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From: TSS ()
Subject: The Response to BSE in the United States INDUSTRY VS FACTS make your 'CHOICES'
Date: July 15, 2005 at 7:25 am PST


CHOICES The magazine of food, farm, and resource issues

2nd Quarter 2005 • 20(2) CHOICES 103

A publication of the

American Agricultural

Economics Association

2nd Quarter 2005 • 20(2)

©1999–2005 CHOICES. All rights reserved. Articles may be reproduced or electronically distributed as long as attribution to Choices and the American

Agricultural Economics Association is maintained. Choices subscriptions are free and can be obtained through

The Response to BSE in the United States

By John Fox, Brian Coffey, James Mintert, Ted Schroeder, and Luc Valentin

Since the emergence of bovine spongiform encephalopathy

(BSE) in the United Kingdom in the late 1980s, the

United States has implemented various measures to prevent

the disease from entering the country, to prevent its

spread if discovered here, and to safeguard human health.

Regulatory actions included import restrictions, a ban on

certain ruminant tissues in ruminant feed, and a surveillance

program. Additional measures, aimed at reassuring

domestic and foreign consumers about the safety of US

beef, were implemented following the December 23, 2003

announcement that a dairy cow in Washington State had

tested positive for BSE. In the sections that follow, we discuss

the US response to BSE under three broad categories

—trade policy, food and feed restrictions, and

surveillance. Our analysis focuses on the costs associated

with various regulatory actions and less so on potential

benefits that are more difficult to quantify.

Trade Policy

Following the announcement of the first US case, 53

countries, including major markets such as Japan, Mexico,

South Korea, and Canada, banned imports of US cattle

and beef products. This came as no surprise—automatic

border closure following such announcements had become

standard procedure. The United States itself blocked

imports of Canadian beef and cattle following the

announcement of the first Canadian case in May 2003.

Border closure in response to a very low BSE incidence

in an exporting country is not endorsed by the World

Organization for Animal Health (OIE), particularly when

control measures are in place. Moreover, although the

United States itself had not adhered to OIE guidance on

trade, the United States Department of Agriculture

(USDA) did initiate regulations to allow imports from

countries, specifically Canada, that presented a "minimal

risk" of introducing BSE. This minimal risk region (MRR)

rule that would reopen the border to imports of Canadian

cattle less than 30 months old was to become effective

March 7, 2005. However, in response to a motion filed by

the Ranchers-Cattlemen Action Legal Fund (R-CALF), a

federal court in Montana granted a preliminary injunction

blocking the measure. A hearing to determine whether a

permanent injunction should be granted is scheduled for

July 27, 2005.

The controversy surrounding the reopening of the

Canadian border illustrates the potential gains and losses

from any change in trade policy. Although R-CALF may

indeed be concerned about the human health risk from

Canadian cattle (though some might doubt it), it is clear

that US cattle producers, particularly those in the northwestern

US, would lose from import competition in the

short run. Marsh, Brester, and Smith (2005) estimate that

Canadian imports would reduce US feeder cattle prices by

$4.57/cwt. However, in the long run, if adequate cattle

supplies are not available locally to keep US packing plants

in the region open, producers in the Northwest will lose

local cattle markets. Similarly, US producers are losing

from the current restrictions on US exports. In 2003, beef

exports were valued at $3.95 billion and accounted for

9.6% of US commercial production. Although some

important markets, including Mexico and Canada, did

partially reopen during 2004, exports for the year were

82% below 2003. Coffey, Mintert, Fox, Schroeder, and

Valentin (2005), in an analysis performed for the Kansas

Department of Agriculture, suggest that US beef industry

losses from export restrictions during 2004 ranged from

$3.2 billion to $4.7 billion.

The question we might ask here is whether these trade

disruptions and associated welfare losses could have been

avoided. Caswell and Sparling (in press) emphasize the

importance of an internationally coordinated response to

managing risks from diseases such as BSE, and Caswell (in

press) argues that the potential trade impacts of BSE discovery

were not sufficiently weighted in the BSE risk management

process. Thus, if MRR legislation had been

enacted prior to the recent discoveries of BSE outside of

104 CHOICES 2nd Quarter 2005 • 20(2)

Europe, we may never have banned

imports of Japanese beef when they

discovered their first case in September

2001, nor vice versa. Of course,

with the benefit of hindsight, it is

easy to point out what might have

been. Nevertheless, both Canada and

the United States had been warned

by the European Union in July 2000

that they were at risk for discovering

the disease (Scientific Steering Committee,



In 2003, the USDA tested approximately

20,000 cattle for BSE. Countries

in which the disease is

established have more intensive surveillance

—for example, the EU has

tested around 8 million head per year

since 2001 (Fox & Peterson, 2004).

Following the Washington State case,

the USDA announced a one-year

enhanced surveillance program. The

objective was to test as many cattle as

possible from high-risk categories—

those exhibiting signs of central nervous

system disorders, nonambulatory

cattle, and those that die on

farms—in addition to a random sample

of healthy older animals. In various

news releases, the USDA stated

that a sample size of 268,000 animals

would allow for the detection of BSE

at a rate of one positive in 10 million

adult cattle with a 99% confidence

level. That claim, however, is based

on the assumption that all cases

occur in the targeted high-risk group

and that the incidence in nontargeted

categories is zero. As of April 2005,

314,000 cattle had been tested under

the new protocol with no positive

cases identified. Table 1 provides an

excerpt from the test results.

