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VETM 422 Virology > Lecture 3: General Virology 3 > Flashcards

Lecture 3: General Virology 3 Flashcards

1
Q

Define vial transmisson

A

Virus Transmission: passing of viral infection between hosts (ether naive or susceptible)

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2
Q

Describe the transmission between species of influenza virus

A
  • Bird reservoir with minimal clinic signs
  • Infect domestic poultry and swine from wild birds
  • Infect people from domestic poultry and swine
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3
Q

What is the most important influenza virus type

A
  • Type A is the most important because it infects the most number of species
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4
Q

what are 2 types of transmission

A

vertical
horizontal

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5
Q

What are the mechanisms of vertical transmission? Add examples of diseases and consequences of infection

A
  • Vertical: parent to offspring
    o in utereo: BVDV/Blue tongue/feline parvo
    o birth: canine herpes
    o After birth/milk: CAE/Meadi-visna
    o Causing abortion (PRRS)/congential dz (BVDV/border dz)/congenital defects (akabana virus/blue tongue/feline parvo)
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6
Q

What are horizontal transmission mechanisms

A
  • Horizontal: Between individuals in a population
    o Direct:
    o Indirect:
    o Aerosols:
    o Arthropods:
    o Iatrogenic:
    o Nosocomial:
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7
Q

What are mechanisms of direct viral transmission + examples

A

o Direct: lick/rub/bite (rabies)/ sexual contact (herpes)/abrasions (papilloma)
o Indirect: iatrogenic/fomite

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8
Q

What are mechanisms of aerosol viral transmission + examples

A

o Aerosols: smaller particles travel farther (Marek’s dz)

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9
Q

What are mechanisms of arthropod viral transmission + examples

A

o Arthropods: mosquito (equine encephalitis)/ticks (African swine fever)/culicoides (blue tongue dz)

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10
Q

What are mechanisms of iatrogenic viral transmission + examples

A

o Iatrogenic: non-sterile/poor hygiene (equine infectious anemia/bovine leukemia)

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11
Q

What are mechanisms of nosocomial viral transmission + examples

A

o Nosocomial: canine parvo/calci virus

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12
Q

How is equine encephalitis virus transmitted

A

o Ex. equine encephalitis: equine/humans are dead end hosts – virus cycles between birds and mosquitoes

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13
Q

How is bovine leukemia virus controlled

A

o Ex. bovine leukemia controlled by good hygiene – milk pasteurization/reduce flies/disinfect equipment

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14
Q

Compare features of low and high stability viruses in the environment (with examples)

A
  • Low environmental stability: respiratory transmission, enveloped
    o Except Marek’s dz (wrapped in keratin)
  • High environmental stability: fecal-oral, non-enveloped (adeno/circo viruses)
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15
Q

Compare the stability of viruses in a clinical vs subclinical infection

A
  • Clinical infection = more productive
  • Subclinical infection = better used for dissemination
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16
Q

What are the strategies are used to impact viral survival/stability

A
  • Factors: maintenance of serial infections
    o Acute/self limiting: Transmission affected by population size
    o Persistent infection
    o Vector maintenance
17
Q

What are the features of transmission of a virus that causes acute/self limiting dz (+examples)

A

o Acute/self limiting: Transmission affected by population size
 Virus disappear with recovery + high load during dz
 Require consistent supply of hosts
 Ex. influenza/rota viral diarrhea/infectious bursal dz

18
Q

What are the 3 features of transmission of a virus that causes persistent dz (+examples)

A

 Persistent: clinical dz after years of subclinical shedding (BVDV)
 Chronic: similar to acute initially (high viral shedding) + low level shedding for years after (foot and mouth/feline calcivirus)
 Latent: intermittent shedding without clinical consequence (herpes)
* +/- clinical signs during re-activation
* Cannot detect infection in latent period (no viral protein prod.)

