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From: TSS ()
Subject: SEAC 88th meeting on Thursday 30th June 2005
Date: June 22, 2005 at 7:37 am PST


88th meeting on Thursday 30th June 2005


Item No
Paper No.

SEAC Chair and Secretary

Approval of draft minutes from SEAC 87
SEAC Chair
88/1 (236 KB)

Current issues
SEAC Chair
88/Current issues

Research on abnormal prions in milk
Mr A Harvey (FSA)
Prof C Bostock (FSA/SEAC Milk Working Group Chair)
88/2* (128 KB)

Differential diagnosis of BSE
Dr P Barrowman (Defra)
88/3 (38 KB)
Annex 3 (51 KB)
Annex B (91 KB)
Annex C (28 KB)

BARB cases

Sequencing PRNP of BARB cases
Response to SEAC ad hoc Epidemiology Subgroup on UK BARB cases
Independent review of the cause(s) of BARB cases

Dr Y Boyd (Defra)
Dr G Saunders (VLA)
Dr A Douglas (DARDNI)
Prof J Wilesmith (Defra)
Prof W Hill (Uni of Edinburgh)

88/4 (52 KB)

88/5* (52 KB)

SEAC Epidemiology Subgroup report
Prof G Medley (Subgroup Chair
88/6 (16 KB)


Update on the National Scrapie Plan
SEAC Chair
88/7 (KB)


*Please note that Annex 4 of Paper 88/2 and Annex 4 of Paper 88/5 have not been circulated outside the committee as these documents contain new scientific data that have not yet been published in a scientific or medical journal. As premature release of unpublished data may prejudice publication the annexes are not released prior to publication. This is in accordance with SEAC's code of practice.

On the afternoon of Thursday 30th June, SEAC will consider research into ‘atypical’ cases of scrapie. These discussions will be held in a closed session to allow discussion of unpublished scientific information. This is in accordance with SEAC's code of practice.


9. In November 2002, SEAC was informed about a study the FSA

was commissioning due to the continuing uncertainty about

potential low levels of BSE infectivity in milk. The purpose of this

study was to develop methods to detect the BSE infection

associated form of the prion protein (PrPBSE) in bovine milk and to

determine whether PrPBSE could be detected in milk samples from

cattle that had been experimentally infected with the BSE agent.

The committee agreed that research relating to milk should be a

key priority, as it was a product that could be derived from

animals over thirty months of age, whose meat would not be

allowed into the food chain under the Over Thirty Month rule. The

committee recommended that a joint FSA/SEAC Working Group

should be convened to monitor the progress of the research,

advise on research approaches, evaluate the diagnostic methods

developed and assess the robustness of the analytical results.

The membership and terms of reference of the Group are given in

Annex 3.

10. The research has recently been completed and the raw data

evaluated by the joint FSA/SEAC Working Group. A

prepublication paper reporting the methods used and the findings

in full is at Annex 4. Please note Annex 4 has not been circulated

outside of the committee. This is at the authors’ request as the

report contains new scientific data that have not yet been

published in a scientific journal. As premature release of

unpublished data may prejudice publication, the report has not

been released more widely in hard copy prior to publication (this

is in accordance with SEAC's code of practice). However, the

authors are content for the committee to discuss the report in the

public meeting.

11. A summary of the research is provided below.



16. Twenty-eight milk samples (out of a total of 541 individual

samples tested) were determined as "final test reactive" using the

adapted BioRad Platelia ELISA test. Confirmatory analysis of

these samples using the SEPRION-PAGE/ Western blot test

resulted in 12 samples, all of which were colostrum samples

collected within one week of calving and represented in all of the

challenge groups, which contained positive staining bands in the

Western blot. Importantly, however, these bands were also

present when the analyses were repeated omitting the prionspecific

monoclonal antibody (6H4), indicating that they

represented non-PrP specific staining material.

