Pox Viruses

Hugh B. Fackrell

Fackrel@Uwindsor.ca

poxvirus.ppt

Pox Viruses

• Structure

• Classification

• Multiplication

• Clinical manifestations

• Epidemiology

• Diagnosis

• Control

Baron’s Web Site

Structure

• Brick shaped complex symmetry
  • 240nm x 300 nm

• Enveloped
  • antibody neutralization sites

• Core contains enzymes for virus uncoating dsDNA

• Inner membrane

• Lateral bodies

Smallpox virus

negatively stained

Thin section

Pox Viruses

Vaccinia

Canary pox virus

Orf virus

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

More Pox Viruses

• Avipoxvirus

• Fowlpox
  • canarypox,pigeonpox, fowlpox

• Leporipoxvirus
  • myxoma, hare fibroma, rabbit fibroma,squirrel fibroma

• Suipoxvirus
  • Swinepox

• Unclassified
  • molluscum contagiosum, Tana, Yaba

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

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

Smallpox pustules

Burn infected with vaccinia

Vaccinia complications

Host Defenses

• unbroken skin represents primary control

• Interferon, nonspecific inflammation

• Cell mediated immunity

• Humoral immunity- outer membrane antigens

Diagnosis

• Clinical manifestations

• History of animal contact

• Electron microscopy of scab material

• Cell cultures

• Chicken embryos

Vaccina Cytopathic Effect

Human amnion cell line

Chick Embryo Lesions

Infected egg

Healthy egg

Vaccinia lesions on Chorio allantoic membrane

Cytopathic Effect of Vaccinia

Early Cytopathic effect

Late Cytopathic Effect

Hep 2 cell line

Smallpox was global

PPT Slide

Human Pox Viruses are acquired from animal reservoirs

Control

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

• improved hygiene molluscum contagiosum

PPT Slide

Eradication of Smallpox

• easily diagnosed

• long incubation period

• low communicability no animal reservoir

• effective vaccine- only one serotype

• long term immunity

• high morbidity & mortality

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

Punch 1802 smallpox vaccine

DONE!!!