FR Doc 07-4595

[Federal Register: September 18, 2007 (Volume 72, Number 180)]
[Rules and Regulations]
[Page 53313-53379]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr18se07-21]

[[Page 53313]]

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Part III

Department of Agriculture

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Animal and Plant Health Inspection Service

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9 CFR Parts 93, 94, 95, and 96

Bovine Spongiform Encephalopathy; Minimal-Risk Regions; Importation of
Live Bovines and Products Derived From Bovines; Final Rule

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DEPARTMENT OF AGRICULTURE

Animal and Plant Health Inspection Service

9 CFR Parts 93, 94, 95, and 96

[Docket No. APHIS-2006-0041]
RIN 0579-AC01

Bovine Spongiform Encephalopathy; Minimal-Risk Regions;
Importation of Live Bovines and Products Derived From Bovines

AGENCY: Animal and Plant Health Inspection Service, USDA.

ACTION: Final rule.

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SUMMARY: We are amending the regulations regarding the importation of
animals and animal products to establish conditions for the importation
of the following commodities from regions that present a minimal risk
of introducing bovine spongiform encephalopathy into the United States:
Live bovines for any use born on or after a date determined by the
Animal and Plant Health Inspection Service to be the date of effective
enforcement of a ruminant-to-ruminant feed ban in the region of export;
blood and blood products derived from bovines; and casings and part of
the small intestine derived from bovines. We are making these
amendments after conducting a risk assessment and comprehensive
evaluation of the issues and concluding that such bovines and bovine
products can be safely imported under the conditions described in this
rule. This document also removes the delay in applicability of certain
provisions of a final rule published in January 2005.

DATES: Effective Date: November 19, 2007.

FOR FURTHER INFORMATION CONTACT: For information regarding ruminant
products, contact Dr. Karen James-Preston, Director, Technical Trade
Services, Animal Products, National Center for Import and Export, VS,
APHIS, 4700 River Road Unit 38, Riverdale, MD 20737-1231; (301) 734-
4356.
For information concerning live ruminants, contact Dr. Lee Ann
Thomas, Director, Technical Trade Services, Animals, Organisms and
Vectors, and Select Agents, National Center for Import and Export, VS,
APHIS, 4700 River Road Unit 38, Riverdale, MD 20737-1231; (301) 734-
4935.
For other information concerning this proposed rule, contact Dr.
Lisa Ferguson, Senior Staff Veterinarian, National Center for Animal
Health Programs, VS, APHIS, 4700 River Road Unit 43, Riverdale, MD
20737-1231; (301) 734-6954.

SUPPLEMENTARY INFORMATION:

Purpose

This document makes final a proposed rule that the Animal and Plant
Health Inspection Service (APHIS) of the U.S. Department of Agriculture
(USDA or the Department) published in the Federal Register on January
9, 2007 (72 FR 1101-1129, Docket No. APHIS-2006-0041). Additionally, it
removes the delay of applicability of certain provisions of a final
rule APHIS published in January 2005. The removal of delay is discussed
below under the heading ``Removal of Partial Delay of Applicability of
Provisions of January 2005 Final Rule.''
In our January 2007 proposed rule, we proposed to amend the
regulations in 9 CFR parts 93, 94, 95, and 96 to establish conditions
for the importation of the following commodities from regions that
present a minimal risk of introducing bovine spongiform encephalopathy
(BSE) into the United States: Live bovines for any use born on or after
a date determined by APHIS to be the date of effective enforcement of a
ruminant-to-ruminant feed ban in the region of export; blood and blood
products derived from bovines; and casings and part of the small
intestine derived from bovines.
In this document, we respond to public comments received on the
proposed rule and its underlying risk assessment and other supporting
analyses. Additionally, we discuss below the history of APHIS
rulemaking related to BSE minimal-risk regions.

Background

APHIS regulates the importation of animals and animal products into
the United States to guard against the introduction of animal diseases.
The regulations in 9 CFR parts 93, 94, 95, and 96 (referred to below as
the regulations) govern the importation of certain animals, birds,
poultry, meat, other animal products and byproducts, hay, and straw
into the United States in order to prevent the introduction of various
animal diseases, including BSE, a chronic degenerative disease
affecting the central nervous system of cattle.
With some exceptions, APHIS' regulations prohibit or restrict the
importation of live ruminants and certain ruminant products and
byproducts from the following three categories of regions with regard
to BSE: (1) Those regions in which BSE is known to exist (listed in
Sec. 94.18(a)(1) of the regulations); (2) those regions that present
an undue risk of introducing BSE into the United States because their
import requirements are less restrictive than those that would be
acceptable for import into the United States and/or because the regions
have inadequate surveillance (listed in Sec. 94.18(a)(2) of the
regulations); and (3) those regions that present a minimal risk of
introducing BSE into the United States via live ruminants and ruminant
products and byproducts (listed in Sec. 94.18(a)(3) of the
regulations).

Chronology of Federal Register Publications Regarding BSE Minimal-Risk
Regions

We added the Sec. 94.18(a)(3) category (BSE minimal-risk regions)
to the regulations in a final rule published in the Federal Register on
January 4, 2005 (70 FR 459-553, Docket No. 03-080-3). In the final
rule, we specified which commodities may be imported from BSE minimal-
risk regions and under what conditions, and recognized Canada as a BSE
minimal-risk region. (At this time, Canada is the only recognized BSE
minimal-risk region.)
The January 2005 final rule was based on a proposed rule we
published in the Federal Register on November 4, 2003 (68 FR 62386-
62405, Docket No. 03-080-1). On December 25, 2003, less than 2 weeks
before the close of the comment period for our proposed rule, a case of
BSE in a dairy cow of Canadian origin in Washington State was verified
by an international reference laboratory.
In response to comments from the public requesting an extension of
the comment period and in order to give the public an additional
opportunity to comment on the proposed rule in light of this
development, on March 8, 2004, we published a document in the Federal
Register (69 FR 10633-10636, Docket No. 03-080-2) reopening the comment
period.
On January 4, 2005, along with the final rule, we published in the
Federal Register a notice (70 FR 554, Docket No. 03-080-4) announcing
the availability of, and requesting comments on, a final environmental
assessment (EA) regarding the potential impact on the quality of the
human environment due to the importation of ruminants and ruminant
products and byproducts from Canada under the conditions specified in
the final rule. On January 21, 2005, we published in the Federal
Register a notice (70 FR 3183-3184, Docket No. 03-080-5) announcing the
availability of a corrected version of the EA for public review and
comment. On April 8, 2005, we published in the Federal Register a
finding (70 FR 18252-18262, Docket No. 03-080-7) that the provisions of
the final rule would not

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have a significant impact on the quality of the human environment.
On March 11, 2005, we published a document in the Federal Register
that gave notice that the Secretary of Agriculture was delaying until
further notice the implementation of certain provisions of the final
rule with regard to certain commodities (70 FR 12112-12113, Docket No.
03-080-6).
On November 28, 2005, we published in the Federal Register an
interim rule (70 FR 71213-71218, Docket No. 03-080-8) that amended
certain provisions established by the January 2005 final rule. The
interim rule broadened the list of who is authorized to break seals on
conveyances and allows transloading under supervision of products
transiting the United States.
On March 14, 2006, we published in the Federal Register a technical
amendment (71 FR 12994-12998, Docket No. 03-080-9) that clarified our
intent with regard to certain provisions in the January 2005 final rule
and corrected several inconsistencies within the rule.
On August 9, 2006, we published in the Federal Register a proposed
rule (71 FR 45439-45444, Docket No. APHIS-2006-0026) that proposed to
amend the provisions established by the January 2005 final rule by
removing several restrictions regarding the identification of animals
and the processing of ruminant materials from BSE minimal-risk regions,
and by relieving BSE-based restrictions on hide-derived gelatin from
BSE minimal-risk regions. We solicited comments concerning our proposal
for 60 days ending October 10, 2006. On November 9, 2006, we published
a document in the Federal Register (71 FR 65758-65759, Docket No.
APHIS-2006-0026) reopening and extended the comment period until
November 24, 2006. We received a total of 10 comments by that date. We
are considering the issues raised by the commenters and will address
them in a separate rulemaking document.

Scope of the January 2005 Final Rule

The regulations established by the January 2005 final rule and
subsequent amendments have allowed the importation from BSE minimal-
risk regions of live bovines that are under 30 months of age when
imported and when slaughtered and that have been subject to a ruminant
feed ban equivalent to that in place in the United States.
We did not attempt, for that rulemaking, to assess the BSE risk
associated with the importation of live bovines 30 months of age or
older from a BSE minimal-risk region. Our March 8, 2004, document that
reopened the comment period on the November 2003 proposed rule stated
that APHIS was evaluating the appropriate approach with regard to the
importation of live animals 30 months of age or older from BSE minimal-
risk regions, and would address that issue in a supplemental rulemaking
proposal in the Federal Register. The provisions in our January 9,
2007, proposed rule regarding live bovines were the result of that
evaluation.
The regulations established by the January 2005 final rule also
provided for the importation of the following commodities derived from
bovines of any age: (1) Meat, meat food products, and meat byproducts;
(2) whole or half carcasses; (3) offal; (4) tallow composed of less
than 0.15 percent insoluble impurities that are not otherwise eligible
for importation under Sec. 95.4(a)(1)(i) of the regulations; and (5)
gelatin derived from bones of bovines that is not otherwise eligible
for importation under Sec. 94.18(c) of the regulations.
The January 2005 final rule and subsequent amendments did not
change the regulations concerning the importation of blood and blood
products from regions listed in Sec. 94.18(a); the requirements for
the importation of blood and blood products from BSE minimal-risk
regions remain the same as the requirements for importation of blood
and blood products from other regions listed in Sec. 94.18(a)--only
serum and serum albumin have been eligible for importation. The January
2005 final rule also did not change the regulations concerning the
importation of bovine casings (defined as intestines, stomachs,
esophagi, and urinary bladders) from regions listed in Sec. 94.18(a);
the requirements for the importation of bovine casings from BSE
minimal-risk regions remain the same as the requirements for
importation of bovine casings from other regions listed in Sec.
94.18(a)--only bovine stomachs are eligible for importation.
The January 2005 final rule and subsequent amendments allowed trade
to resume in many, but not all, of the commodities that had been
prohibited importation from Canada following detection of a BSE-
infected cow in Canada in May 2003. Following our January 2005 final
rule, we continued to consider the BSE risk associated with older
bovines and other bovine products from BSE minimal-risk regions--and
Canada in particular--including bovine blood and blood products, bovine
small intestine other than the distal ileum, and bovine casings, and
included provisions in our January 2007 proposed rule for the
importation of those commodities.\1\
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\1\ The regulations regarding BSE minimal-risk regions apply to
bison as well as cattle. In Sec. Sec. 93.400, 94.0, and 95.1 of the
regulations, bovine is defined as Bos taurus, Bos indicus, and Bison
bison. Although the research and other data cited in this rulemaking
refer to bovines other than bison (i.e., to ``cattle''), there is no
evidence to indicate that the BSE susceptibility of bison differs
from that of cattle. We therefore assume that our conclusions based
on cattle-specific evidence discussed in this rulemaking are also
applicable to bison. Given that no cases of BSE have been detected
in bison, this is likely a conservative assumption. The provisions
of this rule apply to bovines as defined in the regulations, which
include bison.
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Peer Review of APHIS' Risk Assessment

As part of this rulemaking, APHIS conducted an assessment that
evaluated the animal health risk to the United States of BSE--i.e., the
likelihood of establishment and the potential impacts of cases that may
occur even without establishment--as a result of importing the bovine
commodities considered in this rule (APHIS 2006b). Our assessment
concluded that, over the 20 years of the analysis, the BSE risk to the
United States is negligible. We made the risk assessment available for
public review and comment at the time the proposed rule was published.
In addition to making the risk assessment available for review and
comment by the general public, we requested an external, formal,
independent peer review of the assessment by recognized experts in the
field, consistent with guidelines of the U.S. Office of Management and
Budget (OMB 2004). The objective of the peer review was to determine
whether the risk assessment was scientifically sound, transparent, and
consistent with international standards (e.g., those by the OIE); the
application of external assessments or models was appropriate; and the
assumptions were justified, supported and reasonable. Comments
submitted by the public on the proposed rule were submitted to the peer
reviewers for their consideration. The peer review process was
coordinated by an independent private contractor.
The full peer review report may be viewed at http://www.aphis.usda.gov/peer_review/peer_review_agenda.shtml.

