Blood donor restrictiction aims at preventing the transmission of the variant Creutzfeldt-Jakob disease (also known as Mad Cow Disease for a layperson), which is a prion disease that leads to irreversible neurodegeneration. Affected patients present with neurological and psychiatric symptoms and eventually die.
Here some historical background to understand the rational behind the blood donor restrictions:
The first description of the vCJD in human occured in 1996 and was quickly followed by more than 22 others mainly in the UK. Clinical symtoms varied from the previously known sporadic/familial/genetic Creutzfeld-Jakob diseases leading to the definition of a variant Creutzfeldt-Jakob disease. Additionally as most cases reported followed an epidemy of bovine spongiform encephalopathy (BSE) (the animal variant of the disease), a direct link between the diseases (and an animal-human transmission) was made.
The issues and the rational for blood donor restrictions:
- Approximately 50,000 infected cattle are estimated to have entered
the human food chain
- at least five cases of transfusion transmission of vCJD have been reported in the UK
- The limits of 1980 and 1996 have been chosen because the first
descriptions of the BSE have been reported in the 80's. After 1996,
due to strict governmental regulations (such as the prohibition on
ruminant-derived proteins in feeds for all animals and poultry and
the banning of consumption of animals over the age of 30 months) a significant decline in BSE cases was noted, limiting the possibility of an animal-human transmission.
- the current prevalence of vCJD in the originally affected countries is unknown and hence makes it difficult to decide on the best approach. In the UK population some studies have suggested that it might be between 120 to 237 per million inhabitants but those values are highly debated (some suggesting it might be lower)
- the incubation period of vCJD is long to very long (several years to decades) so people who are infected might be asymptomatic at the time they donate blood.
Blood donor restrictions vary between countries, some beeing more restrictive than others according to their respective public health policy.
Brown GH. Variant Creutzfeldt-Jakob disease. UpToDate. Sept 2016. https://www.uptodate.com/contents/variant-creutzfeldt-jakob-disease/print?source=see_link§ionName=Relationship%20with%20BSE&anchor=H3