Food safety in alternative production systems: What are the trade offs?

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Food safety in alternative production systems
What are the trade offs?
Peter Davies BVSc, PhD Leman Chair of Swine
Health and Productivity College of Veterinary
Medicine University of Minnesota
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How safe is the US food supply?

• More than ever before, Americans are worried
  about the safety of the food they put in their
  mouths and with good reason
• The food safety issue is inescapably linked to
  the ongoing revolution in U.S. agriculture, with
  the emergence of mega-farms, mega-distribution
  centers and mega-transporters
• Amanda Gardner, USA Today, 2008

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Impact of intensive production?

• Modern intensive animal husbandry practices have
  been used to maximize production. This has
  resulted in the emergence and increased
  prevalence of several human pathogens, like
  Salmonella and Campylobacter, in flocks or herds
  of all the most important production animals
• CSPI 2005

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Foodborne hazards

• Physical
• Toxins and chemicals
• Natural
• Artificial
• Microbiological
• Parasitic
• Bacterial
• Viral
• Prion
• Genes (resistant)

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Risk of foodborne disease Not meeting
expectations!

• 76 million cases annually in USA (Mead et al,
  1999)
• Estimated
• Most cases without defined agent
• High profile outbreaks and recalls
• Consumer demands for better 'protection'
• 1 case per 4000 meals
• Safest in the world?

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Foodborne outbreaks by source(CSPI, 2002)
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USDA/FDA ranking of foodborne pathogens (1995)
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Estimated Food-Related Cases of Selected
Foodborne Pathogens in the USA (Mead, et al 1999)
Agent Food-Related Cases
()

• Norwalk-like Viruses 9,200,000
  (66.6)
• Campylobacter 1,963,141 (14.2)
• Salmonella 1,341,873
  (9.7)
• C. perfringens 248,520 (1.8)
  
• Giardia 200,000
  (1.4)
• S. aureus 185,060 (1.3)
• Shigella 89,648
  (0.6)
• E. coli O157H7 62,458
  (0.5)
• Rotavirus 39,000
  (0.3)
• Cryptosporidium 30,000 (0.2)
• Hepatitis A Virus 4,170
  (0.0)

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Food Safety Paradigms
CONSUMER
Strengthen the weakest link
Attack the root of the problem
PRODUCER
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Farm to table strategy

• All participants in food production or
  consumption bear some responsibility for reducing
  the risk of foodborne disease
• High level of consensus
• How do we do it?
• How effective are on farm interventions
• In reducing hazards in animals
• In reducing risk of foodborne disease

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Preharvest food safety

• Management decisions to reduce risk of hazards in
  animals, and thereby consumers
• Knowledge of risk factors and efficacy and cost
  of interventions
• Successes
• Anthrax, Brucellosis, TB
• Meat borne parasites
• BSE
• Chemical and antimicrobial residues

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Chemical and physical hazards

• Drug residues
• Antibiotics, Pesticides, Disinfectants
• Environmental contaminants (dioxins, PCBs, heavy
  metals, radioactive isotopes,
• Foreign bodies (needles, fragments of glass,
  pieces of plastic or metal, etc.)
• Implications for alternative systems
• Reduced residue risk to exclusion (antibiotics)
• Increase risks due to environmental exposures?

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Foodborne Pathogens and Pork
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Foodborne disease outbreaks and pork
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Life cycle of Trichinella spiralis
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Trichinella spiralis

• Marked decline in 20th century
• 20 to 25 human cases per year
• Pig prevalence 0.013 (NAHMS 95)
• Result of preharvest control
• Large outbreak in IA in 1990
• Asian immigrants eating raw pork sausage
• Most cases due to game (bears,..)
• Importance of wildlife reservoirs recognized in
  many countries

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TrichinellaControl by management

• Already achieved in modern systems
• No feeding of garbage
• Total confinement
• Rodent control
• Rapid removal of deads
• National certification program
• Implications for alternative systems
• Access of pigs to wildlife

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Outdoor rearing and Trichinella
Locations of pastured-pig operations (green
dots) and previous records of Trichinella
spiralis in domestic pigs (red squares) and
wildlife (red triangles)
Burke et al, 2008
Transmission of T. spiralis into sylvatic hosts
from infected farms can lead to persistence in
reservoir hosts and remain a long-term threat to
domestic pigs in a pasture/dry lot environments
Burke et al, 2008
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Toxoplasma gondii

