Questions and Answers on TSE in sheep and goats
European Commission - MEMO/01/357 07/11/2001
Brussels, 7 November 2001
Questions and Answers on TSE in sheep and goats
What are Transmissible Spongiform Encephalopathies (TSEs)?
TSE 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 (CJD) Disease in human, 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 and to pose a risk to man. However EU legislation in place to protect spread and transmission of BSE applies also to sheep and to goats as a precautionary measure (i.e 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 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
A. General facts about TSE and sheep and goats
How long do sheep and goats live?
Sheep and goats are ruminants mostly 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 thse older animals are usually used in meat products or 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. 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, there little is known about genotype and resistance in goats.
In which countries do we find TSEs in sheep and goats at present?
Scrapie is found in most Member States and in most continents. In ten Member States scrapie has been reported to national authorities (Austria, Belgium, France, Germany, Greece, Ireland, Italy, Netherlands, UK and Spain). Denmark, Luxembourg, Finland, Portugal and Sweden have not reported any cases of scrapie over the past five years.
Scrapie has been reported in US, Canada and Japan. It is not known to exist in Australia or New Zealand, both major sheep producing countries.
The reported incidence of scrapie is, however, very low. Less than 1000 cases were reported in 2000 in a Community sheep and goat population of over 100 million animals. Even allowing for the suspicion that the true incidence is higher and there is underreporting it is clear that scrapie is an uncommon disease.
See table of cases per Member State in Annex 1.
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. Estimates reckon there is a total of 95 million sheep and 12 million goats. Eurostat figures indicate that there were approximately 68 million breeding ewes and 9 million breeding goats in the EU in 2000.
Figures for individual Member States, where available, are detailed below:
B. Scientific Information about TSE in sheep and goats
What scientific advice has the Commission at present on the subject of BSE in sheep?
The most recent opinion of the Scientific Steering Committee (SSC) on the subject of BSE in small ruminants was adopted in October 2001 (http://ec.europa.eu/food/fs/sc/ssc/out234_en.pdf, updating previous opinions of February 2001 (http://ec.europa.eu/food/fs/sc/ssc/out170_en.pdf) and September 1998 (http://ec.europa.eu/food/fs/sc/ssc/out24_en.html). It states that the infection of the sheep population with BSE cannot be excluded but has not been proven to exist in sheep under natural conditions. In the absence of new scientific evidence, the scientists advise to continue to remove a defined list of specified risk materials from the food chain as a precautionary measure to protect consumers. They also recommend additional measures such as improved identification and registration of sheep, increased research efforts to strain-type natural scrapie cases, and the introduction of systematic TSE testing. Alongside these tests, the genotype of the animals tested should be identified in order to ascertain whether specific species of sheep show genetic resistance to TSE.
What research activities on TSEs are ongoing in the EU?
An inventory of national research activities on TSEs in Europe was made publicly available in April 2001 in response to a request from the November 2000 Research Council of Ministers. This inventory contains details on a wide array of TSE related research activities that are being carried out in most of the Member States, including at least nine EC-funded research projects addressing TSEs in sheep.
The results from these projects are being provided to the TSE Ad-hoc group to serve as input for the formulation of scientific advice to the Commission. The specific call for proposals by the Commission on TSE research, with closing date of 18 October, includes among its priority areas the development of in-vivo tests for pre-clinical diagnosis as well as investigation into BSE in sheep and differentiation of BSE from scrapie.
C. 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 which 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?
The Regulation 999/2001 on TSEs sets out the rules for intra-community 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. The Regulation also lays down reinforced rules on monitoring which will take effect from 1 January 2002 (see below).
Council Directive 92/102/EEC requires identification of sheep and goats leaving a holding of origin by ear tags and tattoos allowing 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 Community 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.
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. Some Member States require within the framework of their national scrapie control plans that all other animals on the same holding are also destroyed.
What has been done at Community level to eradicate scrapie?
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 proposing to contribute to the costs of monitoring in all Member States and of slaughter and genotyping measures in some Member States to the tune of over 4 million euros.
D. 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 a Community 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, epidemiology of TSE's and laboratory staff carrying out checks most have competence in interpreting laboratory findings relating to TSEs. All sheep also undergo ante-mortem inspection by a veterinarian before slaughter.
Active surveillance by using the BSE-rapid test will be mandatory from January 2002 onwards. Up to now, a total of 164,000 tests have been required across the EU, although some Member States are considering testing larger numbers. The surveillance will concentrate on healthy stock, fallen stock and clinically suspect animals over the age of 18 months. It will utilise the same tests as used for BSE-testing in cattle since those are designed to recognise TSEs (thus including scrapie).
Is there a test to distinguish between scrapie and BSE ?
There is no rapid test available that is capable of distinguishing BSE in sheep and goats from scrapie. For the moment the mouse bioassay is the only test capable of distinguishing the two and it takes two years to perform. However, the EU is continuing its efforts to encourage the development of validated, rapid tests that can distinguish scrapie from BSE in sheep and goats.
Number of Scrapie cases in Member States
(1)Animals affected by the disease (sick animals + animals that died from the disease). Figures in brackets : flocks affected
(2)Positives in monitoring and testing.Figures in brackets : flocks affected