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From: TSS (216-119-144-34.ipset24.wt.net)
Subject: Working Group Report on the Assessment of the Geographical BSE-Risk (GBR III) of USA 2004 ''extremely/very unstable BSE/cattle system''
Date: August 20, 2004 at 11:28 am PST
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 1 -
European Food Safety Authority
Scientific Expert Working Group on GBR
Working Group Report on
the Assessment of the Geographical BSE-Risk (GBR) of
UNITED STATES OF AMERICA
2004
NOTE TO THE READER
Independent experts of the EFSA Scientific Expert Working Group on
GBR have produced this report, applying an innovative methodology
by a complex process to data that were supplied by the responsible
country authorities. Both, the methodology and the process are
described in detail in the final opinion of the Scientific Steering
Committee (SSC) on "the Geographical Risk of Bovine Spongiform
Encephalopathy (GBR)" of 6 July 2000 and its update of 11 January
2002. These opinions are available at the following Internet address:
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 2 -
1. DATA
• The available information was sufficient to carry out the qualitative assessment of
the GBR.
• Reasonable worst case assumptions have been used in cases where the available
information was not fully adequate.
Sources of data
• Country dossier (CD) consisting of information provided from the country’s
authorities in 1997-2004, including the study entitled “Harvard Risk Assessment”
(hereafter abbreviated as HRS).
Other sources:
• EUROSTAT data on export of "live bovine animals" and on "flour, meal and
pellets of meat or offal, unfit for human consumption; greaves" (customs code
230110), covering the period 1980 to 2003.
• UK-export data (UK) on "live bovine animals", and on "Mammalian Flours,
Meals and Pellets" MBM1, 1980-1996.
• Available export data from other BSE-risk countries.
2. EXTERNAL CHALLENGES
2.1 Import of cattle from BSE-Risk2 countries
An overview of the data on live cattle imports is presented in table 1 and is based on
data as provided in the country dossier (CD) and corresponding data on relevant
exports as available from BSE risk countries that exported to the USA. Only data
from risk periods are indicated, i.e. those periods when exports from a BSE risk
country already represented an external challenge, according to the SSC opinion on
the GBR (SSC July 2000 and updated January 2002).
• According to the country dossier, 323 cattle were imported directly from the UK,
all between 1980 and 1989, and 10 via Canada in 90, 91 and 92. According to
Eurostat, 327 cattle were imported from UK. Of these cattle 96% were beef
breeding cattle, 4% were dairy cattle. After 1989 an import stop for UK cattle was
in effect.
1 For the purpose of the GBR assessment the abbreviation “MBM” refers to rendering products, in
particular the commodities Meat and Bone Meal as such; Meat Meal; Bone Meal; and Greaves. With
regard to imports it refers to the customs code 230110 “flours, meals and pellets, made from meat or
offal, not fit for human consumption; greaves”.
2 BSE-Risk countries are all countries already assessed as GBR III or IV or with at least one confirmed
domestic BSE case.
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 3 -
• Cattle imported from the UK were traced-back in 1995. This trace back exercise
provided the details on which the assessment of the HRS of the import risk
assessment is based. The animals still alive in 1995 (117 cattle) have been
purchased, diagnostic samples were taken, and the carcasses were incinerated.
These animals were not taken into account for the external challenge. All these
animals tested negative for BSE (histopathology and IHC). Of these 117 cattle 52
came from UK-herds in which one or more cases of BSE later on developed.
• For 173 cattle imported from the UK in the 80s, information on their final use is,
according to the HRS, lacking and it is indicated that it is possible that some of
these animals could have been rendered. In the HRS it is also noted that these
animals were imported before the peak of the epidemic and none came from a
birth cohort in which a BSE case is known to be developed. However, based on
realistic worst case assumptions it has to be assumed that they created a risk if
rendered for feed.
• EU export data show that from the EU (excluding UK), 1,663 cattle were exported
to the USA since 1980; according to the CD only 460 cattle have been imported
from the EU.
• According to the CD, 162 cattle were imported from Ireland between 1980 and
1988 (according to Eurostat 233). The trace back of these animals showed that 22
were found as being excluded from rendering in the US system and 4 were born in
US quarantine and were therefore not taken into account for the external
challenge.
