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=Introduction=
=Introduction=
Poxviruses are among the most easily recognized of all viruses, owing to the lesion by which they have gained their name. Once inside cell, proliferation then lysis, giving way to a characteristic pock with a necrotic center. Poxviruses have risen to fame both for their ability to be eradicated (small pox) as well as their use in fighting other viruses (canarypox vaccines).
=Morphology=
=Morphology=
*Non-structural proteins:
*Non-structural proteins:
**Viral epidermal growth factor, which stimulates cell growth causing the raised edge of pustule
**Viral epidermal growth factor, which stimulates cell growth causing the raised edge of pustule
**Viral tumor necrosis factor, which is non-functioning and acts as an anti-inflammatory by competing with TNF-<alpha>
**Viral tumor necrosis factor, which is non-functioning and acts as an anti-inflammatory by competing with TNF-alpha
**Viral IL-10, which reduces the Th-1 cell mediated response
=Therapeutic Use=
Recombinant Vaccines
*Poxviruses can be used as heat-stable vectors for vaccines against other viruses
*Grown in host cell lines or on the surface of chick chorioallantoic membranes in ovo (primordial ectoderm)
*This was first accomplished by the recombination of cowpox and variola (smallpox) in the creation of the smallpox vaccine (vaccinia)
*More recently, the French used this technique in the creation of the oral rabies vaccine used among the wild fox population:
**Recombinant virus inserts a plasmid encoding rabies gene in place of thymidine kinase gene
*Canarypox vaccines now exist for [[Feline Leukemia Virus (FeLV)|FeLV]] and [[Rabies]]
**Undergoes a single cycle of replication without producing infectious virus in mammals
=Virulence and Pathogenesis=
=Virulence and Pathogenesis=
*Once inside cell, proliferation then lysis, giving way to a characteristic pock with a necrotic center
*Primary replication in abraded squamous epithelium
*Viremia followed by multiple epidermal infections
*Ballooning then necrosis (hydropic degeneration) of epidermal cells
*Concurrent proliferation or adjacent epidermis (GF driven), creating more cells for the virus to infect
*All three result in classical sequence of lesions:
**Papule (proliferation)
**Vesicle (fluid filled)
**Pustule (lesion breaks)
**Scab formation (healing begins)
*Pock center can succumb to secondary infection
*Resolution in 3-4 weeks
*Some poxviruses can spread to the upper respiratory tract or viscera, causing more serious pathology
=Epidemiology=
=Epidemiology=
*Spread quickly in unhygienic circumstances
*Spread quickly in unhygienic circumstances
*Can survive for years in dust
*Can survive for years in dust
=Diagnosis=
*Clinical signs
*Histology
*Electron microscopy
*PCR, IIF
=Types and Subtypes=
=Types and Subtypes=
*[[Cow pox]], which also causes cat pox
*[[Cow pox]], which also causes cat pox
*Small pox (variola)
*Small pox (variola)
*Orf
*[[Orf]]
*Seal pox
*Seal pox
*Pig pox
*Pig pox
*Sheep pox (exotic to EU)
*Sheep/Goat pox (exotic to EU)
*[[Myxomatosis]]
*Myxomatosis
*Fowl pox
*Fowl pox
*Pigeon pox
*Pigeon pox
*Canary pox
*Canary pox
*Ectromelia (mice)
*[[Ectromelia]]
*Camel pox
*Camel pox
*Monkey pox
*Monkey pox
==Parapoxviruses==
==Parapoxviruses==