BSE: Science & research - Atypical scrapie
In Great Britain, scrapie has been known to be present in sheep for more than 200 years. However, following the introduction of new scientific tests, a hitherto unrecognised brain disease belonging to the same family of diseases as scrapie was found in UK sheep. This disease is called atypical scrapie and was first identified in 1998 in Norway. Cases of atypical scrapie have now been identified throughout Europe including the UK, with the earliest known case originating in 1989.
Research on various aspects of atypical scrapie is being undertaken to increase our understanding of this newly characterised disease and to determine whether it poses any risk to human health. Defra is funding research on the following areas:
- Retrospective search for atypical scrapie
- Transmissibility of atypical scrapie in sheep
- PRNP genotypes and atypical scrapie susceptibility
- Atypical scrapie mouse models
Retrospective search for atypical scrapie
One of the key gaps in knowledge is whether atypical scrapie is a new disease or if it has existed for a while but not been detected by previous testing regimes. In 2006 the SEAC Sheep subgroup recommended that a retrospective analysis of historical samples should be conducted to help ascertain whether atypical scrapie is a new disease. Such research, analysing historical samples for atypical scrapie using new tests, is currently underway (projects SE0248, SE0251).
Transmissibility of atypical scrapie in sheep
The transmissibility of atypical scrapie by intracerebral injection and oral inoculation in sheep of various genotypes is currently being investigated. This study includes investigation of whether lymphoreticular tissue from clinical cases of atypical scrapie carry infectivity as determined by mouse bioassay (project SE1847).
PRNP genotypes and atypical scrapie susceptibility
Defra-funded research was conducted to identify whether PrP genotypes (other than the amino acids at position 136, 154 and 171 of the prion protein) influence susceptibility to atypical scrapie infection in the Great Britain (GB) (project SE0240). This study confirmed that phenylalanine (F) at codon 141, increases the susceptibility of the ARQ allele to atypical scrapie in the GB. In addition, genotypes resistant to classical scrapie such as the ARR and ARQ allele were also found to be susceptible to atypical scrapie. Similar findings have been reported from other European countries.
Atypical scrapie mouse models
When atypical scrapie was first recognised, the first priority was to establish if it was an infectious disease. The first research implemented (project SE1850) aimed to determine if the GB cases of atypical scrapie could be transmitted to both conventional wild type mice and also to transgenic mice, which over-express the sheep prion protein (PrPVRQ and PrPARQ). European studies have indicated that atypical scrapie is experimentally transmissible to both wild type and transgenic mice.
Research is also being funded by Defra to compare the transmissibility of atypical scrapie, sheep BSE and classical scrapie to humans using transgenic mice which express the human prion protein (project SE1441).
Links to further information
- Research on atypical scrapie is being funded by a number of organisations within Europe, including the Food Standards Agency.
- In May 2007 advice was sought from the SEAC committee on atypical scrapie research contingency planning.
- In February 2006 the SEAC sheep subgroup published a position statement on atypical scrapie.
- Atypical Scrapie diagnostic research: see TSE Diagnostics: Strain typing.
Page last modified: 14 February, 2008