Viral Pathogenesis

Question 1

What is viral pathogenesis?

Answer 1

The process by which a viral infection leads to disease

Question 2

What is virulence

Answer 2

Harm of a virus compared to a closely related virus

Question 3

T/F - most virus infections are subclinical

Answer 3

True

Its not in the interest of the virus to kill its host!

Question 4

What do consequences of viral infections depend on

Answer 4

Viral
Host
Environment

Question 5

What is the course of viral infection

Answer 5

Primary replication
Systemic spread
Secondary replication

Question 6

What are methods of viral spread

Answer 6

1) Viremia (through blood)

2) Centripedal/centrifugal (through nerves)

Question 7

Acute infections: shedding occurs ____ disease. Detection is possible ___ and ____ clinical signs

Answer 7

shedding with clinical disease

detection possible before and after c/s

Question 8

Possible outcomes of acute infections

Answer 8

Recovery w/o residual effects
Recovery with residual effects
Death
Chronic infections

Question 9

Latent infections: shedding occurs ____ disease. Detection is possible ___ and ____ clinical signs

Answer 9

with clinical disease (so without clinical signs, no shedding)

detection is only possible during clinical signs. when there is no clinical disease, the virus is still in the body just not in target tissues

Question 10

With each outbreak of latent infection, does it become more or less severe

Answer 10

Less - because you already have immunity to it

Question 11

Chronic infections: shedding occurs ____ disease. Detection is possible ___clinical signs

Answer 11

constantly

detection possible before clinical disease

Question 12

Outcomes of latent/chronic infections

Answer 12

• Silent subclinical infection for life
• Long silent period before disease
• Reactivation to acute disease
• Chronic disease with relapses and exacerbations
• Cancer

Question 13

Why is skin difficult for virus to penetrate

Answer 13

Virus needs living cells

Question 14

Ports of viral entry

Answer 14

1. Skin
2. Conjunctiva
3. Resp tract
4. GI tract
5. Genital tract
6. Iatrogenic (needles, etc

Question 15

Which viruses are best at entering via GI tract

Answer 15

Naked viruses (more resilient)

Question 16

What determines whether a viral infection will be localized or spread systemically

Answer 16

The cells that they enter

Cells are polarized - some viruses wont be able to leave basal end of cell. In this case, they cause local infection

If virus can leave basal end, they can cause systemic infection

Question 17

Primary and secondary viremia

Answer 17

Primary: when virus first enters bloodstream after entry
- Low titers

Secondary: after replication in target tissue
- High titers

Question 18

What is secondary replication

Answer 18

Occurs at susceptible organs/tissues after systemic spread

Question 19

What is tropism determined by

Answer 19

• Cell receptor
• Cell transcription factors that recognize promoters and enhancer sequences
• Physical barriers
• Local temperature, pH, oxygen tension enzymes
• Digestive enzymes and bile in GIT

Question 20

Three ways cells can respond to viral infection

Answer 20

No change
Death
Transformation

Question 21

Mechanisms of viral shedding

Answer 21

Respiratory (aerosols, droplets, nasal secretions)
GI (feces, vomit, saliva)
Skin (scabs, vesicles, dander)
Urinary tract
Genital
Milk
Blood, tissues
CNS - no shedding!