The surveillance program has

been a source of controversy in areas

related to testing protocol, announcement

of inconclusive results,

and an incident in Texas in May

2004 in which an animal exhibiting

central nervous system symptoms

was not tested for the disease. Inconclusive

(or false positive) test results

are expected with the Bio-Rad rapid

screening test used by USDA. The

false positive rate is variously estimated

at between one in 50,000 to as

little as one in 300,000 tests. Thus

far, the USDA has announced three

inconclusive results—two in June

2004 and one in November 2004—

all of which, upon confirmatory testing

using immunohistochemistry

(IHC), were found to be negative.

The initial announcements of inconclusive

cases were controversial and

led the Animal and Plant Health

Inspection Service (APHIS) to revise

their announcement procedure—

delaying announcement until a sample

produced two inconclusive results

with the rapid test. Concern about

potential market disruption due to

false positives is one reason cited by

opponents of wider scale or voluntary

testing. For example, following the

announcement of the third inconclusive

test result on the morning of

November 18, 2004, most live cattle

futures contracts opened around $2/

cwt lower than the previous day’s

close, and many moved limit down

that day. Very light sales in the cash

market in the following days were

likely the short-run cash market reaction

to the news.

At the same time, there has been

speculation that the USDA deliberately

chose a test with a relatively

high rate of inconclusive results as a

means of desensitizing markets to the

possible discovery of true positive

cases (Mitchell, 2004). Also controversial

is the USDA’s choice of IHC

as their "gold standard" test. In February

2005, Consumers Union called

on the USDA to retest inconclusive

samples using the Western Blot test,

which, they argued, was more sensitive

and more objective. According to

the Consumers Union, the Western

Blot test is used as the confirmatory

test in Japan and Europe and had

been used previously by the USDA

to confirm the December 2003

Washington State case. (See Pruisner,

2004, for more information on

BSE testing.)

The future of the surveillance

program has not yet been decided.

Industry officials have called for it to

be scaled back. Not surprisingly,

some consumer advocacy groups

favor wider scale testing. For example,

a March 16, 2005 editorial in

The New York Times proposed that

"the only responsible way to resume

international trade in beef is to

ensure the health of the cattle. And

the only way to do that is to test the

cattle—all of them, if need be."

In what turned out to be a particularly

thorny issue for the USDA, in

July 2004 the agency denied an

application by a small Kansas beef

processor, Creekstone Farms, for permission

to voluntarily test slaughter

cattle in an attempt to regain access

to the Japanese export market. The

beef industry is sharply divided on

the issue of voluntary testing. Proponents

tend to view it in terms of a

marketing decision with expected

benefits outweighing costs, at least in

the short run. Indeed, our analysis

for the Kansas Department of Agriculture

(Coffey et al., 2005) suggests

a potential net benefit ranging from

$27.50 to $48.50 per head (before

fixed costs) if voluntary testing

restored full access to the Japanese

and South Korean markets. Opponents

argue that BSE testing is

unnecessary and costly, that it sets a

dangerous precedent in terms of

acquiescing to an unreasonable customer

demand, and that it is not scientifically

valid and provides no risk-

2nd Quarter 2005 • 20(2) CHOICES 105

reduction benefit to consumers.

Large US meat processor stances

regarding BSE testing suggest that

the investments and logistics of largescale

testing, in addition to the

potential impact on demand of a positive

case, are such that it is a losing

proposition for bigger firms—perhaps

in particular for those diversified

either internationally or across

meat products. For a single small

firm, on the other hand—especially

one more heavily reliant on export

sales to high-quality foreign markets

than the major packers—the situation

is different. If voluntary testing

provided export market access, it

could produce substantial monopolytype

benefits in the short run. Creekstone

officials have stated that their

increased revenue from regaining

access to the Japanese market would

far exceed the testing cost of $20 or

less per head. Thus, for Creekstone,

the private incentive to pursue testing

was fairly clear. It is worth noting

however, that this scenario would

produce no benefit for producers,

because increased demand from a

single small firm would have a negligible

impact on cattle prices. However,

if testing did provide market

access, more firms would be attracted

to testing, and domestic cattle prices

would increase.

Finally, regarding the current surveillance

effort, it is not yet clear how

successful the USDA has been in its

efforts to sample the targeted highrisk

groups. The APHIS website provides

no breakdown of samples by

animal categories (Table 1), in contrast

to the UK, where detailed

breakdowns for various risk categories

in the active surveillance programs

are provided (Table 2). Clearly,

no one associated with the US beef

industry wants to find this disease.

However, the perception that officials

may have latitude in terms of sample

selection, rumors about animals not

sampled, and allegations by at least

one former USDA employee about

the mishandling of potentially positive

test samples, does not help

engender confidence among foreign

buyers or policy decision makers.

Critics have commented that Germany

did not begin to find BSE until

it allowed private testing. If the disease

is truly not present in the US

herd, then the industry has little to

fear from allowing expanded private

testing. However, what are the odds

that the surveillance program in place

during 2003 managed to detect the

only BSE-infected cow in a herd of

100 million?

