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From: TSS ()
Subject: Opinion of the Scientific Panel on Biological Hazards on the assessment of the age limit in cattle for the removal of certain SRM
Date: May 29, 2005 at 6:01 pm PST

----- Original Message -----
From: Terry S. Singeltary Sr.
To: Bovine Spongiform Encephalopathy
Sent: Sunday, May 29, 2005 7:46 PM
Subject: Opinion of the Scientific Panel on Biological Hazards on the assessment of the age limit in cattle for the removal of certain Specified Risk Materials (SRM)


Opinion of the BIOHAZ Panel on the assessment of the age limit in cattle for the removal of certain Specified Risk Materials (SRM).
Last updated: 25 May 2005
Adopted on 28 April 2005 (Question N° EFSA-Q-2004-146)

Opinion
Summary
Summary of the Opinion

The European Food Safety Authority (EFSA) was invited by the European Commission to review the previous scientific opinions (Scientific Steering Committee, SSC) on the age limit for the removal of certain bovine tissues as specified risk material (SRM) taking into account a report from the referred OIE-consultation group of experts and additional information.

The assessment of the exclusion of certain SRM at a certain age limit is based on available data of ongoing experimental pathogenesis and dose/incubation period studies and on knowledge of the epidemiology of BSE with respect to age at infection and age at detection by clinical and active surveillance.

On the basis of pathogenesis studies results it can be assumed that in CNS the likely detectable PrPSc, and consequently the likely detectable infectivity appears at about ¾ of the incubation time. Based on the earliest clinical manifestation seen in pathogenesis studies and assuming that the last quarter of the incubation period would be positive for infectivity, the earliest infectivity would have to be assumed at 26 months. However, this would reflect uptake of the BSE agent via the gut only. Other modes of prion uptake, e.g. via the oral mucosa and neural spread, cannot be completely excluded and theoretically might significantly shorten the incubation time. However, there are no observational data at present to support this. As for tonsil and intestine, there is no scientific basis to raise the age limit for their removal.

From the analysis of the epidemiological data, it is observed that the average age of BSE positive cases reported in the EU has been increasing from 86 to 108 months over the period 2001-2004, most likely due to effective control measures. It is further observed that the number of BSE cases reported at an age less than 35 months in past years in the EU has been only 4 out of a total number of 6520 BSE cases on a total of close to 41 million animals tested. The minimum age of BSE cases in EU has been 28 and 29 months (2 animals) in 2001, 32 and 34 months in 2002, 36 months in 2003 and 42 months in 2004. The three youngest animals were emergency slaughter, whereas the remainder of BSE cases in young animals (i.e. younger then 48 months, table 1) included all target groups.

If the cautious approach of the former SSC is followed and the minimum age is taken as the denominator for the age at which SRM are to be removed, then a cut-off at 30 months would not cover such young animals if assuming ¾ of the incubation period for the appearance of infectivity in CNS. A cut-off at 21 months would cover the last quarter of incubation time of even the single youngest animal observed since the start of the EU surveillance in 2001.

If the BSE cases in very young animals are not taken into account and the mean age at which BSE is detected in the field is taken as the denominator, then a cut-off at 30 months would represent a considerable but not an absolute safety margin with respect to detectable BSE infectivity.

Present BSE surveillance appears to be equally effective in the EU member states. Nevertheless, there could be important differences between EU Member States according to differences in culling rates and other factors like stage in the epidemic.

Keywords: BSE, specified risk materials, cattle, age, epidemiology.


Publication date: 25 May 2005
EFSA provides new scientific assessment on the age limit for the removal of specified risk materials from cattle with regard to BSE
Last updated: 26 May 2005
The removal of specified risk materials (SRMs) is one of the most important risk management measures to protect the health of consumers against the risk of Bovine Spongiform Encephalopathy (BSE). SRMs are the animal tissues in cattle, such as brain and spinal cord, which are most at risk of carrying the infective agent.

