Outcomes Analysis of E. coli O157:H7 Vaccination in Beef Cattle

Outcomes Analysis of E. coli O157:H7 Vaccination in Beef Cattle
H. Scott Hurd
College of Veterinary Medicine, Department of Production Animal Medicine
Former Deputy Undersecretary of Food Safety, USDA
Director of World Health Organization Collaborating Center for Risk Analysis and Hazard Surveillance and Intervention in Food Animals
Co-Director Collaboration for Comparative Outcomes Research Evaluation (CCORE), Iowa State University, Ames IA 50011
shurd@iastate.edu

Overview of Today’s Topics
Why Does the Industry Worry About E. coli O157:H7?
Pre-harvest Interventions Work Sometimes,But Not Other Times
E. coli 0157:H7 Vaccination is One of Those Times That Works
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E coli O157:H7 has a litter

Pre-harvest Interventions Work Sometimes
The pathogen originates solely on the farm
Food animal is the primary host
Pathogen does not live well outside the host
The % of positive farms is relatively low
Post-harvest methods are “maxed-out”
Dealing with outlier events
4

Control of Salmonella in Denmark – 10 Years Experience – Preharvest Not Most Effective
Hurd HS, Enøe C, Sørensen L, Wachmann H, Corns SM, Bryden KM, Greiner M: Risk-based analysis of the Danish pork Salmonella program past and future. Risk Analysis. 28:2 pp 341-351, 2008
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Funded as a project of the International EpiLab
Danish Institute for Food and Veterinary Research (DFVF)
Guest Scientist at the EpiLab in Denmark,
Employed at the National Animal Disease Center:USDA:ARS, Ames, Iowa, USA

Systems Model (Simulation) of Pork Attributable Human Cases (PAHC) of Salmonellosis
Probability of
Carcass Swab Positive Given Herd Seroprevalence
Category
Distribution of
Herds By
Seroprevalence
Category and Size
Attributes Human
Cases as aFunction of Positive Carcasses
Production
Module
Slaughter
module
Attribution
Module
Pigs from Each Seroprevalence Category
Carcass Swab Positive Pigs
Human Cases per Year
6

Historical: Combined Effect of On-farm (Pre-harvest) Changes and Abattoir (Post-harvest)
Simulated Pork Attributable Human Cases (Total Cases)
Significant (P <0.05) Changes in Risk Occurred 1998–2000
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Switch off the Post-harvest see Effect of On-farm (Pre-harvest) Program Only
Only 19% Decrease,69 Cases (P>0.05)
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Switch off the Pre-harvest Program see Abattoir (Post-harvest) Improvements Only
A Difference of 81 Cases (P>0.05). Due to Abattoir Improvements Only
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Future: Major Reduction in on-farm Seroprevalence (<25% for all herds)
Distribution of Herds by Average Annual Seroprevalence
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Future: Reduce All Herds to <25% Average Annual Seroprevalence
Attributable Human Cases
Still End Up with 110 Cases/Year
Cases While Steadily Improving Abattoir Methods for All On-farm Values Set at 25% or Less (AllFarm25); Reverting On-farm to 1995 Values While Keeping Abattoir Values Constant (RevF); and Continuing to Improve On-farm While Keeping Abattoir Values Constant (ImpF)
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What Else Can Be Done?Carcass Decontamination (Post-harvest)
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The pathogen originates solely on the farm
Food animal is the primary host
Pathogen does not live well outside the host
The % of positive farms is relatively low
Post-harvest methods are “maxed-out”
Dealing with outlier events
13

Post-harvest Methods Are “Maxed-out”
Further reduction of the mean exhausted
Law of diminishing returns
Dealing with Outlier Events
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We Have MANY Post-harvest Processes in Place Which “On Average” Work Well
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Pre-harvest Methods “Maxed Out” – Law of Diminishing Returns
Or “half the distance to the goal line”
Diminishing utility = “meaning that the first unit of consumption of a good or service yields more utility than the second and subsequent units” (Wikipedia)
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Outlier Events – Why Do They Happen?
Poisson Probability Distribution
Prevalence and concentration of E. coli in cattle is not abell curve
It is Poisson distributed
Average is low
Occasional HIGH levels
“On Average”

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When Multiple ProcessesAre Poisson Distributed
Cattle Prevalence
Carcass Prevalence
Concentration
Event Day