Food and Feed Restrictions

In January 2004, the Food Safety

Inspection Service (FSIS) banned

nonambulatory animals and certain

tissues designated as specified risk

material (SRM) from the human

food supply. The new regulations

require firms to age animals using

postmortem dentition, to deal with

nonambulatory animals, and to segregate

SRM material. Using data

from a survey of meat processors,

Coffey et al. (2005) estimated the

Table 1. Excerpts from the USDA’s BSE test results report.

Date Negative Inconclusive


result Positive Total

Week 45


9,138 0 — 0 9,138

Week 44


10,663 0 — 0 10,663

Week 25


7,900 1 Negative 0 7,901

Note. Data from USDA Animal and Plant Health Inspection Service (2005).

Table 2. Excerpts from the UK BSE test results report—2005.

Ongoing surveys (cattle) Tested



BSE not




Fallen stock 18,574 3 18,558 13

Casualties on farm 30,825 11 30,788 26

Casualties at OTMS abattoirs 3,165 0 3,164 1

24–30 month casualty cattle at fresh

meat abattoirs

211 0 211 0

Over thirty months (OTM) scheme—

random animals (born before August

1996) (before feed ban)

2420 0 2417 3

OTM scheme—animals born after July


28,613 0 28,613 0

Animals sampled as 96/97 cohort

(excluding fallen stock, casualties, etc.)

26,726 0 26,726 0

Birth cohorts of BSE cases 380 0 380 0

BSE offspring 43 0 43 0

Animals slaughtered for human

consumption: OTM (beef assurance


22 0 22 0

Note. Data from Defra UK (2005).

106 CHOICES 2nd Quarter 2005 • 20(2)

additional labor costs of these tasks at

approximately $0.45 per head of

plant capacity.

As currently defined, SRM

includes the brain, skull, eyes,

trigeminal ganglia, dorsal root ganglia,

spinal cord, and vertebral column

from cattle 30 months of age

and older, and the tonsils and the distal

ileum of all cattle. In order to

ensure complete removal of the distal

ileum, the rules required that the

entire small intestine be disposed of

as inedible. The small intestine rule

has been the most controversial

aspect of the SRM regulation because

for some firms it was a valuable byproduct,

particularly in some export

markets. Coffey et al. (2005) estimated

that on average, firms that

previously sold small intestines were

losing from $3.23 to $4.13 per head

because of the rule. Other products

condemned as a result of BSE regulations

include bone-in cuts from overthirty-

month (OTM) animals that

contain vertebral column (i.e., Tbone

steaks) and product obtained

from advanced meat recovery (AMR)

using OTM vertebral columns. Coffey

et al. (2005) estimated that

restrictions on bone-in cuts and

AMR reduce per-head revenues by

approximately $8.50 and $9.36,

respectively, on affected OTM animals,

while the ban on nonambulatory

(downer) cattle resulted in an

aggregate loss of approximately $63


On February 2, 2004, a panel of

experts (the International Review

Team or IRT) commissioned by the

USDA provided recommendations

for future actions for managing BSE

risk. With regard to feed regulations,

the IRT recommended that (a) unless

aggressive surveillance showed BSE

risk to be minimal, SRM should

include the brains and spinal cords of

all animals over 12 months and the

entire intestine of all animals; (b)

SRM should be excluded from all

animal feed including pet food; and

(c) all meat and bone meal (MBM),

including avian, be excluded from

ruminant feed. Earlier, on January

26, the Food and Drug Administration

(FDA) announced plans to

strengthen the ruminant feed ban

that had been in place since 1997. In

particular, the FDA said it would

eliminate exemptions for bovine

blood and plate waste and ban the

feeding of poultry litter. In July

2004, the FDA published an

Advance Notice of Proposed Rulemaking

(ANPR) with an invitation

to comment on several aspects of the

ruminant feed ban, including the recommendations

of the IRT. The comment

period for this notice ended on

September 13, 2004, but as of April

2005, the FDA had not implemented

any of its proposed actions, and the

exemptions for plate waste and

bovine blood products in the 1997

feed ban remained in place.

Additional restrictions on SRM

or ruminant feed would hurt the cattle

sector by eliminating markets for

certain products or increasing feed

costs. Ruminant blood meal, for

example, is widely used in cattle feed,

particularly for dairy cows and in

milk replacement rations for calves.

When FDA announced plans to

eliminate the blood exemption, the

values of ruminant and porcine

blood meal, which had been similar,

diverged. During 2004, ruminant

blood meal traded at an average discount

of $250 per ton compared to

the porcine product. Coffey et al.

(2005) estimated that if the blood

exemption were eliminated, the value

of ruminant blood meal would fall by

an additional $225 per ton, resulting

in a combined loss of approximately

$1.43 for an average steer. Similarly,

the cost of banning currently defined

SRM from all animal feed was estimated

at $2.16 per head, and if the

SRM definition were extended (as

recommended by the IRT), the cost

would be $6.77 per head.

If additional cases of BSE are

found in the United States, it seems

likely that some of the changes proposed

by the FDA will become law.

The benefits of implementing those

measures are more difficult to quantify

than their costs. The Harvard/

Tuskegee risk analysis (Cohen et al.,

2001) estimated that a ban on SRM

in both human and animal feed

would reduce the predicted number

of BSE cases (in the event it is

present) by 80% and the potential

human exposure by 95%. However,

the baseline level of exposure is so

low that further reductions appear to

have minimal value. As testing technologies

develop and testing costs

fall, it may be more efficient to test

animals for the disease instead of

condemning their products. Testing,

even at current prices, appears preferable

to a total ban on feeding any

ruminant derived proteins to animals

—a measure currently in place

in the EU and Japan. Coffey et al.