• Common infection but rare disease
• pregnant
• immunocompromised
• Cat is definitive host - oocysts in feces
• All homeothermic animals susceptible
• Contaminated soil common
• Human infection by
• ingestion or inhalation of sporulated oocysts in
  environment (cat)
• ingestion of bradyzooites in meat
• transplacental transmission of tachyzoites

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Pork as a source of human Toxoplasma infection in
the USA

• Pork implicated as a major source
• High seroprevalence in commercial swine
• Long term persistence of cysts following
  experimental infection of pigs
• Viable T. gondii in 17 of sows in IA
• Seroprevalence increases with age - culled sows
  may be greatest risk

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Toxoplasma Sources of infection for pigs

• Sporulated ooysts from cat feces
• highly resistant
• water
• feed
• soil
• Bradyzoites in meat
• other pigs
• rodents, birds, wildlife

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Toxoplasma - preharvest control

• No cats on farms !!
• Total confinement
• Bird proof cat proof?
• Rodent control
• Feed storage in silos
• No feeding of garbage
• Rapid removal of deads
• Now well controlled in most intensive systems

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Prevalence of T. gondii in US swine (Pyburn
2003)
No control program but changes in production
practices
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Seroprevalence of T. gondii in pigs from
different housing systems in The Netherlands

• Study of 40 organic, 9 free-range and 24
  intensive farms
• Pig prevalence N
• Organic 2.74 11/402
• Free-range 5.62 10/178
• Intensive 0.38 1/265
• Farm prevalence
• Organic 25 10/40
• Free-range 33 3/9
• Intensive 4 2/24
• Prevalence of parasites higher in outdoor systems
• Need to monitor outdoor pigs for foodborne
  parasites

van der Giessen et al, 2007
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Serorevalence of foodborne pathogens in ABF and
conventional pigs in USA
Gebreyes et al, 2008
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Major enteric foodborne bacteria

• Campylobacter spp.
• Salmonella spp.
• Yersinia enterocolitica
• Listeria monocytogenes
• E. coli
• Common inhabitants of the intestinal flora of
  healthy pigs

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Preharvest food safety The microbial problem

• Limited information on risk factors
• Complicated - numerous variables
• Specific reservoirs poorly understood
• Some pathogens ubiquitous
• Poor detection methods in animals
• Interventions not well identified
• Verification?

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Salmonella spp.

• Common in healthy pigs (preceding
  intensification)
• Great effort for preharvest control over last 15
  years
• Progress very modest!!
• Lack of controlled studies demonstrating efficacy
  and reliability of interventions
• Danish industry increasing focus on slaughter
  hygiene

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Campylobacter spp.

• Most common bacterial cause of foodborne diarrhea
  in USA
• 2 main species (C. jejuni and C. coli)
• C. coli very common in pigs (normal flora)
• Uncommon source of human infections (?)
• Resistance common
• High prevalence of multiresistant C. coli in both
  ABF and conventional pigs (Thakur 2005)
• TC/EM resistance less prevalent in ABF pigs
• Fluoroquinolone resistance in both systems
• No known preharvest interventions

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Yersinia enterocolitica

• Swine considered most important reservoir of
  pathogenic strains
• Limited information in pigs in USA
• 28 IL herds had pathogenic strains (Funk et al,
  1998)
• Finishing pigs most likely positive (Funk et al.
  2007)
• 13 of finishing pigs, 53 of farms in 2001
  (NAHMS)
• No known preharvest interventions
• Declining problem post HACCP

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Relative rates of confirmed cases of enteric
disesase in USA (CDC Foodnet)
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Relative rates of confirmed cases of enteric
disesase in USA (CDC Foodnet)
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Listeria monocytogenes

• Importance of foodborne infection recently
  recognized (dairy)
• 450 adult and 100 fetal deaths per year in USA
• Great diversity of strains in farm environments -
  few linked to human disease
• Different serovars in live animals and on meat
• Cross-contamination in processing major source of
  contamination of meat
• No known preharvest interventions

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Antimicrobial resistance

• Phenomenally complex and poorly understood
• Resistance elements common in nature in absence
  of anthropogenic pressures
• Removal of antimicrobials often not resulted in
  marked reductions in resistant bacteria
• Multiresistant bacteria not uncommon in ABF
  systems
• Salmonella, Campylobacter (Thakur et al 2005,
  2007)
• Advantage for alternative systems
• elimination of Ab use vs. proof of risk reduction
• MRSA the baby gorilla!

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Bolivian women inspecting pigs tongues for pork
measles (Taenia solium)
Questions?