Additionally, we have included below, under the heading ``Final Report
from Peer Review of APHIS' Risk Assessment and Responses to Peer
Reviewer Questions and Recommendations,'' APHIS' responses to reviewer
comments that we consider representative of the content-related
questions and recommendations of the report, and our response to those
questions and recommendations. In summary, the

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reviewers found that the methods used in the risk assessment were
scientifically rigorous in terms of using existing literature and
models appropriately and making sound assumptions and that the risk
assessment itself adhered to international risk assessment standards.
The reviewers also agreed with the conclusion that the likelihood of
establishment of BSE in the U.S. cattle population is negligible.
In addition to being supportive of the methods, evidence, and
conclusions presented by APHIS in the risk assessment, the reviewers
made several useful suggestions for its improvement. We made several
clarifications and updates in consideration of these comments. While we
expect that the changes improve the transparency and accuracy of the
document, they do not alter our conclusion that the risk to the United
States of BSE--i.e., the likelihood of establishment and the potential
impacts of cases that may occur even without establishment--resulting
from the changes outlined in the proposed rule is negligible.

Removal of Partial Delay of Applicability of Provisions of January 2005
Final Rule

Our January 2005 final rule made eligible for importation from
Canada meat that is derived from bovines slaughtered in BSE minimal-
risk regions, as well as certain other specified commodities derived
from such bovines, provided certain specified risk-mitigating
conditions have been met. The risk analysis we conducted for that
rulemaking indicated a low BSE risk from such commodities derived from
bovines of any age if certain conditions are met (APHIS 2004). These
conditions include the removal of those tissues considered at
particular risk of containing the BSE agent in infected animals
(specified risk materials, or SRMs). In that rulemaking, we discussed
regulatory requirements implemented by FSIS in 2004 that banned SRMs
from the human food supply in the United States, and we stated that the
Canadian Government had established similar safeguards in Canada.
Consequently, we provided that meat, meat byproducts, meat food
products, and offal derived from bovines are eligible for importation
from BSE minimal-risk regions if the following conditions, as well as
all other applicable requirements of the regulations, are met:
The commodity is derived from bovines that have been
subject to a ruminant feed ban equivalent to the requirements
established by the U.S. Food and Drug Administration at 21 CFR
589.2000;
The commodity is derived from bovines for which an air-
injected stunning process was not used at slaughter; and
The SRMs and small intestine of the bovines from which the
commodity was derived were removed at slaughter.
Additionally we provided that tallow composed of less than 0.15
percent insoluble impurities that is not otherwise eligible for
importation under 9 CFR 95.4(a)(1)(i), and gelatin derived from bones
of bovines that is not otherwise eligible for importation under 9 CFR
94.18(c) are eligible for importation from BSE minimal-risk regions,
provided certain specified conditions are met.
In the economic analysis we conducted for the January 2005 final
rule, we evaluated the potential economic effects of implementing that
rulemaking, including implementation of the provisions allowing the
importation of meat and other commodities derived from bovines
slaughtered in BSE minimal-risk regions (APHIS 2004a).
In March 2005, APHIS published a document in the Federal Register
that, pursuant to an announcement by the Secretary of Agriculture on
February 9, 2005, delayed the applicability of the provisions in our
January 2005 final rule as they apply to the importation from Canada of
the following commodities when derived from bovines 30 months of age or
older when slaughtered: (1) Meat, meat food products, and meat
byproducts other than liver; (2) whole or half carcasses; (3) offal;
(4) tallow composed of less than 0.15 percent insoluble impurities that
is not otherwise eligible for importation under 9 CFR 95.4(a)(1)(i);
and (5) gelatin derived from bones of bovines that is not otherwise
eligible for importation under 9 CFR 94.18(c).
In his February 9, 2005, announcement, the Secretary stated that
because ongoing investigations into recent finds of BSE in Canada in
animals over 30 months of age were not complete, he felt it prudent to
delay the effective date for allowing imports of meat from bovines 30
months of age and over. He also indicated that the delay of
applicability would address concerns that the January 2005 final rule
allowed the importation of beef from bovines 30 months of age or older,
while continuing to prohibit the importation of live cattle 30 months
of age or older for processing in the United States. The Secretary
stated that the Department would consider and develop a plan--based on
the latest scientific information and with the protection of public and
animal health as the highest priority--to allow imports of live bovines
30 months of age or older as well as beef from animals 30 months of age
and older.
Since the date of the partial delay of applicability of our January
2005 final rule, we have obtained additional information regarding all
aspects of the issues that prompted the delay of applicability and have
conducted additional analyses in line with the plan as described. The
risk assessment for this final rule demonstrates the negligible BSE
risk from the importation of additional classes of live cattle,
including those 30 months of age or older. This includes acknowledging
the potential risk pathway that could be available if the SRMs from
infected imported cattle entered the ruminant feed supply in
contravention of current feed regulations. The negligible risk from the
importation of live older cattle therefore gives further support to the
conclusion of the risk analysis conducted for our January 2005 final
rule regarding meat and meat products derived from bovines of any age
in BSE minimal-risk regions. Specifically, the risk is even lower for
the importation of meat and meat products, as the SRMs will be removed
in accordance with the regulations, than for live bovines.
Therefore, this document will remove the partial delay of
applicability of the January 2005 final rule. The removal of the
partial delay of applicability will become effective on the date that
the other provisions of this document become applicable. Including the
removal of the partial delay of applicability in this final rule and
making it effective along with the other provisions of this rule will
enable APHIS to more efficiently communicate the necessary
implementation instructions to U.S. Customs and Border Protection and
to APHIS field personnel. Additionally, it will provide commercial
entities more flexibility in carrying out import planning based on the
relative economic merits of importing live bovines or meat and other
products derived from bovines.
Because, for reasons of efficiency for APHIS and the regulated
community, the Secretary has decided to remove the delay in
applicability as part of this document, we looked at the economic
effects of doing so in combination with allowing the importation of
bovines born on or after March 1, 1999. Although we previously analyzed
the economic effects of allowing the importation of meat and other
products derived from bovines 30 months of age

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or older, the economic analysis for this rule provides an updated
analysis.

Public Comments on the January 2007 Proposed Rule

We solicited comments concerning our January 2007 proposal for 60
days ending March 12, 2007. We received close to 400 comments by that
date. The commenters included cattle industry and farm bureau
associations, consumer groups, representatives of the Canadian
Government and other foreign countries, State Departments of
Agriculture, food processing companies, individual cattle producers,
and other members of the public.

Subjects of Comments Received

A number of commenters supported the rule and recommended no
changes to the proposed provisions. Other commenters supported the rule
in general but recommended certain changes or actions. Other comments
consisted only of recommended changes, objections to the rule in
general or to specific provisions, or requests for clarification. We
discuss below by topic the issues raised by commenters and our response
to those comments.

General Opposition to Imports

Issue: A number of commenters expressed general opposition to the
importation of any bovines or bovine products from BSE minimal-risk
regions.
Response: It appears to us that these commenters are not addressing
just our January 2007 proposed rule, but, rather, also the January 2005
final rule that recognized the category of BSE minimal-risk regions and
established conditions for the importation of certain ruminants and
ruminant products from such regions.
As we discussed in the January 2005 final rule, the comprehensive
analysis and evaluation we conducted for that rulemaking led to the
conclusion that the conditions specified in that rule for the
importation of ruminants and ruminant products from BSE minimal-risk
regions would be effective and would therefore protect against the
introduction of BSE into the United States. Our January 2007 proposed
rule considered expansion of the types of commodities allowed
importation from BSE minimal-risk regions, based on an evaluation of
the risk (i.e., the likelihood of establishment and the potential
impacts of cases that may occur even without establishment) of
importing from Canada live animals, blood and blood products, and the
small intestine excluding distal ileum.) Given the determination of
negligible BSE risk associated with the provisions of this final rule,
and the findings associated with our 2005 final rule, there is no
scientific basis for increasing restrictions from those already in
effect or being established in this rule.
Issue: A number of commenters expressed opposition, without further
explanation, to the importation from BSE minimal-risk regions of live
bovines 30 months of age or older and to the importation of products
derived from such bovines.
Response: We discussed in our January 2007 proposed rule the
rationale for our proposal to allow the importation, under certain
conditions, of live bovines 30 months or older from BSE minimal-risk
regions. We discussed further the assessment of the disease risk of
allowing such imports that we conducted before issuing our proposal. It
is not clear to us which factors in our risk assessment or discussion
of rationale were being addressed by those commenters who expressed
general opposition to the importation of live bovines 30 months of age
or older. We continue to consider the BSE risk from importing live
bovines under the conditions specified in this rule to be negligible.
Issue: Several commenters who expressed opposition to the proposed
rule expressed concern that the agent that causes BSE has yet to be
fully characterized. The commenters stated that what we know about BSE
is mostly supposition, which should be a compelling reason not to allow
the importation of cattle from a region of known BSE outbreaks. One
commenter stated that research recently conducted at Yale University
suggests that one of the agents that activates BSE may be viral, which,
according to the commenter, implies that a feed ban is effective only
when the virus is not present or active.
Response: As one of the commenters noted, some researchers
(Manuelidis et al., 2007) suggest that diseases characterized as
transmissible spongiform encephalopathies (TSEs), such as BSE, may be
caused by viruses, although, at this point, no infection-specific
nucleic acids have been identified.
Experimental data and epidemiological studies strongly suggest that
contaminated feed containing ruminant proteins derived from infected
animals was the source of the epidemic, and that the epidemic was
perpetuated through the use of these materials in ruminant feed. APHIS
considers that regardless of the characteristics of the BSE causal
agent, it is clear that the epidemic was sustained and amplified by the
recycling of BSE infected cattle into cattle feed. Despite the
difficulty in definitively determining the causal agent of BSE, risk
factors for transmission of the agent have been identified. The
identification and characterization of these risk factors through
epidemiological and experimental study have allowed the development of
effective mitigations to prevent BSE spread. The development and
demonstrated effectiveness of those mitigations does not require
identification of the agent itself. We consider mitigation measures
that address the risk factors for BSE to be effective regardless of the
precise nature of the BSE agent.

Prevalence of BSE in Canada

Although the provisions of this rule apply to any region recognized
by APHIS as a BSE minimal-risk region, at present APHIS recognizes only
one country, Canada, as such a region. Therefore, in evaluating the BSE
risk of implementing this rule, we conducted an assessment of the risk
of importing bovines and bovine products from Canada under the
provisions of our proposed rule (APHIS 2006b). In our risk assessment,
we laid out the likely risk pathway (i.e., a series of occurrences or
steps necessary for disease to enter and become established).
In conducting our risk assessment, one of the factors we took into
account was the prevalence of BSE in Canada, since prevalence is one
factor that affects the likelihood of a BSE-infected bovine being
imported into the United States. We received a number of comments from
the public that addressed our estimate of the prevalence of BSE in
Canada. Although some of the comments supported our estimate of BSE
prevalence in Canada, in general the commenters maintained that such
prevalence is either higher than we estimated, may be increasing, or is
uncertain, or that our methods of estimating it were flawed. The
methodology we used to arrive at such estimates is discussed in detail
in our risk assessment. However, to provide some context for the issues
raised by commenters and discussed below, we summarize here the models
that we used in conducting our assessment.
The number of BSE cases detected through surveillance understates
the disease prevalence because exposed animals may be incubating
disease and carrying infectious material in their tissues without
presenting clinical symptoms. Like many transmissible spongiform
encephalopathies (TSEs),