• According to the CD, 6 cattle from Belgium (Eurostat also 6), 46 from Germany
(Eurostat 430), 3 from Austria (Eurostat 0) and 8 from Italy (Eurostat 21) have
been imported. The 40 breeding-cattle imported from these countries in 1996 and
1997 were all traced back and none of them entered the US system.
• According to Eurostat, 12 cattle from Denmark and 558 cattle from the
Netherlands were imported to the USA. These imports were not indicated in the
CD.
• Additionally according to the CD, 235 cattle have been imported from France
(403 according to Eurostat) and 103 cattle from Switzerland (48 according to
other sources).
• The discrepancy in the EU export data and the import data in the CD (See table 1)
can in some cases, be explained by the use of the fiscal year data (from October to
September) in the CD.
• Between 235.000 and 1.7 Million (CD and Other sources) cattle per year are
imported to the USA from Canada. According to the CD, feeder/slaughter cattle
represent typically more around 80% of the imported cattle from Canada;
therefore, only 20% of the imported cattle have been taken into account.
• From Japan, 242 animals from a special beef breed were imported. These animals
were traced, and were mostly excluded from the US rendering system. At most 39
of these animals have been rendered.
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the Geographical BSE Risk of USA
- 4 -
Live cattle imports, raw data
Country: Data 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 0 1 2 3
Total
(R1+R2)
Austria CD 3 3
other 0
Belgium CD 6 6
other 6 6
Canada CD 584732 873791 904688 1273226 1201787 1010299 1132691 1510285 1378825 1316213 989885 968435 1308670 1688814 513344 13019248
other 234732 165853 363884 511118 603576 820997 1104555 1190675 998374 832705 1480514 1267385 1369353 737887 944798 1296135 1572146 11689972
Denmark CD 0
other 7 5 12
France CD 5 166 64 235
other 2 50 176 90 1 82 2 403
Germany CD 14 4 23 5 46
other 31 6 360 24 9 430
Ireland CD 70 21 62 0 0 9 0 0 0 0 0 0 162
other 67 2 76 59 14 6 1 8 233
Italy CD 5 3 8
other 2 5 11 3 2 21
Japan CD 0 0 0 0 0 0 0 0 36 48 0 81 63 9 5 0 0 242
other 0 0
Netherlands CD 0
other 49 382 9 77 8 41 41 558
Switzerland CD 45 41 17 103
other 35 13 48
UK CD 1 23 21 87 48 28 58 25 22 6 3 1 0 0
other 8 35 20 23 37 59 30 62 19 25 8 1
ALL
TOTALS
non UK CD 70 0 0 71 283 90 0 0 9 584732 873791 904688 1273226 1201787 1010335 1132739 1510314 1378917 1316276 989894 968440 1308670 1688814 513344 16656490
other 69 2 101 287 198 21 235121 165853 363890 511118 603587 821006 1104635 1190767 998780 832746 1480544 1267395 1369355 737887 944806 1296135 1572146 0 15496449
UK CD 1 0 23 21 87 48 28 58 25 22 6 3 1 0 0 0 0 0 0 0 0 0 0 0 323
other 8 35 20 23 37 59 30 62 19 25 0 0 8 0 1 0 0 0 0 0 0 0 0 0 327
Table 1: Live cattle imports into the USA (CD) and corresponding exports from BSE risk countries. Source for export data: Eurostat and UK export statistics and, where available,
export statistics from other BSE risk countries. Note: Only imports in risk periods (shaded) are taken into account for assessing the external challenge. Risk periods are defined according to the
SSC opinion of January 2002. The numbers shown in the table are the raw import figures and are not reflecting the adjusted imports for the assessment of the external challenge
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 5 -
2.2 Import of MBM or MBM-containing feedstuffs from BSE-Risk
countries
An overview of the data on MBM imports is presented in table 2 and is based on data
provided in the country dossier (CD) and corresponding data on relevant exports as
available from BSE risk countries that exported to the USA. Only data from risk
periods are indicated, i.e. those periods when exports from a BSE risk country already
represented an external challenge, according to the SSC opinion on the GBR (SSC,
July 2000 and updated January 2002).
