Questions and Answers on TSE in sheep and goats
European Commission - MEMO/03/157 24/07/2003
Brussels, 24 July 2003
Questions and Answers on TSE in sheep and goats
What are Transmissible Spongiform Encephalopathies (TSEs)?
TSEs are a family of diseases occurring in man and animals that are characterised by a degeneration of brain tissue giving a sponge-like appearance. The family includes diseases such as Creutzfeldt Jakob Disease (CJD) in humans, Bovine Spongiform Encephalopathy (BSE) in cattle and scrapie in sheep and goats. While BSE has only recently been identified, scrapie has been known for centuries and on the basis of the available data is not considered to be transmissible to humans nor to pose a risk to man. However EU legislation in place to prevent the spread and transmission of BSE applies also to sheep and to goats as a precautionary measure (eg. removal of specific risk material like brain and spinal cord since 2000, ban of feeding mammalian meat-and-bone-meal to ruminants since 1994).
Is there any evidence or reason to suspect sheep and goats can also have BSE?
BSE has never been found amongst sheep living in the fields. It is known however that sheep were partially fed in UK and elsewhere during the 1980s and early 1990s with feedstuffs containing the same type of contaminated meat and bone meal (MBM) that was responsible for causing the spread of BSE in cattle. This has caused scientists to query whether BSE might also have infected the small ruminant population. The feeding of MBM to ruminants has been forbidden in the EU since 1994 - a total ban of feeding MBM to farmed animals is in place since January 2001. MBM is thought to be the transmission route of BSE if derived from material from infected animals.
It has also been known for some time that a BSE-like disease can be experimentally transmitted to sheep by feeding them material derived from the brains of BSE-affected cows. This artificially produced disease in research trials cannot be distinguished from scrapie by examination of clinical symptoms or by rapid tests on the brains. It can only be distinguished with certainty from scrapie by the use of a mouse bioassay, a testing technique that may take up to two years to complete.
The limited number of mouse bioassays that have been done on natural scrapie cases so far have failed to yield a BSE-like strain, and to date we have no evidence of the existence of BSE in the sheep and goat population under natural conditions. Any new evidence is constantly kept under review by the EU scientific committees.
General facts about tse and sheep and goats
How long do sheep and goats live?
Sheep and goats are ruminants with a short economic life span. Depending on the intended market, most lambs are slaughtered between the ages of three months and a year; there is a limited market for lambs a few weeks old. On average, female sheep and goats are culled between 6 to 7 years of age. The carcasses of these older animals are usually used in meat products for human consumption or in petfood.
How are sheep and goats fed?
Sheep and goats which are kept for the production of milk are commonly fed concentrate rations. It is also common practice to feed concentrates to suckling ewes for a few weeks after lambing. Creep (a feeding system whereby only the lambs and not the older animals can gain access to the concentrate) feeding of early born lambs with a highly palatable ration is also common. In general however there is much less use of concentrate feeds in the sheep and goat industry than in the cattle industry.
What do we know about scrapie?
Scrapie is a TSE affecting goats and sheep. It has been known for almost three centuries. It is assumed that scrapie can be transmitted horizontally, from one animal to another or via environmental routes, or vertically, from ewe to lamb. Young lambs, aged less than twelve months, may develop scrapie, but clinical signs are predominantly in animals aged 2 to 5 years. The clinical signs are repeated rubbing or scratching of the body, changes in behaviour such as depression, excitability or aggression and changes in posture and movement such as trembling and stumbling, leading eventually to death.
Are all sheep and goats equally susceptible to TSEs?
No. Research has shown that some genotypes of sheep are resistant to scrapie, some are rather susceptible, and in between there is a range of genotypes that vary in the level of their resistance to the disease. The ratio of resistant/susceptible genotypes varies from breed to breed. Available research so far has also shown a similar pattern of resistance in sheep to experimentally produced BSE. At the moment, little is known about genotype and resistance in goats.
In which countries do we find TSEs in sheep and goats at present and how common is it?
Scrapie has been found in twelve Member States (Austria, Belgium, Finland, France, Germany, Greece, Ireland, Italy, Netherlands, Sweden, UK and Spain). Denmark, Luxembourg and Portugal have not reported any cases of scrapie. It has been reported in 3 candidate countries Cyprus, Romania and Slovakia.For years, clinical cases of the disease have been regularly diagnosed in the EU by farmers and veterinarians.
However, since 1 January 2002, the Member States have undertaken a major active testing programme to try to discover how common scrapie is in the EU. Results so far reveal that scrapie is more common in sheep and goats than is BSE in cattle. Full results for testing carried out in the EU in 2002 are available at :
Scrapie has been reported in the US, Canada, Brazil and Japan. It is not known to exist in Australia or New Zealand, both major sheep producing countries.
How many sheep and goats are there in the EU, and in each of the Member States?
The number of animals and their progeny is a figure that varies with the time of year (more in spring after lambing) and therefore it is difficult to establish accurate figures. Eurostat figures indicate that there were a total of 90 million sheep and 12 million goats in the EU in 2001, of which there were approximately 65 million breeding ewes and 9 million breeding goats .
