Prion diseases

Question 1

What are the general characteristics of TSE diseases?

Answer 1

Long incubation periods, progressive, usually fatal, gives brain spongiform texture, no other signs of infection! (inflammation, fever etc)

Question 2

Describe a prion.

Answer 2

A proteinaceous infective agent - x nucleic acids but can replicate. There are two types - normal and infectious

Question 3

What histological changes are associated with brain tissue in TSEs?

Answer 3

Neuron loss, astrocytic gliosis, aggregates of PrPsc, spongiform changes, vacuolation

Question 4

What is meant by the TSE species barrier?

Answer 4

For prions to cause disease in a separate species to which they originated a VERY large dose of the PrPsc is needed.

Question 5

Describe the clinical signs of Scrapie.

Answer 5

Ataxia, tremors, rubbing/ scratching, loss of condition, death in 1-3 months

Question 6

What is the incubation period for Scrapie infection?

Answer 6

2-5 years

Question 7

Outline the methods of transmission of Scrapie.

Answer 7

Vertical - ewe to lamb. 
Pseudo-vertical - ewe to lamb through infected birth tissues. 
Horizontal - Adult to adult. 
Contaminated land - very resilient. 
Iatrogenic - Needle contamination.

Question 8

Which condons are linked to Scrapie related disease?

Answer 8

136, 154, 171 (AVHQ alleles)

Question 9

Which alleles are considered susceptible to Scrapie?

Answer 9

ARQ, ARH/VRQ, VRQ

Question 10

Which allele combination is considered resistant to Scrapie?

Answer 10

ARR, AHQ/VRQ

Question 11

Outline the national Scrapie control plan.

Answer 11

No cost genotyping within VRQ being culled for non-infected farms.
Infected farms - slaughter of entire flock (and restock) or genotyping of entire flock and culling of VRQ

Question 12

Which gene is involved in Atypical Scrapie? Describe the condition.

Answer 12

NOR98 - abnormal PrPsc distribution, usually around 6.5 years old, usually only single cases

Question 13

What is the average incubation period for BSE?

Answer 13

5 years

Question 14

What is the main method of transmission of BSE?

Answer 14

Oral route - surviving rendering in meat and bone meal

Question 15

What control methods have been used to reduce BSE?

Answer 15

EU-wide ban of feeding processed animal proteins to food-animals (2001)

Question 16

Atypical BSE?

Answer 16

Sporadic cases, low and high MV prions

Question 17

Chronic Wasting Disease is a disease of which species? Why is it considered a potential zoonotic risk?

Answer 17

Deer and Elk (USA) - zoonotic potential is not know. These animals are hunted and could spread disease to human population.

Question 18

Describe the clinical signs associated with CWD.

Answer 18

Reduced condition, away from herd, listless, ataxia, nervous, PUPD, aspiration pneumonia = death

Question 19

What is the incubation period of CWD?

Answer 19

16 months

Question 20

How can CWD be transmitted to other individuals?

Answer 20

Faecal-oral 
Urine
Saliva
Lateral (direct animal-animal)
Shed into the environment