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FOOD-BORNE DISEASES
Jutta Tebje-Kelly
EpiCentre, Wool Building, Rm 2.04
116.407 VeterinaryPublic Health & Meat
Hygiene
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Introduction
Causes of food-borne
diseases/illnesses:1. Chemical toxins (residues)
2. Biotoxins endotoxins & exotoxins
3. Infectious agents exogenous &endogenous (zoonoses)
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Introduction contd
endotoxins & exotoxins
lipopolysaccharide (LPS) : proteinpart of bacterium : extracellular
no toxoid : toxoidlow potency : high potencylow specificity : high specificity
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Mode of action of somebacterial toxins
S. aureus A(alpha-toxin)
E. coli B
(shiga toxin)
C. botulinum C(exo-enzyme)
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Introduction contd
Food hygiene vs food safety
food hygiene microbiological safety offood
food safety abscence of
chemicals/residues Not necessary to have sterile
food
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Prevention of food-bornediseases
Organisms -
characteristics1. where from
2. types & strains
3. behaviour in food4. survive or are killed by
measures to inactivate
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Prevention of food-bornediseases, contd
Food characteristics
Water activity (aw), pH andtemperature
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What influences occurrence offood-borne diseases/illnesses?
Food source
Food storage
Food preparation
Food handlers
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What influences occurrence offood-borne diseases/illnesses?
Time-temperature abuse Infected food handlers or
inadequate hygiene during handlingof food
Consumption/use of unsafe foodsources
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Types of illnesses/diseases
Upper GIT nausea & vomiting
Lower GIT cramps & diarrhoea
Neurological signs
General symptoms
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Types of illnesses/diseases
Upper GIT signsNausea, retching, vomiting, abdominal pain,
diarrhoea & prostration
S. aureus and its toxins
B. cereus and its toxin
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Types of illnesses/diseasesLower GIT signs
Lower abdominal cramps & diarrhoea
Clostridium perfringens, Bacilluscereus
Salmonella, Shigella, ETE. coli,Yersinia enterocolitica,Campylobacter jejuni, Vibrio cholera
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Types of illnesses/diseases
Lower GIT signs, continuedLower abdominal cramps & diarrhoea
Giardia intestinalis
Cryptosporidium parvum
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Types of illnesses/diseases
Neurological signsVisual disturbances, vertigo, tingling
sensation & paralysis
Clostridium botulinum
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Risks of contracting food-borne disease depend on:
Host susceptibilityAge
General health
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Infective dose
Frequently exptrapolated
Feeding studies (healthy, young adultvolunteers)
Estimates (data from outbreaks)
Worst case estimates
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Risk assessment variable infective doses
Interaction food substrate &environment
pH susceptibility
Type and strain
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Control of food contamination Micro-organisms in food & water
shellfishfruits & nuts
beans
watermelonsspices & herbsvegetables
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Control of food contamination
Infection of animals milk,eggs or meat
Contaminated skins and guts- slaughter & dressing
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Pathogenic Bacteria
C. botulinum, C. perfringens - Soil, hide, faecal material
Staphylococcus aureus toxin - Human (nostrils and hands)
Listeria monocytogenes - Soil, hide, faecal material
Campylobacter spp. - GIT (esp. poultry)
E. coli O157:H7 - GIT
Salmonella spp. - GIT / Hide
Yersinia enterocolitica - GIT
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Control of food contamination Ideal = growing & harvesting stages
But world is not sterile
Prevent, reduce or limit by:
Not allowing products from clinically ill
animals to enter food chainClassical meat inspection - gross
HACCP - microscopic
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The chain of production from farm to fork
of food from animals
Production
Processing
Final preparationand cooking
Farm, Feedlot, Fishing site
Slaughter Plant, Cannery,Packer, Food Factory
Final Kitchen:commercial,institutional or domestic
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The chain of production from farm to fork -
prevention can occur at each step
Production
Processing
Final preparationand cooking
Feed, water, manure treatment,biosecurity, probiotics, vaccines
HACCP, slaughter hygiene,pathogen reduction andelimination (pasteurization,irradiation)
Cooking, preventingcross-contamination,worker education and handwashing
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Prevention of Food PoisoningWHO ten golden rules
Food processed for safety
Thoroughly cook
Eat immediately
Store carefully
Reheat thoroughly
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Prevention of Food PoisoningWHO ten golden rules contd
No contact between raw & cooked Wash hands
Keep food preparation surfaces clean
Protect from pests
Use potable water
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Food-borne disease outbreaks& food spoilage
Contamination with undesirablemicro-organisms
Unacceptable levels of micro-organisms
Treatment did not result ininactivation
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Food-borne disease outbreaks& food spoilage
Preventing/limiting contamination Preventing/limiting spread
Preventing growth
Preventing survival of organisms& persistence of metabolites
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Microbiological/chemicalhazards
Micro-organisms part of nature
Chemicals many are man-made
Micro-organisms change numbers
Uneven distribution in food
Clinical symptoms acute Variable consumer susceptibility
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