• The CD reports import of 5 tons of MBM from the UK. According to Eurostat, 63
tons have been exported from the UK to the USA between 1980 and 1996;
however, according the updated MBM statistics from the UK (August 2001) 24
tons of MBM were exported from the UK to the USA between 1980 and 1996; 39
tons exported in 1989 were not confirmed by the updated UK export statistic and
therefore not taken into account. A further 38 tons were exported in 1997-1998
and 39 tons in 1999. As it was illegal to export mammalian meat meal, bone meal
and MBM from UK since 27/03/1996, exports indicated after that date should
only have included non-mammalian MBM. Therefore, these imports were not
taken into account.
• According to the CD, MBM was imported from Denmark, France, Italy and the
Netherlands. It was claimed but not substantiated that these imports were not
from ruminant origin, and therefore did not contribute to the BSE risk of the
USA.
• The Eurostat export statistics indicated additional exports from Belgium, Greece,
Ireland and Spain.
• Very large amounts of MBM (CD and other sources) between 18.000 and 44.000
tons annually were imported from Canada.
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the Geographical BSE Risk of USA
- 6 -
MBM imports, raw data
Country: Data 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 0 1 2 3
Total
(R1+R2)
Belgium CD 0
other 10 10
Canada CD 21350 0 20816 33755 23299 18472 23263 31340 30840 20595 33740 29524 36709 43670 38490 329942
other 30948 20595 33740 29524 36709 43189 32867 227572
Denmark CD 0 0 0 0 0 0 18 78 63 127 39 139 0 0 0 464
other 72 19 37 83 62 19 90 382
France CD 0 0 0 0 0 0 6 0 0 0 1 19 37 39 63 165
other 0
Greece CD 0
other 55 55
Ireland CD 0
other 20 2 3 14 141 180
Italy CD 0 0 0 0 21 0 0 0 0 0 0 15 0 0 0 36
other 100 65 123 7 15 315 126 514 111 1376
Netherlands CD 0 0 0 0 0 0 0 0 0 0 0 19 0 0 0 19
other 46 23 3 5 3 38 118
Spain CD 0
other 8 8
UK CD 5 0 0 0 0 0 0 0 0 0 0 0
other 12 10 2 39 37 1 39
ALL
TOTALS
non UK CD 0 0 0 0 0 0 0 0 0 21350 0 20816 33755 23320 18472 23287 31418 30903 20722 33780 29716 36746 43709 38553 406547
other 0 0 0 0 0 20 0 0 0 146 90 123 3 65 106 488 163 31545 20665 33759 29763 36709 43189 32867 229701
UK CD 0 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0 0 0 0 0 0 0 5
other 0 12 0 0 10 2 0 0 0 39 0 0 0 0 0 0 0 37 1 0 0 0 0 0 101
Table 2: MBM imports into the USA (CD) and corresponding exports from BSE risk countries. Source for export data: Eurostat and UK export statistics and, where available, export statistics from other BSE risk countries. Note:
Only imports in risk periods (shaded) are taken into account for assessing the external risk. Risk periods are defined according to the SSC opinion of January 2002.The numbers shown in the table are the raw import figures and are not reflecting
the adjusted imports for the assessment of the external challenge
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 7 -
2.3 Overall assessment of the external challenge
The level of the external challenge that has to be met by the BSE/cattle system is
estimated according to the guidance given by the SSC in its final opinion on the GBR
of July 2000 (as updated in January 2002).
Live cattle imports:
In total the country imported 2038 (other sources) or 1128 (CD) live cattle from BSE
risk countries other than Canada, of which 327 (other sources) or 323 (CD) came
from the UK. From Canada the imports were >500,000 animals per year. The
numbers shown in table 1 are the raw import figures and are not reflecting the
adjusted imports for the assessment of the external challenge. Broken down to 5 year
periods the resulting external challenge is as given in table 3. This assessment takes
into account the different aspects discussed above that allow to assume that certain
imported cattle did not enter the domestic BSE-cattle system, i.e. were not rendered
into feed. In the case of the USA, all the animals for which tracing information
showed that they were not rendered were excluded from the external challenge.
