: best for finding PI
Blood: use capture ELISA, but won’t identify virus that is covered in Ig
o Vaccination: modified live and killed
Effective but must be strain specific (can be vaccinated for one type and infected by another)
1a and 2a in vx – 2b not in vaccine but is more prevalent
What is a ‘wreck’ in relation to BVDV
o Wrecks: unvaccinated herds introduced to virus with synchronous breeding
Result in almost all calves being PI
Mainly affecting beef – cow calf
Vaccinate with cytopathic strains of BVDV – if vx PI with cytopathic strain they will develop mucosal dz (will occur in 25% of PI’s) – not recommended (low efficacy/inhumane euthanasia)
What are the main impacts of BLV
Impacts: dairy industry
* 3% less milk/cow
* 23% more likely to be culled/die
* If clinical = death, and carcass condemnation
* Animal welfare/export restrictions/consumer concerns
How is BLV transmitted
blood
colostrum/milk
natural breeding
in utero