Opinion
EFSA provides new scientific assessment on the age limit for the removal of specified risk materials from cattle with regard to BSE

The removal of specified risk materials (SRMs) is one of the most important risk management measures to protect the health of consumers against the risk of Bovine Spongiform Encephalopathy (BSE). SRMs are the animal tissues in cattle, such as brain and spinal cord, which are most at risk of carrying the infective agent. The European Food Safety Authority (EFSA) has today published an opinion of its Scientific Panel on Biological Hazards assessing the age limit for the removal of SRMs. In its opinion, EFSA has reviewed new and existing scientific information and provided the European Commission (EC) with updated scientific advice with which to consider possible new age limit scenarios for the removal of SRMs. Presently, most SRMs in all Member States (except the UK) are removed at 12 months and it is now up to the European Commission to consider proposing any changes to this rule.

Since 2000, slaughter houses across the EU (except the UK where more specific rules apply*) have to remove SRMs from all cattle aged over 12 months of age entering the food chain. The European Commission asked EFSA to review the opinions of the former EC Scientific Steering Committee, upon which these measures were based, taking into account new information from the World Organisation for Animal Health (OIE) on the age limit and, if necessary, to provide scientific advice on the current age limit.

The existing age limit for the removal of SRMs in cattle in the EU is currently fixed at 12 months*. Although recognizing that infection of the central nervous system in cattle below the age of 30 months was unlikely, the former EU Scientific Steering Committee took this cautious approach of recommending the removal of SRMs from cattle over the age of 12 months. The exceptional detection of young animals with clinical signs of BSE supported this assessment.

EFSA’s Scientific Panel on Biological Hazards and its Working group have based their assessment on surveillance data as well as on existing and new scientific research related to the development of BSE in cattle. According to epidemiological data, the average age of BSE positive cases reported in the EU increased from 86 to 108 months between 2001 and 2004, most likely due to the introduction of effective control measures. Furthermore, only 4 BSE cases under the age of 35 months have been reported since 2001 and the minimum age of animals detected every year with the disease has risen steadily from 28 to 42 months over the 2001-2004 period. From experimental scientific studies, it is now believed that cattle incubating BSE could become infectious later in the incubation period than previously thought (i.e. during the last quarter of the incubation period before the disease actually becomes detectable).

Based on the above scientific information, EFSA’s Biological Hazards Panel concluded that raising the age at which SRMs should be removed to that of 30 months would be a considerable but not an absolute safety margin. Alternatively, raising the age limit at which SRMs should be removed to 21 months would cover even the youngest animals detected with the disease since monitoring began in 2001 and would thus be a more cautious approach.

Based on EFSA’s scientific assessment concerning the age limit for the removal of SRMs, the European Commission will now consider if changes to the existing 12 month age limit should be proposed and, if so, at which age the limit should be set.

The full text of the opinion

For media enquiries, please contact:

Alun Jones, Press Officer
Tel: + 32 2 337 2487
E-mail: Alun.Jones@efsa.eu.int

or

Anne-Laure Gassin, EFSA Communications Director
Tel : + 32 2 337 2248
GSM: + 32 478 330 19 68
E-mail: Anne-Laure.Gassin@efsa.eu.int

For more background information about the European Food Safety Authority


_______________________________

Note for editors:
*Specified Risk Materials (SRMs) are brain, spinal cord, skull, vertebral column, dorsal root ganglia and eyes. Tonsils and intestines which are also SRMs are removed from all animals in all countries regardless of the age of the animal.