Cut-off the First Tail and Subsequent Ones Not as Likely to Occur
Cattle Prevalence
Carcass Prevalence
Concentration
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Overview of Today’s Topics
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Thomson DU, Loneragen GH, Thornton AB, et al., Use of a Siderophore Receptor and Porin Proteins-Based Vaccine to Control the Burden of Eschericia coli O157:H7 in Feedlot Cattle. Foodborne Pathogens and Disease 2009; Vol. 6, Number 7, 871-877
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E. coli Bacterial Extract Vaccine: Results
E. coli 0157 Prevalence
85% reduction in shedding

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85% reduction in shedding
98% reduction in concentration
Log10 MPN/g

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Consistent significant impact of vaccination on E. coli prevalence
Every study to date has yielded a significant reduction in E. coli shedding
Reductions from 50-85% based on protocols and E. coli challenge

Best Available Data
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Mathematical Model “Converts” 0157:H7 Shedding Cattle to Human Illnesses
Production
Slaughter
Consumption

How Does Vaccine Help ReduceEvent Days? -Individual Carcasses Modeled
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Scenarios Evaluated
Additionally, Simulated for Various Levels of
Product Adoption by Producers 0%, 40%, 80%, 100%
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Four Outcome Measures Considered
Mean annual number of human E. coli O157:H7 illnesses due to consumption of ground beef from steers and heifers (Public Health)
1
Probability of detecting E. coli O157:H7 per ground beef or ground beef trim sample tested by FSIS (in a 10,000 lb lot) (Regulatory)
2
Mean annual number of events where multiple E. coli 0157:H7 human illnesses (outbreaks) occur due to consumption of ground beef from a single production lot (Outbreak)
3
Mean annual number of a “hot” production lots (hot lot = more than 1,000 E. coli O157:H7 contaminated ground beef servings from a single lot) (Event Days)
4
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Outcome. Annual Number ofE. coli O157:H7 Illnesses
Annual 0157 Illnesses by Efficacy an Adoption

Discussion of Results –Annual Number of Illnesses
If vaccine is 80% effective and used by all producers, the projected number of cases is reduced from 20,000 to 8,000 (60% decrease)
However, partial adoption is also useful
80% effective with 40% adoption  23% reduction in illness
60% effective with 80% adoption  36% reduction in illness
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Outcome. Annual E. coli O157:H7 Illnesses Decreases with Adoption
Number of E. coli 0157:h7 Illnesses Due to Consumptionof Ground Beef from Feedlot Cattle
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National public health utility is largely a function of adoption, not vaccine efficacy
If 40% effective and 100% adoption there will be 40% reduction in illnesses
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Impact on Illness Due to Reduced Cattle Prevalence and Concentration on Carcass
Distribution of Herds by Average Annual Seroprevalence
Number of Human Cases
Fraction Reduction in Prevalence
Log CFU/g Reduction in Concentration of E. coli 0157: H7 in Feces
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Illness is impacted by BOTH decreased concentration and frequency of positive carcasses (prevalence)
Most Post-harvest methods just reduce concentration
Evaluated by “log reduction”
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Outcome. Probability of Detection viaFSIS Sampling (Regulatory)
Assumed FSIS testing of raw ground beef detects 1 CFUin a 325 g sample
Based on average probability of detection per sample tested for different slaughter plants and for different production lots from the same plant
Impact of additional industry test and hold is not considered
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Outcome. Detection by FSIS
Probability of Regulatory Positive by Efficacy and Adoption
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Outcome. Outbreaks
Number of lots resulting in outbreak defined as:
>2 illnesses
5 illnesses, or
10 illnesses
From a single production lot
Assuming 100% vaccination of cattle
Typical large plant (16,000 lots/yr)
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Number of Lots Resulting in >2, 5,or 10 Illnesses (Assuming 100% of Herds Vaccinated)
Mean Number of Lots per YearResulting in Multiple Illnesses
Vaccination (100% Herds), Virtually Eliminates Chance of a Large >10 Case Outbreak
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Outcome. “Hot” Production Lots
There is a high degree of variance in the E. coli O157:H7 numbers/concentration in a production lot
Consequently a small fraction of production lots may be contaminated to a high degree (“hot” lots), although the average load per production lot is relatively small
We defined a production lot (10,000 lbs) containing more than 1,000 contaminated servings as “hot” lot
Results are for hypothetical slaughter establishment producing 16,000 production lots per year