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BSE has an incubation period of several years. Therefore, the disease
is not detectable in its early stages with current technology.
Moreover, surveillance will miss a proportion of detectable cases.
Therefore, we applied statistical methods to the available
epidemiologic and surveillance data to estimate, with attendant
uncertainty, the prevalence of BSE in Canada.
We used two related, but distinct, methods to estimate BSE
prevalence in Canada: the BSurvE model and the Bayesian Birth Cohort
(BBC) model. Given its international prominence, we used the European
Union (EU) BSurvE model (Wilesmith et al., 2004, 2005), recently
developed for the purpose of estimating BSE prevalence in national
herds. The BSurvE model is noteworthy for its sound epidemiologic
structure, including stratifying cattle by age and cause of death
(i.e., healthy slaughter, fallen stock, casualty slaughter, or clinical
suspect) and accounting for the relative likelihood of detecting BSE in
various strata (EFSA 2004). The BSurvE model structure calculates BSE
surveillance point values (random sample size equivalents) represented
by targeted Canadian sampling of certain groups of cattle in which BSE
cases are more likely to be detected. This approach allows for the
inclusion of infected, but undetected, cases (such as young animals in
the early stages of incubation) in the estimate, which would be ignored
by conventional methods.
The other prevalence estimation model that we used is the BBC
model. This model uses the BSurvE model structure and incorporates
additional information. Unlike BSurvE, the BBC model adopts a Bayesian
statistical framework to incorporate prior information about the
decreased incidence of BSE observed in animals born after a feed ban
equivalent to the initial ruminant-to-ruminant feed ban introduced in
the United Kingdom in 1988.
Issue: One commenter stated that BSE has become ``firmly
established'' in Canada.
Response: We disagree with the comment, which we consider to
erroneously equate disease presence, which may be transient, with
disease establishment. In epidemiology, an infectious disease has
become established in a population when the disease is perpetuated in
the population without the need for reintroduction from an external
source. For example, OIE's sister agency, the international Commission
on Phytosanitary Measures (CPM) defines plant pest establishment as
``the perpetuation, for the foreseeable future, of a nonindigenous
biological agent within an area after entry'' (CPM 2001). With the
implementation and continuation of a feed ban in Canada, all evidence
points toward eventual eradication, rather than perpetuation of BSE in
that country.
Issue: One commenter stated that, since the time APHIS published
its January 2005 final rule classifying Canada as a BSE minimal-risk
region, the Agency has presented no new evidence that would support
allowing the importation from Canada of the additional commodities
discussed in the proposed rule. In fact, stated the commenter, evidence
points to Canada having a higher prevalence of BSE than APHIS had
previously determined.
Response: As discussed in our January 2007 proposed rule, we
revisited our earlier conclusions and policies by conducting a rigorous
risk assessment based on current available scientific knowledge of the
disease. We used peer reviewed risk assessment models in our analysis
to estimate the prevalence of the disease in Canada and to analyze the
likelihood of BSE establishment in the United States and the potential
impacts of cases that may occur even without establishment as a result
of the importation into the United States of the bovine commodities
considered in this rule. The risk assessment itself was peer reviewed
by experts in the field. As noted above, the reviewers agreed with the
conclusion that the risk of establishment of BSE in the U.S. cattle
population is negligible and noted that several assumptions in the risk
assessment actually over-estimate the risk, so the overall finding that
the BSE risk is negligible is reasonable. Based on the results of the
risk assessment, we concluded that we could safely import Canadian
cattle born on or after March 1, 1999, blood and blood products, and
small intestines, excluding the distal ileum.
Issue: Several commenters raised questions about the ability to
statistically determine BSE prevalence ``trends'' in Canada, but
reached different conclusions. Some commenters stated that the
trajectory of BSE prevalence in Canada cannot be determined by
available surveillance data and that, therefore, BSE prevalence in
Canada may be increasing. On the other hand, another commenter
requested that APHIS make clear that, despite the Agency's use of the
BSurvE Prevalence B estimate, prevalence should not be assumed constant
over time. The commenter requested that APHIS emphasize that lack of
statistical evidence that prevalence varies from cohort to cohort is
likely the result of inadequate statistical power,\2\ and that,
nevertheless, BSE prevalence in Canada is most likely decreasing.
---------------------------------------------------------------------------

\2\ The power of a statistical test is the probability of
rejecting the null hypothesis when it is false. The power depends on
the test level of significance, the magnitude of effect under the
alternative hypothesis, sample size, and variability in the
population. Rice (1988, pp.361-364) describes the calculation of
statistical power for comparing two independent samples.
---------------------------------------------------------------------------

Response: In our risk assessment for this rule, we acknowledge
that, given the rarity of BSE cases in Canada, the surveillance data
are unlikely to provide adequate statistical power to detect any trend.
However, as discussed in the risk assessment, we consider it likely
that the prevalence of BSE in Canada will decrease over time. With so
few total BSE cases observed in Canada, the statistical power to detect
differences in prevalence between cohorts is low. The peer reviewers of
our risk assessment concur with our conclusion. (RTI 2007, pp. 6-26, 6-
27).
Issue: One commenter estimated the Canadian BSE prevalence to be
6.4 cases per million cattle. Further, the commenter stated that this
prevalence estimate is smaller than the risk estimate provided by one
of APHIS' own risk assessments for a more pessimistic value of the
misfeeding rate. The commenter suggested that this discrepancy reflects
optimistic modeling assumptions in APHIS' risk assessment.
Response: We disagree with the commenter's analysis. Although the
commenter's alternative prevalence estimate, based on a simple
extrapolation method, falls within the 90 percent confidence interval
\3\ of APHIS' BSurvE Prevalence B estimate (2.4 to 6.8 cases per
million adult cattle) with an expected value of 3.9 per million case
per million adult cattle (APHIS 2006c, table 5), it is based on
different assumptions. Based on an analysis of BSE testing in the EU in
2001 and 2002, the commenter's prevalence estimate assumes that
targeted ``risk cattle'' are only 10 times more likely to test positive
for BSE than non-targeted routinely slaughtered cattle. Considering the
BSE testing conducted in the EU during 2001-2004 (EC 2005a, table 3, p.
23), cattle in the

[[Page 53319]]

European BSE risk animals category (emergency slaughter, clinical
suspects, and fallen stock) are 22 times more likely to test BSE
positive than cattle in the healthy slaughter category. Using the
commenter's simple extrapolation method and these more up-to-date data
on BSE test positive ratio, the resulting BSE prevalence estimate would
be 2.9 per million cattle. Although actually lower than the expected
value for the BSurvE estimate, this value also falls within the 90
percent confidence interval of the Agency's BSurvE Prevalence B
estimate, described above. APHIS calculated both the BSurvE Prevalence
B estimate and the Bayesian Birth Cohort (BBC) prevalence estimate, but
judged the latter to better characterize the BSE prevalence in Canada
over the next 20 years, due to the expected downward pressure exerted
on the disease by a feed ban.
---------------------------------------------------------------------------

\3\ A confidence interval is a statistical range with a
specified probability that a given parameter lies within the range.
For example, the 90 percent confidence interval of a distribution
indicates the range of values that we are 90 percent certain include
the parameter value of interest. It extends from the 5th percentile,
or 5 percent confidence level, at the low end of the distribution of
the 95th percentile, or 95 percent confidence level at the high end
of the distribution. Similarly, a 95 percent confidence interval
would extend from the2.5 percent confidence level to the 97.5
percent confidence level.
---------------------------------------------------------------------------

With regard to the commenter's suggestion of a discrepancy, the
commenter provides no specific reference to ``the risk estimate
provided by one of APHIS' own risk assessments,'' but appears to refer
to the main body of the 2005 report of Cohen and Gray (available at
http://www.fsis.usda.gov/PDF/BSE_Risk_Assess_Report_2005.pdf),

which was prepared for the USDA's Food Safety and Inspection Service
(FSIS). Cohen and Gray (2005) do not estimate Canadian BSE prevalence,
but rather the effect of introducing 500 BSE-infected cattle into the
United States, and the pessimistic misfeeding assumption estimates that
introduction would result in an expected 2,600 new cases over 20 years.
There is no discrepancy because this aspect of the Cohen and Gray 2005
report is not relevant to our estimate of Canadian BSE prevalence.
Issue: Based on APHIS'' statements that animals are infected within
their first year, and that feed produced prior to the feed ban would
not be available for longer than a year, one commenter stated that
additional undetected infected animals must have existed and been
rendered in order to provide infectivity to detected cases. Therefore,
stated the commenter, adding in these ``undetected'' animals raises the
number of Canada's known and measurable BSE cases rises from 10 to 14,
and APHIS' estimate of BSE prevalence in Canada based on 10 animals is
low.
Response: We disagree with the commenter's analysis and conclusion,
which assumes that we did not take into account the possibility of
undetected cases of BSE in arriving at our prevalence estimate. APHIS'
estimate of the prevalence of BSE in Canada was adjusted to account for
cases that would not be tested and for false negative test results.
Also, although the bulk of feed will be consumed within a year after it
is produced, residual infectivity may remain in the feed supply chain
for an extended period. For example, examination of BSE cases in
animals born in the United Kingdom after the 1996 ``reinforced feed
ban'' suggests that these animals may have been infected from the
persistence of the BSE agent in residual feed in storage bins (SEAC
2005).
Issue: One commenter suggested that it is likely that Canada has
numerous cattle over 30 months of age that are presently incubating the
BSE disease, rather than just a few (4.1) as suggested by APHIS.
Response: The estimate of 4.1 BSE-infected animals in the standing
Canadian adult cattle population was based on the expected BSE
prevalence in Canada under the BBC model. Using the estimated
prevalence under BSurvE Prevalence B resulted in an estimate of 23.2
BSE-infected animals in the standing Canadian adult cattle population.
Although, quantitatively, our risk assessment did not assume a decline
in BSE prevalence over the next 20 years, we qualitatively consider
such a decline to be likely because of continued compliance with the
feed ban. Therefore, in assessing the BSE risk associated with imports
from Canada over the next 20 years, we consider the result of the BBC
model to be the more applicable prevalence estimate for use in our
quantitative exposure model.
Issue: One commenter indicated that although it is unclear whether
the APHIS estimates of Canadian BSE prevalence included the BSE case
confirmed on August 23, 2006, the APHIS estimates certainly do not take
into account the case confirmed on February 7, 2007.
Response: We estimated Canadian BSE prevalence based on a 7-year
surveillance period through August 15, 2006. This surveillance period
included the detection of nine BSE cases of Canadian origin reported
through August 2006. Through surveillance conducted from August 16,
2006, through April 2007, Canada detected one BSE case born in 2000 and
another born in 2001 (CFIA 2007). The BSE prevalence estimation methods
used by APHIS (2006a) require detailed data to stratify tested cattle
by age and cause of death (healthy slaughter, fallen stock, casualty
slaughter, or clinical suspect) that are unavailable for the more
recent surveillance period. However, we can assess the sensitivity of
our previous Canadian BSE prevalence estimates by adding the two
additional cases without changing the BSE surveillance points
accumulated by Canada during the 7-year surveillance period through
August 15, 2006 (APHIS 2006a, table 4). \4\ This approach results in a
revised table of BSurvE points and BSE cases by birth year cohort that
reflects a total of 11 BSE cases of Canadian origin reported through
April 2007 (APHIS 2007, table i).
---------------------------------------------------------------------------

\4\ In the BsurveE model, specific ``point values'' are assigned
to each test sample, based on the surveillance stream or
subpopulation of animals from which it was collected, as well as the
likelihood of detecting infected cattle in that subpopulation. A
sample from the specific surveillance subpopulation where BSE is
most likely to be detected--i.e., a middle adult clinical suspect--
provides the most surveillance points. Conversely, a sample from the
subpopulation where BSE is least likely to be detected--generally
routine slaughter--provides the least points.
---------------------------------------------------------------------------

Using the same methods described in USDA's estimate of BSE
prevalence in Canada (APHIS 2006c), we obtain updated Canadian BSE
prevalence estimates:
BSurvE Prevalence B: 90 percent confidence interval = 3.0-
8.0 cases per million adult cattle
Bayesian Birth Cohort (BBC, Winbugs): 90 percent
confidence interval = 0.47-1.2 cases per million adult cattle
Because the updated confidence intervals contain the previous
expected value estimates of 0.68 per million (BBC) and 3.9 per million
(BSurvE Prevalence B) (APHIS 2006c), we conclude that the prevalence
estimate is not sensitive to the addition of the two additional BSE
cases discovered in Canada in August 2006 and February 2007.
Issue: One commenter stated that APHIS' expectation that the
prevalence of BSE in Canada will continue to decline from its present
minimal level does not acknowledge that the prevalence of BSE in Canada
right now is very uncertain. The commenter's independent estimate of
the current Canadian BSE prevalence is ``on the order of 4-6 per
million.''
Response: APHIS' risk assessment addresses the uncertainty in the
prevalence of BSE in Canada by considering estimates that differ by
more than a factor of five (APHIS 2006b). The BBC prevalence estimate
has an expected value of 0.68 cases per million adult cattle.\5\ The
BSurvE Prevalence B estimate has an expected value of 3.9 per million.
The

[[Page 53320]]

commenter's own method of estimation--``on the order of 4-6 per
million----provides an estimate on the same order of magnitude as the
BSurvE Prevalence B estimate of current prevalence. In either case,
prevalence is extremely low.
---------------------------------------------------------------------------

\5\ The BBC model provides a more precise estimate of BSE
prevalence in Canada by combining the epidemiologic theory and
application of surveillance data underlying the BSurvE model with
additional information about the effect of the feed ban on
prevalence.
---------------------------------------------------------------------------