**T-bone steak (being part of the vertebral column) is a fresh meat product affected by the introduction in 2000 of the 12-month age limit for the removal of SRMs. This particular cut of meat was banned in the EU given the obligation to remove the vertebral column as an SRM (except in the UK where the vertebral column is removed from the food chain with the rest of the animal at 30 months).



http://www.efsa.eu.int/science/biohaz/biohaz_opinions/938_en.html

Publication date: 26 May 2005


http://www.efsa.eu.int/press_room/press_release/939_en.html

The EFSA Journal (2005) 220, 1-7. Opinion on the assessment of the age limit in cattle

for removal of certain specified risk materials (SRM).

http://www.efsa.eu.int

1 of 7

Opinion of the Scientific Panel on Biological Hazards on the assessment of

the age limit in cattle for the removal of certain Specified Risk Materials

(SRM).

Question N° EFSA-Q-2004-146

Adopted on 28 April 2005

Summary of Opinion

The European Food Safety Authority (EFSA) was invited by the European Commission to

review the previous scientific opinions (Scientific Steering Committee, SSC) on the age limit

for the removal of certain bovine tissues as specified risk material (SRM) taking into account

a report from the referred OIE-consultation group of experts and additional information.

The assessment of the exclusion of certain SRM at a certain age limit is based on available

data of ongoing experimental pathogenesis and dose/incubation period studies and on

knowledge of the epidemiology of BSE with respect to age at infection and age at detection

by clinical and active surveillance.

On the basis of pathogenesis studies results it can be assumed that in CNS the likely

detectable PrPSc, and consequently the likely detectable infectivity appears at about ¾ of the

incubation time. Based on the earliest clinical manifestation seen in pathogenesis studies and

assuming that the last quarter of the incubation period would be positive for infectivity, the

earliest infectivity would have to be assumed at 26 months. However, this would reflect

uptake of the BSE agent via the gut only. Other modes of prion uptake, e.g. via the oral

mucosa and neural spread, cannot be completely excluded and theoretically might

significantly shorten the incubation time. However, there are no observational data at present

to support this. As for tonsil and intestine, there is no scientific basis to raise the age limit for

their removal.

From the analysis of the epidemiological data, it is observed that the average age of BSE

positive cases reported in the EU has been increasing from 86 to 108 months over the period

2001-2004, most likely due to effective control measures. It is further observed that the

number of BSE cases reported at an age less than 35 months in past years in the EU has been

only 4 out of a total number of 6520 BSE cases on a total of close to 41 million animals

tested. The minimum age of BSE cases in EU has been 28 and 29 months (2 animals) in

2001, 32 and 34 months in 2002, 36 months in 2003 and 42 months in 2004. The three

youngest animals were emergency slaughter, whereas the remainder of BSE cases in young

animals (i.e. younger then 48 months, table 1) included all target groups.

If the cautious approach of the former SSC is followed and the minimum age is taken as the

denominator for the age at which SRM are to be removed, then a cut-off at 30 months would

not cover such young animals if assuming ¾ of the incubation period for the appearance of

infectivity in CNS. A cut-off at 21 months would cover the last quarter of incubation time of

even the single youngest animal observed since the start of the EU surveillance in 2001.

The EFSA Journal (2005) 220, 1-7. Opinion on the assessment of the age limit in cattle

for removal of certain specified risk materials (SRM).

http://www.efsa.eu.int

2 of 7

If the BSE cases in very young animals are not taken into account and the mean age at which

BSE is detected in the field is taken as the denominator, then a cut-off at 30 months would

represent a considerable but not an absolute safety margin with respect to detectable BSE

infectivity.

Present BSE surveillance appears to be equally effective in the EU member states.

Nevertheless, there could be important differences between EU Member States according to

differences in culling rates and other factors like stage in the epidemic.

Key words: BSE, specified risk materials, cattle, age, epidemiology.

The EFSA Journal (2005) 220, 1-7. Opinion on the assessment of the age limit in cattle

for removal of certain specified risk materials (SRM).

http://www.efsa.eu.int

3 of 7

Background

1. Historical background

(a) In its Opinion of 9 December 1997 the Scientific Steering Committee (SSC) suggested a

list of specified risk materials (SRM) to be excluded from human and animal consumption

on the basis of relative tissue infectivity, species and age. The SSC concluded that the

intestine of young animals should be seen as risk as it is the presumed route of infection.

