FOOD-BORNE DISEASES by Rabia06

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									FOOD-BORNE DISEASES

      116.407 Veterinary
     Public Health & Meat
            Hygiene




         Jutta Tebje-Kelly
  EpiCentre, Wool Building, Rm 2.04
                   Introduction
• Causes of food-borne
  diseases/illnesses:
1. Chemical toxins (‘residues’)
2. Biotoxins – endotoxins & exotoxins
3. Infectious agents – exogenous &
   endogenous (‘zoonoses’)

  September 2005      116.407 VPH & MH   2
            Introduction contd
      endotoxins & exotoxins

lipopolysaccharide (LPS) : protein
 part of bacterium : extracellular
         no toxoid : toxoid
    low potency : high potency
 low specificity : high specificity
 September 2005   116.407 VPH & MH    3
      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   4
            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
  1.    where from
  2.    types & strains
  3.    behaviour in food
  4.    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?

            •     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 food-
  borne 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


    September 2005      116.407 VPH & MH                  21
    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 chain
       Classical meat inspection - gross
              HACCP - microscopic

    September 2005    116.407 VPH & MH           22
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    Final Kitchen:
 and cooking          commercial,
                      institutional or domestic
  September 2005     116.407 VPH & MH          23
The chain of production from farm to fork -
     prevention can occur at each step

   Production       Feed, water, manure treatment,
                    biosecurity, probiotics, vaccines

                    HACCP, slaughter hygiene,
  Processing        pathogen reduction and
                    elimination (pasteurization,
                    irradiation)
Final preparation Cooking, preventing
   and cooking    cross-contamination,
                    worker education and hand
                    washing
   September 2005     116.407 VPH & MH             24
Prevention of Food Poisoning
      WHO ‘ten golden rules’

      •   Food processed for safety
      •   Thoroughly cook
      •   Eat immediately
      •   Store carefully
      •   Reheat thoroughly

 September 2005     116.407 VPH & MH   25
Prevention of Food Poisoning
  WHO ‘ten golden rules’ contd

 •    No contact between raw & cooked
 •    Wash hands
 •    Keep food preparation surfaces clean
 •    Protect from pests
 •    Use potable water



 September 2005    116.407 VPH & MH          26
Food-borne disease outbreaks
      & food spoilage

    • Contamination with undesirable
      micro-organisms
    • Unacceptable levels of micro-
      organisms
    • Treatment did not result in
      inactivation

 September 2005   116.407 VPH & MH     27
Food-borne disease outbreaks
      & food spoilage

 •   Preventing/limiting contamination
 •   Preventing/limiting spread
 •   Preventing growth
 •   Preventing survival of organisms
     & persistence of metabolites

 September 2005   116.407 VPH & MH       28
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


September 2005   116.407 VPH & MH       29

								
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