(2005) estimated the cost of such a

ban at $14.00 per head in lost revenue

plus $4.50 per head in additional

feed costs. However, for reasons that

are not clear to us, the testing option

is not currently applied to nonambulatory

animals—even in cases in

which an animal sustains an injury in



Although the US response to BSE

can be critiqued in some areas, the

overall response appears to be far

more efficient than, for example, that

of Japan, which removed all cattle

over 30 months from the food chain,

instituted universal BSE testing, and

banned meat and bone meal for all

2nd Quarter 2005 • 20(2) CHOICES 107

uses. US policy makers appear to

have considered the costs and benefits

of various approaches and recognized

that the risk to human health is

extremely low.

How low is the risk? In the

United Kingdom, the human version

of BSE has claimed around 150 victims.

However, they have had more

than 180,000 BSE infected cows,

most of which were found before the

connection to human disease was recognized.

Estimates of the total number

of animals infected in the United

Kingdom run to as high as two million.

Had Canadian and US authorities

taken no precautions to eliminate

SRM tissues from food, four Canadian

BSE cases might have led to

0.004 human cases in the next 10–15

years. The human health risk from

BSE is probably far lower than the

risk of choking on a toothbrush.

Thus, to suggest, as did Judge Richard

Cebull in granting the injunction

blocking imports of Canadian cattle,

that BSE poses a "genuine risk of

death for US customers" is a complete

distortion of the concept of

what is really risky.

Beef, like any other food, is not

and never can be 100% risk free.

However, today’s salient risk is not

mad cow disease. Instead, it is the

more familiar bacterial pathogens like

Salmonella and E. coli, the incidences

of which have dropped significantly

in recent years. By refusing to implement

drastic measures in response to

a virtually nonexistent threat, policy

makers may foster a more rational

perception of the risk associated with

the disease. Not permitting voluntary

testing of young animals, because it

provides no useful information for

consumers, could well be viewed as

part of that strategy. The wider

impact of such a measured response

may be one of enhancing the overall

stability of food demand and making

it less responsive to food scares that

occur from time to time.

For More Information

Caswell, J. (in press). A food scare a

day: Why aren’t we better at managing

dietary risk? Human and

Ecological Risk Assessment.

Caswell, J., & Sparling, D. (in press).

Risk management in the integrated

NAFTA market: Lessons

from the case of BSE. In Karen

Huff (Ed.), Proceedings of the First

Annual North American Agrifood

Market Integration Workshop.

Guelph, Ontario: University of


Coffey, B., Mintert, J., Fox, J.,

Schroeder, T., & Valentin, L.

(2005). The economic impact of

BSE on the US beef industry: Product

value losses, regulatory costs,

and consumer reactions. (Extension

Bulletin MF-2678). Manhattan,

KS: Kansas State

University Agricultural Experiment

Station and Cooperative

Extension Service.

Cohen, J., Duggar, K., Gray, G., Kreindel,

S., Abdelrahman, H.,

Habtemariam, T., et al. (2001).

Evaluation of the potential for

bovine spongiform encephalopathy

in the United States. Boston, MA:

Harvard Center for Risk Analysis.

Available on the World Wide

Web: http://www.hcra.harvard.


Defra UK. (2005). BSE: Statistics -

BSE - GB weekly cumulative statistics.

London: Defra. Available on

the World Wide Web: http://


Fox, J., & Peterson, H. (2004). Risks

and implications of bovine

spongiform encephalopathy for

the United States: Insights from

other countries. Food Policy,

29(1), 45-60.

Marsh, J., Brester, G., & Smith, V.

(2005). The impacts on US cattle

prices of re-establishing beef trade

relations (Briefing No. 74). Bozeman,

MT: Montana State University

Agricultural Marketing

Policy Center.

Mitchell, S. (2004). USDA advised

against mad cow test in 2002.

United Press International. Available

on the World Wide Web:



Pruisner, S. (2004, July). Detecting

mad cow disease. Scientific American,

291(1), 86-93.

Scientific Steering Committee of the

European Union. (2000). Report

on the assessment of the geographical

BSE-risk (GBR) of the United

States of America. Brussels: European

Commission. Available on

the World Wide Web: http://


United States Department of Agriculture

Animal and Plant Health

Inspection Service. (2005).

USDA’s BSE testing: Protecting

America’s herd. Washington, DC:

United States Department of

Agriculture. Available on the

World Wide Web: http://


Vina, S. (2004). The private testing of

mad cow disease: Legal issues

(report RL32414). Washington,

DC: Congressional Research Service.

Available on the World

Wide Web: http://www.ncseonline.



John Fox, James Mintert, and Ted

Schroeder are professors and Brian

Coffey and Luc Valentin are research

assistants in the Department of Agricultural

Economics at Kansas State

University, Manhattan, Kansas.

108 CHOICES 2nd Quarter 2005 • 20(2)

SEAC Draft Minutes of the 74th meeting held on 13th June 2002 at DEFRA



7.19 The Committee were informed that the inclusion of blood and blood products is

banned from animal feed. Under current Animal By-Products Regulations it can be spread on

land or incorporated into fertilisers as well as being used in veterinary products. Thus, there

was scope for intra-species recycling through these routes.