However, it was considered extremely unlikely that the central nervous system was

detectably infected below the age of 30 months even in cattle exposed to infection as

calves. Nevertheless, the exceptional detection of young animals with clinical signs of

BSE supported a cautious approach and, therefore, the SSC recommended the removal of

various SRM from cattle 12 months of age or older.

This Opinion was revised and updated by SSC opinions on the human exposure risk via

food with respect to BSE (10 December 1999), on the oral exposure of humans to the BSE

agent (14 April 2000) and on TSE infectivity distribution in ruminant tissues (11 January

2002).

All those opinions led to the management decision to set the age limit for the removal of

SRM (excluding intestine and tonsils) at 12 months.

(b) Cattle born after the total feed ban bear a low risk of being infected if the feed ban is

properly implemented. This opens the possibility of raising the age limit for the removal

of certain SRM from cattle born after a certain date.

(c) Other assessments of the human BSE risk, such as the assessments carried out by Det

Norske Veritas (DNV) Consulting on the exposure of the human population to BSE

infectivity over the course of the BSE epidemic in Great Britain (2003), assumes

exponential growth of infectivity in CNS tissues in cattle. This means that the infectivity

is 1000 times lower when 70% of the incubation period has passed compared to the

infectivity in the clinical phase of the disease. Halfway through the incubation period the

infectivity would be 15000 times lower than in the clinical phase.

(d) In the framework of the OIE-facilitated consultation between EU and USA on the

interpretation and implementation of the OIE standard on BSE a group of relevant experts

has produced a final report on SRM. In the report its is stated that "results from an

ongoing experimental oral exposure study in cattle (VLA) suggest potential minimum

ranges of first detection of PrPd to the end of the incubation period of 27-35 and 28-35

months, providing an average figure of approximately 78% of the way through the

incubation period". The group of experts recommends various SRMs (brain, spinal cord,

skull, vertebral column, dorsal root ganglia, eyes) to be excluded from cattle 30 months of

age or older.

The EFSA Journal (2005) 220, 1-7. Opinion on the assessment of the age limit in cattle

for removal of certain specified risk materials (SRM).

http://www.efsa.eu.int

4 of 7

2. Age distribution of BSE cases in the on-going monitoring programme

In 2001, 10 cases of BSE were detected below 48 months of age. Two positive cases were

found in animals below 30 months (two emergency slaughtered animals of 28 and 29 months

of age). The youngest healthy slaughtered animal found positive in 2001 was 42 months.

In 2002, 7 cases of BSE were detected below 48 months of age. The youngest positive case

was found in a 32 months old casualty slaughtered animal in UK. The youngest case in

animals born outside UK and Portugal was a 39 months old healthy slaughtered animal born

in Denmark and slaughtered in Portugal.

In 2003, 4 BSE cases below 48 months had been reported in the EU15: a 36 months old

healthy slaughtered animal in Spain, one 45 months old suspect animal in Germany, one 46

months old dead-on-farm animal in Germany and a 46 months old casualty slaughtered

animal in UK. In addition, Slovenia reported a 44 months old dead-on-farm animal and the

Czech Republic reported one 36 months old and one 42 months old healthy slaughtered

animal.

In 2004, 7 cases below 48 months were detected in the EU25, aged 42 to 47 months. The

youngest case (42 months) was a healthy slaughtered animal in Slovakia.

Another observation was that the mean age of the BSE cases in 2003 increased by 6 months

compared to 2002 and 17 months compared to 2001.

