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Stackyard News Oct 03
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NSP The National Scrapie Plan (NSP) for Great Britain was launched in July 2001 following recommendations in 1999 from the sheep sub-group of the Spongiform Encephalopathy Advisory Committee (SEAC), writes Dr Richard Warner, scientific adviser with NSPAC.

The NSP is a long-term voluntary initiative to eradicate scrapie (and hence address the theoretical risk of BSE) from the national flock through a programme of selective breeding under which sheep which are genetically susceptible to TSEs are removed over time.

Scrapie is a transmissible and invariably fatal brain disease of sheep that is estimated to cause illness in somewhere between 5-10 000 animals in the GB every year.

Presently the NSP provides a voluntary blood sampling, genotyping and advisory service to the pure-breeding sector. More recently however, the EU has adopted legislation that requires the introduction of compulsory genotype based breeding programmes in all Member States from April 2005. The NSP wishes to encourage as many breeders to join the voluntary schemes in advance of 2005.

The testing process
The central genotyping/ breeding programmes are the NSP Ram Genotyping Schemes. Once the membership contract is authorised, the National Scrapie Plan Administration Centre (NSPAC) agrees dates on which an NSP sampler will visit the holding (usually one visit per year for three years).

Over the period we hope to collect blood samples from all stock rams, and a proportion of that year's ram lamb crop. Precise numbers of animals tested depend on the size of the flock and the proportion of ram lambs/ shearlings sold on for breeding but will not be less than 40 animals per visit.

If the number of male animals available for testing falls below this minimum then we will make up the difference by testing females. Blood samples are sent to our laboratories directly after sampling and we undertake to return genotype results to the breeder within 15 working days.

Sampled animals receive an Electronic Identification (EID) Device in the form of a ruminal bolus. This is a very important aspect of the sampling visit, and allows NSPAC to maintain a traceable link between the animal, blood sample and genotype result.

NSP restrictions on breeding and sale
There is good evidence from field cases and from experimental studies that scrapie infection and disease progression has a strong genetic basis.

The genetic element exists in 5 forms in sheep, defined by a three-letter code. These are ARR, AHQ, ARH, ARQ and VRQ. Broadly, ARR is associated with a low degree of scrapie susceptibility whereas VRQ (and to some extent ARQ) are linked to disease susceptibility. A sheep will inherit two copies of the gene from its parents and the NSPAC two-part result (or "genotype") describes both copies (e.g. ARR/VRQ or ARQ/ARQ). NSPAC have sorted the 15 known genotypes into 5 categories or 'NSP types' defined by the restrictions placed on the use of male animals sampled within the Ram Genotyping Schemes.

No restrictions apply currently to use of females, whatever genotype. Of course several breeds have long-promoted their own genotype based schemes for scrapie resistance, including the Swaledale, and participating flocks should be well positioned when joining the NSP.

The table below shows how the Swaledale classification relates to the genotypes (2-part result) and types employed by the NSP. NSPAC issues genotype certificates for males with results of type 1-3, and for females of type 1 & 2 and breeders are obliged to arrange the slaughter or sterilisation of male animals with type 4 & 5 results. Males with type 3 results, ARQ/ARQ especially, are viewed as having relatively disadvantageous genotypes.

These animals are themselves susceptible and pose the problem that if used for breeding will pass on risk-associated genes to all progeny. However, as type 3s can account for a sizeable proportion of all animals tested (the proportion differs from breed to breed) and can contain breeding animals with desirable performance traits, breeders are permitted to use them for on farm breeding and to sell for a restricted period.

Recently, the time-windows for use and sale have been further extended for hill breeds in response to industry concerns. Results to date The chart above shows the patterns of accumulated NSP genotype results for three breeds - the Texel, Swaledale and Bluefaced Leicester (correct as of start September 2003, both males and females represented).

          Texel       Bluefaced Leicester   Swaledale  
    1   2   3   4   5
NSP Type


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