BSE: Other TSEs - Scrapie
Scrapie is a fatal brain disease (a transmissible spongiform encephalopathy) of sheep and goats. Experimentally scrapie can be transmitted to several other animal species. The disease has been reported in many countries and has been recognised in British sheep flocks since 1732. It is notably absent in Australia and New Zealand.
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The importance of scrapie
Scrapie
is important because it is a significant cause of disease in sheep and
to a lesser extent in goats, but also because it is a Transmissible Spongiform
Encephalopathy (TSE) which is potentially transmissible to humans; to
date there is no evidence that this occurs.
An additional concern in this respect is the possibility of bovine spongiform encephalopathy (BSE) infection occurring in sheep. The clinical signs of scrapie and experimental BSE in sheep are very similar and there is a possibility that BSE in sheep may have occurred but this may have been masked by scrapie. Again, to date, there is no evidence that natural infection of sheep with BSE has occurred. For further information on TSEs see the Spongiform Encephalopathy Advisory Committee website.
Since 1993, by law, any animal suspected of having scrapie must be reported to the local Animal Health Divisional Office (AHDO).
Further information on how to recognise scrapie is given in the leaflet:
Scrapie: Advisory Notes for Farmers 
(287 KB) produced by the Agriculture Departments of Great Britain.
Factors which influence the spread and incidence of scrapie
Scrapie is an infectious disease. Although the nature of the agent which
causes scrapie is not fully understood, and although the way in which
the disease spreads is unclear, it is well established that the scrapie
agent can persist for some years in the environment and that it is relatively
resistant to most disinfectants. In sheep it is suspected that a significant
route of transmission is the ingestion of placental material from infected
ewes at lambing.
There is now also much evidence that clarifies the role of the sheep prion
protein (PrP) gene in conferring susceptibilty or resistance to the development
of scrapie. (This association has not been identified in goats). As a
result, in Britain since July 2001, selective breeding of sheep flocks
to increase resistance to scrapie has been in progress under the National
Scrapie Plan.
Further information on the interplay between sheep genotypes and scrapie including whether resistant genotypes can still carry infection but not develop disease is available at the European Commission Scientific Steering Committee's opinion on 'The policy of breeding and genotyping of sheep.
Clinical signs
In most sheep flocks and goat herds, because clinical signs of disease appear a long time after infection, cases generally appear singly. In such flocks and herds, as the interval between exposure and disease increases, the variability of this interval also increases, so that cases are less likely to occur at the same time. However in some relatively contained flocks, where a high level of exposure occurs, the incidence of disease can be high.
In sheep, scrapie occurs most commonly at about 3½ years of age. The onset is insidious and frequently subtle.
Most sheep show a combination of the following clinical signs. None of these clinical signs in combination or individually are a definite indication of scrapie.
In goats scrapie is similar although goats scratch less against fixed objects but often scratch vigorously with horns or feet.
Skin irritation
- repeated scratching of the flanks and hindquarters against fixed objects
- repeated scratching of the shoulder or ear with a hind foot
- nibbling or grinding teeth when scratching themselves or when rubbed firmly on the back
- nibbling of the feet, legs or other parts of the body
- excessive wool loss or skin damage
Behavioural changes
- excitability
- increased nervousness or fear
- lagging behind
- aggression
- depression or vacant stare
Changes in posture and gait
- incoordination and weakness leading to recumbency
Later clinical signs
- weight loss
- death
Control of scrapie
Methods which reduce the spread of infectious diseases are used in the control of scrapie in some countries. These controls are based on flock certification (ie. knowing which flocks are believed to be affected with scrapie and which are free of scrapie).
On affected premises, movement restrictions, removal of affected animals and use of cleansing and disinfection are employed. In some countries whole or partial flock slaughter is carried out. These methods are employed as appropriate and sometimes in addition to changes in genotypes as indicated above. For a global perspective, see the World Organisation for Animal Health website.
In Britain, current legislation (TSE Regs 2002) provides for removing affected animals. See the section on surveillance and control for further details.
However from 1 October 2003, an EU wide control program was introduced
by EU
Regulation 1915/2003
(111 KB). Where infected animals are identified, this will involve genotyping
of sheep and removal of less resistant genotypes. Goats will be slaughtered.
Further information on this is available from the European
Commission
(193 KB).
This program is designed to reduce the possibility of scrapie infected sheep products entering the human food chain by increasing the resistance of sheep in these affected flocks according to the principles of the National Scrapie Plan (see above).
The National Scrapie Plan Compulsory Flocks Scheme, implementing the EU Regulation 999/2001, was launched on 20 July 2004 in England and Scotland (November 2004 in Wales.)
Scrapie Surveillance
Sheep & Goat Abattoir Guidance: Protocol - specimen copy ( information only).
This sheep and goat abattoir guidance (60 KB) sets out the procedures an abattoir needs to have in place before they can start TSE Surveillance for over 18 month sheep and goats for human consumption.
Research
In addition to work on the role of the PrP genotypes in scrapie susceptibility, a large research effort is being directed at the epidemiology, modes of transmission and diagnosis of TSEs in sheep and goats. See the Medical Research Council website.
Page last reviewed:
1 August, 2007
Page last modified: 23 November, 2006