Figures for individual Member States, where available, are detailed below:
What scientific advice does the Commission have at present on the subject of BSE in sheep?
The most recent opinions of the Scientific Steering Committee (SSC) on the subject of BSE in small ruminants were adopted in
April 2002: http://ec.europa.eu/food/fs/sc/ssc/out257_en.pdf
updating previous opinions of
October 2001 http://ec.europa.eu/food/fs/sc/ssc/out234_en.pdf
and September 1998 http://ec.europa.eu/food/fs/sc/ssc/out24_en.html
The opinion reaffirms the SSC's view that there is no evidence that BSE is present in small ruminants under field conditions. It issues a range of recommendations in terms of specified risk material, use of rapid tests, individual identification, breeding for resistance, flock certification, and culling measures. It also describes how a combination of approaches might be used to protect public health in the event of BSE being confirmed in small ruminants under field conditions.
Many of these and other SSC recommendations have already been included in legislation by the Commission (see section C on legislation).
What research activities on TSEs are ongoing in the EU?
An update of the inventory of national research activities on TSEs in Europe will be published shortly (this was originally made publicly available in April 2001 in response to a request from the November 2000 Research Council of Ministers). This updated inventory contains details on a wide array of TSE related research activities that are being carried out in most of the Member States, including eight ongoing EC-funded research projects addressing TSEs in sheep directly. Amongst these projects are included a European network for surveillance and control of TSE in small ruminants (with emphasis on epidemiology, pathology and diagnostic tests), another project which monitors the effects of genetically based scrapie control policies in different countries, and a project which will probe the many questions associated with the threat of field infection of small ruminants with BSE. Another project aims to develop the immunocapillary electrophoresis test (ICE) for the detection of TSEs in easily accesible small ruminant tissues and fluids.
In previous years, the results from EU funded projects were provided to the TSE Ad-hoc group to serve as input for the formulation of scientific advice to the Commission. Results from ongoing work will be supplied to the newly established European Food Safety Authority (EFSA) in order to maintain this important link.
Legislation to address tse in sheep and goats
What legislative measures are in place to deal with BSE in sheep and goats?
Notwithstanding the absence of evidence that BSE exists in sheep under natural conditions, much of the legislation that applies to BSE in bovines applies also to sheep. This is a precautionary measure in the light of the unanswered questions over the existence or not of BSE in sheep.
Therefore, for example, legislation such as the ban on feeding of MBM, removal of specific risk material, notification of cases, surveillance measures and trade rules also provide protection against the possible presence of BSE in the sheep population.
The most important are:
What are the current measures to prevent the spread of scrapie?
Regulation 999/2001 on TSEs sets out the rules for intra-EU trade in sheep and goats. Sheep and goats for breeding must come from a holding which is subject to regular veterinary checks, where no case of scrapie has been confirmed for at least three years and where sampling of cull ewes is carried out. Imports must provide equivalent guarantees. From 1 October 2003 extra rules will enter into force (see “What happens to other animals in flocks which have a case of scrapie?”).
Council Directive 92/102/EEC requires identification of sheep and goats leaving a holding of origin by ear tags and tattoos making it possible to trace the animals back to the holding. This is a requirement even for movement within a Member State. A register with an up to date tally of animals on the holding and a record of movements on and off the farm is also a requirement. Some Member States (France, Ireland) have gone beyond the requirements of EU law by introducing an individual identification system for sheep.
Only when the animal goes from one Member State to another is the mark allowed to be changed. In such cases the change from the old to the new mark must be recorded in the register.
The Commission has recently made a proposal to the Council for a new Regulation governing the identification of sheep and goats. Under the proposal, each animal would be individually identified by means of two eartags with the possibility for Member States to authorise electronic means of identification. The identification code of an animal shall remain the same throughout life. The other main elements of this proposal constitutes: 1) registers to be kept up-to-date on each holding recording births, movements and deaths, 2) movement documents to accompany groups of animals throughout any movement, 3) a central register of all sheep and goat holdings in a Member State, and 4) a central computer database to be set up with all sheep and goat holdings and as a second step recording of movements of groups of animals. (see also press release IP/02/1915 from December 2002).
Is it true that some sheep are resistant to scrapie and is anything being done to increase the level of resistance against scrapie of the EU's sheep population?
It has been known for many years that sheep of a certain genetic make-up are more resistant to scrapie than others. The difference lies in the make-up of the gene responsible for the prion protein (the rogue form of which is responsible for causing scrapie). Many factors such as breed of sheep and strain of agent play a part in this resistance. In general, sheep which carry one ARR allele (half-gene) seem to have a raised level of resistance and sheep which carry two ARR alleles (ARR/ARR sheep) appear to be highly resistant to developing the disease, although we do not know if this resistance is absolute.
