PERSPECTIVES ON THE SCIENCE: WHAT DO WE KNOW AND WHAT DO WE NEED TO KNOW ABOUT MICROBIOLOGICAL RISKS

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PERSPECTIVES ON THE SCIENCE WHAT DO WE KNOW AND
WHAT DO WE NEED TO KNOW ABOUT MICROBIOLOGICAL
RISKS OF FOOD ANIMAL PRODUCTION?

• Ellen K. Silbergeld
• Professor, Environmental Health Sciences,
  Epidemiology, and Health Policy
• Johns Hopkins Bloomberg School of Public Health
• Baltimore MD USA

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TOPICS

• WHAT ARE THE CRITICAL ISSUES?
• DO WE KNOW ALL THE RISKS?
• CAN WE DO RISK ASSESSMENTS?
• WHAT INFORMATION DO WE NEED?
• DO WE HAVE THE METHODS WE NEED?
• WHAT INFORMATION DO WE HAVE
• SOURCES -- OPERATIONS
• RELEASES WASTES, DISCHARGES, FUGITIVES
• FATE AND TRANSPORT TRANSFORMATIONS?
• ROUTES OF EXPOSURE ENVIR, PERSON-PERSON,
  ANIMAL-HUMAN, ANIMAL-ANIMAL
• MONITORING

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WHAT ARE THE CRITICAL ISSUES

• FOOD SAFETY
• ANIMAL WELFARE
• SUSTAINABILITY
• ECOLOGICAL IMPACTS
• HEALTH IMPACTS
• FOCUS ON HUMAN, BUT ZOONOSES ALSO IMPORTANT!

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HEALTH IMPACTS OF CAFOs

• MEDIA
• AIR
• WATER SURFACE, GROUNDWATER
• SOILS and DUSTS
• AGENTS
• PARTICULATES and VAPORS
• CHEMICALS and DRUGS
• ALLERGENS and BIOTOXINS
• BACTERIA and VIRUSES

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ANTIBIOTICS, ANIMALS and BIOSOLIDS A NEXUS of
CONCERN

• All uses of antibiotics inevitably select for
  resistance
• Antibiotic resistant infections are an
  increasingly serious clinical problem
• The same classes of drugs are used in food animal
  production as in clinical medicine

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ANTIBIOTIC USE IN FOOD ANIMAL PRODUCTION United
States, 2002

• Growth Promotion
• 3.1 million lbs/yr (AHI)
• 27.6 million lbs/yr (UCS)
• Prophylaxis and Disease Treatment
• 14.7 million lbs/yr (AHI)
• 2.0 million lbs/yr (UCS)
• COMPARED TO Human Uses
• 32.3 million lbs/yr (AHI)
• 4.5 million/lbs yr (UCS)

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Conditions Promoting Resistance in Agriculture

• a) Failure of Infection Control
• -Crowding
• -Often sub-optimal hygiene
• b) Exposure to Antibiotics
• -Widespread
• -Prolonged
• -Sub-lethal doses
• -Often little dose control
• c) Stress Reaction
• -Increases Bacterial Shedding

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Changes in Agriculture Promoting Dissemination of
Pathogens and AR

• Increases in Factory Farms
• Concentrated, high volume slaughter
• Broad food distribution
• Methods of waste management

http//www.hsus.org/programs/farm/factory/life_on_
factory.html
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Why are we concerned?

• More biosolids applied than
  land can handle
• Contributes to surface and groundwater
  contamination
• Increased nutrient runoff into surface waters
• Detectable presence of drugs and resistance
  determinants in groundwater

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Releases after storms hog farms, US
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Quinolone-resistance in Human Isolates of C.
jejuni/coli in Spain
Smith in CAMPYLOBACTER ASM Press, 2000
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What is the problem pathogens, antimicrobial
resistant pathogens, or antimicrobial resistance?
http//www.sciam.com/1998/0398issue/0398levybox3.h
tml
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AMR is not a drug/bug problem Flow of
Resistance Genes among Species

• Gene Transfer in the Environment. Levy Miller,
  1989

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WHAT SHOULD WE STUDY?

• PATHOGENS OF CLINICAL IMPORTANCE?
• HUMAN COMMENSALS AND PATHOGENS?
• AMR PATHOGENS? COMMENSALS?
• RESISTANCE DETERMINANTS?

