Viral infection and Pathogenesis 1 Flashcards Preview

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Flashcards in Viral infection and Pathogenesis 1 Deck (26)
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1
Q

Methods of breaching the skin to cause infection

A

Abrasion- pox, papilloma
Bite- rabies
Injection- arbo eg west nile

2
Q

Local skin infection eg

A

Papilloma virus -DNA, non enveloped, wide host range
Doesn’t breach BM so no blood supply or imm resp so not elim
Rare to spread towards BM usually spread away as it needs the cell in cell cycle to repl and cells mature and go into cell cycle as they move away from the BM

3
Q

Major GI tract barriers and eg viruses

A

Low pH
Proteases
Bile

Rota, parvo, corona, calici, astro

4
Q

GIT route of transmission

A

Faeces/diarrhoea eg enteric

Saliva in licking, grooming, biting eg herpes and rabies

5
Q

Local gut infection eg

A

Rotavirus rna virus nonenveloped
Infects cells at tips of villi in small intestine that absorb fluid and causes diarrhoea
Villi shorten as preferentialy infects the tips and kills the tip cells which grow back post infection

6
Q

Major resp tract barriers and eg viruses

A

Ciliated epi
Mucous lining
Temp

Influenza, rhino, RSV

7
Q

Local Resp tract infection transmission routes

A

Saliva
Coughs
Sneezes causing airborne droplets

8
Q

Local Resp tract infection influences

A

Less than 5mM persist longer and penetrate deep in lung
Over 5mM cleared from lung
Temp influence as rhinovirus infect cooler regions of upper resp tract whereas RSV infect lower regions of resp tract (warmer regions)

9
Q

Entry into blood system

A

Directly eg via arthropod vector or via lymphatics (common route)

10
Q

Lymphatic spread to blood

A

Virus traverse epi and exposed to tissue macro can enter lymphatic syst
Carried to local lymph nodes and exposed to further macro at each stage virus may be engulfed, degraded and antigens presented to t cells to initiate imm resp, but some viruses repl inside macrophages eg FIPV, canine distemper, maedi-visna causing incr virus output. Some virions will pass straight through the lymphatics into the blood

11
Q

Viremia

A

Presence of virus in the blood. Once in blood can localise to any body part in minutes
Either cell free - FMD, flavi, toga, entero
Or cell assoc; mono (maedi-visna), lympho (CDV), neutro (FeLV), macro (african swine fever)

12
Q

Cells encountered by virus in blood that determine pathogenesis

A

Reticulo-endo cells (eg macro)

Vascular endo cells

13
Q

Virus interaction with RE cells

A

Maybe phagocyt, sestroyed and presented to imm syst (v efficient so viremia only maintained if virions enter blood as quickly as they are removed)
May res phagocyt causing prolonged viremia
Post phagocyt virus could repl in macro causing incr viremia

14
Q

Virus interaction with endo cells

A

Vasc endo is blood-tissue interface and so is barrier for particles eg virions
Parenchymal invasion by virus in most organs dep on localisation of birus in capillary and venule endo cells where barrier is thinnest
Virions can passively transfer accross or may infect endo cells to pass through

15
Q

Mouse pox description

A

Dna virus with several hijacked genes from host cells (key virulence determinants)

16
Q

Mouse pox pathogenesis

A
Virus enters body
Into lymph node (1d)
Into blood
Into spleen and or liver (3-4d)
2o viraemia back into blood
Into skin (6d)
Mild moderate or sever pox lesions appear after 7-11d
17
Q

Nervous system barriers to infection

A

Well protected from entry of blood pros by blood brain barrier and choroid plexus

18
Q

Nervous system infectious methods

A

Infection of endo cells eg some arbo
Dam to bbb allowng virus entry
Entry via leukocytes eg maedi visna
Direct entry into pns and cns via nerves eg rabies, some herpes

19
Q

Rabies infection route

A

Enveloped -ve ssrna
Bite inserts virus which repl in muscle cells
Enters sensory and motor nerve endings and travel via intra axonal transport to cns
Accends bia connecting nerves to the limbic syst where it can cause furious rabies
Also spreads to various other tissues eg salivary gland at this juncture when virus max in sal gland the animal is most aggressive
Continued spread to neocortex causes dumb rabies leading to depression and coma
Death from resp arrest

20
Q

Viral infection of the foetus

A

Many viral infect in dam have no negative impact on foetus but some can cross the placenta to reach foetal circ
Infection in first two trimesters is kist dam with severe cytolytic infect can cause abortion and foetal death (parvo) and sone can have teratogenic effects (BVD)
In 2nd half of pregnancy course of infection can be affected by deving imm syst and can cause viral clearance

21
Q

Viral shedding from skin

A

Only a few shes from skin in a way leadin to transmission
FMD
pox
Some herpes

22
Q

Viral shedding from resp tract

A

Shes in fluid expelled
Small drops evap and remain airborne as small droplet nuclei
Large droplets may fall to the ground and contam fomites
Eg RSV, IBR, paramyxo and some corona shed from both nasal and oral secr

23
Q

Viral shedding from digestive tract

A

Enteric viruses shed in faeces and are gen more res to enviro inact

24
Q

Viral shedding from urogen tract

A

Many shed in urine eg rinderpest, FMD, infectious canine hep

Some shed in semen (STD) eg IBR FMD

25
Q

Viruses shed in milk and colostrum

A

FMD

Visna maedi

26
Q

Viruses transferred via nlood stream

A

By arthropods or vet needles
Mechanical transfer
Eg arbo