Title: Food safety in alternative production systems: What are the trade offs?
1Food 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
2How 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
3Impact 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
4Foodborne hazards
- Physical
- Toxins and chemicals
- Natural
- Artificial
- Microbiological
- Parasitic
- Bacterial
- Viral
- Prion
- Genes (resistant)
5Risk 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?
6Foodborne outbreaks by source(CSPI, 2002)
7USDA/FDA ranking of foodborne pathogens (1995)
8Estimated 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) -
9Food Safety Paradigms
CONSUMER
Strengthen the weakest link
Attack the root of the problem
PRODUCER
10Farm 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
11Preharvest 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
12Chemical 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?
13Foodborne Pathogens and Pork
14Foodborne disease outbreaks and pork
15Life cycle of Trichinella spiralis
16Trichinella 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
17TrichinellaControl 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
18Outdoor 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
19Toxoplasma 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
20Pork 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
21Toxoplasma Sources of infection for pigs
- Sporulated ooysts from cat feces
- highly resistant
- water
- feed
- soil
- Bradyzoites in meat
- other pigs
- rodents, birds, wildlife
22Toxoplasma - 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
23Prevalence of T. gondii in US swine (Pyburn
2003)
No control program but changes in production
practices
24Seroprevalence 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
25Serorevalence of foodborne pathogens in ABF and
conventional pigs in USA
Gebreyes et al, 2008
26Major enteric foodborne bacteria
- Campylobacter spp.
- Salmonella spp.
- Yersinia enterocolitica
- Listeria monocytogenes
- E. coli
- Common inhabitants of the intestinal flora of
healthy pigs
27Preharvest 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?
28Salmonella 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
29Campylobacter 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
30Yersinia 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
31Relative rates of confirmed cases of enteric
disesase in USA (CDC Foodnet)
32Relative rates of confirmed cases of enteric
disesase in USA (CDC Foodnet)
33Listeria 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
34Antimicrobial 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!
35Bolivian women inspecting pigs tongues for pork
measles (Taenia solium)
Questions?