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From: TSS ()
Subject: SEAC Subgroups - SEAC Sheep subgroup statement
Date: July 30, 2005 at 6:45 am PST

SEAC Subgroups


SEAC Epidemiology Subgroup
Membership of the SEAC Epidemiology Subgroup
SEAC Sheep Subgroup
SEAC ad hoc Epidemiology Subgroup on UK BARB cases
Membership of the SEAC ad hoc Epidemiology Subgroup on UK BARB cases

The Chairman of SEAC can authorise the setting up of ad hoc subgroups to discharge specific tasks. Subgroups have clear terms of reference and are required to report to the main Committee. There is considerable flexibility about how subgroups are set up, depending on the issue in question. Expanded use of subgroups, as recommended in the 2002 SEAC Review, allows the Committee to delegate initial consideration of some of the highly specialised issues which require a substantial input from experts not on the main Committee.

SEAC Epidemiology Subgroup
The CJD Epidemiology Subgroup has been disbanded and reconvened as the SEAC Epidemiology Subgroup with new terms of reference to cover both the animal and human epidemiology of prion diseases. Its terms of reference are:

To report to SEAC on the significance of emerging and published epidemiological data about human and animal TSEs, and on such specific epidemiological questions as SEAC refers to it for advice.

The Subgroup meets on an ad hoc basis. After meetings the Chair of the Subgroup reports to SEAC. A report was given at SEAC 88; draft minutes of SEAC 88 (217 KB) are now available.

Membership of the SEAC Epidemiology Subgroup
Professor Graham Medley (Chair)
University of Warwick

Professor Sheila Bird
MRC Biostatistics Unit

Gareth Davies
Independent Consultant

Dr Azra Ghani
London School of Hygiene and Tropical Medicine

Professor Noel Gill
Health Protection Agency

Professor Peter Smith
London School of Hygiene and Tropical Medicine

Dr Hester Ward
National CJD Surveillance Unit

Professor John Wilesmith

SEAC Sheep Subgroup
The Sheep Subgroup was convened in April 1999 to review progress on research and surveillance programmes for TSEs in sheep and goats, and recommend further work needed. The Subgroup recommended that a long term control and eradication plan for TSEs in sheep should be established (see link below).

The National Scrapie Plan (NSP) was initiated on the basis of this recommendation. The approach of the NSP was endorsed both by the SEAC Sheep Subgroup and SEAC, prior to the launch of the NSP in July 2001.

Since 2001 the Sheep Subgroup has met on an ad hoc basis to consider emerging scientific data relevant to the NSP. In December 2002 the Sheep Subgroup issued a statement, endorsed by SEAC, on susceptibility of different genotypes in sheep to experimental BSE.

In July 2004, the Sheep Subgroup considered options for the NSP in the light of current scientific knowledge as part of Defra’s consultation of stakeholders on future NSP strategy. A statement, endorsed by SEAC, was issued to Defra in October 2004.

Professor Chris Higgins (Chair of SEAC) is the Chair of the Sheep Subgroup. Membership of the Subgroup depends on the topics for consideration. The Subgroup comprises a core of SEAC members and co-opted experts drawn from the veterinary, TSE surveillance, TSE pathogenesis, epidemiology, prion genetics, TSE testing, protein chemistry and mathematical modelling fields.

The current terms of reference are:

To review new research findings and to assess the scientific implications of these results for the National Scrapie Plan.

SEAC ad hoc Epidemiology Subgroup on UK BARB cases
Cases of BSE in cows born after the 1996 reinforced feed ban are known as BARB cases.

At SEAC 80 (Nov 2003) it was recommended that further investigations, such as a case control study, are important to aid understanding of BARB cases. The ad hoc Epidemiology Subgroup on UK BARB cases was convened with the following terms of reference:

To provide scientifically based advice on the design of an epidemiological study to examine and distinguish the various hypotheses for the source of infection of BSE in BARB cattle in the UK

To advise on the type of statistical analysis of the surveillance data, collected half-yearly by the State Veterinary Service

To recommend and prioritise further work that should be undertaken to help resolve outstanding epidemiological issues identified by the expert group.
The Subgroup convened in March 2004 to discuss the plans for, and preliminary design of, a case control study.

The Subgroup reconvened in April 2005 to comment on the preliminary findings of the case control study of the BARB cases and to consider what further analysis was needed. The Subgroup’s recommendations were endorsed by SEAC in April 2005.

