11. Lecture

Question 1

how is a successful infection measuredd

Answer 1

Survival of viruses

Question 2

extent of virus propagation in the host organism

Answer 2

• Localized infection (certain tissues, organs)

* Generalized infection (spread by e.g. blood)

Question 3

•Transcutaneous infection

Answer 3

•keratinized cells on the surface – no virus infection
•injuries: papilloma(ketratinized cells as well, rabies (bite)
•arthropod vector – arthropod-borne: arbovirus
→ mosquito, tick, fly, louse
- mechanic vector(transfer only, no multiplication in the vector) – biological vector (multiplication in the vector sometimes, overwinter, transfer to later generations - eggs also infected)
•special: conjunctiva (herpes) in humans

Question 4

Airborne infection

Answer 4

– via the respiratory tract
•droplet infection 
•aerosol particles between 5 and 0.5 μm
•UV light, drying out
•defence systems
•mucosal immunity (IgA, lymphoid cells, alv. macrophage)
•temperature: 33°C – polymerase activity low
•microvilli
•respiratory diseases

Question 5

Oral infection

Answer 5

Via the enteric system:
•oral cavity – lysozyme
•stomach: acidic pH, proteolytic enzymes
•small intestine: digestive enzymes, bile (detergent)
→ resistant viruses (mainly non-enveloped)
-proteolytic enzymes sometimes activate virus receptors!

Question 6

Venereal infection

Answer 6

Via the urogenital tract
•sexual intercourses
•sensitive viruses too
•often cell-associated transmission

Question 7

Transplacental- or intrauterine infection

Answer 7

Via the placenta
• different placenta structures – diff. barriers
• age / development of the embryo!
→ resorption, tolerance, abortion, mummification…

no immune response is developed against viruses - they can be recognized as the body’s own cells

Question 8

Germinative infection

Answer 8

Via the egg (birds)
• on the surface of the egg – at hatching (ie.: herpes)
• inside the egg - inside bird during development
• yolk immunity! (like immunity from placenta)

Question 9

Latrogenic infection

Answer 9

– by veterinarians
• non-sterile equipment (papilloma-, flaviviruses)
• needle, syringe (flavi-, arteri-, retroviruses)

Question 10

Mixed forms

Answer 10

•oronasal - influenza

Question 11

Factors influencing the result of infection: susceptibility

Answer 11

•abortive infection – non pathogenic, not suitable route
→ host spectrum
•stenoxen (one)
•euryxen (multiple)

Question 12

Factors influencing the result of infection: infectivity

Answer 12

•viral receptors, nucleic acid

Question 13

Factors influencing the result of infection: amount of viruses

Answer 13

~chances of successful infection

~capacity of the immune system

Question 14

Factors influencing the result of infection: pathogenicity

Answer 14

•overt disease ↔ adaptation

- interaction btw. virus and host e.g. co-evolution

Question 15

Factors influencing the result of infection: virulence

Answer 15

degree of expression (pathogenicity)

Question 16

types of virus infection: virus multiplication

Answer 16

•effect on the cell
•effect on the host organism
→ course of the disease

Question 17

types of virus infection: parameters

Answer 17

•presence of infectious virions in the host
•intracellular and extracellular
~ virus multiplication
•shedding of infective virions
~spread of the virus in the population
•clinical signs (disease)
•immune response (serum antibodies)

Question 18

acute infection

Answer 18

normalkurve
•Virus multiplication and shedding happen simultaneously
•Clinical signs occur at a certain virus concentration
•Immune response highest after recovery
•Can lead to death
•Can turn into a chronic infection

Question 19

Latent infection

Answer 19

chronic infection
• Acute phase: virus replication, immune response, shedding, clinical signs
• Weak antigens – antireceptor induce low level of antibodies, and decrease further quickly -> body is not protected against infection
• Immune response occur after acute phase but decrease quite quickly, when low a reactivation of the virus can occur

Question 20

tolerated infection

Answer 20

chronic infection
• Usually happen at second trimester of pregnancy -> self recognision phase (which ag’s part of body) -> no reaction against viruses as they are though to be part of the body -> no neutralization -> continous shedding -> constant source of infection in a herd until death
• Clinical signs might be seen during whole life
• Sigmoid curve

Question 21

direct (viruses) and indirect (antibodies) are seen in beginning and later in: tolerated infection

Answer 21

indirect: –
direct: ++

Question 22

direct (viruses) and indirect (antibodies) are seen in beginning and later in: acute infection

Answer 22

indirect: -+
direct: -+

Question 23

direct (viruses) and indirect (antibodies) are seen in beginning and later in: non-infected

Answer 23

indirect: –
direct: –

Question 24

persisting infection

Answer 24

chronic infection
• hidden neutralization antigen
• Acute phase with clinical signs – may lead to death
• If survive virus multiplication and immune response occur whole life, but shedding and clinical signs are seen from time to time
• Shedding even with antibodies in body by hiding at specific places such as CNS, hoof, bladder
• Ig not effective
• hidden virus

Question 25

slow infection

Answer 25

chronic infection, retroviruses, e.g. HIV
• Integration with genome – slow
• Frequent antigenic changes – difficult to clear the viruses from the body

HIV:
• Virus multiplication increasing thoughout life
• Clinical symptoms in older age, infection at young age typically
• Immune response but inefective bc of the destruction of the immune system – new antibody prod as the antigens change
• Shedding here and there at young age, constant at old age
• Prions
- No antigenic prod agains prions -> accumilation in brain -> e.g. changes in behavior or other clinical symptoms depending on where in the brain the infection occur