Prevalence and ConcentrationAre NOT Normally Distributed
Poisson Distribution of E. coli Prevalences
Prevalence and concentration of E. coli in cattle is not abell curve
It is Poisson distributed
Occasional HIGH levels
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Outcome. Hot Lots for a Plant Producing 16,000 Production Lots Per Year
Annual Number Hot Lots for Large Plant by Efficacy and Adoption
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Outcome. Hot Lots for a Plant Producing 16,000 Production Lots Per Year
Annual Number Hot Lots for Large Plant by Efficacy and Adoption
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Discussion of Results – Hot Lots
All levels of efficacy and adoption reduce the risk to packer
Full adoption of 80% effective vaccine virtually eliminates chance of Hot Lots (96% reduction)
40% adoption of an 80% effective vaccine results in 43% reduction in probability of Hot Lots
80% adoption of 60% effective vaccine results in 49% reduction in probability of detection by FSIS
What is a 20%, 30%, 40% reduction in risk worth?

Annual Hot Lots – Vaccine Reduces Variation and Extreme Doses
Box-Whisker Plot Comparison
More Variation and More “Event Days”
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Impact of Vaccination on Number of ProductionLots with High E. coli 0157 Prevalence (>5%)in 325 Gram Samples
E. coli 0157 Prevalence in 325 Ground Beef Portions from the Production Lot
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How Does Vaccine Help ReduceEvent Days, Hot Lots
Cattle Prevalence
Carcass Prevalence
Concentration
Event Day

Cut-off the First Tail and Subsequent Ones Not as Likely to Occur
Cattle Prevalence
Carcass Prevalence
Concentration
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Vaccination Reduces Variation = Risk
The overall average prevalence of O157:H7 in cattle and ground beef is low
Occasional “event days” or “hot lots” drive the risk
Small fraction of carcasses are highly contaminated
Vaccination has a disproportionate impact on thesetail-end events, reducing frequency of high prevalence cattle and high concentration of bacteria
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Summary
Analysis included impact of biological variation and uncertainty in parameters
Modeled from “farm to fork” using best available scientific data
Showed that vaccination reduces
Human 0157:H7 cases
Risk of FSIS regulatory detection
Chance of large outbreak from a lot
Frequency and magnitude of “event days”
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Questions
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Appendix A
Materials & Methods

Materials and Methods
Stochastic simulation model using a farm to fork approach (Excel®, @Risk®)
Stochastic – pick numbers randomly from defined distribution
Impact of E. coli O157:H7 vaccination in reducing the prevalence (% fecal positive cattle) and concentration (log CFU in trim) modeled
Consists of three modules
Production
Slaughter
Consumption
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Mathematical Model “Converts” 0157:H7 Shedding Cattle to Human Illnesses
(Best Available Data)
Production
Slaughter
Consumption
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What is a “Stochastic Simulation”?
Probability of Various E. coliPrevalence Occurrences
Exact cattle prevalence and other variables are unknown and changing
Studies give a range and statistical distribution which is often non-normal (Poisson)
Computer uses all those possible numbers to calculate multiple results (n=10,000)
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Slaughter Module – Individual Carcass Modeled
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Stochastic Variables

Modeling Assumptions
The E. coli O157:H7 prevalence in pre-evisceration beef carcasses is proportional to the fecal prevalence in the feedlot
All beef imported (~40%) into the US is destined for mixing withdomestic ground beef
The E. coli O157:H7 prevalence and concentration in imported ground beef is similar to that in ground beef from unvaccinated domestic steerand heifer slaughter
The ground beef processed in this US is consumed domestically
The number (CFU/serving or CFU/325g sample) of E. coli O157:H7 in a portion of ground beef from a production lot is Poisson distributed
The impact of internal test-and-hold protocols is not considered
The FSIS ground beef test data are assumed to be from a representative random sample of ground beef production lots in the US
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Production Module
Estimates the E. coli O157:H7 Prevalence in Vaccinated and Unvaccinated Feedlots
Prevalence among feedlots and within feedlots estimated.
Vaccination reduces prevalence by fixed percent on average. Multiple different efficacy scenarios can be run
Variability in feedlot prevalence and impact of vaccination modeled stochastically by exponential and binomial distributions
Production
Slaughter
Consumption