The number of cases in the ongoing surveillance programme between 49-60 months is listed

below:

Number of BSE cases in cattle aged between 49 - 60 months

BSE cases Healthy slaughter Emergency slaughter/fallen stock Suspects/culled animals

2001 38 50 33

2002 14 40 15

2003 16 14 9

2004 17 + 3* 19 +4* 5

*: BSE cases in new Member States; all other cases were in the EU15

3. Implementation of the feed ban

According to European Commission services (DG SANCO), a progressive improvement of

the implementation of the feed ban has been observed since its application on 1 January 2001

but low levels of contaminated feed continue to be reported. In 2002, 31 (0.12%) breaches

were detected in more than 26,000 targeted samples in ruminant feed and the levels of

contamination were very low. The same tendency is observed on the partial data available for

2003.

Terms of reference

The European Food Safety Authority (EFSA) is invited to give a technical advice on the

relevance of the report from the referred OIE-consultation group of experts and, should its

conclusions be found relevant, to review the previous scientific opinions on the age limit for

The EFSA Journal (2005) 220, 1-7. Opinion on the assessment of the age limit in cattle

for removal of certain specified risk materials (SRM).

http://www.efsa.eu.int

5 of 7

the removal of certain bovine tissues as specified risk material taking into account the OIE

report and additional information.

Assessment

The Scientific Panel on Biological Hazards refers to the report of the Working Group in

Annex for full details on the assessment.

Conclusions:

1.1 The OIE consultation report

The Scientific Panel on Biological Hazards agrees with the relevance of the OIE consultation

report for the review of the age limit for SRM removal, with some minor changes.

http://www.efsa.eu.int/science/biohaz/biohaz_opinions/opinion_annexes/934_en.html

In the absence of definitive evidence we recommend an approach based on experimental

studies and knowledge of the age distribution of BSE affected cattle in the European Union

and elsewhere, the Specified Risk Materials (SRM’s) to be excluded will have to be assessed

in view of the probability of BSE cases at certain age points in the different EU 25 Member

States.

1.2 Justification to eventually change the age limit on the basis of the results of

pathogenesis studies and epidemiological data.

• On the basis of pathogenesis studies it can be assumed that in Central Nervous System

(CNS) the likely detectable PrPd, and consequently the likely detectable infectivity

appears at about ¾ of the incubation time. However, it remains unclear as to the

relationship between first detectable PrPd in the CNS and the incubation period in

relation to dose and the age of the animals infected in a natural setting.

• Based on the earliest clinical manifestation seen in pathogenesis studies and assuming

that the last quarter of the incubation period would be positive for infectivity, the

earliest infectivity would have to be assumed at 26 months. However, this would

reflect uptake of the BSE agent via the gut only.

• The average age of BSE positive cases reported in the EU has been increasing from 86

months in 2001 to 108 in 2004.

• The number of BSE cases reported at an age less than 35 months in past years (as

from the start in 2001 till end of 2004) in the EU accounted for 0.06 % of all BSE

cases reported since 2001.

• The minimum age of BSE cases in EU has been 28 and 29 months (2 animals) in

2001, 32 and 34 months in 2002, 36 months in 2003 and 42 months in 2004.

• If the cautious approach of the former Scientific Steering Committee (SSC) is

followed and the minimum age is taken as the denominator for the age at which SRM

are to be removed, then a cut-off at 30 months would not cover such young animals if

assuming ¾ of the incubation period for the appearance of infectivity in CNS; a cut-

The EFSA Journal (2005) 220, 1-7. Opinion on the assessment of the age limit in cattle

for removal of certain specified risk materials (SRM).

http://www.efsa.eu.int

6 of 7

off at 21 months would cover the last quarter of incubation time of even the single

youngest animal observed since the start of the EU surveillance in 2001.

• If the BSE cases in very young animals are not taken into account and the mean age at

which BSE is detected in the field, is taken as the denominator, then a cut-off at 30

months would represent a considerable but not an absolute safety margin with respect

to detectable BSE infectivity.

• However the most appropriate approach would be to conduct back calculation

modelling that is depending on data availability from individual countries.

• There may be important differences between EU Member States according e.g. to

differences in the length of implemented surveillance, in culling rates and other factors

like stage in the epidemic.

• There is no scientific basis to raise the age limit for removal of tonsil and intestine.

