FOOD-BORNE DISEASES

2 Introduction Causes of food-borne diseases/illnesses: 1.Chemical toxins (‘residues’) 2.Biotoxins – endotoxins & exotoxins 3.Infectious agents – exogenous & endogenous (‘zoonoses’)

3 Introduction contd endotoxins & exotoxins lipopolysaccharide (LPS) : protein part of bacterium : extracellular no toxoid : toxoid low potency : high potency low specificity : high specificity

September VPH & MH4 Mode of action of some bacterial toxins S. aureus – A (alpha-toxin) E. coli – B (shiga toxin) C. botulinum – C (exo-enzyme)

5 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

6 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

7 Prevention of food-borne diseases, contd Food – characteristics Water activity (a w ), pH and temperature

8 What influences occurrence of food-borne diseases/illnesses? Food source Food storage Food preparation Food handlers

9 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

10 Types of illnesses/diseases Upper GIT – nausea & vomiting Lower GIT – cramps & diarrhoea Neurological signs General symptoms

11 Types of illnesses/diseases Upper GIT signs Nausea, retching, vomiting, abdominal pain, diarrhoea & prostration S. aureus and its toxins B. cereus and its toxin

12 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

13 Types of illnesses/diseases Lower GIT signs, continued Lower abdominal cramps & diarrhoea Giardia intestinalis Cryptosporidium parvum

14 Types of illnesses/diseases Neurological signs Visual disturbances, vertigo, tingling sensation & paralysis Clostridium botulinum

15 Types of illnesses/diseases General symptoms Fever, chills, malaise, prostration, aches, swollen lymph nodes S. typhi, L. monocytogenes, C. jejuni Hepatitis A

16 Risks of contracting food- borne disease depend on: Host susceptibility Age General health

17 Infective dose Frequently exptrapolated Feeding studies (healthy, young adult volunteers) Estimates (data from outbreaks) ‘Worst case’ estimates

18 Risk assessment – variable infective doses Interaction – food substrate & environment pH susceptibility Type and strain

19 Control of food contamination Micro-organisms in food & water shellfish fruits & nuts beans watermelons spices & herbs vegetables

20 Control of food contamination Infection of animals – milk, eggs or meat Contaminated skins and guts - slaughter & dressing

21 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

22 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

23 The chain of production from ‘farm to fork’ of food from animals Production Processing Final preparation and cooking Farm, Feedlot, Fishing site Slaughter Plant, Cannery, Packer, Food Factory Final Kitchen: commercial, institutional or domestic

24 The chain of production from farm to fork - prevention can occur at each step Production Processing Final preparation and cooking Feed, water, manure treatment, biosecurity, probiotics, vaccines HACCP, slaughter hygiene, pathogen reduction and elimination (pasteurization, irradiation) Cooking, preventing cross-contamination, worker education and hand washing

25 Prevention of Food Poisoning WHO ‘ten golden rules’ Food processed for safety Thoroughly cook Eat immediately Store carefully Reheat thoroughly

26 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

27 Food-borne disease outbreaks & food spoilage Contamination with undesirable micro-organisms Unacceptable levels of micro- organisms Treatment did not result in inactivation

28 Food-borne disease outbreaks & food spoilage Preventing/limiting contamination Preventing/limiting spread Preventing growth Preventing survival of organisms & persistence of metabolites

29 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