MBM imports:
In total the country imported 689 tons MBM (CD) or 2,230 tons MBM (other sources)
from BSE risk countries other than Canada, of which 5 tons (CD) or 101 tons (other
sources) were exported from the UK (UK export data). From Canada, the imports
were about 30 000 tons per year. The numbers shown in table 2 are the raw import
figures and are not reflecting the adjusted imports for the assessment of the external
challenge. Broken down to 5 year periods the resulting external challenge is as given
in table 3. This assessment takes into account the different aspects discussed above
that allow to assume that certain imported MBM did not enter the domestic
BSE/cattle system or did not represent an external challenge for other reasons. As it
was illegal to export mammalian MBM from UK since 27/03/1996, exports indicated
after that date should only have included non-mammalian MBM. In the case of the
USA imported MBM from UK in 1989 and between 1997 and 1999 was not taken
into account.
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 8 -
External Challenge experienced by the USA
External challenge Reason for this external challenge
Period Overall Level Cattle imports MBM imports Comment
1980 to 1985 Moderate Negligible
1986 to 1990
Moderate
Negligible Low
1991 to 1995 Very high High High
1996 to 2000 Very high
2001 to 2003
Extremely high Very high
Extremely high
When Canadian
import data are
excluded from
the assessment,
the overall level
varies from low
to high.
Table 3: External challenge resulting from live cattle and/or MBM imports from the UK and other
BSE risk countries. The challenge level is determined according to the SSC-opinion on the GBR of
July 2000 (as updated in January 2002).
On the basis of the available information, the overall assessment of the external challenge
is as given in table 3.
3. STABILITY
3.1 Overall appreciation of the ability to avoid recycling of BSE
infectivity, should it enter processing
Feeding
Use of MBM in cattle feed
• Until 1997 ruminant MBM (RMBM) could legally be included in cattle feed and
was indeed commonly fed to cattle of different age and type. Prior to the feed ban
the US authorities estimated that 10% of all MBM would deliberately have been
fed to cattle.
Feed bans
• A ban to feed (several types of) MMBM to ruminants was put in place in August
1997. Derogation from the ban was granted for pure porcine and equine protein
(MBM) coming from designated (single species) rendering plants. This MMBM
might still be fed to cattle. Therefore this feed ban is a ruminant to ruminant ban.
• It is planned to prohibit the use of all mammalian and poultry protein in ruminant
feed and prohibiting materials from non-ambulatory disabled cattle and dead stock
from use in all animal feed.
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 9 -
Potential for cross-contamination and measures taken against
• The animal production chain in the USA is large-scale industry, which allows for
a high level of specialisation and many farm and factories for slaughter, rendering
and feed production are dedicated to one species only. This reduces the risk of
cross-contamination to a large extend, but this does not apply to regions with a lot
of mixed farming.
• Cross-contamination of non-ruminant MBM with RMBM is theoretically possible
whenever transport of this material from rendering to feed plants is done in bulk
and with the same means of transport. It is unknown if this can be excluded.
• Cross-contamination in feed mills is possible as many feed mills produce
compound feeds for different species on the same production line. No data on the
structure of the feed industry in the USA were provided by the US authorities that
would allow estimating the amount of cattle feed annually produced in mixed feed
mills throughout the period 1980-2001. Information on inspection of feed mills
shows that this problem is still found, by 2003, in a very small fraction of the
industry.
• Since 1997, FDA regulations provide for either the use of separate lines in the
production of ruminant feed or specify detailed clean-out procedures to be used
between production batches. However, experience in Europe shows that flushing
batches etc are not capable to eliminate cross-contamination, even though they
reduce it. The efficiency of the required measures cannot be assessed as detailed
control data are lacking and samples are not taken for this purpose.
• Feed containing RMBM has labels not to be fed to ruminants, but “on-farm”
cross-contamination is regarded to be possible.
• Hence, as reasonable worst case scenario, it is assumed that cattle, in particular
dairy cattle, can still be exposed to RMBM and hence to BSE-infectivity, should it
enter the feed chain.
• Rendering plants and feed mills are, according to the CD, regularly inspected for
compliance with the regulations, throughout the country.
• It is planned to require dedicated equipment or facilities for handling and storing
feed and ingredients during manufacturing and transportation, to prevent cross
contamination.
