Lecture 24 Food contamination and food borne diseases

Transcription

1 Faculty of Medicine Epidemiology and Biostatistics الوبائيات واإلحصاء الحيوي ( ) Lecture 24 Food contamination and food borne diseases By Hatim Jaber MD MPH JBCM PhD

2 1. Basic epidemiological concepts/ Epidemiological study types 2. Association and causation 3. Bias and confounding 4. Screening tests and result interpretation 5. Communicable diseases Epidemiology 6. Transmission of infectious diseases 7. Chronic Non-communicable Diseases Epidemiology 8. Risk factors of NCD 9. Workplace Hazards Radiation and Noise at workplace 10. Current global environmental problems, their causes, effects, and prevention measures.(1) 11.Food contamination and food borne diseases

3 Presentation outline Time Introduction to Contamination 10:30 to 10:40 Food poisoning 10:40 to 10:50 Food borne diseases 10: 50 to 11:10 Food borne infections vs intoxication 11:10 to 11:25 Emerging foodborne viruses 11:25 to 11:35 3

4 Contamination Contamination of food Definition: The presence in food of any harmful or objectionable substance or object.

5 Factors contributing to the global incidence of foodborne disease Poor sanitary conditions Malnutrition Changing demographics (increasing population of infants, elderly) Inadequate public health infrastructure Inadequate hygienic and technological conditions of food production Inadequate cooking, reheating and storage conditions Increasing tourism and international trade Increasing animal movement and insufficient control of borders Increasing international trade of animal and food Inadequate legislation and official control system Emerging/reemerging foodborne pathogens Acquisition of virulence and antibiotic genes by nonpathogenic bacteria Adaptation and enhanced survival of pathogens in food Inadequate consumer education

6 Routes of Food Contamination Contamination of raw food or failure to eliminate acceptable contamination of raw food Farming practice/abattoir practice/zoonotic problems Pasteurisation failure Undercooking, inadequate cooling Contamination during food preparation Infected food handler Environmental contamination Cross contamination (from raw or processed ingredients) Contamination after food preparation Infected food handler Inadequate storage, cooling or reheating Environmental contamination Cross contamination from raw food

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8 Cross-Contamination What is Cross-Contamination? Cross contamination is the transfer of harmful bacteria from one food via means of utensils, equipment or human hands to another food. It also can occur when a raw food touches or drips onto a cooked or ready-to-eat food.

9 Contamination of food Bacterial cross-contamination may be defined as: the transfer of harmful / pathogenic bacteria from one item / food / surface / person to food. Direct cross-contamination This occurs in food when there is direct contact between the source of the bacteria and food. Indirect cross-contamination This occurs when harmful bacteria are transferred from the source to the food via a vehicle.

10 Contamination Sources of Contamination Worker hygiene Melted fat and juices Coughs and sneezes Mishandling of foods

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13 Cross-Contamination Preventing Cross-Contamination Wash, rinse and sanitize cutting boards, knives, utensils and countertops after contact with raw meat. Store raw meat below and away from all readyto-eat foods. Wash, rinse and sanitize food- contact equipment (slicers, knives, cutting boards) at least every 4 hours. Wash hands before handling food and after touching raw meat.

14 Foodborne hazards

15 Staphylococcus aureus, Bacillus cereus Produce toxin in food Generally cause vomiting Quick onset Campylobacter jejuni, Salmonella, E. coli, Clostridium perfringens Originate in the gut Generally cause diarrhoea Slower onset

16 High risk foods These are ready-to-eat foods which can support the growth of pathogenic bacteria and are intended for consumption without further processing or cooking. These foods are usually high in protein and moisture and require refrigerated storage. Examples of high risk food: 1. Cooked meat and poultry 2. Cooked meat products including gravy, stock, meat pies 3. Sausage rolls & chicken nuggets 4. Milk, cream, custards and dairy produce, custard slices & cream cakes 5. Cooked eggs and products made from eggs mayonnaise, meringue or home-made icecream 6. Shellfish and other seafood, prawn cocktail & smoked salmon 7. Cooked rice, rice pudding or egg fried rice 8. Ready to eat salads, coleslaw or potato salad etc.

