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Infectious Diseases > Transmissible Spongiform Encephalopathies > Flashcards

Transmissible Spongiform Encephalopathies Flashcards

1
Q

What is TSE in sheep?

A

Scrapie

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2
Q

What is TSE in cattle?

A

BSE

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3
Q

What is TSE in deer?

A

CWD
chronic wasting disease

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4
Q

What is TSE in humans?

A

variant Creutzfelt-Jakob disease

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5
Q

What causes TSE?

A

*PRP - protease resistant protein
*PRPc + PRPsc = identical amino acid sequence but different tertiary structure
*PRPsc converts PRPc into itself - PRPsc is partially resistant to digestion + accumulates = disease + death

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6
Q

What are the characteristics of TSE?

A
  • Long incubation period
  • Progressive and invariably fatal
  • Holes in brain give spongiform texture
  • No signs of fever
  • No signs of inflammation
  • No antibody response
  • No signs of a pathogen with a genome
  • No sign of infection
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7
Q

What are the clinical signs of scrapie?

A

*Ataxia
*Tremors
*Rubbing / scratching
*Loss of condition
*Death in 1-3 months

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8
Q

What is the incubation period of scrapie?

A

2-5 years

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9
Q

How can sheep catch scrapie?

A

*Vertical
*Pseudo-vertical
*Horizontal
*Contaminated land
*Iatrogenic

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10
Q

How does Vertical transmission of scrapie occur?

A

Mother to offspring
*in utero

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11
Q

How does Pseudo-vertical transmission of scrapie occur?

A

Parent to offspring
*Lambs infected at birth - from infected birth tissues

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12
Q

How does horizontal transmission of scrapie occur?

A

Adult to adult / lamb
*Infected sheep spread infection to naive adult sheep in same flock

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13
Q

How does contaminated land transmission of scrapie occur?

A

Sheep catch scrapie on land where infected sheep used to live - decades before

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14
Q

How does Iatrogenic transmission of scrapie occur?

A

Needle contamination

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15
Q

What are the important PrP alleles in
UK sheep?
What codons are disease linked with scrapie?

A

*ARR - resistance
*AHQ - resistance with VRQ
*ARQ - susceptibility
*ARH - susceptibility with VRQ
*VRQ - susceptibility
Codons = 136, 154 + 171
(ARR = Alanine coded at 136, aRginine coded at 154 + 171)

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16
Q

What is the highest risk genotype?

A

VRQ/VRQ
most cases = ARQ/VRQ - common genotype

17
Q

What are the clinical signs of BSE?

A

*Ataxia
*Nervous / aggressive behaviour
*Loss of condition
*Death in 1-6months

18
Q

What is the incubation period of BSE?

A

5 years or more

19
Q

What is the most common transmission route of BSE?

A

Oral route

20
Q

Why were dairy cattle more predisposed to BSE?

A

Ate more ‘meat + bone meal’ (MBM)

21
Q

What were the BSE controls to prevent transmission?

A
  • 1988: ban on the use of ruminant-derived protein in ruminant feedstuffs; aka “The Ban”
  • 1990: ban on the use of Specified Bovine Offals in all animal feed (including pet food) in GB
    *1994: ban on the use of mammalian protein in ruminant feed stuffs;
  • 1996: prohibited the feeding of mammalian Meat and Bone
    Meal (MBM) to all farmed livestock including fish and horses; aka “The Real Ban”
  • 2001: Europe-wide ban on the feeding of processed animal protein to food-animals.
22
Q

What were the BSE controls to prevent risk to consumers?

A
  • Specified risk material control – remove parts of animal most likely to contain BSE from food chain
  • Removed brain and spinal cord [brain was often used as thickener – cheaper than eggs!]
  • Later, removed beef-on-the-bone
  • Ban on ‘mechanically-recovered meat’ from rendering plants
  • Used in burgers, sausages, pies and mince
  • Over 30 months rule – no cattle to enter food chain if over 30 months old
23
Q

What is the only naturally transmitted TSE?

A

Chronic wasting disease in deer
CWD

24
Q

What is the incubation period of CWD?

A

16 months

25
Q

What are the clinical signs of CWD?

A

*Loss of condition
*Standing apart from herd
*Listlessness
*Ataxia
*Nervousness
*Excessive drinking + urination

26
Q

What is a common cause of death of CWD?

A

Aspiration penumonia

27
Q

How is CWD transmitted?

A

Urine + saliva infectious
= deer shed infectious prions ono herbage which is the eaten by other deer

28
Q

What are the clinical signs of vCJD?

A
  • psychiatric: depression, anxiety, delusions, hallucinations;
  • Neurological: ataxia, chorea (dance-like motion of twisting & turning), myoclonus (involuntary muscle spasm), dementia
29
Q

How was human to human transmission of vCJD reduced?

A
  • Restrictions on use of UK blood for transfusions
  • Disposable surgical equipment
  • Non-sharing of contact lenses

Infectious Diseases (20 decks)

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