7.20 The Committee were informed that the new EU Animal By-Products Regulations,

which are expected to come into force in early 2003, would place many additional restrictions

on the manner in which blood can be disposed. For example, for inclusion in fertilisers,

mammalian blood would first have to pass an anti-mortem inspection, then rendered to a

pressure cooking standard. Similarly mammalian blood which had passed both ante and post

mortem inspections before rendering (although not to pressure cooking standards), could also

be used in pet food. However fertilisers containing blood or blood products would not be

allowed to be applied on pastureland on which animals graze. Furthermore the mammalian

blood would be from animals that were going into the human food chain and as such would be

classified as low risk.

7.21 The Committee were content with the position although some concern was expressed

over the potential recycling link of sheep blood, which could be distributed on fields

containing sugar beet where sheep may graze.



Environment and Rural Affairs Department

Interested Parties

Room 358

Pentland House

47 Robb's Loan

Edinburgh EH14 1TY

Telephone: 0131-244 6005

Fax: 0131-244 4755

27 June 2005

Dear Consultee

This letter seeks your comments on our proposals to
consolidate the
TSE (Scotland) Regulations which would
replace the existing
TSE (Scotland) Regulations 2002.

The new
TSE Regulations would consolidate and
update the existing
TSE (Scotland) Regulations 2002; reduce
repetition in the Regulations; restructure certain
provisions; and address a number of other issues, in
particular enforcement of feed controls and the appeals
procedures. Stakeholders' comments we received on the
consultation "
BSE testing to facilitate trade in
cattle aged over thirty months for human consumption" which
was sent out on 7 March will also be considered during this

A draft
SSI to give effect of these proposals is
currently being prepared. Should stakeholders wish to
comment on the detailed technical aspects of these
legislative proposals they should contact Andrew Taylor at
the above address.

Separate consultations on proposals to make similar
changes in England, Wales and Northern Ireland are

The Food Standards Agency has been fully involved in the
preparation of these consultation papers.

Key Proposals

Many of the existing provisions of the
TSE (Scotland) Regulations 2002 will be
included in the new
TSE (Scotland) Regulations 2005.
However, some provisions will be consolidated to avoid
unnecessary repetition. In addition, a number of
deregulatory changes will be made in the Regulations, such
as revoking the need for slaughterhouses extracting spinal
cord from sheep and goats to be additionally licensed.
These changes have been made in response to several factors
including reviews of procedure, changes in European
obligations, and detailed risk assessments.

We invite your views on a number of issues which have
been summarised in our accompanying consultation document
'Summary of Issues for Comment' and include proposed major
changes along with possible additional measures. Of
particular note, are a number of changes relating to feed
enforcement issues. These are set out in more detail in the
consultation document.

Partial Regulatory Impact Assessment (

The partial
RIA (also enclosed) provides further
detail on these proposals and gives information on other
changes that will be made in the draft Regulations.

We invite your comments on the proposed changes plus any
additional estimates on benefits and costs likely to result
from the changes. In particular we welcome feedback from
the fertiliser and rendering industries on the likely value
generated and amounts of material involved in the changes
proposed to moderate controls on low-risk mammalian
MBM in agricultural fertilisers.

Please send your comments on this paper and attached
permissions form to Robert Sutherland, no later than
6 September 2005, at the address above.
Alternatively responses can be emailed to:

Your response cannot be made public until the respondee
information form is returned to us and we are obligated to
write to those who respond without completing it.

If you have any queries contact Andrew Taylor 0131 244
6642 or Anna Murray on 0131 244 6413.

Martin Morgan signature

Yours faithfully

Martin Morgan

Animal Health and Welfare 4


Current issues

SEAC Chair



Early phase of vCJD infection in recipients of blood transfusions

Dr Marc Turner (NBS)

87/3 (54 KB)

2. As a pre-symptomatic diagnostic test for vCJD is currently not
available, blood, bone, tissue or organ donors with a sub- or preclinical
vCJD infection cannot be identified prior to donation.
3. Two cases of vCJD infection in recipients of blood from blood
donors that subsequently developed vCJD suggest that the
disease may be transmitted between individuals by blood
transfusion prior to development of clinical disease in the donor1,2.
Experimental evidence of BSE transmission via blood transfusion
from infected asymptomatic donor sheep to BSE-free recipient
sheep supports the possible transfer of infection by this route3,4.
4. There have been no definite or suspected cases of vCJD
transmission between humans via bone, tissue or organ
1 Llewelyn et al. (2004) Possible transmission of variant
Creutzfeldt-Jakob disease by blood
transfusion. Lancet 363, 417-421.
2 SEAC statement on the second presumed case of blood transfusion-
associated infection
with vCJD (2004).
3 Houston et al. (2000) Transmission of BSE by blood transfusion in
sheep. Lancet 356, 999-
4 Hunter et al. (2002) Transmission of prion disease by blood
transfusion. J. Gen. Virol. 83,
transplantation. However, epidemiological evidence of iatrogenic
transmission of sCJD5 suggests that there is a potential risk of
vCJD transmission via some surgical procedures. ...snip...end


First probable case of blood transfusion associated transmission of


17. In February, SEAC was updated about the Transfusion Medicine

Epidemiology Review (TMER) funded by the Department of Health

(DH) to examine possible links between vCJD and blood transfusion.

