Creutzfeldt-Jakob Disease, all types
Reporting Obligations
All confirmed, probable and suspect cases shall be reported to the local Health Unit.
Epidemiology
Aetiologic Agent
The infectious agents associated with CJD are abnormally folded, unique proteins called prions which potentially become a template causing the further conversion of normal proteins.
Clinical Presentation
CJD is a prion disease and part of a group of rare, rapidly progressive, universally fatal neuro-degenerative syndromes that are characterized by neuronal degeneration, spongiform vacuolation in the cerebral gray matter, reactive proliferation of astrocytes and microglia, and accumulation of abnormal misfolded protease-resistant prion protein.
Clinical presentation most commonly manifests as a rapidly progressive syndrome with confusion, behavioural and cognitive abnormalities, dementia, and variable other symptoms such as ataxia and myoclonus.
Classic CJD can be sporadic (sCJD), familial or iatrogenic. It typically presents as a subacute illness in the middle-aged and elderly.
Variant CJD (vCJD) is another category, first described in 1996 and associated with ingesting meat from bovine spongiform encephalopathy (BSE) infected cattle. vCJD has a longer clinical course than sCJD and usually presents with psychiatric or behavioural abnormalities, followed by signs of neurologic dysfunction, usually delayed by several months after the onset of illness.
Modes of Transmission
The mode of transmission for sporadic disease is unknown; some cases of CJD have occurred iatrogenically and some have a genetic component. vCJD is believed to be transmitted by consumption of specific risk materials from BSE-infected cattle. Three cases of vCJD have also been transmitted by blood transfusion.
Incubation Period
Incubation periods in prion diseases can be extremely long and are not applicable to naturally occurring sporadic and genetic cases, since these do not involve exposure to an external source of infection. In iatrogenic cases, the route of exposure influences the length of the incubation period: direct CNS exposure results in an incubation period from 1 to 30 years, while peripheral exposure results in an incubation period of 5 to 42 years. It is estimated that the incubation period for vCJD cases related to exposure of BSE-infected cattle is from 10 to 20 years. vCJD contracted via a transfusion of red cells has an incubation period estimated to be from 6.6 to 8.5 years.
Period of Communicability
Transmissibility and period of communicability varies with disease, tissue involved and stage of disease. CNS and other tissues are infectious throughout symptomatic illness; lymphoid and other organs are probably infectious before signs of illness appear. Blood has been proven infectious in the preclinical phase of vCJD.
Risk Factors/Susceptibility
Genetic differences in susceptibility, resembling those of autosomal dominant traits, have been shown to explain patterns of occurrence of the disease in families.
Diagnosis and Laboratory Testing
NOTE: The CJD Surveillance System (phone 1-888-489-2999) provides support for pathological evaluation (autopsies and biopsies), CSF testing, and genetic testing.
Sporadic Creutzfeldt-Jakob Disease (sCJD)
Confirmed Case:
- Neuropathologically confirmed, with confirmation of protease-resistant prion protein (immunohistochemistry, PET blot, or Western Blot).
Probable Case:
- Rapidly progressive dementia AND
- At least two additional neurological manifestations (See Clinical Evidence) AND
- One of three clinical tests:
- Typical electroencephalography (EEG): generalized bilateral or unilateral triphasic periodic complexes at approximately one per second, lasting continuously for at least 10 seconds.
- MRI with caudate nucleus and/or (anterior) putamen attenuation (preferred sequence DWI or FLAIR).
- Positive assay for 14-3-3 protein in cerebrospinal fluid (CSF) AND total disease duration less than 24 months.
Suspect Case:
- Rapidly progressive dementia AND
- At least two additional neurological manifestations (See Clinical Evidence) AND
- Duration of illness less than 2 years in the absence of a conclusive MRI and 14-3-3 protein assay.
Clinical Evidence:
Additional neurological manifestations include:
- Myoclonus
- Visual or cerebellar disturbances such as ataxia
- Pyramidal or extrapyramidal symptoms
- Akinetic mutism
Treatment and Case Management
There is no specific treatment available. Infected persons as well as their family members should be excluded from donating blood, organs and other body tissues. Investigation of cases is in collaboration the Ministry of Health and Long-Term Care, PHO and the Public Health Agency of Canada.
Additional Resources
Centers for Disease Control and Prevention. “CJD (Creutzfeldt-Jakob Disease, Classic).”
Centers for Disease Control and Prevention. “vCJD (Variant Creutzfeldt-Jakob Disease).”
WHO Guidelines on Tissue infectivity distribution in Transmissible Spongiform Encephalopathies
References
Ministry of Health and Long-Term Care, Infectious Diseases Protocol, 2022.