Poxviridae Flashcards
Poxviridae is the
largest virus (oval brick shape) of dsDNA
- enveloped however breaks a lot of rules
- can survive in environment
What makes poxviridae unusal?
- It is the only DNA virus to replicate in the cytoplasm (cytoplasmic inclusion bodies)
- released from cells by budding rather than lysis
- considerable serological cross-reactivity within genus
Orthopoxvirus
- Smallpox
- Vaccinia
- cowpox
- camelpox
- mousepox
Parapoxvirus
- Orf
- pseudocowpox
- bovine popular stomatitis virus
- crocodile and caiman poc
Orf
Scabby mouth; eyelids, lower legs teats
- lesions of muzzle and lp
Pseudocowpox
- horshoe or ring scab on teats
Capripoxvirus
- sheeppox and goatpox
- Neethling virus
- Swinepox
Sheeppox and goatpox
- viraemia
- exotic to Oz
Neethling virus
- Lumpy Skin Disease Virus (LSDV) in cattle
Suipoxvirus- Swinepox
- mild skin lesions in pigs, sporadic outbreaks
Leporipoxvirus
Myxomavirus: myxomatosis
- biological rabbit control
- swelling and fever- viraemia
- spread through biting arthropods
Avipoxvirus
Fowlpox
- papules on comb, wattle and around beak (drypox)
- mucous membrane of mouth, pharynx and trachea (wetpox)
- serious disease of poultry in aus
Pathogenesis of poxviruses
- contagious
Poxviruses are spread between animals by:
- Small abrasions (direct contact, indirect from contaminated environments or fomites. biting arthropods)
- Aerosols (droplets infected by respiratory route)
All poxviruses cause
SKIN LESIONS
Virions are relseased via
- Enveloped virions –> budding
- Non-enveloped virions –> exocytosis or cell lysis
- cellular and humoral immunity important
For most enveloped viruses, what type of vaccines are required?
Live vaccines
Diagnostics of poxviruses
- clinical appearance
- histopathology
- isolation of virus in cell culture
- PCR
- EM
Myxoma virus
Fatality rate was 99% dropped to 50% due to genetic resistant population pools. So RHDV released as another biological control
Pathogenesis myxomatosis
- Virus is transmitted between animals mechanically on mouthparts of mosquitoes and fleas
- Virus replicates on skin then goes to lymph nodes and then viraemia is mainly cell associated
Myxomatosis vaccination
- only for commercial and lab rabbits
- live modified vaccine; fear this will enter feral population and reduce overall efficacy of virus as biological control
- not permitted for pet rabbits
Myxomatosis ectoparasite control
- co proofing ntrol of flea infestation and insect
Scabby mouth (Orf)
- sheep and goats
- mostly young
- pustular dermatitis; contagious, lip and muzzle scabs
- zoonotic
Scabby mouth epidemiology
- direct and indirect contact
- stable in dry env
- scabs `is rich infectious source- virus can survive years in scab material
- requires skin abrasions
Predisposing factors of scabby mouth
- contaminated feed, communal feed trough
- rough forage
- overcrowding and stress
- hygiene
Pathogenesis of scabby mouth
- Popular lesion–> vesicles–> pustules–> scabs
- death only occurs due to starvation
- heals usually in 4 weeks
scabby mouth immunity
- can be infected again however lesions less severe and heal more rapidly
- humoral and cell mediated needed
Scabby mouth diagnosis
- clinical lesions
- EM for evidence of virus in scabs
Scabby mouth treatment control
- no specific treatment Vaccine: if endemic - given 8 weeks prior to lambing - prior to marking/docking/mulsing - Enhanced hygiene, disinfect - isolation of suspect cases - cull chronics - quarantine new arrvals - screening - avoid course feed
What can be done to reduce scabby mouth risk in live animal export?
- vaccinate 4-8 weeks prior to boarding
- enhance screening and surveillance prior to boarding; on farm or in holding facilities prior to boarding
- reduce numbers/stocking density per ship load