In the course of the study, a case of possible transmission of vCJD by

blood transfusion had been identified. The recipient received blood in

1996 from a donor who, at the time of donation, was free of clinical

signs of vCJD, although went on to develop vCJD in 1999. The blood

recipient died of vCJD in 2003. Although the possibility could not be

ruled out that the blood recipient was infected as a consequence of

consuming meat products contaminated with the BSE agent,

statistical analysis suggested that it was unlikely that the association

between the blood recipient and the blood donor was due to chance.

18. SEAC agreed that the case raised the possibility that the infection

may have been transmitted by the blood transfusion. However, it was

SEAC Annual Report 2004

noted that this was a single case. The recipient had received blood

before leucodepletion of blood donations had been adopted in the UK

in 1998, as a precautionary measure. The measure was introduced

as it was considered that leucodepletion of blood would significantly

reduce the risk of blood transfusion associated transmission of vCJD.

SEAC noted the importance of the TMER in identifying potential

transfusion associated vCJD cases.



Second probable case of blood transfusion associated transmission

of the vCJD agent

27. In June, DH asked the committee to advise on the public health

implications of a second probable case of blood transfusion

associated transmission of the vCJD agent. The patient who died in

2004, from a cause unrelated to vCJD, showing no clinical signs of

vCJD, had received a single unit of blood in 1999. This blood was

donated by an individual who subsequently developed vCJD in 2000

and died in 2001. Post mortem findings in the blood transfusion

recipient suggested a possible preclinical case of iatrogenic vCJD

associated with blood transfusion. However, the patient resided in the

UK, and oral exposure to the BSE infectious agent could not be

excluded as a possible cause of infection.

28. On the basis of a statistical analysis of the possible causes of

infection, the committee agreed that the case was much more likely to

be attributable to blood transfusion, than food borne infection. The

report strengthened the evidence for the transmission of vCJD via

blood. However, the committee noted that in this instance, although

vCJD infection appeared to have been transmitted, it was not known if

clinical vCJD would have developed if the patient had lived longer.

SEAC Annual Report 2004

29. The committee agreed that the new case strengthened its opinion,

first stated in October 1997, that human blood from persons

incubating vCJD may be infective. Additionally, it was a public health

priority for all recipients of blood transfusions from donors incubating

vCJD to be subject to post mortem investigation, to help quantify the

nature and magnitude of the risks of transmission of vCJD via blood.

A statement summarising the committee’s consideration of the case is

given at Annex 7.


Atypical BSE cases

55. In February, SEAC considered the findings of a research paper

(Casalone et al. 2004)6 suggesting that a second bovine amyloidotic

spongiform encephalopathy had been identified with a molecular

signature similar to that of a subtype of sCJD. The committee agreed

that the results were very interesting, but without information on the

transmissibility of the disease in bioassays, it was premature at this

stage to conclude it was a new strain of BSE. SEAC agreed it would

follow further research on these samples with interest.

- - 16



- - 17

54. Mr Steve Wyllie (Defra) provided the background to the issue. In

1996 the use of MMBM in fertiliser for agricultural land was banned

to cut off potential routes of TSE exposure to livestock. In 2002,

EU legislation was introduced that classified animal by-products

(ABP) into Category 1 (high risk material from animals with

suspected or confirmed TSE), Category 2 (condemned meat from

diseased animals) and Category 3 material (fit for human

consumption). Category 2 and 3 material was permitted to be

used as fertiliser, but in the case of all Category 2 material, and

Category 3 material of mammalian origin, only if reduced to a

particle size <50 mm and pressure cooked (>133ºC and 3 bar for

20 minutes). In addition, category 3 material could be used in

compost if reduced to <12 mm and heated to 70ºC for at least one

hour. Appropriately-treated Category 2 and 3 ABP could be

applied to non-pasture land. Non-pasture land included a period

when farmed animals cannot graze. A three week non-grazing

period is currently being proposed by the Commission, based on

an EFSA opinion.

55. Mr Wyllie explained that, in contrast to the EU regulations, no

rendered MMBM is allowed in fertiliser spread on any agricultural

land under current UK regulations. An anomaly also exists within

UK legislation as category 3 ABP can be treated in a biogas or

composting plant and applied to land. However, if it is treated in a

rendering plant it is designated as MMBM and cannot be applied to

agricultural land even though it is treated under more severe

conditions than it would in a composting/biogas plant. Defra is

considering amending the UK legislation to address the anomalies

and align UK with EU regulations. As an initial step, Defra

commissioned VLA to conduct a release assessment (RA) to

estimate the TSE-related risks associated with the use of rendered

Category 3 ABP as fertiliser on non-pastureland.

56. Dr Amie Adkin (VLA) presented the methods, inputs and

assumptions made in the RA together with the results. The RA

considered scenarios of scrapie in sheep, theoretical BSE in

sheep, and BSE in cattle, under current conditions, and assessed

the impact of removal of the OTM Rule. The RA consisted of four

successive modules:

Farm Module

57. The farm module estimated the numbers of cattle and sheep within

the last 12 months of incubation of scrapie or BSE, that are

slaughtered for human consumption per year. It was assumed that

BSE is present in the national sheep flock and the prevalence of

- - 18

BSE or scrapie is not stratified by age, a lamb having the same

probability of being infected in the national flock as an adult sheep.

