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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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September 2005 116.407 VPH & MH 2

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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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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Lower GIT signs, continuedLower abdominal cramps & diarrhoea

Giardia intestinalis

Cryptosporidium parvum

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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

Documents

05VPH & MH Lecture 1[1]