Issue: One commenter stated that, although APHIS estimates that BSE
prevalence in Canada is about 6.8 or more times greater than in the
United States (0.68 vs. 0.1 per million), this does not adjust for the
important fact that the first BSE case in the United States was
imported from Canada.
Response: The APHIS October 2006 estimate of BSE prevalence in
Canada is based on the nine BSE cases of Canadian origin that had been
confirmed in North America as of August 23, 2006. This total includes a
case of BSE that was confirmed in Washington State on December 25, 2003
(APHIS 2006c, p. 1). The estimate of BSE prevalence in the United
States excludes this case.
Issue: One commenter stated that the calculation of BSE prevalence
in Canada used in APHIS' risk assessment excluded the European-born
case detected in 1993.
Response: The 1993 Canadian BSE case of European origin was likely
part of the original exogenous source of BSE infectivity introduced
into Canada that caused the subsequent generation of indigenous cases.
Imported cases of BSE reflect an exposure to the disease that occurred
elsewhere, and, therefore, are not generally included in estimates of
prevalence that reflect native exposure. Similarly, when APHIS
estimated the prevalence of BSE in the United States, the BSE-infected
cow of Canadian origin that was detected in Washington State in
December 2003 was excluded from the analysis, because it was an
imported animal. In addition, as noted in APHIS' estimation of BSE
prevalence in Canada (APHIS 2006c, p. 5), in accordance with OIE
guidelines (which indicate that surveillance points totals taken into
account in assessing a country's BSE risk be accumulated over a maximum
of 7 consecutive years), the estimated prevalence of BSE in Canada is
based on surveillance data accumulated over a 7-year period beginning
August 16, 1999. The 1993 case predates the OIE 7-year period.
Issue: One commenter indicated that APHIS should not take action on
the proposal until real surveillance data (not model-based predictions)
show that the BSE problem has abated. The commenter stated further that
denying Canada's BSE problem, or assuming it away with unvalidated and
incorrect risk modeling assumptions, does not responsibly manage BSE
risks to the United States.
Response: We disagree with the commenter. In low BSE prevalence
populations such as Canada, surveillance at levels that meet or even
greatly exceed OIE guidelines provide insufficient statistical power to
reliably detect changes in BSE prevalence over time. In other words,
starting with a very low number of infected animals makes it very
difficult to statistically demonstrate decreases in that number, even
when testing a relatively large number of animals.
The OIE Guidelines for BSE Surveillance (Type A) call for countries
to accumulate 300,000 BSE surveillance points over 7 consecutive years
in order to detect with 95 percent confidence a prevalence level of at
least one case of BSE per 100,000 animals (OIE 2006, Appendix 3.8.4).
To illustrate the comparative difficulty in demonstrating trends in
low versus high prevalence populations, consider two hypothetical
countries that have accumulated 1 million BSE surveillance points for
each of two cohorts: Animals born before and animals born after the
introduction of a ruminant-to-ruminant feed ban. Under this scenario,
sampling levels in both countries far exceed the OIE guidelines.
Assume, however, that the two countries differ with respect to their
initial prevalence--i.e., the initial prevalence in ``Country A'' is 1
infected animal per 10,000 animals, while that in ``Country B'' is 1
infected animal per 100,000 animals.
For a given surveillance level, the statistical power of a
hypothesis test can be evaluated as a function of the supposed change
in BSE prevalence between cohort 1 (pre-feed ban) and cohort 2 (post-
feed ban). The conventional minimum statistical power criterion is 80
percent. In other words, the probability that a statistical analysis
will detect a true difference across groups should be at least 80
percent. The conventional significance level is 5 percent, meaning that
we would conclude that a result was nonrandom if it were 5 percent or
less likely to occur by chance alone. In our hypothetical scenario, the
power of the surveillance in the country with higher prevalence,
Country A, to detect a 50 percent decline in BSE prevalence is 98
percent. In comparison, the power of the surveillance in the lower
prevalence Country B to detect a 50 percent decline in BSE prevalence
is only 25 percent. In other words, if the Country B feed ban actually
led to a 50 percent decline in BSE prevalence and the equivalent of 2
million random samples were collected (6.7 times the level under the
OIE guidelines), there would still be a 75 percent chance of concluding
that the prevalence was unchanged from its initial level of 1 infected
animal per 100,000 animals.
An important implication of the low statistical power of sampling
in low prevalence populations is that BSE surveillance data are
unlikely to provide a purely statistical basis for making a
determination about the date when a specific intervention (e.g., a
ruminant-to-ruminant feed ban) becomes effective, even when large
amounts of surveillance data are available. For example, according to
the OIE (2007a), the annual incidence of reported BSE cases in the
Netherlands dropped from 13.2 to 0.8 per million adult cattle from
2001-2005.\6\ Despite the EU BSE surveillance requirements for testing
all risk animals over 24 months of age and all healthy slaughter cattle
over 30 months of age, Figure 1 shows that application of the BSurvE
(Prevalence A) model to Netherlands BSE surveillance data does not
yield sufficient statistical power to draw clear distinctions among
birth year cohorts as prevalence declines (Figure 1).
---------------------------------------------------------------------------

\6\ The OIE Terrestrial Animal Code (Chapter 1.1.1., Article
1.1.1.1) defines incidence as ``the number of new cases or outbreaks
of a disease that occur in a population at risk in a particular
geographical area within a defined time interval (OIE 2006b).''

---------------------------------------------------------------------------

[[Page 53321]]

[GRAPHIC] [TIFF OMITTED] TR18SE07.023

Note that, in figure 1, there is a decrease in estimated prevalence
between 1998 birth-year cohorts and 1999 birth-year cohorts, while, at
the same time, there is an increase in the upper confidence limit. This
apparent paradox is indicative of another shortcoming of relying on
surveillance data alone to determine whether BSE prevalence has been
reduced. Because fewer animals from the most recent birth year cohorts
are tested when sent to slaughter, uncertainty about the prevalence in
the most recent cohorts is much greater than in older cohorts.
Furthermore, the lower likelihood of detecting BSE in young infected
animals means that the young animals that are tested contribute
relatively little to reducing uncertainty in the true (as opposed to
apparent) BSE prevalence. These two sources of uncertainty in young
birth cohorts (low numbers of animals tested, and little value in the
surveillance data that are gathered from them) cause an asymmetrical
increase in the upper limit of the confidence interval compared to the
lower confidence limit. This effect on the upper confidence limit on
BSE prevalence is most pronounced for the most recent birth year
cohorts which are less likely to be tested and will not have lived long
enough to manifest BSE, even if they have been infected. Wilesmith et
al. (2004, figure 3) further illustrates this same concept.
Consequently, if the effectiveness of a country's safeguards
against BSE amplification were determined strictly by setting a
tolerance for the upper confidence limit on BSE prevalence associated
with the ``real surveillance data,'' one might reach the incorrect
conclusion that prevalence is increasing, when in actuality, the result
is simply due to testing fewer and younger animals in the most recent
birth year cohorts. Finally, relying solely on surveillance data fails
to account for under reporting of disease due to the lack of diagnostic
sensitivity to detect BSE at an early stage of disease. By accounting
for the possibility of false negative test results, epidemiologic
models such as BSurvE are recognized as providing a more accurate
estimate of true BSE prevalence than the apparent prevalence measured
by surveillance data alone.
Issue: One commenter stated that the output from the BSurvE model
used by Canada in 2005 grossly underestimated Canada's 2006 and 2007
BSE prevalence and, therefore, the BSurvE model is unreliable for
estimating Canada's BSE prevalence. The commenter stated further that,
at the minimum, APHIS should determine the erroneous inputs that
resulted in the failed prediction in 2005 and correct them.
Response: In the risk assessment conducted for this rulemaking,
APHIS used its own prevalence estimate, not that of the Canadian Food
Inspection Agency's (CFIA's) 2006 prevalence estimate, which was not
based on BSurvE, but on a modified version that appears similar to the
APHIS BBC model. The commenter cites CFIA's Assessment of the North
American BSE Cases Diagnosed from 2003-2005 (Part II), which states
that ``when the BSurvE model was recently applied to Canada's
statistics and adjusted to account for the effectiveness of the 1997
feed ban (based on experiences with the 1988 feed ban in the United
Kingdom), the resulting prediction was that it could be expected that
three infected animals remain within the national herd'' (CFIA 2006, p.
13).
APHIS' estimation of BSE prevalence in Canada (APHIS 2006c) is that
the expected prevalence values under the BBC and BSurvE Prevalence B
models correspond to an expected number of BSE-infected animals in the
standing Canadian adult cattle population of 4.1 and 23.2,
respectively. APHIS further explains that it is important to note that
this range of prevalence estimates represents uncertainty and not
variability. BSE-infected animals are recruited into and exit from the
adult cattle population over time, but at a given point in time, the
number of infected animals in the population is a fixed but uncertain
value.
Assuming the overall probability of infection remains constant over
time, the actual number of infected cattle in the population at any
given point in time would still vary randomly about the mean. This
variability is incorporated in the model supporting the exposure
assessment for live bovines by means of the Poisson variability
distribution. Assuming a fixed mean prevalence of 4.1 and 23.2 BSE
infected animals in the standing adult cattle population in Canada, the
95th percentile of the Poisson distribution are 7 and 31 BSE-infected
animals in any given year, respectively. We note that these numbers are
greater than the

[[Page 53322]]

five BSE cases detected in Canada in 2006, which means that the
greatest number of Canadian BSE cases identified in a single
surveillance year is lower than even the 95th percentile of
distribution.
Issue: One commenter stated that, if the United States were finding
BSE cases at the same rate as in Canada, this would translate into
roughly 40 BSE cases detected in the United States since January 2006,
which would be regarded as a large number. The commenter stated further
that, at this time, the BSE situation in Canada does not appear to be
improving.
Response: We do not agree with the commenter. The commenter's
conclusion appears to be based on a cursory estimate and does not
provide an accurate comparison of BSE cases detected in Canada with a
comparable number that would have been detected in the United States,
given the larger U.S. cattle population. The commenter's comparison
fails to take into account other years of surveillance, as well as the
age and surveillance stream of tested animals. These data are extremely
important for estimating BSE prevalence. A comparison based solely on
the number of detected cases ignores infected animals with unapparent
or undetected infections.
Table 1 provides a direct comparison of the estimated BSE
prevalence in the current standing adult cattle population of the
United States and Canada, respectively, using identical estimation
methods (APHIS 2006a; 2006c).

Table 1.--Comparison of Estimated BSE Prevalence in the Current Standing
Adult Cattle Population of U.S. and Canada
------------------------------------------------------------------------
BSE Prevalence Estimation Method
----------------------------------------
Country BSurvE prevalence
B BBC
------------------------------------------------------------------------
Expected value
------------------------------------------------------------------------
US............................. 0.18 x 10-6........ 0.10 x 10-6
Canada......................... 3.9 x 10-6......... 0.68 x 10-6
------------------------------------------------------------------------

Despite the higher estimated BSE prevalence in the current standing
adult cattle population in Canada compared to the prevalence of BSE in
the standing adult cattle population in the United States, APHIS finds
that, because of the extremely low BSE prevalence in Canada and the
high levels of BSE controls in both Canada and the United States, the
risk to the United States (i.e., the likelihood of establishment of BSE
in the United States and the potential impacts of cases that may occur
even without establishment) as a result of importing from Canada the
bovine commodities considered in this rule is negligible (APHIS 2006b).
Furthermore, as stated in our risk assessment, we expect that the
prevalence of BSE in Canada will decrease continuously over the next
several years. Peer reviewers of our risk assessment agreed (RTI 2007).
Issue: One commenter stated that Canada's ratio of positive cases
per 10,000 cattle tested exceeds the ratio of 22 of the 25 EU-member
countries; that only the ratios for the United Kingdom, Portugal, and
Spain exceed Canada's 2006 ratio. The commenter noted further that even
the countries of Ireland, Germany, and France, each of which are
considered to have had widespread BSE exposure, have a lower ratio for
positive cases detected per 10,000 head tested than does Canada.
Another commenter stated that Canada's BSE prevalence is higher than
that for Denmark, Belgium, and Austria, and is comparable to the rate
in Germany. This commenter, who estimated the Canadian BSE prevalence
to be 6.4 cases per million cattle, stated further that no one
considers countries with a reported BSE rate of 1 to 2 cases per
million animals (e.g., Denmark, Belgium and Austria) to have a minimal
BSE risk, and that Canada is not a BSE minimal-risk region in any
ordinary sense.
Response: The commenters' statements ignore important differences
in BSE surveillance and cattle populations among countries, and a
comparison based simply on the proportion of positive cases per number
of cattle tested is inconsistent with the prevalence estimate approach
taken by one of the commenters, as well as the prevalence estimate used
by APHIS. Although calculating the proportion of infected animals
detected per number of tested animals can serve as a useful tool,
depending on the purpose for the calculation, it is not an estimate of
prevalence. Rather, prevalence is defined as the number of infected
animals in the total population at a given point in time. On the other
hand, the calculation conducted by the commenter who referred to the
ratio of positive cases per 10,000 cattle tested is similar to that
conducted by the U.S. Department of Health and Human Services, Centers
for Disease Control and Prevention (CDC). In May 2007, using data
similar to that analyzed by APHIS for this rulemaking, CDC calculated
the proportion of Canadian-born BSE cases identified by Canadian
authorities in relation to the total number of animals tested in that
country. CDC then made a like calculation regarding BSE cases in U.S.-
born cattle and compared the Canadian and U.S. results (CDC 2007).
Unlike the estimate used by APHIS in the risk assessment for this rule,
the CDC calculation is not an estimate of the prevalence of BSE in
Canada, nor of the prevalence in the United States. Although the type
of calculations conducted by CDC can be useful in comparing relative
proportions of BSE detections per number of cattle tested, they do not,
as noted above, constitute an estimate of prevalence.
The number of disease detections per total number of animals tested
can be influenced by the criteria used for choosing animals for
testing. For instance, Canada, like the United States, conducts
targeted BSE surveillance, sampling those animals where disease is most
likely to be detected if present. In contrast, EU countries routinely
test large numbers of healthy animals at slaughter. Approximately 80
percent of cattle tested for BSE in the EU during 2001-2004 were
healthy slaughtered animals, but ``risk animals'' were 22 times more
likely to test positive (EC 2005a). One study (Giovannini et al., 2005)
estimates the true prevalence of BSE infection in several EU countries.
Based on BSE testing in 2001, although Denmark, Finland, and the
Netherlands had a lower proportion of positives per test than Canada,
the estimated prevalences from this study for those three countries
were higher than the expected values of our Canadian BSE prevalence
estimates using the BBC estimation method (0.68 cases per million adult
cattle) or BSurveE Prevalence B (3.9 cases per million adult cattle).
Giovannini et al. (2005) estimated the following 90 percent confidence
intervals for the prevalence of BSE infection: Denmark, 9 to 38 cases
per million animals; Finland, 29 to 110 cases per million animals; and
Netherlands, 8 to 34 cases per million animals. The methods used by
APHIS to estimate Canada's BSE prevalence, including the BSurvE model
developed by the EU Transmissible Spongiform Encephalopathies Community
Reference Laboratory, account for the cattle population demographics,
the age and surveillance category of animals tested, and the
insensitivity of BSE diagnostics with regard to detection of the
disease at an early stage of development.
The comments are based on an inappropriate comparison of a
statistical estimate of the true BSE prevalence in Canada to the crude
rate. Table 2 below compares the crude reported BSE rates in all five
countries in 2005. Comparing the reported BSE rate of Canada to those
of the countries listed by the commenters shows that Canada's

