Poxviridae Flashcards
Pocks
Caused by small pox (variola) virus
- has now been eradicated
Poxvirus diseases occur in _______
Most animal species
Vaccinia virus
Used as a vector for delivering a wide range of viral antigens
- originally derived from cowpox
Is smallpox completely eradicated?
No, can be used as a biological weapon
What is the largest and most complex family of all viruses?
Poxviruses
What are 2 subfamilies of poxvirus?
- chordopoxvirinae: poxviruses of vertebrates (8 genera)
- entomopoxvirinae: poxviruses of insects
Properties of chordopoxvirinae
Brick-shaped virion, irregular arrangement of tubules on outer membrane
- parapoxvirus: ovoid, regular spiral arrangement of tubules on outer membrane
Components of chordopoxvirinae structure
- core
- lateral bodies
- outer membrane
- sometimes an envelope
Chordopoxvirinae genomic properties
Linear dsDNA genome
- resistant to ambient temperatures, may survive years in dried scabs
- approx 200 genes in the genome
- cytoplasmic replication!!
Orthopoxvirus
Vaccinia virus
Parapoxvirus
Pseudocowpox virus
Capripoxvirus
Sheeppox virus
Suipoxvirus
Swinepox virus
Leporipoxvirus
Infects rabbits, myxoma virus
Avipoxvirus
Fowlpox virus
Molluscipoxvirus
Specific for humans
- molluscum contagiosum virus
Yatapoxvirus
Yaba monkey tumor poxvirus
When does cross-neutralization and cross-protection occur?
Occurs between viruses belonging to the same genus, but not between viruses of different genera
When does genetic recombination occur?
Between viruses of the same genus, but rarely between those of different genera
Poxviruses have ______ immunity
Long term
Do all pox viruses have an envelope?
No
- non enveloped enter via endocytosis –> replication does not overwhelm the host
What facilitates DNA replication?
Early mRNA
What facilitates early transcription factor and structural proteins?
Late mRNA
Entry of poxviruses
Via fusion or endocytosis
- cytoplasmic replication, enveloped particles released by exocytosis, nonenveloped particles released by cell lysis
Are enveloped or noneveloped particles infectious?
Both
All poxvirus infections are associated with ________
Lesions of the skin
Several poxviruses, such as sheeppox, cause _______
Generalized disease throughout the viscera and cause significant mortality
Cell-associated viremia
Leads to localization in the skin and to a lesser extent in internal organs
- found in generalized poxvirus
- can carry the virus without detection by host immune system
Immunity induced by poxviruses
Long immunity
- induced by parapoxviruses is short and reinfection is common
Laboratory diagnosis
- electron microscopic examination
- inoculation of chorioallantoic membrane of chicken embryonated eggs = pocks lesions
- cell cultures
- ELISA
- histology-intracytoplasmatic inclusion bodies
Which methods can not be used for parapoxviruses and molluscum contagiosum virus?
Inoculation of chorioallantoic membrane of chicken-embryonated eggs, and cell cultures
Poxvirus transmission
Direct contact from skin lesions
- contaminated environment (orf)
- droplet infection of the respiratory tract (sheeppox)
- mechanical transmission by insects (swinepox, fowlpox, and myxomatosis)
Vaccinia virus
Numerous, man, cow, buffalo, pig, rabbit
Cowpox virus
Numerous, cow, man, rats, cats, large felines
Monkeypox virus
Numerous, squirrels, prairie dog, monkey, great apes, man
Raccoon poxvirus
Raccoon
35 confirmed human cases of monkeypox have been associated with ________
Prairie dogs
- infected thru contact with Gambian giant rats and dormice
- humans get a vesicular rash
- prairie dogs get bronchopneumonia, conjunctivits, tongue ulceration
What are the 3 parapoxvirus zoonotic diseases?
- pseudocowpox virus: cattle, man
- bovine papular stomatitis virus: cattle, man
- orf virus: sheep, goat, man
Pseudocowpox
Common endemic infection in cattle in most countries
- small papule on the teat, develops into a small, dark red scab
- ring or horseshoe scab
- similar lesions can develop on muzzles
Transmission of pseudocowpox virus
- cross suckling of calves
- contaminated milking machines
- mechanical transmission by flies
Orf
Contagious pustular dermatitis, scabby mouth
- affects muzzle and lips, eyelids, feet, and teats of ewes
- sheep are susceptible to reinfection and chronic infection can occur
- difficult to eradicate
- ewes can be vaccinated with live-virus vaccines before lambing
- short-lived immunity
All parapoxviruses have ________ immunity
Short lived!!
Capripoxvirus genus
- sheeppox virus: sheep, goat
- goatpox virus: goat, sheep
- lumpyskin disease virus: cattle, buffalo
Does capripoxvirus cross protect with orf?
No, do not share common antigens
Suipoxvirus
Swinepox virus
- swine
Leporipoxvirus
Myxoma virus
- rabbits
Avipoxvirus
Fowlpox virus
- chickens, turkey, other birds
Yatapoxvirus
Yaba monkey tumor poxvirus
- monkeys
Fowlpox
Occurred worldwide
- characterized by small papules on the comb, wattles, around beak/feet
- wet pox (diphtheritic) involves infection of mucous membranes of mouth, pharyns, larynx and sometimes trachea
Results of fowlpox
- declines in egg production
- little mortality
- recovered birds are immune
- poultry can be protected by vaccination with pigeonpox
Which genus of poxvirus only induces short term immunity?
Paramyxovirus
How does a poxvirus replicate?
Cytoplasm
What is Variola virus? What is Vaccinia virus?
Smallpox; cowpox derived
Is chicken pox a poxvirus?
No, it is a herpes virus
