Pestiviruses and Teratogenic viruses Flashcards
What is a teratogen?
A teratogen is an agent that can disturb the development of an embryo or fetus
What are some examples of teratogens?
- radiation
- maternal infections
- chemicals
- drugs
Give 4 examples of teratogenic viruses
- Blue tongue
- Japanese B encephalitis
- Epizootic haemorrhagic disease
- BVD
What is the genome organisation of a pestivirus?
- Single-stranded, positive-sense RNA virus of genome 12.3kb
- single open reading frame is translated to different polyproteins
- the virion is enveloped- size 40-60nm is diameter
What is the structure of the pestivirus virion?
- Enveloped
- spherical
- 50nm in diameter
How many encoded proteins do mature pestivirus virions have?
three virus-encoded proteins
Erns, E1, E2
What is the immundominant glycoprotein in pestiviruses?
E2
carries neutralising epitopes
What are the two main genotypes of BVDV?
BVDV-1 and BVDV-2
What is the most common BVDV genotype in the UK?
BVDV-1
What is the host range of BVDV?
- Sheep
- Goats
- Pigs
What is the clinical presentation of BVDV?
- Acute enteric, respiratory disease
- Reproductive and foetal disease in susceptible breeding females
- Mucousal disease
What are the two biotypes of BVDV?
- Non-Cytopathogenic
- Cytopathogenic
What does infection of a seronegative animal with BVDV lead to?
a transient, acute, infection that usually causes no or mild clinical symptoms
When does persistent BVDV infection occur?
Infection of ncp but not cp
occurs in month 2-4
persistent infection of the fetus
What happens when a BVDV infection occurs late in gestation?
abortion and malformation
What is the definition of a persistent infection?
animal is already infected with the virus when it is born and remains infected throughout its entire life
What happens when the foetus is infected in the first 90 days of life?
BVDV
- The foetus becomes immunotolerant to the virus
- Virus therefore survives and replicates
- the animals can act as a reservoir of infection to the rest of the herd
- they are also susceptible to mucousal disease
In what cattle does mucousal disease develop?
Only develops in PI cattle
associated with the mutation of BVDV
Where is BVDV localised?
lymphoid tissue before spreading to the gastrointestinal epithelium
What does mucousal disease cause in keratinocytes?
Causes necrosis of keratinocytes, causing erosion/ ulceration
What does fluid leakage from the ulceration post BVDV lead to?
Diarrhoea, Dehydration and bacterial infection
inevitably fatal
What are the three different ways bulls can get BVDV?
- Male calves are born PI (persistent infection)
- Post-pubertal bulls can be exposed to BVDV as a transient infection (they shed the virus in semen for up to 28 days)- bulls then mount an immune response to the virus
- Post-pubertal bulls exposed to BVDV can be acutely infected but develop persistent testicular infection- this virus is cleared systemically
What are the three ways you can diagnose BVDV?
- Virus/ antigen detection- virus isolation from the semen
- BVDV-specific antigen detection assays (blood samples, ear notches, milk testing)- fluorescent antibody test
- BVDV- specific antibody detection- serum neutralisation test
How can you control BVDV within a herd?
- Target PI animals alongside a good vaccination programme
- Test and cull schemes
Why are BVDV vaccinations important?
- Prevent the infection of the fetus
- Reduce reproductive losses
- Prevent production of PI animals and reduce the transmission cycle
In what animal species is Classical Swine Fever Virus notifiable?
Notifiable in pigs and wild boar
Where does classical swine fever virus survive?
fomites and pig meat such as sausage
At what pH is CSFV inactivated?
rapidly inactivated at <3 or >10
How thermally stable is classical swine fever?
- Inactivated by 36 minutes at 70 degrees
- the thermal stability is dependent on the matrix
What CSFV sensitive to?
Organic solvents, Detergents and UV
How can CSFV be transmissed directly?
- Pig to pig contact
- Oral, Nasal secretions
- Feces, Urine, Blood, Semen
- Transplacental
- Contact with wild boar
How is CSFV transmissed indirectly?
- Arthropods, birds
- Rodents, foxes
- Infected pig pens
- Lorries, equipment
What is vertical CSFV transmission?
transmission across the placenta during gestation to produce congenitally infected piglets
What is the pathogenesis of CSFV?
- Virus enters the oral pharynx and replicates in the palatine tonsil
- pyrexia, anorexia, leucopenia, generalised petechia
- Haemorrhagic lymphadenitis in young pigs
- Intestinal lesions of lymphoid tissue
- CNS lesions can occur with tremors and incoordination
What does CSFV in-utero transmission look like?
- Cross-uterine congenital infection with cerebellar hypoplasia or growth retardation
- Foetal death, abortion, congenital damage
How can you prevent CSFV?
- Do not feed uncooked food to swine
- Disinfect boots/ Clean overalls
- Quarantine newly introduced animals
- Protect animals from feral pigs/ boar
What species does border disease affect?
- ewes, goats, ocassionally cattle
What does border disease cause in flocks?
- Significant abortion
- classic outcome = ‘hairy-shaker lamb’
What are the clinical signs of mucousal disease?
- BVDV is localised to the lymphoid tissue then spreads to the gastrointestinal epithelium
- There is then necrosis of keratinocytes
- Fluid leakahe leads to diarrhea, dehydration and bacterial infection -> inevitably fatal
How long does the shed BVDV virus last in semen?
Up to 28 days
* Bulls will mount an immune response to the virus which prevents further shedding
What do persiently infect animals act as a d what are they susceptible to?
- they act as reservoirs of infection
- they are susceptible to mucousal disease
What are the two vaccines for BVDV?
- Inactivated
- Modified Live vaccine