[[Page 53323]]

reported rate is at least an order of magnitude below that of the
others.

Table 2.--Reported BSE Rates in 5 Countries
------------------------------------------------------------------------
Reported BSE
cases per
Country million adult
cattle--2005
------------------------------------------------------------------------
Canada................................................. 0.145
Denmark................................................ 1.289
Belgium................................................ 1.448
Austria................................................ 2.114
Germany................................................ 4.965
------------------------------------------------------------------------
Source: OIE (2007a).

The problem with comparing the crude reported rate of BSE detection
to the estimated true BSE prevalence is illustrated by the situation in
Belgium. The reported rate of BSE in Belgium peaked in the 2001
surveillance year at 28.22 cases detected per million adult cattle (OIE
2007a). In comparison, Saegerman et al. (2004) applied the BSurvE model
to the Belgian BSE surveillance data and estimated that the actual BSE
prevalence in Belgium peaked at approximately 400 cases per million
adult cattle in the 1995 birth year cohort. (The lag between the 1995
birth year and the 2001 surveillance year is consistent with the long
BSE incubation period.)
With regard to the comment that countries with 1 to 2 cases per
million animals are not considered to present minimal risk, APHIS notes
that, prior to the 2005 revisions in the OIE guidelines on BSE,
countries with a reported BSE rate of 1 to 2 cases per million animals
could satisfy the prevalence criterion for the pre-2005 OIE BSE
minimal-risk classification. Under the 2004 OIE Terrestrial Animal
Health Code (Article 2.3.13.5), the criteria for a BSE minimal-risk
country included a reported rate of less than two cases per million
during each of the last four consecutive 12-month periods within the
cattle population over 24 months of age. The OIE Code was modified in
2005 to include a revised country categorization system which more
accurately reflected current scientific understanding of BSE. These
modifications streamlined the number of country categories to three
(negligible, controlled, or undetermined BSE risk) and also eliminated
the numeric prevalence criteria for classifying the BSE risk status.
The previous OIE minimal-risk category is now incorporated into the
controlled risk category. We note that in 2007, the OIE recognized
Switzerland as a BSE controlled risk region. Switzerland had a reported
rate of 5.4 BSE cases per million adult animals in 2006 (OIE 2007a),
greater than the 1 to 2 cases per million animals cited by the
commenters.
APHIS disagrees with the commenter's statement that Canada does not
qualify as a BSE minimal-risk region. APHIS regulations at Sec. 94.0
define the standards for a region to be designated as a minimal-risk
region. These include the standard that the region maintain ``risk
mitigation measures adequate to prevent widespread exposure and/or
establishment of the disease.'' Canada continues to meet this standard.
The commenters provided no specific evidence to document how or why
Canada does not meet the APHIS standards.
Issue: One commenter stated that the prior information [information
using data from the United Kingdom feed ban] incorporated into the
Bayesian models used to estimate prevalence of BSE-infected cattle in
Canada may have resulted in estimates that are biased downward (to a
limited degree) from the true burden. However, stated the commenter,
the Bayesian models used to estimate prevalence in Canada (as of August
2006) are basically sound and a better approach than relying on the
BSurvE Prevalence B estimate. Further, said the commenter, given the
proviso that the models could overestimate the effectiveness of the
feed ban, it is most likely that the actual prevalence of infected
animals is between 0.68 and 3.9 animals per million adult cattle. The
commenter stated that because it is likely that the Canadian feed ban
was at least as effective as the initial United Kingdom feed ban, and
based on available data, the true BSE prevalence in Canada is probably
substantially closer to 0.68 cases per million animals than to 3.9
cases per million animals.
Conversely, several commenters suggested that APHIS rejected the
higher prevalence estimate of the BSurvE model for the lower prevalence
estimate of the BBC model, and that the BBC model prevalence estimate
is not realistic in light of recent data.
Response: Although APHIS considered the results of both the BSurvE
and the BBC prevalence estimation models, we consider the result of the
BBC model as the more likely prevalence estimate to apply to the
assessment of BSE risks associated with imports from Canada over the
next 20 years in our quantitative exposure model, for the following
reasons. APHIS estimated Canadian BSE prevalence based on surveillance
conducted through August 15, 2006. (Note: This time period includes all
cases of Canadian origin reported through August 2006 (APHIS 2006c).)
From August 16, 2006, through April 2007, Canada accumulated
approximately 44,980 additional BSE samples and detected two BSE cases
(one confirmed on February 7, 2007, and another confirmed on May 2,
2007). Based on the negative binomial likelihood ratio, which considers
the number of negative tests prior to one or more positives, the BSurvE
Prevalence B estimate (with expected value of 3.9 cases per million
animals) is indeed far more likely to be true than is the BBC
prevalence estimate (with an expected value of 0.68 cases per million
animals) for the current standing Canadian cattle population. However,
the primary purpose of characterizing BSE prevalence in Canada's
current standing herd (APHIS 2006c) was not to discuss or assume its
implications for the present, but rather, to estimate prevalence for
use as an input for the Harvard exposure model used in the Exposure
Assessment of the analysis. Because BSE has a long amplification cycle
(it takes an average of 7 years from the time that one animal is
exposed, to the time that another might be exposed from infectivity
produced by the first animal), the Harvard model is typically run with
20-year simulations to include roughly 3 amplification cycles. The
prevalence estimates contained in APHIS' estimation of BSE prevalence
in Canada (APHIS 2006c) are applied, unchanged, to the cattle imports
projected over the next 20 years (2007-2026). Since we expect that the
true prevalence will drop from its current level (whatever that may
be), we anticipate that the lower, BBC estimate is a more realistic
prediction (or even an overestimate) of average prevalence levels over
this time frame. Consequently, APHIS considers the result of the BBC
model, which incorporates the effect of a feed ban, to be better for
application to the quantitative assessment of BSE risks associated with
imports from Canada over this time period. In order to determine the
impact of this assumption on the results, we applied the BSurvE
estimate to the exposure model. We note that the likelihood of BSE
establishment remained negligible (R0 of 0.079, which is far
less than 1), as did the potential impact of cases even without
establishment (less than 4 clinical cases) over the 20 years of the
analysis.
Issue: One commenter suggested that the APHIS risk model is not
trustworthy because it has not been shown to have predictive validity
and does not explain or predict a sustained flow of BSE cases from one
geographic area (the Alberta region in Canada).

[[Page 53324]]

Response: It is not clear to us from the comment which model the
commenter is referring to. Consequently, in this response, we discuss
the Harvard model and the prevalence models used by APHIS. In either
case, we disagree with the commenter's conclusion that the APHIS risk
model is not trustworthy. The plausibility of the Harvard model was
established by comparing its predictions for Switzerland against the
observed progression of BSE within that country's cattle herd (Cohen et
al., 2003). It is not clear from the comment how the predictive
validity of an infectious disease model is to be demonstrated over a
20-year time horizon, or how the model has failed to explain or predict
the observed data. Regarding a sustained flow of BSE cases from one
geographic area, assuming a constant proportion of BSE infected cattle
in the herd, more BSE cases are found where large cattle populations
exist.
As we discuss above in response to another issue raised by
commenters, APHIS' estimation of BSE prevalence in Canada (APHIS 2006c)
concludes that the expected prevalence values under the BBC and BSurvE
Prevalence B models correspond to an expected number of BSE-infected
animals in the standing Canadian adult cattle population of 4.1 and
23.2, respectively. Further, the prevalence estimates represent
uncertainty and not variability. At any given point in time, the number
of infected animals in the population is a fixed (although uncertain)
value, although over time the actual number of infected cattle in the
population would vary randomly about the mean of the probability
distribution, as BSE-infected animals are recruited into and exit from
the adult cattle population (i.e., some are newly infected and some
die). Even assuming that the probability of infection remains constant,
over time the actual number of infected cattle in the population would
vary. This variability is incorporated in the model supporting our
exposure assessment for live bovines by means of the Poisson
variability distribution. Assuming a fixed mean prevalence of 4.1 and
23.2 BSE-infected animals in the standing adult cattle population in
Canada, the 95th percentile of the Poisson distribution is respectively
7 and 31 BSE-infected animals in any given year. As we noted above,
these numbers are greater than the five BSE cases detected in Canada in
2006, which means that the greatest number of Canadian BSE cases
identified in a single surveillance year is lower than even the 95th
percentile of distribution. While this observation does not
statistically validate (confirm) the APHIS estimates of Canadian BSE
prevalence, neither does it invalidate them, as the commenter seems to
suggest. Furthermore, the prevalence estimates are applied not only to
the current standing population, but also to the next 20 years.

BSE Data From the United Kingdom

In our January 2007 proposed rule and its supporting risk
assessment, we discussed data associated with a ruminant-to-ruminant
feed ban in the United Kingdom and indicated that experience in the
United Kingdom demonstrates that implementation of a ruminant-to-
ruminant feed ban causes BSE prevalence to decrease. We noted that
animal feed restrictions were implemented in the United Kingdom in
1988, when the use of ruminant MBM in ruminant animal feed was banned.
In September 1990, the use of specified bovine offals was banned for
use in any animal feed. This ban prohibited the use in any animal feed
of bovine tissues with the highest potential concentration of
infectivity. In 1994, the use of mammalian protein--not just ruminant
protein--was banned from ruminant feed. In 1996, feeding of any farmed
livestock, including fish and horses, with mammalian MBM was completely
banned. As a result of reducing the recycling of infectivity, the
annual incidence of BSE fell by 99.4 percent, from 36,680 in 1992 to
203 in 2005 (DEFRA 2006b). There is, therefore, every reason to expect
downward pressure on the prevalence of BSE in any country that
implements a feed ban.
Issue: One commenter stated that, of 180,986 confirmed cases of BSE
in Great Britain, the year of birth of the infected animal is unknown
in 43,342 cases, and the large percentage of animals whose birth year
is unknown casts doubt on the ability to determine the timeframe of an
effective feed ban and, and further, makes it doubtful that all BSE-
infected cattle in Canada are going to show clinical signs of the
disease only if they were born before March 1, 1999. The commenter also
stated that Japan has reported cattle as young as possibly 20 months of
age or younger as testing positive for BSE.
Response: It is not clear to us how the information presented by
the commenter supports the conclusions the commenter reached. However,
we consider it useful to provide some clarification regarding the
information presented. With regard to the proportion of BSE cases in
Great Britain for which the date of birth is unknown, our risk
assessment included a sensitivity analysis that takes into account that
general source of uncertainty. (Sensitivity analysis evaluates the
degree to which changes in the assumptions used in a model affect the
model's results.) We made no assumptions as to whether Great Britain's
feed ban is or has been effective, but applied the same proportional
drop in cases observed in the United Kingdom to the Bayesian analysis
that was performed to estimate BSE prevalence in Canada's standing
cattle herd.
The commenter's statement that it is doubtful that only animals
born before March 1, 1999, would show clinical signs of BSE indicates a
potential confusion between the likelihood of exposure as expressed in
terms of the date of the effectively enforced feed ban (and, thus, the
potential for exposure) and the likelihood of an exposed animal
developing clinical signs (which is based on age and amount of
exposure, and the amount of time that has elapsed since exposure). In
neither our risk assessment nor our proposed rule do we conclude that
only infected animals born before March 1, 1999, would show clinical
signs of the disease. Based on Canada's system of regulations,
compliance and enforcement, and the length of time we expect pre-feed
ban feed to persist in the system, we conclude that animals born on or
after March 1, 1999, have an extremely low likelihood of exposure to
BSE. Any animal, however, exposed to an infectious dose of the BSE
agent and allowed to live to the end of its incubation period, would
likely exhibit clinical signs.
Regarding the age of cattle diagnosed with BSE in Japan, the
comment did not contain sufficient information for us to determine and
respond to the relevance of the statement to the remainder of the
comment.
Issue: One commenter questioned the effectiveness of APHIS' use of
United Kingdom surveillance numerators to estimate Canada's BSE
prevalence. Specifically, the commenter stated that ``Nowhere * * * is
incidence reported. Cases (without reference to a population at risk)
are used. This may be important because the manner in which BSE cases
were counted changed over time in the [United Kingdom].''
Response: We acknowledge that changes over time in BSE surveillance
and in the size and demographics of the cattle population do contribute
to the uncertainty about the efficacy of the initial, ruminant-to-
ruminant feed ban introduced in the United Kingdom in 1998. However,
the United Kingdom's Department for Environment, Food, and

