17 - Types of viral infections

Question 1

What does virus multiplication effect?

Answer 1

• Effect on the cell
• Effect on the host organism

→ Course of the disease

Question 2

Parameters of viral infection

Answer 2

• Presence of infectious virions in the host
  
  • Intracellular (10%) and extracellular (90%)
  • Leads to viral multiplication
• Shredding of infective virions
  
  • Leads to spreading of the virus in the population
• Clinical signs (disease)
• Immune response (serum antibodies)

Question 3

List the different types of viral infections

Answer 3

1. Acute infection
2. Latent infection
3. Tolerated infection
4. Persisting infection
5. Slow infection

Question 4

1. Acute infection

Answer 4

• Example:
  
  • Parvoenteritis
  • Influenza
• Outcome:
  
  • Recovery
  • Death
  • Chronic infection

Question 5

2. Latent infection

Answer 5

• Chronic infection
• Example:
  
  • Aujeszky’s disease
  • Herpes simplex
• Phases:
  
  • Acute phase
  • Latent phase
  • Reactivation
    
    • Immunosuppression

Question 6

3. Tolerated infection

Answer 6

• Chronic infection
• Example:
  
  • Bovine Viral Diarrhea (BVD)
  • Rubella
• Occurs during pregnancy:
  
  • Occurs during the 2^nd trimester of pregnancey, which is a self recognition phase
  • Virus antigen is regarded as own → no immune response → continous shedding

Question 7

4. Persisting infection

Answer 7

• Chronic infection
• Exampel: african swine fever
• Hidden neutralizing antigen, so Ig is not effective → immunocomplex deposition
• Hidden viruses:
  
  • Equine arteritis (in stallion venereal tract)
  • Foot and mout disease (in lymphoid tissue)
  • Canine distemper (in CNS)

Question 8

5. Slow infections

Answer 8

• Chronic infection

1. From *retroviruses*
   
   • ​Examples:
     
     • Eqine anemia
     • HIV
   • Integration into the genome
   • Antigenic changes
   • Destruction of the immune system
2. From *prions*
   
   • Not immunogenic
   • Usually no shedding in living animals