19
Q

What type of strategy does bovine herpes virus use to maintain infection/transmission

A
  • Ex. BVH-1 (bovine herpes) replicated in nasal mucosa – latent in trigeminal ganglia/t cells in tonsils -> stress/low immunity re-activates to create productive infection in primary replication sites
20
Q

What are 3 factors that affect how emerging viral dz develop

A
  • Host: must overcome host defences
  • Environmental change: ecological or human (translocation of virus/vector)
  • Viral determinants: evolution with short generation time/high mutation rate
21
Q

What are some mechanisms viruses evolve slowly/gradually

A

o Variants depend on selective pressure – vary in virulence/tropism
o Antigenic drift: DNA virus (except Pox) use cell proofreading – RNA virus don’t = mutate more
o Higher mutation size = lower genome size
o Quasi species: small variations in virus due to mutation

22
Q

What are some mechanisms viruses uses to evolve quickly

A

o Recombination;
o Reassortment:

23
Q

How do viruses change via recombination + an example

A

o Recombination; 2 viral genomes combine – require co-infection
 Ex. sinbis-like virus + eastern equine encephalitis = western equine encephalitis
 Single stranded RNA or DNA viruses

24
Q

How do viruses change via reassortment + examples

A

o Reassortment: exchange segments of genome
 2 segments: arena/birna
 3 segments: bunyaviridae
 6-8 segments: orthomyzoviridae
 12 segments: Reoviridae

25
Q

What is the mechanism influenza uses to evolve

A

 Influenza A: can do triple reassortment (swine + human + avian = NA swine flu, + euro-asian swine flue = H1N1 )
* HA binds sialic acid receptors on host
* Avian = highest affinity for 2-3 sialic receptors in gut/lung
* Human = affinity for 2-6 sialic receptors in airway
* Quail and pig type viruses have both types of receptors
* Receptor types/affinities can change due to reassortment and antigenic shift (quail/pig)
* Quails and pigs act at ‘mixing pot’ for reassortment – because both types of viruses can enter one cell
* Infected cell will produce both initially infecting viruses + new reassorted virus

26
Q

Briefly explain the genetic interaction you can expect if a
quail is infected with human adapted H1N1 and avian
adapted H6N2 influenza A viruses. (3 marks)

A

mark 1:Quail have a2-3 and a2-6 (human and avian) receptors for influenza.

mark 2: If they infect the same cell, reassortment can occur.

mark 3: If reassortment occurs there will be a novel progeny that is different from the initially infecting parent viruses.

27
Q

Which animal species can act as a mixing
vessel for influenza virus reassortment
A Cattle
B Chicken
C Swine
D Felines
E Bovines

A

C

28
Q

During latency of herpes virus infection, you
may observe
A Virus replication
B Viral protein synthesis
C Mild clinical signs
D Severe clinical signs
E No virus shedding

A

E

29
Q

Can a virus replicate in a target cell with nonfunctional
ribosomes? Briefly explain your answer. (2 marks)

A

No. Viruses rely on host cell machinery to produce viral proteins. Without ribosomes no protein production can occur.

30
Q

What are the consequences (at least 2 points) of mutation in
viral genome? (2 marks)

A

mark 1: A mutation may lead to a new biological variant that

mark 2: The tropism may change. Resulting in the colonization of different host or organs.

mark 3: A change in virulence may occur. It can increase or decrease

mark 4: The virus may be non-viable.

31
Q

What is meant by ‘vertical transmission’? How is this
different from ‘horizontal transmission? (2 marks)

A

Vertical transmission occurs between mother and offspring. It can occur trans-placentally, during birth, or via milk.

Horizontal transmission occurs between individuals in the population at risk. It can be direct or indirectly transmitted for example via airborne aerosols, consumption of milk/meat, nosocomial.

32
Q

What are the 3 types of ‘emerging’ viral dz

A

Types:
* Newly recognized
* Newly evolved
* Increased incidence

VETM 422 Virology (16 decks)

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