17 Low risk foods Bacteria do not like low risk foods. The bacteria cannot grow on low risk foods because the optimum conditions (food, moisture, temperature and time) are generally not right for growth. For example, they may contain too much sugar, vinegar, salt or acid. For this reason these foods are considered relatively safe foods. Examples include: 1. Acid fruits - there is too much acid in the fruit and bacteria will not grow - e.g. oranges, lemons 2. Vegetables in vinegar - the vinegar acts as a preservative - e.g. pickled onions 3. Jams and preserves - the sugar acts as a preservative 4. Salted or smoked meats the bacteria cannot survive in the salty environment. 5. Bread does not contain high moisture levels and therefore is not favourable for bacterial growth

18 FOOD POISONING

19 FOOD-BORNE DISEASES

20 Introduction Food borne diseases-(intoxications and infections) Covers illnesses acquired through consumption of contaminated food-food poisoning Food borne disease outbreaks- Occurrence of 2 or more cases of similar illness resulting from ingestion of common food OR When observed number of particular disease exceeds expected number

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22 Classification of food borne diseases Food borne diseases are classified into: 1. Food borne infections and 2. Food borne intoxications

23 Food borne infections vs intoxication Infections Bacterial / Viral / parasite Invade and or multiply in lining of intestine Incubation period- hours to days Intoxications toxins ( natural / preformed bacterial / chemical) No invasion or multiplication Incubation period- minutes to hours S/s Diarrhoea, nausea, vomitting, abdominal cramps, fever Communicable-spreads from person to person Factors-inadequate cooking, cross contamination, poor personal hygiene, bare hand contact S/s Vomitting, nausea, diarrhea, diplopia, weakness, resp. failure, numbness, sensory/motor dysfunction Not communicable Factors-inadequate cooking, improper handling temperatures

24 Introduction Global burden- high morbidity and mortality Infectious diarrhoea- 3 to 5 billion cases and 1.8 million deaths annually CDC- 76 million cases of food borne diseases in US annually with appx.5000 deaths In India- Integrated disease surveillance Project (IDSP) - Food poisoning outbreak reporting increased to more than double in 2009 from 2008 (120 in 2009 and 50 in 2008)

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26 The global burden of foodborne disease (DALYS per population) by hazard groups and by subregion, 2010.

27 Relative contribution of Years of Life Lost due to premature mortality (YLL) and Years Lived with Disability (YLD) to the global burden of 31 hazards in food, 2010.

28 The global burden of foodborne disease by subregion (DALYS per population) caused by enteric hazards, 2010.

29 The relative proportion of the burden of each of the foodborne parasitic diseases contributed by YLLs and YLDs

30 The relative contribution to the DALY incidence by each of four chemicals for each of the WHO Regions

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32 Major transmission routes of human foodborne diseases indicate two points of attribution: the reservoir level and the exposure level.

33 Who is the most vulnerable to foodborne illness? Young children (infants and school-aged) Older adults (elderly) Individuals with compromised immune systems (pregnant, sick, etc.)

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36 Causes of Foodborne Illness: Let s look at bacteria The types of bacteria are: Beneficial bacteria Beneficial bacteria lives in our environment and in our bodies, helping us with digestion, vitamin production and helping to prevent the growth of harmful bacteria. Spoilage Bacteria There are bacteria that live and grow in food that can cause damage to the flavor, appearance, texture or composition of food. Pathogens These are the bacteria that produce disease in the human body. These bacteria are our main concern, as they are responsible for foodborne illness.

37 Some important food-borne pathogens, toxins and chemicals 1. Bacteria - Bacillus cereus, Brucella, Campylobacter, Clostridium sp, E.coli, Salmonella sp, Listeria, Staph aureus, Vibrio cholera and V.parahemolyticus 2. Viruses - Hepatitis A and E, Rotavirus, Norvovirus 3. Protozoa Cryptosporidium, Cyclospora, Entamoeba, Giardia, T. gondii 4. Trematodes, Cestodes and Nematodes

38 Food borne pathogens-toxins and chemicals Toxins - marine biotoxins, tetrodotoxin (puffer fish), pyrrolizidine alka (Endemic ascites), mushroom toxins, shellfish toxins, mycotoxins-(aflatoxins,ergot and Fusarium), plant intoxicants, BOAA (Lathyrism) Chemicals - pesticides (OPP,sb), radionuclides, nitrites (food preservatives) toxic metals - cd, cu, hg, pb, sn, fluoride, MSG

39 Pathogenesis and Transmission Inoculum / size of infective dose -Can be as small as bacterial cysts for Shigella, EHEC, Giardia, E. histolytica or 10^ 5-10^ 8 for Vibrio cholera, variable for salmonella Animals / humans harbouring infection shed in feces contaminate water, fruits, vegetables inadequate cooking / improper storage infection Warm temperature(10-50 degree cent.)- multiplication of pathogens

40 Some common bacterial food poisons Incubation period Cause Symptoms Common foods 1-6 hours Staph aureus (enterotoxin) Bacillus cereus (enterotoxin) Nausea, vomitting, diarrhea Nausea, vomitting, (emetic form) Milk n milk products, ham, poultry, salads, custards Fried rice