The Commission and Member State experts have now decided that the time has come to increase the level of resistance in the Community's sheep flock. From 1 January 2004 Member States will be introducing a programme to select for scrapie resistance in their most common sheep breeds. In preparation for this, a survey of the distribution of gentoypes in their purebred sheep populations in each Member State is currently being conducted.
The breeding programme will have the general aim of increasing the level of the ARR allele within the sheep population, while decreasing the level of those alleles contributing to susceptibility to the disease. Safeguards are included to protect rare breeds and breeds with a low natural level of the ARR allele and to prevent the unintended selection of undesirable characteristics. Member States meeting certain criteria can apply to derogate from the programme.
Allied to this programme Member States must, from 1 January 2004 also, introduce a programme to recognise the TSE-resistant status of certain sheep flocks. Level I flocks will be those composed entirely of ARR/ARR sheep. Level II flocks will be those whose lambs are sired exclusively by ARR/ARR rams this means that the lambs are guaranteed to carry at least one ARR allele. This programme is designed to encourage farmers to breed for scrapie resistance and to provide a known source of resistant animals.
Is it not possible that the breeding programme may also select for undesirable features in the sheep population?
So far there is no evidence that breeding for resistance to scrapie produces any serious ill effects in the sheep population, but this is a possibility which the Commission and Member States are well aware must be borne in mind. The legislation contains provisions allowing for a review of the programme should a serious negative effect be demonstrated.
Similarly, the programme is kept under review with relation to scientific research. The Commission has already signalled that it will ask the European Food Safety Authority (EFSA) to assess the results of an experiment in the UK which produced BSE in an ARR/ARR sheep by injecting infected material into the animal's brains, and also a recent suspect scrapie case in an ARR/ARR sheep in Germany. EFSA will be asked to advise on whether these results justify a review of breeding and eradication measures.
What happens to sheep and goats with scrapie?
EU legislation requires that sheep and goats having scrapie cannot enter the food or feed chains. The carcasses of animals which are confirmed to have scrapie must be disposed of by incineration or by landfill following high temperature rendering designed to remove any infectivity.
What happens to the other animals in flocks which have a case of scrapie?
Up to now, it has been left up to each Member State to decide what to do with other animals in infected flocks. From 1 October 2003, however, new EU rules will come into force. All animals in infected goat herds will have to be destroyed. For sheep, Member States will have the choice of destroying all sheep on the holding, or of genotyping the sheep and destroying only the most susceptible ones. There are also rules about the re-introduction of animals to the infected premises.
In conjunction with these new culling rules, it will be permitted for breeding sheep of the ARR/ARR genotype (animals which are considered to be resistant to scrapie) to be traded without restrictions.
As regards imports, sheep and goats imported from third countries will have to fulfil more stringent requirements than previously. They will have to come from flocks that have never reported a case of scrapie unless they are ARR/ARR sheep. Even ARR/ARR sheep must come from a holding that has had no case of scrapie in the previous six months.
Does the EU participate in the financing of scrapie eradication?
Scrapie eradication programmes in the Member States can be co-financed by the EU under Council Decision 90/424/EEC. The first national eradication programmes were co-financed in 1998. For 2002 the Commission is contributing over 4 million Euros to the costs of monitoring, genotyping and eradication measures in the Community.
Surveillance and testing for tse in sheep and goats
Is there systematic surveillance for TSE in sheep and goats?
Yes. Monitoring and passive surveillance of the sheep and goats population for the presence of scrapie has been an EU requirement since 1998. Scrapie is a notifiable animal disease since 1993. Farmers must notify all suspected TSEs in animals to the Member State authorities. Tissues from sheep or goats suspected of suffering from scrapie or any other TSE must be examined in a laboratory. The TSE Regulation also requires Member States to ensure that veterinarians, farmers and relevant staff are familiar with the clinical signs and epidemiology of TSEs and laboratory staff carrying out checks must have competence in interpreting laboratory findings relating to TSEs. All sheep also undergo ante-mortem inspection by a veterinarian before slaughter.
Active surveillance of a sample of healthy slaughter and risk animals over the age of 18 months by using the TSE-rapid test was introduced in January 2002. It utilises the same tests as used for BSE-testing in cattle since those are designed to recognise TSEs (thus including scrapie). The level of testing was greatly increased from 1 April 2002. During 2002, over 370,000 animals were tested.
Results of surveillance for scrapie in sheep and goats in the EU since January 2002 can be found on http://ec.europa.eu/food/fs/bse/testing/bse_results_en.html
Is there a test to distinguish between scrapie and BSE ?
There is no validated rapid test available that is capable of distinguishing BSE in sheep and goats from scrapie. For the moment the mouse bioassay is the only validated test capable of distinguishing the two and it takes up to two years to perform.
However, there are a number of biochemical tests in development, which appear to be able to distinguish between the two diseases. On the recommendation of the Scientific Steering Committee (SSC), the Commission has asked the Community Reference Laboratory (CRL) for TSEs to set up a system whereby routine scrapie positives arising from surveillance in the Member States can be submitted for differential testing using a combination of these tests. Any BSE-like results would then be assessed by a group of experts co-ordinated by the CRL.