17. The data generated in this study do not provide any evidence for

the presence of the abnormal BSE-infection associated prion in

the milk from cattle incubating BSE at levels defined by the limits

of sensitivity of the two analytical methods used.





In view of the findings of the analyses that are summarised above, the

Subcommittee concludes that there is some evidence for direct

maternal transmission of BSE at a low level, but some variation in

genetic susceptibility to BSE following feed-borne exposure may occur.

The risk of transmission of BSE from dam to calf is likely to be less than

10%, and appears to be confined to animals born after the onset of BSE

in the dam or up to two years beforehand. This level of transmission is

not sufficient, by itself, to perpetuate BSE in the cattle population and is

likely to have only a minor effect on the rate at which the incidence of

BSE declines. It is inevitable that cases infected via animal feed will

continue to appear in diminishing numbers for several years. Therefore,

although the number of cases infected maternally will be small, they

may represent an increasing proportion of the remaining cases


Given the evidence that variation in genetic susceptibility may have

contributed to the results of the cohort study, and of the importance of

genetic factors in TSEs in other species, the Subcommittee considers

that further research is necessary to clarify whether or not variations in

the PrP gene or other genes may be influencing the transmission of, or

susceptibility to, BSE in cattle. Research should seek to identify

polymorphisms of the PrP gene which may be associated with BSE

susceptibility, including stored samples from the cohort study. There

should also be a search [AVMC1] for other genetic markers, outside the

PrP gene, which may be associated with an increased BSE risk in







1. The SEAC Epidemiology Subgroup held its first meeting in London

on 11th May 2005 to discuss the nature and future profile of the

vCJD epidemic. A summary of the meeting is given below.


2. Projections of the profile of the vCJD epidemic, based on data from

clinical vCJD cases, suggest the number of additional cases may

be relatively small. However, recent experimental and

epidemiological findings suggest that the nature of the epidemic

might be more complex. There may be a substantial number of

people who are carriers of infectivity and who will not develop

clinical disease or will do so on a prolonged timescale.

Furthermore, potential human to human infection via medical

procedures (e.g. use of contaminated surgical instruments or

blood) might influence the profile of the epidemic such that, if

appropriate intervention is not taken, a self-sustaining epidemic

could be arising.

3. SEAC agreed (03/03/05) that further epidemiological analysis and

modelling work is required to comprehensively reassess the nature

and future profile of the vCJD epidemic. The Committee tasked

the SEAC Epidemiology Subgroup to conduct this assessment,

taking into account new research, and the possibility of human to

human transmission. The Subgroup was also asked to identify

critical factors that could influence the nature of the epidemic and

to consider the likelihood of a self-sustaining epidemic and

possible preventative interventions. Consideration would also be

given to potential information barriers to assessment of the public

health risks.

Meeting summary

4. The Subgroup considered the available sources of data for direct

ascertainment of the prevalence of vCJD infection. An update on


the progress of the National Anonymous Tonsil Archive that is

prospectively collecting tonsils for PrPSc screening was presented.

Potential additional sources of data to allow direct ascertainment of

infection prevalence and assessment of transmission risks were

discussed. A summary table of additional surveillance options and

the data they could provide together with associated

practical/ethical considerations will be developed for further

consideration. This will be a key output from the Subgroup.

5. Preliminary results were presented from new modelling work to

examine the influence of age and PrP genotype on infection

prevalence (clinical cases and pre- or sub-clinical infection carriers)

using the published and some unpublished data. The scope of the

modelling was discussed. The Subgroup will review the results

from this continuing work at its next meeting in the autumn.

6. Routes of secondary transmission and potential data sources to

define the extent of their possible interactions were considered. A

summary table of routes in terms of their importance (i.e. likelihood

to contribute to a secondary epidemic) and possible major

interactions will be developed for further discussion. This will be a

key output from the Subgroup.

7. It was agreed that a second Subgroup meeting will be held in

September 2005 to consider the issues further. A draft position

statement that addresses the issues identified by SEAC will be

prepared for the Subgroup’s consideration.



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