Variant Creutzfeldt-Jakob disease and the Quebec blood supply

In the mid-1980s bovine spongiform encephalopathy (BSE) was recognized as an emerging prion disease of epidemic proportions in the United Kingdom. In April 1996, researchers in the UK announced that they had identified 11 patients with a new form of spongiform encephalopathy, now called variant Creutzfeldt-Jakob disease (vCJD).(1) Since then, more than 70 definite or probable cases of vCJD have been identified, all of them in the UK, except 1 in Ireland and 3 in France (1 of which has not been officially confirmed).(2) Although definite proof is still lacking, current evidence indicates that these human cases were infected with the same strain of prion that causes BSE. In all likelihood the infections resulted from the ingestion of BSE-contaminated food. Because of the very long incubation period of transmissible spongiform encephalopathies, the true epidemic potential of vCJD in humans exposed to BSE is still unknown.(3) Furthermore, the potential for transmission of vCJD through transfusion has not been defined,(4) simply because the relevant laboratory and epidemiologic data are not yet available for this emerging disease. However, all the available data strongly suggest that classic CJD is not transmissible by transfusion. At the same time as Hema-Quebec implemented the 1-month deferral criterion for travel to the UK, the Canadian Blood Services began deferring donors who had spent 6 months or more in the UK since 1980. Based on the donor survey, this exclusion criterion also translates into about a 3% loss of blood donors for the Canadian Blood Services, similar to the impact of the 1-month criterion for the Quebec donor pool. Therefore, both agencies applied the same rule for defining eligibility, namely, the maximum tolerable impact on the blood supply. Since Quebec donors travel less often to the UK compared with donors elsewhere in Canada, this resulted in a smaller threshold of time spent in the UK for Hema-Quebec donors.