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Creutzfeldt-Jakob Disease

Epidemiology of Infectious Disease: Creutzfeldt-Jakob Disease

Transmissible spongiform encephalopathies (TSEs) are a family of rare diseases of humans and animals that are characterised by spongy degeneration of the brain and severe and fatal neurological signs and symptoms. They include Creutzfeldt-Jakobdisease (CJD), variant Creutzfeldt-Jakob disease (vCJD) and Kuru.

Creutzfeldt - Jakob disease (CJD)

CJD in it classic form is the commonest of the human TSEs. The majority (85%) of cases of CJD occur sporadically. An estimated 5-15% of cases are due to inherited mutations of the prion protein gene. A smaller percentage of cases, <5% areiatrogenic (resulting from the accidental transmission of the causative agent via contaminated surgical equipment or as a result of corneal or dura mater transplants).

Variant Creutzfeldt - Jakob disease (vCJD)

A new variant of Creutzfeldt-Jakob (vCJD) disease was first recognized in 1996 in the UK. The age distribution for vCJD is younger than for classic CJD. The median age of deaths is around 29 years (range14-74 years) of age compared with 65 years for classic CJD.  

Kuru

Kuru is a disease of certain tribes in Papua New Guinea who traditionally practice cannibalism.

Causal agent
PrP, a prion protein.

Common clinical features
The onset of vCJD is with variable psychiatric symptoms followed by abnormal sensation at 2 months, ataxia at 5 months, myoclonus at 8 months, akinetic mutism at 11 months and death within 12-24 months2.

Epidemiology

  • Classic CJD occurs worldwide but is rare. The annual worldwide incidence is approximately 1 case per million population per year. The risk of CJD increases with age with annual incidence of approximately 2.4 cases per million per year among those aged over 50 years.
  • In the UK there are approximately 35 cases per year of CJD, with an average age of onset of 55-75 years2.
  • It is estimated that between 3,800 and 11,000 people are currently incubating vCJD in the UK2.

Reservoir
Believed to be cattle infected with Bovine spongiform encephalopathy (BSE)1.

Mode of transmission
Unknown - probable consumption of infected bovine neural tissue.

Incubation period
The incubation period for vCJD is unknown but is probably years2. 

Treatment
No specific treatment is available. Treatment is supportive only.

Prevention and control
The national surveillance programme for CJD in the UK was initiated in May 1990. All reported cases of CJD and vCJD are investigated in detail.

References

  1. Heymann D L, editor, Control of Communicable Disease Manual. 18th ed. American Public Health Association; 2004.  
     
  2. Hawker J, Begg N, Blair I, Reintjes R, Weinberg J. Communicable Disease Control Handbook, Blackwell, 2005.

© CM Kirwan 2006