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From: TSS ()
Date: March 10, 2006 at 7:36 am PST


© SEAC 2006



The Spongiform Encephalopathy Advisory Committee held its 91st

meeting in London on 24th February 2006.


SEAC was informed about the following issues:

• The Chair had received a positive response from the Chief

Medical Officer on the recommendations made in the SEAC

Epidemiology Subgroup statement on the vCJD epidemic1

and subsequent SEAC statement2. SEAC recommended

that better data on the prevalence, age and genotype

distribution, based on population studies, are required with

some urgency. This data could be obtained through testing

tissues collected from autopsies. The Department of Health

will convene an expert group to consider ethical, practical

and legal issues to take the recommendations forward.

• SEAC responded to a consultation from the European

Commission. This requested comments on the opinion of

the Scientific Committee on Emerging and Newly Identified

Health Risks on the safety of human-derived products with

regard to vCJD.

• A third case of vCJD transmission associated with blood

transfusion was announced by the Health Protection Agency

(HPA) on 9th February 2006. The recipient developed

symptoms of vCJD about 8 years after receiving a blood

transfusion from a donor, who developed symptoms of vCJD




© SEAC 2006

about 20 months later. SEAC was informed about the HPA

notification exercise, follow up arrangements, and further

actions relating to the remainder of the exposed group of 26

individuals. Members agreed that the case indicates that

there is significant risk of transmission of vCJD by blood

transfusion. A paper on the case is being prepared by the

Transfusion Medicine Epidemiology Review.

• Interviews had taken place for two new members for SEAC,

submissions to Ministers are in preparation.


SEAC was presented with figures showing the annual number of

BSE cases in cattle in Great Britain (GB) since the 1980s and the

reductions in the number of cases after the introduction of control

measures. Members noted data on BSE cases reported in other

countries. In GB, the BSE epidemic peaked in 1992, with over 36

000 cases confirmed, and thereafter the number of cases declined

considerably. There have only been 124 cases confirmed in

animals born after the introduction of the reinforced ban in 1996.

Overall the GB epidemic is in steep decline with only 203 cases

confirmed in 2005.


SEAC considered the risk to human health from medical implants

that include bovine material sourced from the USA. This material

was used for a wide range of medical devices, some of which are

life saving and for which there are no alternative products.

SEAC considered that the source of the animal was crucial to

manage the risk. The committee suggested that other

precautionary steps be taken where practicable, such as using

material from young animals, sourcing material from countries with

good surveillance procedures and a low prevalence of disease.

SEAC noted the lack of clarity in the regulations, which did not give

an indication of what level of risk is acceptable, and the British

Standards Institution committee scheme, which serves to assist

judgments of acceptability by determining whether the BSE risk

from a medical device utilising bovine material has been

minimised. The committee considered that a single risk


© SEAC 2006

assessment model would not be appropriate due to the variety of

devices and risk control options that are involved and the varying

degrees of risk. A risk assessment should be developed for each

specific medical device.



SEAC welcomed the opportunity to comment on experimental

models to evaluate prion reduction methodologies that were

developed to reduce the potential for vCJD transmission via blood


SEAC considered that it was important to replicate the

experiments that the companies had done to test the efficacy and

reproducibility of the filters. The committee suggested that the use

of an additional rodent strain and three different forms of inoculum

of TSE agent as the spiking material was important. This may

indicate differences in the efficacy of filters against different strains

or TSE agent. It is critical to include the BSE agent in these


SEAC considered that experiments that tested the removal of

endogenous infectivity were important and that it was crucial to try

and get a model that was as close as possible to the human

situation. The committee noted that knowledge of the prevalence

of vCJD in the population was important to the risk management

issue of implementation of prion reduction filters.


Since the introduction of an ELISA rapid test for active surveillance

in 2002, around 100 cases of what is called atypical scrapie have

been detected in the UK. The SEAC Sheep Subgroup met on 24th

January 2006 to consider emerging scientific developments on

atypical scrapie and possible implications for the National Scrapie

Plan (NSP) and human and animal health. In its position

statement, the Sheep Subgroup concluded that the new scientific

data and identification of atypical scrapie, while of concern, do not

justify immediate changes to the NSP. Nevertheless, the

Subgroup strongly recommended that the NSP should be kept

under continuous review as new findings emerge. SEAC

concurred with this view.


© SEAC 2006

The Subgroup concluded that there is currently insufficient data to

make any conclusions about the risk to human health from the

finding of atypical scrapie in UK and European small ruminant

flocks. However, as transmission to humans is theoretically

possible, the Subgroup stressed the importance of research on

transmission of atypical scrapie in transgenic mice expressing the

human prion protein gene to inform on this issue.

SEAC agreed with the Sheep Subgroup’s conclusions and

recommendations and endorsed its position statement. The

statement can be accessed at:


Defra and FSA asked SEAC to review the arrangements for

disposal of manure, crops and livestock from an experimental

farm. BSE research projects in cattle have been ongoing here

since 1998 and are nearing completion. The TSE projects in

sheep have been ongoing since 2002. SEAC previously advised

that waste from orally-challenged animals should be incinerated for

the first 28 days, thereafter the excreta should be composted for a

year and then could be used to fertilise arable land. The crops

grown subsequently could in principle be used for both human

food and animal feed.

All excreta from the orally and intracerebrally inoculated cattle

were incinerated for the first 28 days after inoculation. A 12 month

composting period was introduced for manure from the BSE

challenged animals. However, only short rotation willow coppices

were planted on the land onto which the composted manure from

the BSE challenged animals was applied.

SEAC considered that, as there is no evidence that BSE is

transmitted through environmental sources, healthy animals could

be housed in the disinfected buildings which previously housed

cattle experimentally infected with BSE. These animals could be

used for commercial slaughter or for other purposes. The current

animal tracing system will monitor the movements of these animals

in the future. There is currently no evidence that the crops

subsequently grown on the land which received composted


© SEAC 2006

excreta from BSE challenged animals pose a significant infectivity

risk to humans or animals.


SEAC considered the findings and implications of a preliminary

risk assessment of potential vCJD transmission via endodontic

procedures. The committee was updated with preliminary data to

assess the oral cavity as a potential route of transmission of vCJD

infectivity. This item was discussed in the reserved business

session as there was consideration of unpublished research.

SEAC considered that further data was required on the infectivity

of oral tissues and the prevalence of vCJD in the population.

However, in the absence of this information, and as there is a

theoretical risk of transmission of vCJD via endodontic procedures,

the committee suggested that the use of single use instruments for

such procedures should be seriously considered.

6 March 2006 - The final minutes (94 KB) of the 90th SEAC

meeting held on 24th November 2005 have now been published.


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