2 Recommendations

• The main issue that needs to be addressed with respect to options for estimation of the

age limit for the removal of SRM is the likelihood of the infectivity in SRM derived

from infected cattle at different age groups. Estimation of this likelihood of infectivity

would require back calculation modelling with further assessment of experimental and

epidemiological data, in particular as indicated in "Approach 4" in the annex.

• Completion of a Quantitative Risk Assessment on SRM including age distribution

would be an additional valuable element when assessing the age-related risk of SRM.

DOCUMENTATION PROVIDED TO EFSA

Letter from the European Commission, DG SANCO (D(2004)/JOV/khk/421060) including

the mandate and supporting documents.

Relevant SSC opinions:

• Opinion of the Scientific Steering Committee on Listing of specified risk materials: a

scheme for assessing relative risks to man. Adopted at its meeting of 9 December

1997.

• Opinion of the Scientific Steering Committee on the Human Exposure Risk (HER) via

food with respect to BSE. Adopted at its meeting of 10 December 1999.

• Opinion of the Scientific Steering Committee on Oral exposure of humans to the BSE

agent: infective dose and species barrier. Adopted at its meeting of 13-14 April 2000.

• Opinion of the Scientific Steering Committee on TSE infectivity distribution in

ruminant tissues (State of knowledge, December 2001). Adopted at its meeting of 10-

11 January 2002.

• Update of opinion on TSE infectivity distribution in ruminant tissues, initially adopted

by the Scientific Steering Committee at its meeting of 10-11 January 2002 and

amended at its meeting of 7-8 November 2002

OIE-facilitated consultation between EU and USA on the interpretation and implementation

of the OIE standard on BSE (May 2004). Draft Report on Specified Risk Materials.

The EFSA Journal (2005) 220, 1-7. Opinion on the assessment of the age limit in cattle

for removal of certain specified risk materials (SRM).

http://www.efsa.eu.int

7 of 7

Exposure of the human population to BSE infectivity over the course of the BSE epidemic in

Great Britain and the impact of changes to the Over Thirty Months Rule" Philip J Comer and

Paul J Huntly, DNV Consulting, 2003.

AFSSA-SAISINE n°2003-SA-0334 du 5 Mars 2004. Avis de l’Agence française de sécurité

sanitaire des aliments concernant la modification de l’âge minimum des bovins concernés par

le retrait de la colonne vertébrale.

EC (2004). EUROPEAN COMMISSION. Report on monitoring and testing of ruminants for

the presence of transmissible spongiform encephalopathy (TSE) in the EU in 2003, including

the results of the survey of prion protein genotypes in sheep breeds.

SCIENTIFIC PANEL MEMBERS

Herbert Budka, Sava Buncic, Pierre Colin, John D Collins, Christian Ducrot, James Hope, Mac

Johnston, Günter Klein, Hilde Kruse, Ernst Lücker, Simone Magnino, Riitta Liisa Maijala, Antonio

Martínez López, Christophe Nguyen-The, Birgit Noerrung, Servé Notermans, George-John E Nychas,

Maurice Pensaert, Terence Roberts, Ivar Vågsholm, Emmanuel Vanopdenbosch.

A

CKNOWLEDGEMENT

The Chairman, rapporteur and members of the working group are acknowledged for their

valuable contribution to this mandate. The members of the working group are:

Paul Brown, Herbert Budka (Chairman), James Hope, Hans Kretzschmar, Ernst Lücker

Mo Salman, Emmanuel Vanopdenbosch (Rapporteur), Gerald Wells and John Wilesmith.

ANNEX

Report of the Working Group (WG) which deals in detail with the assessment:

http://www.efsa.eu.int/science/biohaz/biohaz_opinions/opinion_annexes/933_en.html

http://www.efsa.eu.int/science/biohaz/biohaz_opinions/938/biohaz_opinion_ej220_srmremove_en1.pdf


TSS



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