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ARCHIVED - Infectious Diseases News Brief - March 11, 2011

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Variant Creutzfeldt-Jakob Disease in a Canadian resident

Canadian Creutzfeldt-Jakob Disease Surveillance System, National Microbiology Laboratory, Public Health Agency of Canada

Working closely with Canadian clinical specialists, the Public Health Agency of Canada’s Creutzfeldt-Jakob Disease Surveillance System (CJDSS) has identified a probable case of variant Creutzfeldt-Jakob disease (variant CJD, also called vCJD) in a Canadian resident. The diagnosis is supported by several lines of clinical, paraclinical and laboratory evidence, in keeping with internationally accepted surveillance case definitions for human prion disease.(Footnote 1, Footnote 2) This is the second case of variant CJD reported in Canada to date. The first such case occurred in 2002, in an individual who is believed to have contracted the disease outside of Canada.(Footnote 3) As explained in more detail below, evidence to date strongly indicates that (i) the risk exposure in the second case also occurred outside Canada; (ii) there are no negative implications for the safety of the Canadian food supply; and (iii) the case poses no secondary risks to the health of Canadians.

Variant CJD belongs to a group of rare, fatal degenerative brain disorders called prion diseases that affect humans and animals and can arise sporadically, genetically, or through infectious transmission.(Footnote 4) Prion diseases are marked by brain tissue vacuolation (spongiform change), neuronal loss, and presence of a pathologically altered form of a host-encoded glycoprotein, PrP, that is considered to constitute the transmissible agent, or prion.(Footnote 5) Among classic types of human prion disease, the most common and widespread is sporadic CJD, which occurs without an apparent infectious or genetic cause mostly in persons 50+ years of age and accounts for 80–90% of the remarkably uniform annual prion disease mortality of ~1–2 per million population.(Footnote 6) Most of the remaining 10–20% of classic human prion diseases are caused by mutations in the PRNP gene that encodes PrP.(Footnote 7) Fewer than 1% of classic cases of CJD are attributed to accidental transmission through surgical and medical procedures such as dura mater grafts, and use of therapeutic hormone preparations that were derived from prion-contaminated cadaveric pituitary tissue.(Footnote 8)

Variant CJD is the only known zoonotic human prion disease, resulting from dietary exposure to a feedborne prion disease of cattle, bovine spongiform encephalopathy (BSE, also known as “mad cow disease”), that emerged internationally in the 1980s and 1990s.(Footnote 9) Most human exposure to BSE is thought to have occurred before regulatory controls were implemented to control BSE in animals and to eliminate the inclusion of high-risk bovine tissues in human food.(Footnote 10) A small number of secondary cases of variant CJD have also been linked to transfusion of fresh blood components (erythrocytes) from pre-symptomatic donors who later developed the disease.(Footnote 11) By October 2010, a total of 222 definite and probable variant CJD cases had been reported worldwide in residents of 12 countries.(Footnote 12) The total numbers of clinical cases of variant CJD that will ultimately emerge remains uncertain, as does the frequency of long-term asymptomatic carriage during which apparently healthy individuals could transmit infection for example through blood donation or invasive medical procedures.(Footnote 13)

Importantly, based on extensive interviews with family members there is no indication that the current patient was ever a blood donor, received a blood transfusion, or underwent a surgical procedure that was not managed to prevent prion transmission as per the Public Health Agency of Canada’s CJD Infection Control Guidelines.(Footnote 14) This indicates the absence of secondary risks to the health of Canadians as a result of this case. Health Canada issued directives to Canadian blood operators in 1999, 2000, 2001 and 2005, requiring deferral of blood donors with a history of residence and/or travel in the United Kingdom (UK), France and Western Europe in the period 1980-1996, as well as other criteria including receipt of blood transfusion in the UK, and has committed to review these deferral policies if new scientific information becomes available. Canada has also reported a small number of cases of BSE,(Footnote 15) and Health Canada and the Canadian Food Inspection Agency have implemented regulations to prevent both the transmission of BSE in animal populations and human exposure to it. Given (i) these protective measures, (ii) the observation that acquired prion diseases have long incubation periods (years to often a decade or more), and (iii) the fact that the current patient experienced onset of symptoms just prior to immigrating to Canada in early 2010, the possibility of BSE exposure in this country can essentially be ruled out as the cause of illness. The patient was born in the Middle East, and also resided in several other countries before arriving in Canada. Apart from a few visits totalling less than three months in duration, there was no history of travel to the UK or Europe.

