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

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.

North American beef production statistics U.S.A.Canada Total Cattle96.1 million13.3 million Slaughtered35.7 million3.6 million Commercial carcass weight (est) 27 billion lbs~3.8 billion lbs Total beef (bone-in)8.75 million metric tons 908,000 metric tons % Beef exported~ 9.8 %> 60%

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

Potential Exposure Pathways – Live Animals A. Cattle Imports from United Kingdom U.S.A.Canada Total Animals imported Disposition known Imports from UK farms with known BSE cases 010 Disposition unknown BSE positives (1993) cow from U.K. 1

Potential Exposure Pathways – Live Animals A. Cattle Imports from BSE countries U.S.A.Canada Total Animals imported , Imports Ireland / Europe before 1986 (low risk) Total Animals imported from U.K. since Other BSE countries since

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 tons in tons in 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 from BSE countries Canada reported no MBM imports from UK since Canada imported ~8,523 metric tons of mammalian flours, meals, meat pellets from from Denmark, Germany, Japan & France.

C.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

C. Cattle trade in North America U.S. Cattle imports and exports 1992 to 2002

C. Beef trade in North America U.S. Beef imports and exports 1992 to 2002

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

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

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.

II. BSE exposure pathways for US population via beef U.S. risk Probability of exposure to infected cow in positive identified – 35 million slaughtered 1 in 35 million ( 3.5 x ) Worst case – Based on statistical analysis USDA surveillance (~20,000 tests) ~1 in 1 million (1 x )

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 x to Quantity of exposure: assume brain late stage BSE-infected cow 5,000 to 6,500 cattle oral ID 50 Conclusions: There is risk of exposure via this route Risk to the U.S. general population is low

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

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

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 x to annually Amount BSE infectivity present – estimated to be low because of dilution via AMR Estimate ~ < 2 x (<4 x to 2 x ) cattle oral ID 50 per average serving Greater than a hundred of servings from each batch of AMR product

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 < 3 x10 -9 (2 x to 3 x10 -9 ) annually in the U.S.

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

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

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

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