Chain of Infection: vCJD

Question 1

Why is vCJD relevant to dentistry?

Answer 1

• strange pathogen
  
  • cross infection and sterilisation rules don’t apply
• evidence of surgical transmission
  
  • currently no evidence of dental based transmission
• difficult to clean and kill
• impact of instrument decontamination services

Question 2

What are the 6 links in the chain of infection?

Answer 2

1. infectious agent
2. reservoir
3. portal of exit
4. transmission
5. portal of entry
6. susceptible hosts

Question 3

What is the infectious agent in vCJD?

Answer 3

• prion protein
  
  • devoid of nucleic acid
    
    • contains beta pleated sheet

Question 4

What are the 3 types of prion disease?

Answer 4

1. infectious
   
   • transmitted from person to person
     
     • contaminated surgical instruments
2. genetic
3. sporadic
   
   • unsure of triggers

Question 5

How do prions cause disease?

Answer 5

• accumulation of an abnormal form of a natural protein
  
  • difficult to detect
    
    • no antibodies
    • no cell mediated immune response

Question 6

How do prions reproduce?

Answer 6

• corrupts template of normal prion protein
  
  • chain reaction
  • increased number of abnormal prion proteins
• function of different cell types affected
  
  • especially neurological
    
    • spongiform appearance of brain

Question 7

What is the reservoir of vCJD?

Answer 7

• cattle
  
  • cross transmission
  • bovine spongiform encephalopathy epidemic
• human carriers
  
  • disease is rare but infection is common

Question 8

What are the possible portals of exit of vCJD?

Answer 8

• brain, spinal cord, spinal/cranial ganglia
• optic nerve and retina
• appendix, tonsil, spleen

Question 9

Where can vCJD be found in the oral cavity?

Answer 9

• trigemical ganglion
• alveolar nerve
• tongue

Question 10

Which oral tissues can become infective with vCJD?

Answer 10

• gingival margin
  
  • shown highest level of infectivity

Question 11

Who are the susceptible hosts to vCJD?

Answer 11

• genetic predisposition
  
  • methionine methionine amino acid
    - almost all cases have this gene code

Question 12

Why are there so few clinical cases of vCJD?

Answer 12

• significant species barrier
  
  • rare exposure to significant dose
• non-PRNP genetic determinants
  
  • restricted susceptible population
• co-factors enhancing chance of infection
  
  • inflammatory bowel disease
• genetic heterogeneity
  
  • longer incubation period
  • lower susceptibility to infection

Question 13

Is it safe to treat patients with vCJD in practice?

Answer 13

• yes
  
  • dispose of instruments involved in high risk tissues
    
    • incineration
  • reprocess instruments involved with low/medium risk tissues