Control of Feed bans and cross-contamination
• Since 1997, feed mills that are allowed to use RMBM, and also produce cattle
feed (without RMBM), are inspected annually, other may also be inspected. Two
types of violations were registered. One type not involving RMBM, the others
involving this, this mainly concerns cross-contamination problems. These firms
were re-inspected soon. In several cases, products were recalled, sales were closed
and/or products were destroyed. Cattle feed is not sampled to test for presence of
illegal MBM.
• According to information provided in 1999/2000 by the feed producers, the
compliance is assumed by the US authorities to be in the order of magnitude of
70% to ≤90% since 1998, and 30% to ≤70% before. Official control data
concerning rendering and feed mill industries were provided and show that action
at shortcomings in the production processes (a few percent of the firms) have
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 10 -
become severe by the beginning of 2003. However, samples from ruminant feed
are not regularly tested for the inclusion of MMBM. Reports from the feed
industry in 2000 and 2001 indicate significant shortcomings in the implementation
of the ban in that period. This does confirm the known difficulty of implementing
and enforcing such a feed ban.
• No examinations are performed to assess cross-contamination with RMBM of the
protein (e.g. through non ruminant MBM) that enters cattle feed.
Rendering
• The domestic MBM production averages 3 million metric tons per year.
• Almost 60% of the MBM produced originate from ruminants (cattle 59%, sheep
0.6%), 20% from pigs and 20% from poultry.
Raw material used for rendering
• Ruminant material is rendered together with material from other species (approx.
50% of all plants). This is particular significant as SRM will be included. "Free
renderers" are known to also process fallen stock.
• Slaughter by-products from different species, including SRM, is the raw material
for most rendering plants that are associated with slaughterhouses.
• Some plants process material from one species, e.g. pigs or horses or poultry only.
• The CD does not provide the numbers of plants falling under each category nor of
their respective annual production.
Rendering processes
• Four major rendering systems are used in the approximately 280 rendering plants
in the USA. All systems operate under atmospheric pressure with temperatures
ranging between 100 and 150 °C and different heating times:
- Batch cooker plants (46): 115-125 C°, 30-240 min.
- Continuous tube and disc cooker systems (220): 131-150 °C, 45-90 min.
- Continuous multi-stage evaporator systems (10): 115-125 °C, 20-40 min.
- Continuous preheat/press/evaporator systems (4): 87-120 °C, 240-270 min.
Due to the fact that they operate under atmospheric pressure only, none of the
described rendering processes are assumed to reduce BSE-infectivity
significantly, should it enter the processing.
SRM and fallen stock
• An SRM-ban for human food has been introduced in 2004. There was however
never an SRM ban for the feed chain.
• SRM are rendered together with other slaughter by-products and, in case of
independent renderers, together with fallen stock.
• It is planned to remove SRM from all animal feed, including pet-food.
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 11 -
Conclusion on the ability to avoid recycling
• Before 1997, US system would not have been able to avoid recycling of the BSEagent
to any measurable extent. If the BSE-agent was introduced into the feed
chain, it could have reached cattle.
• After the introduction of the 1997 ban in August 1997, the ability to avoid
recycling of BSE-infectivity was somewhat improved. However, the rendering of
ruminant material (including SRM and fallen stock) is inadequate (non
pressurized), and cross-contamination potentials of cattle feed with other feeds
remain.
• Therefore, the system is still unable to avoid recycling of BSE-infectivity if
already present in the system or incoming.
3.2 Overall appreciation of the ability to identify BSE-cases and to
eliminate animals at risk of being infected before they are
processed
Cattle population structure
• The total cattle population of the USA was approximately 111 Million cattle in
1980, 99 Million in 1990, 102.8 Million cattle in 1995 and 99.5 Million cattle in
1998. Of these, approximately 17.6 % (17.5 Million) were dairy cattle and 82.4%
beef cattle (based on data 1995-1998). However, the HRS recognised that the
official slaughter figures were only compatible with a stable total cattle population
of about 140 million.
• Between 17% and 19% of all cattle slaughtered were >2 years of age. The average
age at slaughter for dairy cattle is between 4 and 5 years.