Slaughter Module

58. Using data from the farm module, the slaughter module estimated

the quantity of infectious material (expressed as oral ID50), passed

as fit for human consumption, leaving slaughterhouses per year.

For BSE in cattle it was assumed there was no risk associated with

liver, kidney, lung, stomach, blood and trimmings. It was also

assumed that animals are fully infected and that carcass

contamination of the food chain could occur via four routes:

insufficient removal of spinal cord, spinal cord contamination from

splitting the carcass, brain tissue from the captive bolt used in

slaughter, and the presence of DRG.

59. For the scrapie and BSE in sheep models it was assumed that

positive animals were fully infected, the infectivity for BSE in sheep

is the same as scrapie, and that carcass contamination of the food

chain could occur via two routes: insufficient removal of spinal cord

and via infectious tissues not designated as SRM.

Rendering module

60. Using the information from the slaughter module, the rendering

module estimated the concentration of infectivity in fertiliser (oral

ID50 per kg). It was assumed that all TSE infectivity remaining on

the carcass after SRM controls subsequently enters category 3

waste. This was a pessimistic assumption as other routes such as

landfill, composting or ingestion which would reduce infectivity

levels were not included. It was assumed that 50-75% of Category

3 MMBM would be used in fertiliser production.

Land module

61. The land module estimated the infectivity of TSE on non-pasture

land three weeks post application (oral ID50 per m3) on the basis of

the estimates from the rendering module. It was assumed there

was no decay of TSE in soil, no leaching of TSE beyond 1 cm of

topsoil, and that the yearly input of fertiliser to land is applied in

one dose.

62. Dr Adkin explained that the final results of the study related to

infectivity in soil available per year, not the probability that a cow

becomes infected. The exposure of cattle to that infectivity was

outside the scope of the RA. Information on the frequency of cattle

- - 19

on non-pasture land, the length of stay and consumption of soil

and vegetation would be required for an exposure assessment.

The final results from the land module were (with 5th and 95


• The average TSE infectivity on non-pasture land per year

from cattle with BSE would be 2.0 x 10-11 bovine oral ID50

per m3 (1.7 x 10-12, 6.1 x 10-11)

• The average TSE infectivity on non-pasture land per year

from sheep with BSE would be 5.0 x 10-9 ovine oral ID50

per m3 (1.3 x 10-10, 1.8 x 10-8)

• The average TSE infectivity on non-pasture land per year

from sheep with scrapie would be 2.4 x 10-6 ovine oral

ID50 per m3 (3.9 x 10-7, 5.8 x 10-6), 500-fold greater than

for BSE in sheep.

63. Dr Adkin indicated that the model was sensitive to the amount of

MMBM fertiliser applied annually, the effect of rendering on TSE

infectivity, the titre of TSE infectivity in tissues and, in the scrapie

model, the proportion of natural scrapie that is BSE. Removal of

the Over Thirty Month Scheme (OTMS) would increase BSE

infectivity 60-fold but infectivity levels would still be extremely low.

A worst case scenario had been modelled assuming a fully

infected entire BSE carcass including SRM was rendered into one

batch of fertiliser (a one in a million million occurrence). In this

case, the BSE infectivity on non-pasture land would increase by 6

orders of magnitude from a mean estimate of 2.0 x 10-11 bovine

oral ID50 per m3 to a mean of 5.0 x 10-5 bovine oral ID50 per m3.

64. In opening the discussion, the Chair indicated that the RA had

been sent to an independent epidemiologist Professor Dirk Pfeiffer

(Royal Veterinary College, London) for review. Professor Pfeiffer

concluded the RA was logically structured and the data and

assumptions clearly described. The results had been presented

with due consideration of the assumptions. He noted that the

processes used in developing the model, obtaining the data and

scrutinising the model were not documented. It was unclear

whether the quality of unpublished and published data was

scrutinised or taken at face value. In summary, the model

structure was appropriate and the conclusions plausible. Improved

documentation would enhance the credibility and transparency of

the model outputs.

65. A member had also reviewed the RA in detail and concurred that

the RA was thoroughly carried out. It was noted that, with the

OTMS, the RA had assumed an infectivity level leaving the

slaughterhouse of 140 bovine oral ID50 per year whereas other risk

- - 20

assessments had used lower values. Dr Adkin commented that

the difference was due to inclusion of a fully infected carcase,

rather than considering carcases at different points in the

incubation period. In addition, the model contained different routes

of contamination of the carcase post SRM controls that are not

included in other assessments. It was suggested that the

assumption of all infectivity remaining on a carcass entering

category 3 waste and being spread as fertiliser was perhaps overly


66. Dr Adkin was asked why no uncertainty estimate had been

included regarding the OTMS removal scenario. Dr Adkin

indicated that the estimates for the number of infected cattle to

slaughter were based on a peer-reviewed back-calculation model

from Arnold and Wilesmith (2003)2. The model had not been set

up to provide the 5th and 95th percentiles in the case of OTMS

removal. This had now been explored and the overall results had

not changed significantly as a result of including the uncertainty

estimate. Dr Matthews added that a previous qualitative risk

assessment indicated the risk was very low, and he felt the correct

approach for a quantitative RA was to use pessimistic

assumptions. There were many uncertainties in terms of the

process once material left the abattoir, regarding rendering plant

used, volumes of waste and how this material would be used

subsequently, therefore estimates had been based on consultation

with industry representatives, and if estimated infectivity levels

remained low even with pessimistic assumptions this could be

considered reassuring.