In Canada, all human prion diseases are both legally reportable at the provincial/territorial level and nationally notifiable, and despite their rarity the public health importance and economic impacts of these diseases have maintained a need for timely diagnosis, reporting, and surveillance. To help meet these requirements the CJDSS has conducted prospective national surveillance of human prion diseases continuously since 1998, and working collaboratively with a network of health professionals sponsors detailed diagnostic and epidemiologic investigation of any suspected case of human prion disease in Canada. Supporting laboratory services are provided for autopsy, neuropathologic examination, molecular genetics, and biochemical testing for 14-3-3 protein in cerebrospinal fluid. Test results are reported directly to referring health professionals, with CJDSS case files maintained centrally to facilitate diagnostic assessment and final case classification. Full patient enrolment with the CJDSS takes place with written informed consent. The CJDSS surveillance protocol has been approved by the Health Canada Research Ethics Board (Certificate REB-2009-0036), and by numerous REBs at collaborating healthcare institutions. For further information on human prion diseases, available services and how to access them, interested health professionals are invited to contact the CJDSS toll-free, at 1-888-489-2999.

References

Footnote 1
World Health Organization (WHO). WHO manual for surveillance of human transmissible spongiform encephalopathies including variant Creutzfeldt-Jakob disease. 2003. (PDF document)External Link
Footnote 2
Heath CA, Cooper SA, Murray K et al. Validation of diagnostic criteria for variant Creutzfeldt-Jakob disease. Ann Neurol 2010;67(6):761-770.
Footnote 3
Jansen GH, Voll CL, Robinson CA et al. First case of variant Creutzfeldt-Jakob disease in Canada. Can Commun Dis Rep 2003;29(13):117-120.
Footnote 4
Aguzzi A, Calella AM. Prions: protein aggregation and infectious diseases. Physiol Rev 2009;89(4):1105-1152.
Footnote 5
Prusiner SB. Prions. Proc Natl Acad Sci USA 1998;95(23):13363-13383.
Footnote 6
Ladogana A, Puopolo M, Croes EA et al. Mortality from Creutzfeldt-Jakob disease and related disorders in Europe, Australia, and Canada. Neurology 2005;64(9):1586-1591.
Footnote 7
Kovacs GG, Puopolo M, Ladogana A et al. Genetic prion disease: the EUROCJD experience. Hum Genet 2005;118(2):166-174.
Footnote 8
Brown P, Brandel JP, Preece M et al. Iatrogenic Creutzfeldt-Jakob disease: The waning of an era. Neurology 2006;67(3):389-393.
Footnote 9
Bradley R, Collee JG, Liberski PP. Variant CJD (vCJD) and bovine spongiform encephalopathy (BSE): 10 and 20 years on: Part 1. Folia Neuropathol 2006;44(2):93-101.
Footnote 10
Collee JG, Bradley R, Liberski PP. Variant CJD (vCJD) and bovine spongiform encephalopathy (BSE): 10 and 20 years on: Part 2. Folia Neuropathol 2006;44(2):102-110.
Footnote 11
Lefrere JJ, Hewitt P. From mad cows to sensible blood transfusion: the risk of prion transmission by labile blood components in the United Kingdom and in France. Transfusion 2009;49(4):797-812.
Footnote 12
European Creutzfeldt-Jakob Disease Surveillance Network. vCJD cases worldwide.External Link
Footnote 13
de Marco MF, Linehan J, Gill ON et al. Large-scale immunohistochemical examination for lymphoreticular prion protein in tonsil specimens collected in Britain. J Pathol 2010;222(4):380-387.
Footnote 14
Public Health Agency of Canada. Infection control guidelines: classic Creutzfeldt-Jakob disease in Canada. Can Commun Dis Rep 2002;28S5:1-110.
Footnote 15
Canadian Food Inspection Agency. BSE in North America.External Link