2 - Propagation of viruses I.

Question 1

Aims

Answer 1

• Detect viruses: virology diagnostics
• Large scale production of viruses: virus analytical studies; vaccine production
• Cell parasites: therefore we need living cells for propagation

Question 2

Name the methods for propagation of viruses

Answer 2

1. Inoculation of embryonated eggs
2. Experimental infection of living animals

Question 3

Inoculation of embryonated eggs

Answer 3

• The egg should be:
  
  • Embryonated
  • Specified pathogen free
  • White shelled (easier to see through)
• Before inoculation:
  
  • Disifected (iodine, ethanol)
  • Drill through the shell
• Place of inoculation:
  
  • _​_Site of inoculation:
    
    • Yolk sac (rickettsia, chlamydia - 5-7 day old embryo)
    • Allantoic or amnitoic cavity (Paramyxo - 9-12 day old embryo)
    • Chorionic-allotoic memebrane (Pox, herpes - 10-13 day old embryos)
    • Intravenous inoculation (bluetongue - 16-17 day old embryo)
• Sealing the egg:
  
  • ​By paraffin, glue
    
    • Incubated at 33-37ºC
    • Contro by translumination
  • Egg necroscopy:
    
    • Dwarfism, distortion, death
    • CAM inoculation:
      
      • cause nodules – “Pocks” – size, inflammation, necrosis measured as specific for virus detection
    • Hemagglutination test with allatoic fluid

Question 4

Experimental infection of living animals

Answer 4

• Decreasing importance due to animal welfare and costs
• Diagnostic approach:
  
  • Rabies, african horse sickness, arboviruses:
    
    • ​Intracerebral inoculation of suckling mice (get blood from infected humans to check for rabies)
  • Classical swine fever: african swine fever differentiation:
    
    • Non vaccinated and classical swine fever vaccinated pigs are infected to check if Classic or African swine fever
• Vaccine production:
  
  • Rabbit hemorrhagic disease: experimentally infected
  • Classical swine fever: vaccine strain
• Vaccine control: harmless and efficient