Canadian and U.S. BSE Risk

1
Canadian and U.S. BSE Risk

• Steven Anderson, Ph.D, MPP
• Office of Biostatistics Epidemiology
• Center for Biologics Evaluation Research
• U.S. Food Drug Administration
• TSE Advisory Committee
• February 12, 2004

2
Policy questions for BSE in North America

• What is the BSE risk for the U.S. and Canada?
• Part I - Estimating BSE risk Potential exposure
  pathways in U.S. and Canada
• What is the risk for the general U.S. population?
  What are the implications for the blood supply?
• Part II Estimating BSE exposure and
  risks in the U.S.

3
North American beef production statistics
4
Part I Estimating BSE risk
Potential exposure pathways in
U.S. and Canada

• Imports from BSE countries of
• A. Live animals
• B. Mammalian-derived feed ingredients
• Meat and bone meal, meals, etc.
• C. U.S. and Canada bilateral imports / exports
• Has implications for movement of potentially
  infected cattle and contaminated products
• Focus on imports from
• U.K. - since 1980
• BSE countries - since 1986

5
Potential Exposure Pathways Live AnimalsA.
Cattle Imports from United Kingdom
6
Potential Exposure Pathways Live Animals A.
Cattle Imports from BSE countries
7
Potential Exposure Pathways Feed B. Feed
ingredients from BSE countries

• U.S.
• feed meal imports from UK since 1980 total 81
  tons
• 12 tons in 1981
• 10 tons in 1984
• 2 tons in 1985
• 20 tons in 1989 (Disputed by U.S. authorities)
• 37 tons in 1997
• U.S.A. imported 10,500 metric tons of inedible
  meat byproducts from 1980-2000 from BSE countries
• Canada
• reported no MBM imports from UK since 1980.
• Canada imported 8,523 metric tons of mammalian
  flours, meals, meat pellets from 1993-2000 from
  Denmark, Germany, Japan France.

8
Cattle and beef trade in North America

• Considerable movement of animals, feed
  ingredients, and beef products
• Trade and production practices similar for each
  country
• Import/export could introduce or spread infected
  animals or contaminated products

9
C. Cattle trade in North America U.S.
Cattle imports and exports 1992 to 2002
10
C. Beef trade in North America U.S. Beef
imports and exports 1992 to 2002
11
Conclusions Part I Estimating BSE risk U.S. and
Canada

• Difficult to estimate absolute risk for U.S. and
  Canada
• Most potential for introduction of BSE agent
  would have occurred prior to 1990
• Potential amount of BSE agent introduced unknown
• Numerous chance events would be involved over
  last 10 to 15 years
• Rendering
• Fed to other cattle, dead on farm, etc.
• Imports of live animals and feed materials from
  BSE countries occurred since 1980 but was small
• Qualitative estimate of risk predicted to be low
  but difficult to estimate with certainty

12
Part II Estimating BSE exposure and risks for
the US population

• Many potential routes for human exposure to beef
  and bovine products
• Primary source of potential BSE exposure
• Food
• High risk tissues brain, spinal cord, eyes,
  dorsal root ganglia, small intestine
• Other sources
• Dietary supplements
• Medical products devices, biologics, drugs

13
II. BSE exposure pathways for US
population via beef

• A. Consumption of large amounts high risk
  tissue (very low probability event)
• Bovine brain or spinal cord
• B. Consumption of small amounts high risk
  tissues in processed foods
• Advanced meat recovery beef product
• Ground beef products, beef sausages, hot dogs,
  processed meat sauces, etc.

14
II. BSE exposure pathways for US
population via beef

• U.S. risk
• Probability of exposure to infected cow in 2003
• 1 positive identified 35 million slaughtered
• 1 in 35 million (3.5 x
  10-7 )
• Worst case Based on statistical analysis USDA
  surveillance (20,000 tests)
• 1 in 1 million (1 x 10-6)

15
A. Consumption of large amounts high risk
tissue bovine brain

• Probability of exposure brain rarely consumed by
  Americans (100,000 180,000 servings)
• Many servings from low risk cattle calf brains,
  etc.
• Probability infected brain in 2003 3.5 x
  10-7 to 10-6
• Quantity of exposure assume brain late stage
  BSE-infected cow 5,000 to 6,500 cattle oral ID50
• Conclusions
• There is risk of exposure via this route
  Risk to the U.S. general population is
  low

16
B. Consumption of small amounts high risk
tissue advanced meat recovery

• Advanced Meat Recovery (AMR)
• Removes remaining meat from carcass, vertebral
  column and bone by machinery
• Spinal cord usually removed before process
• Dorsal root ganglia on vertebral column
• 70 of carcasses processed with AMR
• Process would mix and dilute residual BSE agent
  present

17
B. Consumption of small amounts high risk
tissue advanced meat recovery

• Machines can process 4,500 to 7,000 lbs bones per
  hour
• Represents material from 20 to 35 animals
• 5 10 lbs meat recovered per carcass
• Estimated as much as 250 million lbs AMR meat
  produced annually

18
B. Consumption of small amounts high risk
tissue advanced meat recovery

• Probability of exposure advanced meat recovery
  (AMR) product consumed frequently
• Dilution of BSE infectivity throughout a batch of
  AMR product
• Probability infected cow in 2003
• 3.5 x 10-7 to 10-6 annually
• Amount BSE infectivity present estimated to be
  low because of dilution via AMR
• Estimate cattle oral ID50 per average serving
• Greater than a hundred of servings from
  each batch of AMR product

19
B. Consumption of small amounts high risk
tissue advanced meat recovery

• Assuming BSE infected animal(s) enter AMR and
  residual infectivity present in vertebral column
• Probability exposure via AMR is low
• 1 x10-7 to 2 x10-5 per serving beef AMR product
  per year
• Probability of infection even lower
• Assuming a species barrier of 1,000
• Reduction by oral route of 90
• Assume 40 population sensitive - methionine
  homozygous at codon 129 of PrP
• Probability of infection would be estimated to be
  less than
  x10-9) annually in the U.S.

20
B. Consumption of small amounts high risk
tissue advanced meat recovery

• Conclusions
• Our preliminary estimates suggest that there is a
  low risk of human exposure to BSE agent via beef
  AMR product
• Probability of human infection even lower
• There is uncertainty in the estimates and some
  assumptions were made to estimate the risk
• Risk to general population and blood supply is low

21
Recent BSE risk-reduction measures for food
supply feed

• Should dramatically reduce small BSE risk for
  U.S.A.
• Recent USDA measures Dec 30, 2003 prohibit
• Use of downers for human food
• High risk tissue in AMR
• Use of animals 30 months in AMR
• January 2003 FDA feed ban prohibits
• Ruminant blood protein in feed
• Plate waste, poultry litter
• Requires dedicated feed processing lines for
  non-prohibited and prohibited feeds

22
Acknowledgements

• Dr. Sonja Sandberg (OBE)
• Rene Suarez-Soto (OBE)
• Dr. David Asher (OBRR)
• Dr. Rolf Taffs (OBRR)
• Dr. Pedro Piccardo (OBRR)
• Others at CBER

23
(No Transcript)
24
Factors considered in estimation

• Total cattle slaughtered annually
• 70 - 80 processed via AMMR
• animals/batch
• 5-9lbs AMR per Animal
• Percentage lost to imports, waste, non-use
• Conversion lbs to servings
• Total est AMR meat servings /yr
• Servings AMR meat contaminated/Total AMR servings
  per yr
• And / or
• Dilution of ID50s from 1 cow in a batch of AMR