67. A member noted that the assumptions in the RA were dependent

on effective enforcement. It was suggested that a 3 week nongrazing

period could be difficult to enforce. In addition, it had been

assumed that no imported MMBM was used in fertiliser.

Enforcement should be considered in developing policy.

68. It was noted that even distribution of infectivity in fertiliser, and its

even distribution across land had been assumed. In reality, TSE

infectivity spread would be heterogeneous. Dr Adkin explained

that this scenario had been addressed to some extent by the worst

case scenario in which a fully infected entire BSE carcass was

rendered into one batch of fertiliser.

69. Dr Adkin added that it had been assumed that there was no

degradation of prion protein during the assumed 3 week non-

2 Arnold M. and Wilesmith J.W. (2003) Modelling studies on BSE occurrence to assist in the

review of the over thirty months rule in Great Britain. Proc Roy Soc Lond B 270, 2141-2145

- - 21

grazing period. Members considered that should TSE agents

persist in soil, infectivity could accumulate over time. Dr Adkin

indicated that the accumulation of infectivity over time was not

addressed, as an exposure assessment had not been carried out.

In order for such accumulation to occur TSE infectivity would have

to be applied on multiple occasions to the same location, which

may be unlikely. One study indicated there would be 98% decay of

the agent over 3 years3. Dr Matthews observed that accumulation

would be against a backdrop of decreasing TSE prevalence. Mr

Wyllie added that Defra- and EU-funded research is being

conducted to investigate the behaviour and degradation of TSE

agents in soil.

70. A member considered that, since the TSE agent is a protein, it was

likely to decay quickly due to the pH of, and bacteria present in,

soil. However, a member pointed out good evidence suggesting

that the Chronic Wasting Disease agent persisted in the

environment. Dr Matthews informed members that a VLA project

on infectivity in sheep exposed to the farm environment indicated

that material on pasture is infectious for at least 2 months.

Members agreed that in view of the resistance of PrPsc to

degradation, evidence from CWD and the VLA studies, it was safer

to assume survival of the agent in soil for a significant amount of


71. In response to members’ questions about the field spreading of

fertiliser, Alan Brewer (Defra) informed the committee that some

dust can arise from the activity, both from the fertiliser distribution

process (that depends on the type of spreading mechanism) and

from tractor wheels kicking up soil in arable situations. But it was

not possible to indicate whether there was any likelihood of dust

particles containing fertiliser drifting onto adjoining fields. He

added that it was recognised as good practice for farmers not to

spread fertiliser into hedges and watercourses.

72. Members asked whether cross-contamination between category 2

and category 3 material could occur on processing. Mr Wyllie

indicated that Category 2 and Category 3 materials had to be

rendered in separate buildings, although these could be on the

same site.

73. Members asked if the final result of the RA could be an

overestimate of scrapie infectivity due to the assumption that all

sheep were adults. Dr Adkin indicated this may be a pessimistic

3 Brown P. and Gajdusek D.C. (1991) Survival of scrapie virus after 3 years’ interment.

Lancet 337, 269-270

- - 22

assumption as adult sheep have larger tissue sizes. Dr Matthews

commented that genotyping studies from the abattoir survey

indicated there is a high prevalence of arginine-carrying sheep at

codon 171 and that therefore infectivity was more likely to be

restricted to the central nervous system rather than other tissues

and the RA had assumed the worst case.

74. Members noted that infectivity in fertiliser has the potential for

intraspecies recycling and poses a different risk from dead-end

infections. It was recommended that surveillance was essential to

detect infected animals and identify such a cycle.

75. It was noted that multiple risk assessments tended to consider

single routes but often routes were cross-linked. It was suggested

that consideration should be given to risk assessments that

consider such links rather than specific routes in isolation.

Members asked whether risk assessments could be produced in a

consistent way and asked if there was a forum to discuss inputs to

risk assessments. Dr Matthews indicated that a "Neuroprion Risk

Assessment" group was looking to peer review data and generate

a consensus for risk assessments. Dr Adkin indicated within the

EU, risk analysts are reviewing parameters to enable comparison

of models.

76. In summary, the committee concluded:

• it was content with the approach used and assumptions

made in the risk assessment.

• the assessment predicted that TSE infectivity levels on land

as a result of the application of fertiliser would be extremely

low. However, because of the likely heterogeneous nature

of infectivity in fertiliser and the uneven spread of fertiliser,

TSE infectivity levels might be higher in some geographical

locations than predicted.

• controls to ensure that category 3 material is processed

separately from Category 1 and Category 2 material be


• a watching brief be kept on CWD and BARB cases to

assess the possible persistence of the agent in the




- 7th June 1996


Recommendations on the handling of waste material from cattle
The Committee noted that blood and gut contents had normally been spread on land. The Committee noted that concern had been expressed about this practice but felt that given the fact that no BSE infectivity had ever been detected in blood and that there was no evidence of horizontal transmission of disease which would suggest that cattle wastes were directly infective to cattle, there was no reason to recommend that this practice should be prohibited or thought to be inadvisable. ...


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