Pox Viruses

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Pox Viruses

• Hugh B. Fackrell
• Fackrel_at_Uwindsor.ca
• poxvirus.ppt

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Pox Viruses

• Structure
• Classification
• Multiplication
• Clinical manifestations
• Epidemiology
• Diagnosis
• Control

Barons Web Site
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Structure

• Brick shaped complex symmetry
• 240nm x 300 nm
• Enveloped
• antibody neutralization sites
• Core contains enzymes for virus uncoating dsDNA
• Inner membrane
• Lateral bodies

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Smallpox virus
negatively stained
Thin section
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Pox Viruses
Canary pox virus
Vaccinia
Orf virus
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Pox Viruses of Vertebrates

• Orthopoxvirus
• smallpox, vaccinia, cowpox, camelpox, mousepox,
  racoonpox
• Parapoxvirus
• ORF( contagious pustuular dermatitis,
  pseudocowpox, bovine papular stomatitis
• Capripoxvirus
• sheeppox, goatpox, lumpy skin disease

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More Pox Viruses

• Avipoxvirus
• Fowlpox
• canarypox,pigeonpox, fowlpox
• Leporipoxvirus
• myxoma, hare fibroma, rabbit fibroma,squirrel
  fibroma
• Suipoxvirus
• Swinepox
• Unclassified
• molluscum contagiosum, Tana, Yaba

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Multiplication

• Attachment
• outer membrane of infectious virion fuses with
  cell membrane
• Penetration
• outer membrane remains with cell membrane
• Uncoating
• yields infectious intracellular virions
• via cellular enzymes
• exposes core proteins
• DNA dependent RNA polymerase

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Clinical manifestations

• Primary localized skin lesion e.g. cowpox
• usually on hand
• occasionally on face or genitals by scratches
• Generalized skin lesions e.g. small pox,
  molluscum
• Encephalitis is rare

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Smallpox pustules
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Burn infected with vaccinia
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Vaccinia complications
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Host Defenses

• unbroken skin represents primary control
• Interferon, nonspecific inflammation
• Cell mediated immunity
• Humoral immunity- outer membrane antigens

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Diagnosis

• Clinical manifestations
• History of animal contact
• Electron microscopy of scab material
• Cell cultures
• Chicken embryos

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Vaccina Cytopathic Effect
Human amnion cell line
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Chick Embryo Lesions
Infected egg
Healthy egg
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Vaccinia lesions on Chorio allantoic membrane
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Cytopathic Effect of Vaccinia
Early Cytopathic effect
Late Cytopathic Effect
Hep 2 cell line
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Smallpox was global
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Human Pox Viruses are acquired from animal
reservoirs
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Control

• infection by zoonotic pox viruses is inevitable
• improved health education
• break link with reservoir
• improved hygiene molluscum contagiosum

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Eradication of Smallpox

• easily diagnosed
• long incubation period
• low communicability no animal reservoir

• effective vaccine- only one serotype
• long term immunity
• high morbidity mortality

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Smallpox Eradication (cont)

• infectious only after incubation period
• no persistent infection
• subclinical infection rare and not a source of
  infections
• no cultural and social barriers
• feasbility of elmination shown in developing
  countries
• save surveillence costs in nonendemic developed
  countries

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Punch 1802 smallpox vaccine
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DONE!!!