Husbandry systems
• According to the country experts it was assumed that mixed farming did exist in
the USA, but at a low (and decreasing) level. No figures were provided.
• The two main cattle husbandry systems are beef (82.4%) and dairy (17.6%).
Within both systems all levels of intensity are existing, however, both segments are
now characterised by large, intensive operations. For dairy cattle a clear trend towards
larger, more efficient holdings can be seen.
Maps were presented by the country experts in 1999 that indicate an overlap of
intensive cattle, swine and poultry industry in certain geographic regions of the USA.
Cattle identification and monitoring system
• The existing animal identification system is jointly operated by State and Federal
representatives and is maintained individually for each State. No centralised USwide
animal identification system is in place.
• It was estimated by the country experts that this system ensures that approx. 95%
of all cattle are officially tagged and registered in State databases.
• A trace-back of individual animals is possible whenever the animal has not moved
several times (through several herds) within a particular State. Intra-State
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
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movements are not recorded in any type of database, and any follow-up would
rely on the documentation (records) or the memory of the respective owners.
BSE surveillance
• All foreign animal diseases (exotic diseases) have been and are notifiable by
Federal legislation. BSE, as an exotic disease, was notifiable since it first was
described as a disease (1986).
• A surveillance targeting animals with clinical signs that could be consistent with
BSE is in place since 1989/1990 and operating with larger sample sizes (900-1600
per year) since 1997. This program officially started in 1990 but some samples
examined under this system go back to 1986. The samples come from:
- Cattle exhibiting signs of neurological disease;
- Cattle condemned at ante-mortem examination in slaughterhouses for
neurological signs;
- Rabies-negative cattle submitted to public-health laboratories (the country
experts confirmed that samples were appropriately taken and should have
allowed finding BSE if present);
- Neurological cases submitted to veterinary diagnostic laboratories and
veterinary schools/teaching hospitals;
- Between 25% and 33% of the animals in the sample were supposed to be aged
dairy cattle which are non-ambulatory (“downer cows”) at slaughter. Detailed
information on the age distribution of those animals was not available.
• In addition to histopathology, immunhistochemistry is applied since 1994,
initially on those animals for which a differential diagnosis could not be
established. Since 1997 it is fully incorporated in the surveillance scheme and
approx. 900-1.600 samples are examined annually by both tests. In 2000, a total
of 2 870 submissions were examined.
• In 2001, the number of submissions doubled, and in 2002 and 2003, submissions
totalled 19.777 and 20.277 respectively. The total number of samples examined
through April 2004 is more than 72.500.
• A BSE case has been detected in December 2003. Intensive research showed that
it was born and raised in Canada, and therefore, it is not a domestic case.
• In addition, since 1 June 2004, an extensive testing of the risk population is
initiated. It is planned to test as many cattle from the risk population (the target is
268.000 cattle) in a 12–to–18–month period. The following categories will be
tested: non-ambulatory cattle, cattle exhibiting signs of a central nervous system
disorder, cattle exhibiting other signs that may be associated with BSE and dead
cattle. The surveillance program will also include a limited number of random
samples from apparently normal, aged animals.
3.3 Overall assessment of the stability
For the overall assessment of the stability, the impact of the three main stability
factors, (i.e. feeding, rendering and SRM-removal) and of the additional stability
factor surveillance has to be estimated. Again, the guidance provided by the SSC in its
opinion on the GBR of July 2000 (as updated in 2002) is applied.
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
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Feeding
Until August 1997, RMBM was legally fed to cattle. Feeding was therefore "not
OK". In August 1997 an RMBM-ban was introduced but feeding of non-ruminant
MBM to cattle remained legal as well as feeding of RMBM to non-ruminant animals
(farm animals and pets). An RMBM ban is difficult to maintain, as only labels can
distinguish the various MMBMs. This makes control of the feed ban very difficult
because analytical differentiation between ruminant and non-ruminant MBM is
difficult if not impossible.
Due to the highly specialised production system in the USA, various mammalian
MBM streams can be separated. Such a feed ban would therefore be assessed as
"reasonably OK", for all regions where this highly specialised system exists.