Scenarios Built Around Reductions in Prevalence and E. coli Concentration
Additionally, Simulated for Various Levels of Product Adoption from 0% to 100%
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Slaughter Module – Carcass Prevalence
Fecal
Prevalence (from Production Module)
Linear Coefficient (Elders 2000, Barkocy-Gallagher 2003 and Arthur 2007)
Pre-evisceration Carcass Prevalence
Effectiveness of Generic Post Slaughter Interventions (Elders et al. 2000, Arthur et al. 2004 and Barkocy Gallagher et al. 2003)
Post Chill Carcass Prevalence
Modeled as a Binomial Distribution
Number Contaminated Carcasses per Production Lot
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Slaughter Module – Bacterial Concentration
Concentration on a Pre-evisceration Carcass
Contaminated Surface Area (8000 cm2/Carcass)
Total CFU/Carcass at Pre-evisceration
Effectiveness of Post Slaughter Interventions Estimated from GenericE. coli and APC Data
Total CFU/Carcass at Post Chill
The Amount (CFU) Added to the Production Lot from Individual Carcasses Was Summed Up. Assumed 70 Percent of Carcass Surface Area Represented in Trim
Total CFU per Production Lot
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Slaughter Module –Individual Carcasses Modeled
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Slaughter Module
Estimates the prevalence and concentration of E. coli O157:H7 in beef carcasses and ground beef production lots
About 68 Simulated carcasses for a 10,000 pound production lot, depends on average carcass weight
Variable E. coli O157:H7 concentrations on contaminated carcasses were modeled
Production
Slaughter
Consumption
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Total Carcass Contamination a Function of Fecal Shedding, Amount of Bacteria and Surface Area
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Slaughter Module – Lot Types
Production Lot from Unvaccinated Cattle
Production Lot from “Vaccinated” Cattle
Includes ground beef trim from domestic and imported sources
E. coli O157:H7 prevalence and concentration in ground beef from domestic and imported sources assumed to be similar
Domestic portion of ground beef in the lot is from vaccinated cattle
Imported ground beef is assumed to be from unvaccinated cattle
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Consumption Module
Estimates overall number of E. coli O157:H7 illnesses due to consumption of ground beef from steers and heifers
Fraction of E. coli O157:H7 illnesses attributed to ground beef consumption estimated from outbreak and epidemiological studies
Similar to the approach used Withee et al., 2009
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Production
Slaughter
Consumption

Consumption Module Attribution Calculation
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Domestic Cattle Slaughter and Beef Import Data
Number of E. coli O157:H7 Contaminated Servings /Year
FSIS Ground Beef Testing Data
Baseline Probability of Illness per Contaminated Serving of Ground Beef
CDC Foodnet Data
Adjusted for Under Diagnosis
Number of Illnesses from Ground Beef per Year
Fraction of Illnesses Attributed to Ground Beef Consumption

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Consumption Module
Outputs – mean number of E. coli O157:H7 illnesses per year in the US due to consumption of ground beef from steers and heifers calculated from:
Variables
Baseline probability of E. coli O157:H7 illness per contaminated serving of ground beef consumed
Estimated number of contaminated servings per production lot
Estimated number of production lots from vaccinated and unvaccinated cattle processed

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Methods Review
Stochastic simulation model to evaluate the impact of O157:H7 vaccination on key epidemiologicaloutcome measures
Considered a reduction in the O157:H7 prevalence as well as concentration in cattle feces due to vaccination
Impact of this reduction on various risk outcomes was evaluated by simulating the relationships between the O157:H7 prevalence and concentration at various points in the ground beef supply chain
The uncertainty and variability associated with the O157:H7 contamination was explicitly modeled on a carcass-by-carcass basis

Methods Review
Included the impact of post harvest interventions, stochastically
Combined best available scientific data about the processes to produce ground beef
Shows the impact of true biological variation on the prevalence and concentration of E coli before and after each process
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Appendix B
Reference Slides

* Total does not add to 100% due to rounding.
Source: 2009 Food & Health Survey, International food Information Council Foundation.
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Consumers Firmly Place Food Safety Responsibility on the Production Chain
Perceived Responsibility for the Safety of theU.S. Food Supply2009 (n=1064)
Perceived Importance ofFood Safety Issues2009 (n=1064)*
In general, who do you believe is responsible for food safety in the U.S.?Select all that apply.
What, in your opinion, is the most important food safety issue today? Select one.
Other 2%
Food Allergens 2%
Imported Foods
Don’t Know
Chemicals in Food
Foodborne Illnesses from Bacteria
More Than Half the Food Safety Concerns Expressed by ConsumersResides with Illnesses Stemming from Bacteria

