Swine Fever Flashcards
(27 cards)
What is Pestivirus C?
Classical Swine Fever
What are the virological features of CSFV?
Single stranded +ve sense RNA genome.
* Genomic RNA is infectious, serves as mRNA too.
* Genome approx. 12kb.
* Replicates in the cytoplasm.
What is the genome organisation of pestivirus?
- Genome 11.3-13kb.
- Single ORF about 11.7kb.
- Polyprotein is made and cleaved:
- No sub-genomic mRNA made.
- Both cellular and viral proteases process
the polyprotein.
What test can detect pestiviruses?
ELISA test
What is the virus inactivated by?
- Detergents and organic solvents
- Low and high pH
- High temperatures
- UV light
What are the most favourable conditions for the virus to survive in?
- Meat- Cool, moist, protein-rich
- In the environment
- Frozen semen
How can classical swine fever be transmissed directly?
- Pig to pig contact
- Oral/ Nasal secretions
- Faeces/ Urine
- Blood
- Semen
- Transplacental
- Contact with wild boar
What is the impact of classical swine fever?
- Notifiable disease
- UK last outbreak in 2000
- by the time CSF is suspected and diagnosed pig movement will have spread the virus across the UK
What are the early clinical signs of clinical swine fever?
Only a few pigs are affected
* drowsy, less active
* straight backs
* reduced appetite, marked anorexia
* drop in leukocyte count
* eyes have marked discharge and conjungtivitis
What are the clinical signs of an established clinical swine fever outbreak?
- gaunt
- hollow-flanked
- posterior paresis
- reddening of the skin
- purplish discolouration ober the abdomen
*
What is the outcome of high virulence?
- Acute disease
- High mortality
- the outcome is generally dependent on host factors
What is the effect of moderate/ low virulence?
- sub-acute or chronic disease
- prolonged incubation
- lower mortality
- outcome can be influenced by host factors
What does clinical swine fever look like in post mortem?
- Multiple haemorrhages of various sizes (e.g haemorrhage of lymph nodes)
- Lymph nodes are swollen
- Petechiae on kidneys (urinary bladder, larynx, epiglottis, heart, intestinal mucosa,)
- infarction of the spleen
What vaccine would you use in farmed pigs?
- Live vaccines are used in endemic areas, eg in eastern european countries
What areas do not use live vaccines?
CSF free areas- e.g parts of the UK
* Risk of vaccine break through
* it complicates detection and control of the disease if an outbreak were to occur
How would you control CSF in wild boar?
Oral vaccination- has been succesful in europe in reducing prevalence but it is important that you use the correct bait for target animals
* also important that bait is timed with local food availability
What are the virological features of ASFV?
- Family is asfarviridae
- Genus is Asfivirus
- Group 1- Baltimore
- Double stranded DNA genome linear
- Structure- icosahedral capsid with inner and outer envelopes
What is the genome organisation of ASFV?
- replicates in the cytoplasm, but requires viral DNA replication particularly in the early stages
- it encodes for many proteins which combat the host cell anti-viral response
How is ASFV transmissed?
- The main infection route is oro-nasal (direct or indirect pig feeding)
- It is the only DNA virus that is transmissed by arthropods (soft ticks, ornithodoros erraticus and moubata)
- can also be transmissed via semen
What are the three cycles of ASF transmission?
- Sylvatic cycle in africa (warthogs and bushpigs)
- domestic cycle
- sylvatic cycle in eurasia (wild boar)
What is the distribution of ASF?
- has 23 different genotypes
- 22 are in eastern and southern africa
- one genotype in europe
What is the pathogenesis of ASF?
- enters via the oral-nasal route
- primary replication is in the tonsils and lymph nodes
- primary viremia then follows- it is a virus assocaited with erythrocytes and leukocytes
- generalised infection- has a high virus titre, all infections carry high amounts of the virus
- haemorrhages occur widely
- marked petechaition
What are the clinical signs of peracute/ highly virulent ASF?
- Sudden death with few or no signs
- highly virulent strain
- pigs becomd depressed, stop eating, huddle together
What are the signs of acute/ highly virulent ASF?
- Fever, depression, loss of appetite, weak hind legs
- vomiting diarrhoea
- nose and eye discharge, mucus membranes are red and congested
- abortion may occur in pregnant sows
- any survivor is a virus carrier for life