41 Some common bacterial food poisons Incubatio n period 8-16 hours Cause Symptoms Common foods Clostridium perfringes (spores) Abd.cramps, diarrhea Nausea and Vomitting -rare Meat, poultry, legumes. gravies Bacillus cereus ( diarrheal formpreformed n stable toxins) Diarrhea, abd.pain, nausea, vomitting/feve r-no

42 Some common bacterial food poisons Incubatio n period Cause >16 hours Vibrio cholera Salmonella spp Symptoms Common foods Rice watery stools Inflammato ry diarrhea Water and ice creams, sea food Meat, milk n milk products, poultry Shigella sp dysentry Potato/raw eggs-salad

43 Early diagnosis and investigations 1.Initial assessment of cases Detailed clinical history including time of onset, duration of illness, symptoms, h /o travel, recent meals, cooking and refrigeration, details of others with similar complaints 2.Detailed clinical examination Vitals and degree of dehydration, systemic signs

44 Lab diagnosis Main objectives- a) To confirm clinical diagnosis by isolation of causative agent from proper samples, eg. stool, vomitus / gastric aspirate, food specimens b) Ensure proper identification of disease c) Determine causative agent if present in food sources with relevant epidemiological markers- eg. Biotyping, serotyping, PCR, Phage typing etc

45 Collection of food samples Using aseptic technique n appropriate containers samples be refrigerated during storage and transport must arrive lab within 3 days of collection Adequate sample - minimum 100 grams Containers - not to be filled >75% of capacity Proper labelling is utmost important labelled specimen be placed in zip lock bag and sealed Vaccine carrier with ice packs for transport and cold chain maintenance ( avoid freezing )

46 Steps of outbreak investigation Establishing existence Co-ordination Collection and transport Lab testing Control and preventive measures Definition of cases, population Description of epidemiology Possible hypotheses Epidemiological study Analysis of data and interpretation Reporting

47 Treatment 1. Initial T/t - Assessment and reversal of dehydration ( ORT / IV Fluids ) 2. Cause specific treatment if any- eg. chelating agents in case of pesticide poisoning 3. Use of antibiotics can be considered if bacterial cause is identified

48 Prevention in community Proper handwashing and personal hygiene Proper storage (refrigeration) Food saftey education community and food handlers Environmental measures - Discourage sewage farming for growing fruits and vegetables

49 Prevention Hazard Analysis and Critical Control Point (HACCP) - Systematic preventive approach to food safety Addresses physical, chemical and biological hazards as means of prevention rather than finished product inspection Food industry - Food safety hazards identified at all stages of food production and preparation processes key action taken at Critical Control Points (CCP s)

50 Principles of Hazard Analysis and Critical Control Point ( HACCP ) Analyse hazards Identify critical control points Establish preventive measures with critical limits for each CCP Establish procedures to monitor CCPS Establish corrective actions when monitoring shows that critical limit has not met Establish procedures to verify that system is working properly Establish effective record keeping for documentation

51 Center for Food Security and Public Health Iowa State University 2004

52 1. Keep Clean Five keys to Safer food Wash hands before handling food and often during preparation Wash hands after going to toilet Wash and sanitise all surfaces & equipment for food preparation-protect kitchen from insects, pets 2. Separate raw and cooked food- Separate raw meat, poultry & seafood from other foods Use separate utensils for handling raw foods Store food in containers to avoid contact between raw and cooked foods

53 Five Keys to Safer Food 3. Cook Thoroughly esp. Meat, poultry, eggs and Seafood Bring soups n stews to boiling (ensure>70degree temp) Reheat cooked food thoroughly 4. Keep food at safe temperature - Dont leave cooked food at room temp.>2 hours Prompt refrigeration of cooked n perishable food Keep cooked food piping hot(>60 de.) prior to serving Don t store food too long even in refrigerator Don t thaw frozen food at room temperature

54 Five keys to safer food 5. Use safe water and raw materials- Use safe water or treat to make it safe Select fresh and wholesome fruits Choose foods processed for safety - pasteurised milk Wash fruits n vegetables if eaten raw Don t use food beyond expiry date

55 Emerging Foodborne Pathogens Definition: those causing illnesses that have only recently appeared or been recognised in a population or that are well recognised but are rapidly increasing in incidence or geographic range

56 Emerging foodborne bacteria Salmonella (multidrug resistant strain) Campylobacter jejuni E. coli O157:H7 Listeria monocytogenes S. aureus MRSA Vibrio vulnificus Yersinia enterocolitica Arcobacter spp. Mycobacterium paratuberculosis

57 Emerging foodborne viruses Hepatit A and E Norovirus (Avian influenza, AI)

58 Emerging foodborne parasites Cryptosporidium parvum Cyclospora cayetanensis Anisakis spp.