[[Page 53325]]

Rural Affairs (DEFRA) does not report BSE surveillance results by birth
year and surveillance class (e.g., active or passive surveillance,
animal health status). Ideally, such data could be entered into BSurvE
or a similar model to estimate true BSE prevalence for all United
Kingdom birth year cohorts since the onset of the epidemic. This
process would permit not only an improved estimate of the effect of the
initial feed ban but also of the incremental impact of additional
measures that were subsequently introduced. DEFRA has reported back-
calculation model estimates of true BSE prevalence in cohorts born
after 1995 to assess the effects of the ``reinforced feed ban''
introduced by the United Kingdom in August 1996 (DEFRA 2005, 2006b).
However, we are unaware of any published estimates of true BSE
prevalence in the United Kingdom for the 1987-1995 birth year cohorts
based on up-to-date surveillance results.
Issue: One commenter stated that APHIS is wrong to assume that the
United Kingdom data regarding the effectiveness of the feed ban can be
applied directly to the situation in Canada.
Response: We acknowledge that the applicability to Canada of the
data from the initial United Kingdom ruminant-to-ruminant feed ban is
uncertain. Nonetheless, the United Kingdom's experience and data are
important and useful to our risk assessment and analyses. In addition,
the Peer Review Report (RTI 2007, p. ES-2) noted that ``[all reviewers]
agreed that the evidence from the United Kingdom * * * and Europe that
the feed ban is effective is reasonable to consider in the case of
Canada.''
Issue: Several commenters noted the differences in the feed bans in
the United Kingdom and Canada in stating that it is not valid to draw
conclusions about the likely prevalence of BSE in Canada by
extrapolating from the rate of decline in BSE cases in the United
Kingdom following implementation of a feed ban there. The commenters
noted that (until expanded this July) the feed ban in Canada prohibited
the feeding of ruminant material to ruminants. In contrast, said one
commenter, significant declines in the number of confirmed BSE cases in
the United Kingdom did not occur until the United Kingdom took stronger
measures, ultimately banning the feeding of all mammalian protein to
food animals in 2001. The commenter suggested that the United Kingdom's
experience in particular clearly shows that ruminant-to-ruminant feed
bans do not drastically curtail the number of confirmed BSE cases and
that much stronger measures are needed to eradicate the disease.
Response: The comments appear to confuse the absolute level of BSE
in the United Kingdom with its rate of decline. The comments also
ignore the BSE incubation period and the effects of other concurrent
measures, trends, and events in the United Kingdom. The number of BSE
cases in United Kingdom birth year cohorts (all cattle born in a given
year) has continued to decline since peaking in 1987. With the
exception of the 1996 birth year cohort, it is not readily apparent
that there has been any significant change in the rate of decline in
birth year cohort prevalence after the United Kingdom introduced the
initial ruminant-to-ruminant feed ban in 1988 (figure 2). As of March
1, 2007, the United Kingdom had confirmed two BSE cases in animals born
after 2001, but due to the long BSE incubation period, it is reasonable
to expect that ongoing surveillance may detect additional cases in
animals born after 1998.
[GRAPHIC] [TIFF OMITTED] TR18SE07.024

[[Page 53326]]

Shortly after the emergence of vCJD was publicly recognized in
March 1996, the United Kingdom introduced several BSE-related measures,
including the ban on the use of mammalian MBM in feed for all farm
animals (the ``reinforced feed ban''), a selective cull, and the over-
30-month rule limiting the age of animals that could be slaughtered for
food. As shown in figure 3, the size of the United Kingdom cattle
population began a marked decline in 1996, punctuated by a drop
associated with the foot and mouth disease (FMD) outbreak in 2001.
[GRAPHIC] [TIFF OMITTED] TR18SE07.025

In addition to the declining cattle population size, other
confounding variables, such as changes in cattle population
demographics and BSE surveillance practices, make it difficult to
ascertain the independent or marginal effect of any single measure on
the decline of BSE in United Kingdom birth year cohorts. At this time,
it appears that the confluence of events and measures of 1996 may have
hastened the waning of BSE in the United Kingdom, but the decline was
underway in 1988.
Issue: One commenter indicated that scientific studies in France
and Britain have found that, after a ruminant-to-ruminant feed ban was
put into place, the subsequent incidence of BSE was correlated to pig
density, and that the new Canadian BSE feed rule, to be implemented in
July 2007, is, according to the commenter, similar to, but weaker than,
the September 1990 United Kingdom SBO [Specified Bovine Offals] ban.
The commenter stated that, by not following the lead of the United
Kingdom [and banning the feeding of all mammalian protein to food
animals], the proposed CFIA SRM ban may reduce but will not eliminate
the risk of BSE in Canada.
Response: Two studies--Abrial et al. (2005) and Stevenson et al.
(2005)--indicate a correlation between cases of BSE born after a
ruminant-to-ruminant feed ban was implemented and areas of higher pig
density in France and Britain. These studies indicate the potential for
cross-contamination of livestock feeds after ruminant-derived protein
was excluded from ruminant feed. Eventually, each country and the EU
adopted regulations prohibiting the inclusion of any animal protein in
livestock feed. At this time, however, it is not possible to ascertain
the extent, if any, to which establishment of a more restrictive feed
ban had any impact on the rate of BSE decline in EU Member States
beyond the feed controls already in effect.
As discussed previously, the number of BSE cases in United Kingdom
birth year cohorts began to decline in 1988, the year the initial
ruminant-to-ruminant feed ban was introduced. Although France initially
introduced a ban on mammalian MBM in cattle feed in July 1990--not a
ruminant-to-ruminant feed ban--the European Commission Scientific
Steering Committee concluded that the French feed ban adopted in 1990
``was likely not effectively enforced until 1994/1995.'' (ECSSC 2000,
p. 30). Based on testing in 2001-2002, Bonnardiere et al. (2004) found
a significant increase in French BSE prevalence between the July 1993-
June 1994 and July 1994-June 1995 cohorts, followed by a significant
decrease in BSE prevalence in birth cohorts born in France after June
1995. More recently, active surveillance during 2001-2005 also
indicates that the number of BSE cases per cohort peaked in France in
the 1995 birth year cohort and declined thereafter (EC 2006, table
B20).
In Europe more generally, based on active surveillance during 2001-
2005, the number of BSE cases per birth year cohort in the original EU
Member States (EU 15), excluding the United Kingdom, was on the decline
after the 1995 birth year cohort. In June 1994, the EU banned the
feeding of mammalian MBM to ruminants. However, among EU members, only
Belgium, Germany, Greece, Italy, Luxembourg, and Spain had no feed ban
in place prior to the 1994 EU-wide measure (Court of Auditors 2001). In
June 2005, the European Commission issued the ``Report on the
Monitoring and Testing of Ruminants for the Presence of Transmissible
Spongiform Encephalopathy in the EU in 2004'' and observed that the
impact of the 2001 ``total feed ban'' (EU Regulation 999/2001) cannot
yet be assessed due to the long BSE incubation period. As noted in the
discussion of the decline of BSE in the United Kingdom, it is
reasonable to expect that ongoing surveillance may detect additional
cases in animals born after 1998.

[[Page 53327]]

The conclusion of our risk assessment that, over the 20 years of
the analysis, the risk to the United States (i.e., the likelihood of
establishment and the potential impacts of cases that may occur even
without establishment of BSE) as a result of importing from Canada the
bovine commodities considered in this rule is negligible, is not
predicated on the eradication of BSE in Canada.
[GRAPHIC] [TIFF OMITTED] TR18SE07.026

Issue: One commenter indicated that year-of-birth data collected by
the EU shows that, based on the number of BSE cases detected in the
United Kingdom since 2001, there was a steady increase in the number of
BSE-positive cattle born in the United Kingdom after its 1988 feed ban,
beginning with cattle born in the year 1990.
Response: We disagree with the commenter. Since July 2001, when the
EU-wide active BSE surveillance program commenced, an increasing
proportion of the total BSE cases in the United Kingdom have been
detected as a result of targeted (active) surveillance (DEFRA 2006b,
figure 4.3). However, as shown by the EC (EC 2006, chart B1), the vast
majority of BSE cases in the United Kingdom were detected by
surveillance prior to 2001. Based on all available United Kingdom BSE
surveillance data (DEFRA 2007), the number of BSE cases in United
Kingdom birth year cohorts began to decline in 1988, the year the
initial ruminant-to-ruminant feed ban was introduced.
For the reasons discussed above, we continue to consider it
appropriate to apply our estimates of BSE prevalence in Canada to our
risk assessment. As noted above, we used two related, but distinct,
methods to estimate BSE prevalence in Canada, and addressed the
uncertainty in the prevalence of BSE in Canada by considering
prevalence estimates that differ by more than a factor of five.
Although we consider the BSurvE Prevalence B estimate to be far more
likely to be true than is the BBC estimate for the current standing
Canadian cattle population, we consider the result of the BBC model as
the more likely prevalence estimate to apply to the assessment of BSE
risks associated with imports from Canada over the next 20 years.

Feed Ban in Canada

As discussed above, in our January 2007 proposed rule, we proposed
to allow the importation of live bovines from BSE minimal-risk regions
if the animals were born on or after a date determined by APHIS to be
the date on and after which a ruminant-to-ruminant feed ban in the
region of export has been effectively enforced. We noted that
experience around the world in countries with BSE has demonstrated that
feed bans are effective control measures, and that the incidence of BSE
worldwide continues to decline because of these measures (OIE 2007a).
We indicated that, because of the demonstrated efficacy of an
effectively enforced feed ban in reducing the possibility of exposure
of cattle to the BSE agent, the OIE provides guidelines for trade in
live cattle from regions that have reported BSE if such regions have an
effective feed ban in place, provided the cattle were born after the
date when the feed ban was effectively enforced (OIE Terrestrial Animal
Health Code, Chapter 2.3.13). We proposed to consider March 1, 1999, as
the date on and after which a feed ban has been effectively enforced in
Canada. A number of commenters addressed Canadian enforcement of its
feed ban, and also addressed the date we proposed to consider as the
date of effective enforcement of a feed ban in Canada. Although some
commenters specifically supported March 1, 1999, as the date of
effective enforcement of a ruminant-to-ruminant feed ban in Canada, a
number of other commenters disagreed that Canada was effectively
enforcing a feed ban as of that date. Some commenters suggested
alternative dates or time frames.
Issue: Several commenters stated that APHIS' determinations of the
level of compliance with the Canadian feed ban and the time at which
compliance was achieved are arbitrary and scientifically
indeterminable.
Response: We disagree with the commenters. In January 2005, USDA
sent a team to Canada to assess Canada's feed ban and its feed
inspection program to determine whether the control measures put in
place by the Canadian Government were achieving compliance with that
country's regulations. APHIS conducted an extensive review of the feed
ban in Canada. As part of its review, APHIS

