Scrapie: no evidence of threat to humans under real-life conditions
Recent scientific evidence reviewed by EFSA does not change the conclusion of a 2011 ECDC-EFSA joint scientific opinion: there is no scientific proof that Classical scrapie can be transmitted from animals to humans under real-life conditions.
A new study reviewed by EFSA shows that under laboratory conditions Classical scrapie could be transmitted from sheep to mice whose genes have been modified to resemble human genes. This transmission caused a disease similar to sporadic CJD, or “sCJD”, which is a form of Creutzfeldt-Jakob Disease.
CJD is a transmissible spongiform encephalopathy (TSE) affecting humans. Various forms of CJD are recognised: sporadic CJD is the most common and its origin is uncertain; variant CJD was identified in the 1990s and is closely linked to exposure – probably through food – to the cattle disease bovine spongiform encephalopathy (BSE).
In their review, EFSA’s experts praise the robustness of the study but conclude that current scientific knowledge does not change the Authority’s previous scientific advice.
EFSA’s experts also conclude that it is not possible to assess scrapie-related public health risks from the consumption of sheep-derived food products.
They highlight that current scientific knowledge on scrapie is limited, e.g. information is lacking on the variability of different strains, their geographical distribution and how they may affect potential crossover to other species.
Scrapie affects sheep and goats and comes in two variants. Classical scrapie is transmitted through exposure to scrapie-infected animals (e.g. via placentae or milk) and their environment. Scientific evidence suggests that Atypical scrapie, the second variant, is spontaneous and non-contagious. In this opinion EFSA experts have considered both variants, with a particular focus on Classical scrapie, which is the topic of the study under review.
- The European Commission asked EFSA to review the article titled ‘Evidence for zoonotic potential of ovine scrapie prions’, published by Cassard et al. in the scientific journal Nature Communications on 16 December 2014.
- Transmissible spongiform encephalopathies (TSE) or so-called prion diseases are a family of diseases that affect the brain and nervous system of humans and animals. Animal TSE include Classical BSE and Atypical (L-type and H-type) BSE, Classical and Atypical scrapie, Chronic Wasting Disease and Transmissible Mink Encephalopathy.