Transcript of food from animals

FOOD-BORNE DISEASES
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) : protein
part of bacterium : extracellular
no toxoid : toxoid
low potency : high potency
low specificity : high specificity
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Mode of action of some
bacterial toxins
S. aureus – A
(alpha-toxin)
E. coli – B
(shiga toxin)
C. botulinum – C
(exo-enzyme)
September 2005
116.407 VPH & MH
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Introduction contd
• Food hygiene vs food safety
food hygiene – microbiological safety of
food
food safety – abscence of
chemicals/residues
• Not necessary to have ‘sterile’
food
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Prevention of food-borne
diseases
• Organisms characteristics
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where from
types & strains
behaviour in food
survive or are killed by
measures to inactivate
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Prevention of food-borne
diseases, contd
• Food –
characteristics
Water activity (aw), pH and
temperature
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What influences occurrence of
food-borne diseases/illnesses?
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Food source
Food storage
Food preparation
Food handlers
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What influences occurrence of
food-borne diseases/illnesses?
• Time-temperature abuse
• Infected food handlers or
inadequate hygiene during handling
of food
• Consumption/use of unsafe food
sources
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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 signs
Nausea, retching, vomiting, abdominal pain,
diarrhoea & prostration
• S. aureus and its toxins
• B. cereus and its toxin
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Types of illnesses/diseases
Lower GIT signs
Lower abdominal cramps & diarrhoea
• Clostridium perfringens, Bacillus
cereus
• Salmonella, Shigella, ET E. coli,
Yersinia enterocolitica,
Campylobacter jejuni, Vibrio cholera
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Types of illnesses/diseases
Lower GIT signs, continued
Lower abdominal cramps & diarrhoea
• Giardia intestinalis
• Cryptosporidium parvum
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Types of illnesses/diseases
Neurological signs
Visual disturbances, vertigo, tingling
sensation & paralysis
• Clostridium botulinum
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Types of illnesses/diseases
General symptoms
Fever, chills, malaise, prostration, aches,
swollen lymph nodes
• S. typhi, L. monocytogenes, C. jejuni
• Hepatitis A
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Risks of contracting foodborne disease depend on:
• Host susceptibility
Age
General health
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Infective dose
• Frequently exptrapolated
• Feeding studies (healthy, young adult
volunteers)
• 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
shellfish
fruits & nuts
beans
watermelons
spices & herbs
vegetables
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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
• Salmonella spp.
- GIT / Hide
• E. coli O157:H7
- GIT
• Campylobacter spp.
- GIT (esp. poultry)
• Staphylococcus aureus toxin - Human (nostrils and hands)
• Yersinia enterocolitica
- GIT
• Listeria monocytogenes
- Soil, hide, faecal material
• C. botulinum, C. perfringens - Soil, hide, faecal material
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Control of food contamination
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Ideal = growing & harvesting stages
But – ‘world is not sterile’
Prevent, reduce or limit by:
Not allowing products from clinically ill
animals to enter food chain
Classical meat inspection - gross
HACCP - microscopic
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The chain of production from ‘farm to fork’
of food from animals
Production
Farm, Feedlot, Fishing site
Processing
Slaughter Plant, Cannery,
Packer, Food Factory
Final preparation
and cooking
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
Feed, water, manure treatment,
biosecurity, probiotics, vaccines
HACCP, slaughter hygiene,
pathogen reduction and
elimination (pasteurization,
irradiation)
Final preparation Cooking, preventing
cross-contamination,
and cooking
worker education and hand
washing
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Prevention of Food Poisoning
WHO ‘ten golden rules’
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Food processed for safety
Thoroughly cook
Eat immediately
Store carefully
Reheat thoroughly
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Prevention of Food Poisoning
WHO ‘ten golden rules’ contd
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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 undesirable
micro-organisms
• Unacceptable levels of microorganisms
• Treatment did not result in
inactivation
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Food-borne disease outbreaks
& food spoilage
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Preventing/limiting contamination
Preventing/limiting spread
Preventing growth
Preventing survival of organisms
& persistence of metabolites
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Microbiological/chemical
hazards
• 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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