However, several areas in the USA do have mixed farming and mixed feed mills, and
in such regions an RMBM ban would not suffice. Additionally, official controls for
cattle feeds to control for compliance with the ban started in 2002. Thus, for the
whole country, the assessment of the feeding after 1997 remains "not OK", but
improving.
Rendering
The rendering industry is operating with processes that are not known to reduce
infectivity. It is therefore concluded that rendering was and is "not OK".
SRM-removal
SRM were and are still rendered for feed, as are (parts of) the fallen stock. SRMremoval
is therefore regarded as "not OK".
BSE-surveillance
Before 1989, the ability of the system to identify (and eliminate) BSE-cases was
limited. Since 1990 this ability is improved, thanks to a specific (passive) BSE
surveillance. The initiated introduction of active surveillance in risk populations
should improve the system significantly.
Stability of the BSE/cattle system in the USA over time
Stability Reasons
Period Level Feeding Rendering SRM removal BSE
surveillance
1980 to
2003
Extremely
unstable Not OK Not OK Not OK
Passive but
improving
with some
testing of risk
groups
Table 4: Stability resulting from the interaction of the three main stability factors and the BSE
surveillance. The stability level is determined according to the SSC-opinion on the GBR of July
2000 (as updated in 2002).
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
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On the basis of the available information, it has to be concluded that the country's
BSE/cattle system was extremely unstable until today, i.e., it would have recycled and
amplified BSE-infectivity very fast, should it have entered the system. The stability of
the BSE/cattle system in the USA overtime is as given in table 4.
The present assessment modifies the stability assessment of the previous GBR report
in 2000 mainly due to a different perception of the impact of BSE surveillance on
stability and of the efficiency of the RMBM feed ban.
4. CONCLUSION ON THE RESULTING RISKS
4.1 Interaction of stability and challenges
In conclusion, the stability of the USA BSE/cattle system in the past and the external
challenge the system has coped with, are summarised in table 5 below.
From the interaction of the two parameters “stability” and “external challenge” a
conclusion is drawn on the level of “internal challenge” that emerged and had to be
met by the system, in addition to external challenges that occurred.
Interaction of stability and external challenge in the USA
Period Stability External Challenge Internal challenge
1980 to
1985
1986 to
1990
Moderate Possibly present
1991 to
1995 Very high
1996 to
2000
2001 to
2003
Extremely
unstable
Extremely high
Likely to be present and
growing
Table 5: Internal challenge resulting from the interaction of the external challenge and stability.
The internal challenge level is determined according to guidance given in the SSC-opinion on
the GBR of July 2000 (as updated in 2002).
An external challenge resulting from cattle import could only lead to an internal
challenge once imported infected cattle were rendered for feed and this contaminated
feed reached domestic cattle. Cattle imported for slaughter would normally be
slaughtered at an age too young to harbour plenty of BSE infectivity or to show signs,
even if infected prior to import. Breeding cattle, however, would normally live much
longer and only animals having problems would be slaughtered younger. If being 4-6
years old when slaughtered, they could suffer from early signs of BSE, being
approaching the end of the BSE-incubation period. In that case, they would harbour,
while being pre-clinical, as much infectivity as a clinical BSE case. Hence cattle
imports could have led to an internal challenge about 3 years after the import of
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 15 -
breeding cattle (that are normally imported at 20-24 months of age) that could have
been infected prior to import.
In the case of the USA a few potentially infected cattle were imported from the UK
and more from other BSE-risk countries. Furthermore, large numbers of imported
animals came from Canada. This implies that cattle imported in the mid eighties could
have been rendered in the late eighties and therefore led to an internal challenge in the
early 90s.
On the other hand imports of contaminated MBM would lead to an internal challenge
in the year of import, if fed to cattle. The feeding system is of utmost importance in
this context. If it could be excluded that imported, potentially contaminated feed stuffs
reached cattle, such imports might not lead to an internal challenge at all.
In case of the USA this implies that it was possible that imported MBM reached
domestic cattle and lead to an internal challenge in the early 90s.
If Canadian imports would be excluded from this assessment, we find that the USA
receives a moderate challenge for all 5-year intervals since 1980, a high challenge
between 1985 and 2000 and a low challenge thereafter. If combining these moderate
to high challenges due to imports with the extremely unstable system, the conclusion
would still be that the occurrence of an internal challenge is possible during the early
80s and likely in the late 80s.