How Concerned Are You About Foodborne Illnesses from Eating Ground Beef?
Source: National Cattlemen’s Beef Association – Consumer Perceptions of Beef Safety – October 2010
Source: IPSOS Public Affairs – July 2010
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Bacterial Contamination is aGrowing Concern for Consumers
Concern about foodborne illness fromeating ground beef has increasedsignificantly since 2008
Bacteria in food currently is the number one rated food safety issue for consumers and has been the leading issue of concern for the past several years
Looking back over the past 10 years, bacterial concerns have been higher than all other issues except mad cow disease which was the issue of highest concern from 2002 until 2009
In 2001, 39 percent of consumers said they were extremely concerned about bacteria while a quarter (24%) said they were not concerned
In July 2010, 40 percent say they are extremely concerned about bacteria and only 7 percent say they are unconcerned
Consumer Food Safety Concerns% Rating a 5 (Extremely Concerned) on a 5-Point Scale
Q: On a Scale of One to Five with One Being No Concern and Five Being Extremely Concerned, How Concerned Are You About…
IrradiatedFoods
Mad CowDisease
Chemical Additives
Antibiotics
GM Foods
Bacteria
Pesticides
Hormones

Source: Pfizer, Consumer Marketing Research 2010, Data on File.
Q: Listed below are some food safety concerns people may have expressed when buying or eating beef. Using the scale below, please tell us how concerned you are, if at all, with each of these issues when buying or eating beef.
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Safety Concerns with Regard to Eating Beef
Beef consumers tend to be more concerned about E. coli than any other well-known beef pathogen. Just over one in four are extremely concerned with E. coli when eating and buying beef, and three in four express at least some level of concern
Base: Total Respondents (N=1,029)
Level of Concern Towards Issue(Base: Those Aware of Issue)
% Aware of Issue
Extremely Concerned
Extremely/Very/Somewhat Concerned

1 Schroeder T., Agricultural Economists, Kansas State University, in National Cattlemen’s Beef Association. A basic look at E. coli O157, 2004
2 Kay S., editor/publisher of Cattle Buyers Weekly (www.cattlebuyersweekly.com), in National Cattlemen’s Beef Association.A basic look at E. coli O157, 2004
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E. coli O157 Costs Duringthe Past 10 Years
Research has shown that beef-product recalls following outbreaks have a negative effect on demand for beef.For instance, boneless beef prices declined an average of 2.5% in the 5 days following one recall. From 1991 through 1999, beef recalls due to safety concerns were estimated to cost the industry as much as $1.6 billion in lost demand1
Producers have invested $20 million in check-off funds during the last decade in beef safety research while the top 10 beef packing companies spent $400 million on beef safety research. Packers have also incurred an estimated $250 million in increased operating costs due to changes at processing plants aimed at improving beef safety. Government and industry have spent at least $65 million since 1993 on E. coli O157 research, with the USDA Agricultural Research Service spending $49 million from 1993 to 2002 to research food safety

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1 BeaconMR, March 2010
Original mission: to solve a turkey salmonella problem, to improve poultry quality and food safety
Key discoveries by WPC staff microbiologists led to numerous patents for a novel vaccine technology
SRP® technology has great potential for multiple veterinary and human medical applications
Salmonella-SRP vaccine for cattle conditionally licensed in 2004
Approximately 5M doses used in US dairy industry annually in 2008 and 20091

Source: Emery, D.A. – “SRP Technology” presentation; Midwest Poultry Federation annual meeting, St. Paul, MN - March, 2002
75
State of Minnesota – Official Salmonella Test Results for Willmar Poultry Company Breeder Flocks
Percent Positive Flocks
10,000 hens per flock
500 cloacal samples/flock
50 flocks per year
25,000 hens tested annually
Implementation of Salmonella SRP® Vaccination Over aTwo-Year Period

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E. coli O157:H7
May 2010, USDA/FSIS announces
“Pre-harvest Management Controls and Intervention Options for Reducing Escherichia coli O157:H7 Shedding in Cattle”
FSIS Guidance notes:
Establishments required to conduct hazard analysis that can occur before, during and after entry into establishment
Fecal shedding is a hazard
FSIS recommends slaughter establishments receive cattle that implement one or more documented pre-harvest management practices to reduce fecal shedding

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Why Vaccines at Pre-harvest
These product licenses are conditional. Efficacy and potency test studies are in progress
Vaccines enable a natural ally: the animal’s immune system
Addressing the problem pre-harvest should allow processing interventions to be more effective
Incoming pathogen burden can overwhelm in-plant processes