The full committee was updated on further progress on the case control study at SEAC 88 (June 2005). Draft minutes of SEAC 88 are at

Membership of the SEAC ad hoc Epidemiology Subgroup on UK BARB cases
Professor Noel Gill (Chair)
Health Protection Agency

Professor Valerie Beral
Cancer Research UK, Radcliffe Infirmary Oxford

Professor Sheila Bird
MRC Biostatistics Unit, Cambridge University

Professor Simon Cousens
London School of Hygiene and Tropical Medicine

Professor Nick Day
Strangeways Research Laboratory, University of Cambridge

Dr Paddy Farrington
Open University

Mr. Peter Jinman

Professor Graham Medley

Professor Dirk Pfeiffer
Royal Veterinary College, London

Professor Peter Smith
London School of Hygiene and Tropical Medicine

Professor John Wilesmith


Page last updated: 29 July 2005

SEAC Sheep subgroup statement

Defra is consulting stakeholders on four strategic options for the future operation of the National Scrapie Plan (NSP). The SEAC sheep subgroup’s views were sought as part of this consultation.

The subgroup concluded that the strategy of the NSP underlying breeding for scrapie resistance remains appropriate. However, the basis for the strategy should be kept under review in the light of emerging scientific findings with respect to the possible detection of scrapie infections in animals of genotypes currently thought to be most resistant to infection.

The subgroup was of the view that those strategies that reduced the prevalence of infection in the national flock most rapidly were the most desirable. On this basis Option A was considered inadequate. The subgroup considered that although Options A and B addressed scrapie in VRQ sheep these would not reduce scrapie in ARQ sheep, which may be more susceptible than assumed in the modelling, or the hypothetical possibility of BSE in sheep, which appears to preferentially target the ARQ allele. The subgroup considered a solution close to Option D was the most scientifically desirable given the importance of reducing the prevalence of scrapie and the potential risk of BSE.

The subgroup recognised there may be potential practical difficulties and in some cases genetic constraints for the sheep industry as well as cost issues associated with option D and therefore recommended that an additional option, Option E (mandatory Option B combined with voluntary Option D) be considered. This option, together with a further option, Option F (Option E combined with voluntary ewe genotyping and removal of VRQ ewes) were modelled. The subgroup considered the outcome of the additional modelling work and agreed that Option D remains the most scientifically desirable. Option F offered no significant advantage over Option E. Members agreed that Option E, given high voluntary take up, was also a scientifically valid strategic option for the NSP.

SEAC sheep subgroup
13 October 2004

Options for the NSP
Option A
EU minimum

The EU minimum rules require the genotype testing of all rams intended for breeding within flocks of ‘high genetic merit’ (Defra are proposing to apply the definition of ‘high genetic merit’ to all pure-bred flocks which sell homebred rams for further breeding) and the subsequent slaughter of those found to be carrying the VRQ allele (compensation will be paid for animals slaughtered). It does not require the genotype testing of rams sold for breeding elsewhere. Consequently, the sale of untested (and hence possibly VRQ) rams for further breeding is not prohibited. However, any untested rams purchased for use within another flock of ‘high genetic merit’ would need to be genotyped before being used for breeding and those carrying the VRQ allele removed in line with the requirements of the EU legislation.

Option B
EU minimum plus additional genotyping of rams\shearlings\ram lambs intended for sale and further breeding elsewhere.

In addition to the EU minimum requirements as described above at Option A, this option would also provide for the genotype testing in all flocks of ‘high genetic merit’ of rams\shearlings\ram lambs intended for sale and further breeding irrespective of whether they are to be used in other flocks of ‘high genetic merit’ or elsewhere further down the breeding pyramid e.g. in a commercial fat\slaughter lamb producing flock.

Option C
EU Minimum plus additional ram testing as Option B and voluntary ewe testing during the period 2005-2010 conditional on the removal of ARQ/ARQ breeding rams in participating flocks from 2010.

As Option B above, with an additional voluntary ewe genotyping scheme\service targeting female replacements conditional on the removal of ARQ/ARQ breeding rams from participating flocks from 2010. The Option is currently based on testing 200,000 female replacements across all sheep sectors per year. This is an indicative figure based on possible field and laboratory testing resource considerations (and may require fine tuning).

Option D
Compulsory NSP Ram Genotyping Scheme (RGS)

The current voluntary NSP’s RGS provides for the genotyping of all existing stock rams and for the removal of those carrying the VRQ allele. It also applies sale and on farm use restrictions for Type 3 (ARQ\AHQ\ARH) rams (end 2005 and 2008 respectively for terminal sire breeds and end 2007 and 2009 respectively for hill breeds). Additionally, it also provides for annual progeny testing of males (and females where there are fewer than 40 male animals available for testing i.e. each testing visit will comprise 40 animals in total) intended for further breeding. Under Option D, these arrangements would be made compulsory for all flocks of ‘high genetic merit’.

Option E

Strategy B (implementation of the minimum requirements set down in EU legislation (EU 2003) with the addition of sale restrictions on VRQ-bearing rams for all flocks of high genetic merit from 2005) and voluntary implementation of the current NSP purebred flock scheme.

Option F

Strategy E with the addition of ewe genotyping (and removal of VRQ-bearing ewes) in those flocks participating in the voluntary NSP scheme.


Page last updated: 29 July 2005


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