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Many Routes of Exposure/Transfer
ENVIRONMENT rivers and streams
Irrigation Drinking water
Sea
Manure spreading
Swimming
Farm effluents
Sewage
Offal
FARMS
HUMANS
Slaughter Harvesting Processing
Handling Preparation Consumption
Animal feeds
Sheep
Cattle
Urban
Rural
Crops
Pigs
Institutions
Poultry
Fish

• High Risk Populations
• Children
• Elderly
• Immunocompromised

Contact
Adapted from Dr. Ruth Etzel USDA
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CASE STUDY IN REGION III DELMARVA POULTRY
INDUSTRY

• 600-800 million broiler chickens produced
  annually.
• 5,729 broiler chicken houses
• 2,492 chicken growers
• 13,795 poultry employees
• Total annual gross income of Delmarva broiler
  industry exceeds 1.3 billion dollars.

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THE OTHER PRODUCT OF CAFOs
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WHO IS AT RISK FOR EXPOSURE?

• WORKERS and GROWERS WHO WORK IN BROILER HOUSES
• WORKERS WHO HANDLE LIVE CHICKENS AT PROCESSING
  PLANTS
• HOUSEHOLD MEMBERS OF THESE PERSONS
• COMMUNITY RESIDENTS

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OCCUPATIONAL AND PERI-OCCUPATONAL EXPOSURES

• WORKERS IN POULTRY PRODUCTION
• Chicken catchers and live hangers no protective
  clothing no wash area direct contact with
  birds, feces etc
• HOUSEHOLD CONTACTS
• Crowded living conditions poor housing little
  access to health care

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Catching chickens occupational risks
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STUDY RESULTS

• WORKERS HANDLING LIVE CHICKENS ARE AT RISK OF
  EXPOSURE TO BACTERIA FROM POULTRY
• THESE BACTERIA ARE OFTEN DRUG RESISTANT
• HOUSEHOLD MEMBERS ARE ALSO AT RISK

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Environmental dispersal of AMR

• FISH
• study of anglers and fish in Delmarva contact
  with AMR pathogens
• BIRDS - Denmark
• Migratory birds likely to carry AMR Campylobacter
  Swedish and Danish surveillance

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Drugs in the environment CAFOs

• Antimicrobials fed to animals pass into wastes
• Detectable levels of antimicrobials measured in
  waste lagoons
• Antimicrobials measured in surface water
  sources unclear
• Arsenic

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Arsenic sources - US
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ARSENIC THE FORGOTTEN ANTIBIOTIC

• EXTENSIVE USE OF ARSENICALS IN BROILER FEEDS
• CONVERSION INTO iAS
• DOCUMENTED CONTAMINATION OF WASTE AND AMENDED
  LAND
• PERCOLATION INTO GROUNDWATER LIKELY
• UPTAKE INTO CROPS KNOWN TO OCCUR

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ARSENIC and POULTRY

• ROXARSONE, ARSANILIC ACID USED IN POULTRY AS
  COCCIDIOSTATS AND GROWTH PROMOTERS 45 g/ton
  feed
• GP CONTINUOUS LIFELONG EXPOSURE IN FEEDS
• ARSENICALS EXCRETED (gt70)
• 100-200 mg/BIRD (900 million/yr)
• 50,000-90,000 mt/YEAR ARSENIC
• ARSENICALS INORGANIC ARSENIC
• LEACH INTO GROUNDWATER

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Can we use population based surveillance?

• NARMS, FOODNET
• Incomplete coverage
• High risk areas usually not covered
• Bias in sampling and analyses

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Epidemiology why dont we know more?

• Reported AMR infections are the tip of the
  iceberg
• NARMS etc assume food borne route, do not fully
  explore other pathways

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Do we have the tools for risk assessment?

• FDA approval and removal of AB drugs requires
  risk-based findings
• WTO risk assessment is the implied method for
  international agreement on standards and
  guidelines
• CODEX development of guidance for risk
  assessment

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RISK ASSESSMENT AND AMR

• WHAT WE CANNOT DO
• Cannot use chemical RA methods
• Cannot evaluate multidrug resistance
• Cannot account for fact that AMR is a
  characteristic of living organisms
• Cannot account for horizontal gene transfer of
  the hazard
• WHAT WE NEED TO DO
• Incorporate molecular understanding from
  theoretical population microbiology
• Understand reservoirs, compensatory mutations,
  etc

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ACKNOWLEDGEMENTS

• STUDENTS
• Jon Furuno, Amy Chapin, Lance Price, Jay Graham,
  Amira Roess
• COLLEAGUES
• Carol Resnick, Sam Joseph, Polly Walker, Kellogg
  Schwab, Rolf Halden, Pat Breysse, Tim Buckley,
  John Bourgeois, Pat Charache, Steve Harvey,
  Yvette Johnson, Rocio Vailes
• Carole Morison, Patrick Harmon, Jim Lewis, Pilar
  Perez, et alia
• FUNDING
• CDC, US FDA, CLF, HHMI, R W Johnson, Winslow,
  Baker Foundations, MD CRF-NCI