78
SRP Technology
Pathogenic Gram-negative bacteria, including E. coli O157:H7 and Salmonella, require iron to liveand replicate
SRP vaccines target the proteins necessary to transport iron into the bacterial cell, using the animals’ immune system to block iron passage
As a result, without iron, the bacteria die

P<0.0001
Data on file, Epitopix LLC Study Report No. 0606, Pfizer Inc.
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Reduced Number of Salmonella Newport Infected Animals
Percent Positive for Salmonella Newport Infection Following Challenge
75% fewer infected animals 14 days post-challenge

P<0.0001
Data on file, Epitopix LLC Study Report No. 0606, Pfizer Inc.
80
Quantity of Salmonella Shedding in Feces: Average Colony Forming Units (CFU) per Gram
Log 10 CFU/ g
28 Samplings (AM/PM for 14 Days)

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2008 Field Study: Salmonella in Cull Dairy Cows
Guy Loneragan – WTAMU (Western Texas A&M University)
Loneragan, GH et al. Salmonella in Cull Dairy Cattle of the Texas High Plains. 89th Annual Meeting of the Conference of Research Workers in Animal Diseases, December 7-9, 2008, Chicago, Illinois
Enrolled 9 West Texas dairies (all >2,000 cows)
Sampled 706 cows culled from the dairies, either on site or at regional sales barn
Cultured for Salmonella
Serotype, susceptibility testing, quantification
Salmonella recovered from 32.6% of samples
Varied by month and dairy
Dairy burden ranged from 4.4% to 86.3%
Within-herd burden remained relatively constant over time

Loneragan, GH et al. Salmonella in Cull Dairy Cattle of the Texas High Plains. 89th Annual Meeting of the Conference of Research Workers in Animal Diseases, December 7-9, 2008, Chicago, Illinois.
Vaccine = Salmonella Newport Bacterial Extract Vaccine
82
Salmonella Prevalence in Cull Dairy Cows: 9 Large Texas Dairies
Vaccine
Vaccine
Vaccine

Hermesch DR, Thomson DU, Loneragan GH, Renter DR, White BJ. Effects of a commercially available vaccine against Salmonella enterica serotype Newport on milk production, somatic cell count, and shedding of Salmonella organisms in female dairy cattle with no clinical signs of salmonellosis. AJVR 2008;69(9):1229-1234
Vaccine = Salmonella Newport Bacterial Extract Vaccine
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Effect of Vaccination on Milk Production in Sub-clinically Infected Cows
Effect of Vaccination with Salmonella Newport Bacterial Extract Vaccineon SCCs (cells/mL)* (P=0.01)
SCCs (cells/mL) x 1,000
* At 30 to 60 days of lactation

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Control of E. coli O157 with E. coli Bacterial Extract Vaccine
Same technology platform as Salmonella Newport Bacterial Extract vaccine
SRPs harvested from stx-negative E. coli O157:H7
Study conducted in commercial feedlot
Thomson et al. FPD. 2009;6:871-877
Animals randomized from source pens into 20 pens of 60 to 70animals per pen
10 pens vaccinated d0, d21, d42
Other 10 matched pens received placebo
Study personnel masked as to treatment allocation
Sampled d0, d42, and d98
Study Led by Daniel U. Thomson, K State

85

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Log10 MPN/g

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A “Food System” Approach to Pathogen Reduction
PreparationInterventions
Harvest & Post-harvestInterventions
Pfizer Animal HealthE. Coli Bacterial Extract Vaccine
Reduction Begins at the Source….

Source: Emerging Options to Control E. coli O157:H7 Pre-harvest; Guy H. Loneragan, West Texas A&M University Canyon, Texas, USA; June 24-25, 2009, Angers, France
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Another Hurdle Within a System
E. coli O157
E. coli O157
Consumers
Harvest
Pre-harvest
Currently Multiple Post-harvest Controls
Most of the time, within plant interventions effectively mitigate what comes in on the cattle

89
E. coli O157
E. coli O157
E. coli O157
Consumers
Harvest
Pre-harvest
Sometimes, these interventions fail – E. coli O157 detected in:
0.9% of trim combos;
0.33% of GB (ground beef) samples

90
E. coli O157
E. coli O157
SRP
Consumers
Harvest
Pre-harvest
For example, if pre-harvest prevalence reduced from x to y, what is the extent of the impact on z (rate of microbial defects)

Outcomes Analysis of E. coli O157:H7 Vaccination in Beef Cattle

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Outcomes Analysis of E. coli O157:H7 Vaccination in Beef Cattle — Presentation Transcript