4.2 Risk that BSE infectivity entered processing
A processing risk developed in the late 80s/early 90s when cattle imports from BSE
risk countries were slaughtered or died and were processed (partly) into feed, together
with some imports of MBM. This risk continued to exist, and grew significantly in the
mid 90s when domestic cattle, infected by imported MBM, reached processing. Given
the low stability of the system, the risk increased over the years with continued
imports of cattle and MBM from BSE risk countries.
4.3 Risk that BSE infectivity was recycled and propagated
A risk that BSE-infectivity was recycled and propagated exists since a processing risk
first appeared, i.e. in the early 90s. Until today this risk persists and increases fast
because of the extremely/very unstable BSE/cattle system in the USA.
5. CONCLUSION ON THE GEOGRAPHICAL BSE-RISK
5.1 The current GBR as function of the past stability and challenge
• The current geographical BSE risk (GBR) level is III, i.e. it is likely but not
confirmed that domestic cattle are (clinically or pre-clinically) infected with the
BSE-agent.
Note1: It is also worth noting that the current GBR conclusions are not dependent on
the large exchange of imports between USA and Canada. External challenge due to
exports to the USA from European countries varied from moderate to high. These
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
- 16 -
challenges indicate that it was likely that BSE infectivity was introduced into the
North American continent.
Note2: This assessment deviates from the previous assessment (SSC opinion, 2000)
because at that time several exporting countries were not considered a potential risk.
5.2 The expected development of the GBR as a function of the past
and present stability and challenge
• As long as there are no significant changes in rendering or feeding, the stability
remains extremely/very unstable. Thus, the probability of cattle to be (preclinically
or clinically) infected with the BSE-agent persistently increases.
• Since recent improvements in the safety of MBM production in many countries
or significant recent reductions in the incidence of BSE are not taken into
account for the assessment of the external challenge, the external challenge
assessed after 2001 could be overestimated and is the worst case assumption.
However all current GBR conclusions are not dependent on these assumptions
in any of the countries assessed. For future assessments and when the impact of
the production, surveillance and true incidence changes have been fully
quantified, these developments should be taken into account.
5.3 Recommendations for influencing the future GBR
• Measures that improve the stability of the system, will, over time, reduce the
probability that cattle could get infected with the BSE-agent. Possible actions
include
- removal of SRM and/or fallen stock from rendering of animal by-products into
feed,
- high pressure standards in rendering processes,
- significant improvement of ban on use of ruminant MBM in cattle feed,
supported by regular sampling of feed for the occurrence of such MBM.
• Improved passive and active surveillance, i.e. sampling of animals not showing
signs compatible with BSE from “at-risk” cattle populations, such as adult cattle
in fallen stock and emergency slaughter, by means of rapid screening, would
allow monitoring the efficiency of stability enhancing measures.
Documentation provided to EFSA
• Letter with the ref D (2003) KVD/ip/420722 from the European
Commission requesting a geographical risk assessment for the
appearance of BSE in a country.
• Country Dossier as prepared by the country in response to the EC and
EFSA data collection request.
• Other sources of data information i.e. exports from third countries and
Eurostat data.
• SSC, July 2000. Final opinion on the Geographical Risk of Bovine
Spongiform Encephalopathy (GBR).
Annex to the EFSA Scientific Report (2004) 3, 1-17 on the Assessment of the
Geographical BSE Risk of USA
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• SSC, January 2002. Updated opinion on the Geographical Risk of
Bovine Spongiform Encephalopathy (GBR).
Acknowledgment
Members of the EFSA Scientific Expert Working Group on GBR are acknowledged
for their valuable contribution to this mandate. The members are: Didier Calavas,
Aline De Koeijer, Michael Gravenor, John Griffin, Dagmar Heim, Matthias Kramer,
Riitta Maijala, Mo Salman, Vittorio Silano, Emmanuel Vanopdenbosch, and Stig
Widell.http://www.efsa.eu.int/science/efsa_scientific_reports/gbr_assessments/scr_annexes/574/sr03_biohaz02_usa_report_annex_en1.pdf TSS
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