[[Page 53328]]

analyzed CFIA's description of past cases of BSE in Canada, as well as
historical inspection and compliance data related to the feed ban for
the previous 3 years, educational materials, published notices, and the
report of the International Review Team that was submitted to the U.S.
Secretary of Agriculture in February 2004. Additionally, the U.S. team
accompanied the CFIA inspection staff on inspections of randomly
selected commercial feed mills and rendering facilities. At the
facilities, the U.S. team observed the application of the inspection
standards, observed manufacturing techniques, and discussed processes
with facility personnel involved in various steps of feed
manufacturing. In its report, the team concluded that Canada has a
robust inspection program, that overall compliance with the feed ban in
Canada is good, and that the feed ban is reducing the risk of
transmission of BSE in the Canadian cattle population (USDA 2005). The
team's findings support our conclusions regarding the level of
compliance with the feed ban in Canada.
Issue: In our January 2007 proposed rule, in discussing our
rationale for considering March 1, 1999, to be the date of effective
enforcement of a feed ban in Canada, we stated that a 12-month period
would generally be sufficient to allow purchased feed products that may
contain MBM to be completely used. One commenter expressed uncertainty
about that estimation and suggested that it might be advisable for
APHIS to conduct a quantitative assessment of compliance with the feed
ban to determine the date of its effective enforcement.
Response: We recognize uncertainty regarding the precise date on
which Canada achieved effective enforcement of its feed ban, but we
note that, given the extremely low prevalence of BSE in Canada along
with the safeguards in the United States, the impact on the overall
risk of a slightly earlier or later date would be minimal. Although
reducing uncertainty can, at times, be achieved by performing more
rigorous quantitative analyses, before attempting to reduce the
uncertainty regarding any given factor or parameter--such as the
precise date on which Canada achieved effective enforcement of its feed
ban--it is important to examine the significance of the parameter to
the overall risk result.
Issue: Several commenters stated that APHIS' calculation of the
amount of time necessary for ruminant feed to cycle through the
Canadian feeding system is irrelevant in the absence of effective
enforcement of feed-ban regulations in Canada. The commenters stated
that it was not until between 2000 and 2002 that Canada implemented
inspections of feed and rendering facilities.
Response: The commenters' statement is not accurate. Inspections of
rendering facilities and feed mills in Canada began immediately with
the implementation of the feed ban in that country in August 1997.
Rendering facilities were required to obtain an annual permit to
operate, and issuance of a permit required an inspection of the
facility. In addition, CFIA immediately began a program for inspection
of commercial feed mills. All commercial feed mills were inspected in
the first year after the implementation of the feed ban, with none of
the feed mills found to be including prohibited material in ruminant
feed. Thereafter, feed mills were on a 3-year inspection interval until
2002, when annual inspection of commercial feed mills was initiated.
Issue: A number of commenters stated that the diagnosis of BSE in
cattle born after the establishment of a feed ban in Canada
demonstrates that Canada's feed ban is either ineffective or not
effectively enforced.
Response: We disagree with the commenters' conclusion. The
commenters suggest that, in order for the Canadian feed ban to be
considered effective, BSE surveillance data would have to demonstrate
that the likelihood of BSE transmission in that country has been
eliminated. However, as noted in our risk assessment, Canadian BSE
surveillance data do not provide a statistical basis for distinguishing
BSE prevalence among birth year cohorts (APHIS 2006b, p. 12); the
overall prevalence is so low that distinguishing any difference is
nearly impossible. In other words, the data cannot distinguish any
significant difference in prevalence among animals born in different
years, which would have been one way to demonstrate the effect of a
feed ban (e.g., if the feed ban were implemented at the beginning of
1997, surveillance data showing a higher BSE prevalence in animals born
in 1996 than in animals born in 1997 would support the effectiveness of
the feed ban). However, in the absence of a feed ban that reduced
exposure to BSE, we would expect the prevalence of the disease to
increase over time. We have no evidence that such an increase has
occurred, but we do have data that the feed ban is being enforced.
Furthermore, as we discussed in our risk assessment, detection of
BSE in an animal born after the date a feed ban was implemented does
not indicate an overall failure of the measures in place to stem
transmission of the disease in that country. Most other countries that
have experienced cases of BSE, have reported similar cases. Of 25
countries that have reported indigenous BSE cases, only 4 reported no
cases in 2005-06 (OIE 2007). Human error is expected, which is why the
feed ban is comprised of a number of interrelated measures that have a
cumulative effect. Our risk assessment does not assume 100 percent
compliance with all measures all of the time. We discussed factors
related to the feed ban in Canada since before its implementation in
1997. We considered activities related to inspection and compliance
with the feed ban, the rendering industry, the risk of cross-
contamination, education activities and industry awareness, and on-farm
practices that might contribute to the efficacy of the feed ban. In
addition, we highlighted the fact that since the implementation of the
feed ban on August 4, 1997, CFIA has continued to revise and strengthen
its processes and procedures to further enhance the effectiveness of
the feed ban. Canada's July 2007 modification of its feed ban to remove
SRMs from all animal feeds, pet food, and fertilizer is a good example
of such enhancements. We concluded that compliance with the feed ban
measures in Canada continues to increase as the program evolves and
that all of these factors have resulted in a cumulative reduction in
the risk that Canadian cattle will be exposed to the BSE agent.
Issue: Several commenters stated that Canada cannot demonstrate
that it has effectively prevented the feeding of ruminant material to
cattle over the past 8 years. Commenters stated that eight or nine
Canadian feedlots were discovered to still be feeding banned bone meal
products, and that, because of their violations of the feed ban, 30,000
Canadian cattle were under quarantine. Additionally, one commenter
stated that in March 2007, nine farms in Saskatchewan and as many as
8,000 cattle, deer, and other ruminants were quarantined after ruminant
MBM was accidentally shipped to those farms from a Saskatoon feed mill.
Another commenter stated that, in December 2006, Canada's Minister of
Agriculture and Agri-Food acknowledged that up to 10,000 head of
Canadian cattle on 113 different farms in the Provinces of Ottawa and
Quebec had recently been fed feed contaminated with ruminant material.
Response: APHIS is aware of the incidents reported in late 2006 and
in March 2007 and considered such incidences very carefully in its
evaluation of the effectiveness of the

[[Page 53329]]

feed ban. However, it is not clear to us what the commenters are
referring to regarding 30,000 Canadian cattle under quarantine.
It should be noted that the use of the term ``contaminated'' above
refers to the potential inclusion in ruminant feed of MBM derived from
ruminants, but not to the feeding of known BSE-contaminated material to
ruminants. Feed control systems, including those in the United States,
are inherently subject to human error such as occurred in these
incidents. These compliance errors require follow up and correction by
CFIA, just as in the United States such incidents would necessitate
follow-up by the U.S. Human Health and Services, Food and Drug
Administration (FDA). Following detection of these occurrences, CFIA
conducted a detailed investigation and traced all potentially
contaminated feed. CFIA accounted for and disposed of all feed that did
not enter the distribution channels, and feed already distributed to
farms was removed, disposed of, and replaced. CFIA conducted risk
assessments to help evaluate the possibility that new cases of BSE
would occur due to the contamination of feed with prohibited material,
and concluded that the overall risk was negligible. Even though this
finding indicated that it was highly unlikely that animals exposed to
the involved feed would develop BSE in the coming years, in those
instances where exposure to the feed could not be ruled out, the CFIA
has excluded these animals and their meat and byproducts from export
eligibility. This measure was established to meet the technical
requirements of various trading partners and does not affect the
movement or marketing of these animals within Canada. These findings,
together with Canada's rapid and comprehensive response to the
incidents, reinforces our confidence in the effective enforcement of
Canada's ruminant feed ban.\7\
---------------------------------------------------------------------------

\7\ In the rulemaking for our 2005 final rule establishing
criteria for recognition of a region as a BSE minimal-risk region,
we discussed in detail our evaluation of Canada's veterinary
infrastructure; disease history; practices for preventing widespread
introduction, exposure, and/or establishment of BSE; and measures
taken following detection of the disease (APHIS 2005).
---------------------------------------------------------------------------

Issue: Some commenters questioned the effectiveness of Canada's
feed ban, given evidence of contamination of ruminant feed with MBM
derived from ruminants. One commenter stated that, in the five cases of
cattle born after March 1, 1999, where investigations of BSE in
Canadian cattle have been completed, the reported cause of BSE
infectivity centered on ruminant MBM used in non-ruminant feeds cross-
contaminating ruminant feeds, either during processing at the feed mill
or during transport. Given that four animals were born after March 1,
1999, the commenters indicated that great care must be given to the
analysis of these animals in the risk assessment and did not feel that
APHIS thoroughly examined the cases.
Response: We agree with the commenters that the investigations of
BSE in animals born in Canada in 2000 and 2002 suggest that these
animals were most likely exposed during their first year of life to
feed contaminated during processing (CFIA 2006a). Reports of the
investigations identified incidents of concern in which ruminant feed
was processed or transported immediately following the handling of
nonruminant feed containing prohibited material. Such incidents were in
contravention of Canadian regulations, which require flushing and/or
clean-out between batches if ruminant feed is processed on the same
lines as feed containing prohibited material.
We considered the issue of cross-contamination and concluded that
Canada has implemented measures to prevent cross-contamination of
ruminant feed with prohibited materials in the rendering and feed
manufacturing industries are essential for implementation of an
effective feed ban. We also considered other factors--including the
regulatory actions taken to implement the feed ban, education and
industry awareness efforts, inspection and compliance activities, and
on-farm feeding practices--in our overall evaluation to determine the
date the feed ban was effectively enforced in Canada and, based on
those factors, identified March 1, 1999 as the date of effective
enforcement of the feed ban.
APHIS did not specifically address each individual case of BSE in
Canada in the risk assessment, as the available details of each
epidemiological investigation did not contribute to the overall risk
estimation. The risk estimation was based on consideration of all
factors relevant in the risk pathway. These included consideration of
the current Canadian feed ban, with explicit recognition that cases
born after the feed ban was implemented in August 1997, or after the
March 1, 1999 date have occurred and could continue to occur. The
prevalence estimate acknowledges that BSE is present in Canada, albeit
at a very low level. The risk reduction factors in the United States,
including feed ban regulatory activities similar to those in Canada,
were considered in the exposure assessment. The combination of all of
these factors, including recognition that human error can occur in any
step of the pathway, supported the conclusion that the risk to the
United States of BSE--i.e, the likelihood of establishment and the
potential impact of cases that may occur even without establishment--as
a result of importing from Canada the bovine commodities considered in
this rule is negligible.
Issue: One commenter stated that Canada has experienced an increase
in the number of BSE cases since it instituted a feed ban in 1997.
Response: It appears that the commenter is equating the number of
detected cases of BSE with the number of infected animals in a national
herd. However, an increased number of detections of BSE does not
necessarily mean an increase in prevalence. A BSE detection rate is
dependent not only on prevalence, but also on intensity of
surveillance. An increased number of BSE cases have been detected in
Canada as that country has increased surveillance for the disease. As
noted above, an APHIS analysis of the Canadian BSE surveillance data
did not find a statistical basis for distinguishing BSE prevalence
among birth year cohorts.
Issue: A number of commenters referred to the number of BSE cases
in cattle born in Canada after March 1, 1999, as evidence that the date
should not be accepted as the date of an effectively enforced feed ban.
Commenters requested that APHIS reassess the proposed rule in light of
recent diagnoses of such cattle.
Response: In the assessment of potential BSE risk we conducted for
this rulemaking, we concluded that there is an extremely low likelihood
that cattle born in Canada on or after March 1, 1999, will have been
exposed to BSE. This conclusion does not mean that effective
enforcement necessarily equals no instances of contravention of the
feed ban, either accidentally or intentionally, just as isolated
transgressions of U.S. laws do not necessarily constitute ineffective
enforcement of those laws.
While specific incidents of cross-contamination can, and most
likely will, happen, since no regulatory effort can ensure 100 percent
compliance, the detection of BSE in several bovines in Canada born
after March 1, 1999 does not negate the overall effect of the feed ban
in decreasing the opportunities for transmission of disease. Empirical
evidence from the United Kingdom has demonstrated, and simulation
studies have reinforced, that implementation of a ruminant-to-ruminant
feed ban leads to continued decrease in prevalence over time (Cohen, et
al., 2001; 2003; DEFRA 2006, EC 2003; 2005). Similar

