Topic 16: General features of Viral INFECTIONS

Question 1

What are the general features of viral infections?

Answer 1

Survival of viruses
Infection routes
Factors influencing virus

Question 2

What does the Survival of viruses depend on?

Answer 2

Successful infection
Extent to which they propagate i/w the host
- Localized or generalised

Question 3

Name the Infection routes

Answer 3

Transcutaneous
Airborne
Venereal
Transplacental
Germinative
Latrogenic
Mixed forms

Question 4

What is the TRANSCUTANEOUS Infection route?

Answer 4

Keratinized cells - No virus multiplication
Injuries - papilloma, rabies (bite,lick)
Arthropod/vector -Arbovirus (mosquiuto,tick)
Special - Conjunctiva (herpes)

Question 5

What is the AIRBORN Infection route?

Answer 5

1. Respiratory tract
   - Droplet
   - Aerosol particles
   - UV light
2. Defence systems:
   - Mucosal immunity (IgA, lymph cells)
   - Temperature -33*c =Polymerase activ. slows
3. Respiratory diseases:
   - Rhinovirus

Question 6

What is the VENERAL Infection route?

Answer 6

1. Urogenital tract
   - Sexual intercourse
   - Sensitive viruses also (cell-associated trans)
   = Herpes, Papiloma, Arteri, Retro

Question 7

What is the PEROAL Infection route?

Answer 7

1. Enteric system
   - Oral cavity: Lysozyme
   - Stomach : Acidic PH, Proteolytic enzymes
   - Small intestines: Enzymes + biles
2. Resistant viruses - Mainly non-enveloped
   - Adeno
   - Reo
   - Picorna
   - Astro

Question 8

What is the TRANSPLACENTAL Infection route?

Answer 8

1. Placenta structures -> Dif. barriers
2. Viruses control age/develop of embryo:
   - Resorbtion
   - Tollerance
   - Abortion
3. Virus:
   - Herpes
   - Parvo
   - Flavi

Question 9

What is the GERMINATIVE Infection route?

Answer 9

1. EGGs - Birds
   - On surface of eggs: at hatching egg;
   * Herpes

• Inside egg:
• Circo
• Adeno
• Retro

2. YOLK = immunity

Question 10

What is the LATROGENIC Infection route?

Answer 10

1. By vets!
   - Non sterile equipment
   * Papiloma
   * Flavi

• Needle
• Flavi
• Retro

Question 11

What is the MIXED Infection route?

Answer 11

1. ORONASAL

* Influenza

Question 12

Factors influencing virus

Answer 12

1. Susceptibility
2. Infectibility
3. Amount of viruses
4. Pathogenicity
5. Virulence - Degree of expression