[[Page 53330]]

effects of a feed ban have been seen in other countries in the EU,
where there have been continued detections of BSE in cattle born after
a feed ban is initially implemented. At the same time, however, the
apparent number of cases of BSE identified in the EU-15 Member States
has decreased every year since 2001. The available evidence leads
firmly to the conclusion that animals born after the date of
implementation of a ruminant-to-ruminant feed ban are far less likely
to be exposed to the BSE agent (Heim and Kihm, 2003).
Issue: A number of commenters recommended various alternative dates
or timeframes for consideration as the date of effective enforcement of
a feed ban in Canada. Most of the commenters who recommended an
alternative date expressed concern regarding the detection of BSE in
bovines born in Canada after March 1, 1999.
The recommended alternative dates or timeframes included the
following: July 1, 2007; the date of birth of the youngest bovine in
Canada that has been determined to be BSE-positive; May 1, 2002; 5 to 7
years after the most recently diagnosed case of BSE in Canada; whenever
Canada can verify 100 percent compliance with its ruminant-to-ruminant
feed ban; a staggered system of dates that would increase the allowable
age of bovines intended for importation from Canada as time progressed
with no additional diagnoses of BSE in Canada.
Some of the commenters who suggested July 2007 as the date of
effective enforcement based their recommendation on the fact that on
July 12, 2007, Canada expanded its feed ban to prohibit the inclusion
of SRMs in any animal feeds, pet foods, or fertilizers. One commenter
asked how APHIS can be satisfied that the United States would be
importing a safe product if Canada itself was not satisfied with the
safeguards in place at the time the proposed rule was published, and
subsequently took additional measures to strengthen its feed ban. A
number of commenters recommended that the provisions of the proposed
rule not be implemented until Canada bans all feeding of animal
material to food animals. One commenter stated that July 2007 would be
an appropriate point to begin the importation of breeding animals that
have had exposure to processed animal feed, and that March 1, 1999
would be an acceptable date for bovines that have not been exposed to
processed animal feeds--such as bison maintained by Parks Canada.
Several commenters, who expressed no animal health concerns with
identifying March 1, 1999 as the date of effective enforcement of a
feed ban in Canada, recommended that APHIS consider harmonizing the
date chosen with the date Canada has identified as the effective date
of a ruminant-to-ruminant feed ban in the United States, January 1,
1999.
Response: In prior rulemaking (APHIS 2005), we evaluated evidence
(regulations in place based on statutory authority, adequate
infrastructure to implement the regulations, and evidence of
implementation and monitoring) in making the determination that
compliance with the feed ban in Canada is good and concluded that the
feed ban was effectively enforced. In our process of identifying the
date of effective enforcement of a ruminant-to-ruminant feed ban in
Canada, we considered Canada's implementation guidance and policies.
For example, we considered the allowance of grace periods for certain
aspects of the industry, in determining the practical implementation
period for the feed regulations. Then we considered a sufficient time
period subsequent to this implementation period to allow most feed
products to cycle through the system, given the management practices in
the country. We concluded, based on the above evaluations, that cattle
born in Canada on or after March 1, 1999, can be imported into the
United States with an extremely low likelihood that they have been
exposed to the BSE agent.
As noted, a number of commenters recommended that APHIS consider
July 2007, when Canada expanded its feed ban, as the date of effective
enforcement of the Canadian feed ban. We consider the July 2007
expansion of the Canadian feed ban to be an enhancement of an already
effective ban. CFIA, in explaining its rationale for the enhanced ban,
emphasizes that, although surveillance results and investigations of
BSE cases indicate that the feed ban in Canada has effectively reduced
the spread of BSE since being implemented in 1997, even compliance with
the ban's requirements left limited opportunities for contamination
during manufacture, transportation, and storage that CFIA considered
worth eliminating. In addition, the accidental misuse of feed on farms
with multiple species could not be discounted. With the enhanced ban,
CFIA projects that the eradication of BSE in Canada will be
accelerated. Following such a regulatory path does not indicate that
the feed ban in Canada prior to July 2007 was not effective or
effectively enforced.
With regard to the recommendation that the date of effective
enforcement of the Canadian feed ban be identified as the date of birth
of the youngest bovine in Canada that has been determined to be BSE-
positive, we do not consider such a change to be necessary or
justified. The risk assessment we conducted for this rulemaking
acknowledged that BSE exists in Canada and that there would likely be
additional cases detected. March 1, 1999 was never intended to be an
absolute cut-off point after which no new cases of BSE would be
acceptable. The risk assessment concluded that, despite the likelihood
of additional diagnoses of BSE in Canadian cattle, the proposed
amendments would pose negligible risk to animal health and food safety
in the United States. If an infected cow were to be imported into the
United States, a series of strong safeguards would have to fail--in
sequence--for that animal to pose any risk.
With regard to the recommendation that APHIS harmonize its
identification of the effective enforcement date of a Canadian feed ban
with the date identified by Canada as the date of effective enforcement
in the United States, we do not agree that such a change would be
appropriate or necessary. APHIS arrived at the March 1, 1999 date for
effective enforcement of the feed ban in Canada by considering not only
the date the feed ban was established in that country but also
information provided by Canada regarding its implementation timetable,
as well as feeding practices in that country. It does not necessarily
follow that implementation events in the United States followed
precisely the same track as those in Canada.
Issue: In our January 2007 proposed rule, we discussed the
diagnosis of BSE in cattle in Canada born after March 1, 1999, and
stated that ``such isolated incidents are not epidemiologically
significant and do not contribute to further spread of BSE, especially
when considered in light of the entire risk pathway and its attendant
risk mitigations.''
Several commenters took issue with APHIS' description of the cases
as ``isolated.'' Some commenters stated that ``isolated'' implies a
solitary or separated condition, which cannot be said of the BSE cases
recently confirmed in Canada. Further, other commenters stated the
cases are linked by a trend in geographic location, with the last three
cases occurring in the Province of Alberta. One commenter stated that
of the nine cases of BSE detected in Canada, four occurred in cattle
born after March 1, 1999, and that four of nine cases--or 44 percent--
do not represent isolated cases and strongly disagreed that this date
corresponds to

[[Page 53331]]

when Canada's feed ban became effectively enforced.
Response: We disagree with the comments, although we acknowledge
that the term ``isolated'' could be interpreted in several ways. The
use of the term in our proposed rule was not intended to imply that the
cases were ``solitary or separated.'' Our use of the term ``isolated''
was intended to characterize the cases as being small in number and not
indicative of a systemic failure of the feed ban in Canada, but rather
the result of individual instances of error in contravention of the
feed ban (e.g., inadequate cleaning between handling of feed for non-
ruminants and feed for ruminants).
For the reasons discussed above, we consider our determination that
March 1, 1999 be deemed the date of effective enforcement of the feed
ban in Canada to be reasonable, grounded firmly in the regulatory basis
and operations of the ban in Canada, and entirely consistent with the
science and with OIE guidelines. Accordingly, we are making no changes
based on the comments.

Likelihood of Exposure of Cattle in the United States to BSE

The assessment is designed to estimate the likelihood of each of
the multiple steps. Although we analyzed the likelihood of each
individual step in the process occurring, we interpreted its
significance in the context of the entire process.
As part of the risk assessment we conducted for our January 2007
proposed rule, we evaluated both the likelihood of ``release'' of the
BSE agent into the United States and the likelihood of susceptible
animals being exposed, given such release. We evaluated the pathways by
which infected Canadian cattle, if imported, might expose U.S. cattle
to BSE, and the likelihood that these pathways might lead to the
establishment of the disease in the U.S. cattle population.
Several steps must take place for BSE to be transmitted to cattle
in the United States from a bovine imported live from another country.
A BSE-infected bovine must be imported into the United States; the
infected bovine must die or be slaughtered; tissues from that animal
that contain the infectious agent must be sent to a rendering facility;
the infectivity present in these tissues must survive inactivation in
the rendering process; the resulting meat-and-bone meal (MBM)
containing the abnormal prion protein must be incorporated into feed;
and this feed must be fed to cattle at a level adequate to infect the
cattle. (The amount of infectious material required in feed for cattle
to become infected is dependent on the age of the cattle; younger
cattle are more susceptible to BSE and require less BSE-contaminated
feed to become infected (Arnold and Wilesmith, 2004). We indicated in
our risk assessment that the nature and likelihood of these pathways
depend in large part on mitigations acting in series and in parallel
that reduce the likelihood that BSE will be established in the United
States.
A number of commenters addressed the issues of the likelihood of
release of the BSE agent into the United States and the likelihood of
exposure of U.S. cattle to BSE due to the importation of bovines from
Canada. In general, the commenters said that we had underestimated the
likelihood of release and/or exposure, or questioned one or more
elements of our assessment.
Issue: One commenter, whose statements were referenced and
supported by a second commenter, discussed the geographic distribution
of BSE cases in Canada and expressed concern that Canada's experience
demonstrates that certain locations in the United States might be more
susceptible to BSE establishment than others. The commenter stated that
events in Canada indicate that an average risk estimate is meaningless
for BSE and demonstrates how ``hot spots'' (i.e., locations that are
more susceptible to spread of disease and, therefore, that have a
localized higher BSE prevalence) allow BSE to propagate and spread. The
commenter stated that the model-based predictions in APHIS' risk
assessment are useless because the models do not account for geographic
and other sources of heterogeneity and pointed to Alberta as a BSE hot
spot. Further, the commenter indicated that the APHIS risk assessment
has not provided any real data or relevant analyses related to BSE hot
spot development and that APHIS has not quantified the risks that
imports will create localized BSE hot spots in the United States. The
commenter calculated that, if 5 percent of U.S. locations are potential
hot spots, and 1 million animals are imported each year with six of
them BSE-positive, the expected probability of at least one hot spot
being activated in the United States is at least 77.7 percent.
Response: We disagree with the commenters. The available evidence
provides no basis for distinguishing BSE prevalence among Canadian
provinces. The commenter who singled out Alberta provides no analysis
to support the hypothesis that the BSE prevalence in Alberta is higher
than in other provinces. Through May 2007, reported BSE cases have
originated in three western Provinces: Alberta (8 cases), British
Columbia (2 cases), and Manitoba (1 case). No cases have been reported
through May 2007 in the eastern Provinces. Intuition might suggest that
the BSE prevalence is higher in Alberta. However, Alberta contains
approximately 40 percent of the Canadian cattle herd. Other factors
being equal, BSE is more likely to be detected in regions with large
cattle populations.
Apart from the detected cases, geographically disaggregated data on
BSE surveillance and Canadian cattle population demographics are not
available. However, assuming that the total BSurvE points accumulated
through August 15, 2006 (APHIS 2006c, table 4) were collected
proportionally to the cattle population size in each province, table 3
presents the allocation of the random sample size equivalents (BSurvE
points).

Table 3.--Allocation of BSurvE Points among Provinces Proportional to Herd Size
----------------------------------------------------------------------------------------------------------------
Cattle BSurvE
Province (000)* Percent points BSE cases**
----------------------------------------------------------------------------------------------------------------
Alberta.................................................. 6,300.0 38.8 594,858.4 7
Manitoba................................................. 1,720.0 10.6 162,405.8 1
British Columbia......................................... 830.0 5.1 78,370.2 1
Saskatchewan............................................. 3,450.0 21.2 325,755.8 0+
Ontario.................................................. 2,203.9 13.6 208,096.6 0
Quebec................................................... 1,455.0 9.0 137,384.0 0
Nova Scotia.............................................. 107.0 0.7 10,103.2 0
New Brunswick............................................ 90.5 0.6 8,545.2 0
Prince Edward Island..................................... 84.5 0.5 7,978.7 0
Newfoundland............................................. 9.1 0.1 ........... ..............

[[Page 53332]]

Labrador................................................. ........... ........... 859.2 ..............
------------------------------------------------------
Total................................................ 16,250.0 ........... 1,534,357 9
----------------------------------------------------------------------------------------------------------------
*Source: Statistics Canada (2007).
**BSE cases reported through August 2006 were included in APHIS (2006c).
+The BSE case confirmed in May 2003 was born in Saskatchewan but reported in Alberta.

Based on this allocation of evidence, a binomial likelihood ratio
test (Fleiss et al., 2003) fails to reject the hypothesis that the
provinces have the same BSE prevalence. That is, the result provides no
basis for concluding that BSE prevalence varies among provinces.
Depending on the method used to estimate provincial BSE prevalence, the
test indicates that 11 to 20 BSE cases would have to have been observed
in Alberta (or 4 to 7 cases in British Columbia) before rejection of
the hypothesis.
The commenters provide no data or analysis related to BSE hot-spot
development. APHIS' risk assessment discusses the apparent geographic
clustering of Canadian BSE cases reported through August 2006 in three
western provinces: Alberta, British Columbia, and Manitoba (APHIS
2006b, pp. 12-13). (In addition, the May 2003 case reported in Alberta
was born in Saskatchewan.) However, APHIS also noted that the Manitoba
BSE case was phenotypically different than the previously detected BSE
cases of Canadian origin (APHIS 2006b). In addition, in its risk
assessment, APHIS considered the CFIA report (CFIA 2006) that discusses
geographic and temporal BSE clustering theories. APHIS concluded that
the detection of further clusters (i.e., linked cases) that might be
defined in the future cannot be ruled out and did not assume that any
Canadian provinces are BSE-free. While BSE case investigations may
reveal associations among individual cases, such as a common feed
source, the question of clustering is scale dependent. At a local
scale, there may be associations between individual cases, but at a
regional or national scale, the clusters themselves may be
geographically dispersed. In additio