Food-borne risks by commodity Flashcards
Outline origin of Listeria
biofilms in drains, floors or stainless steel surfaces in cheese plant
Give possible origins of E. coli 0157
contamination of vegetables from water exposed to cattle faceces
Outline possible origin of Campylobacter or Salmonella
linked to sick food handlers
Which foodborne dz has highest mortality rate?
listeria monocytogenes
List examples of biological food borne hazard by category
ANIMAL: Brucella, Campylobacter, E. coli 0157, Yersinia spp, Listeria monocytogenes, Mycobacterium sp, Salmonella, BSE/vCJD, Taenia spp, Toxoplasma spp, Trichinella spp, Vibrio vulnificus
HUMAN: Hepatitis A, rotavirus, norovirus, Salmonella spp, Shigella sp, S. aureus, Vibrio cholerae
ENVIRONMENT: Bacillus spp, Clostridium sp, Listeria spp, Mycotoxins, Marine biotoxins
What does public health impact depend on?
- total # cases
- severity of cases (# hospitalised, deaths)
- overall L.monocytogenes, E.coli 0157, Salmonella, Norovirus
What are the 2 biological hazards in chicken meat?
- Campylobacter
- Salmonella (S. enteritidis)
Main source of human campylobacteriosis
Broiler meat
T/F: campylobacter is endemic in animals (poultry, cattle, sheep and pigs)
True (sources include food and non-food such as untreated water). Mainly found in poultry, also red meat, raw milk, untreated water.
CS - campylobacter in humans
- low infectious dose
- incubation period 2-5d
- diarrhoea
- abdominal pain
- self-limiting within 10d
- rare sequelae (Gillan-Barre syndrome = serious autoimmune condition that has been associated with campylobacteirosis)
When is there a seasonal peak in Campylobacter?
late spring and summer (humans and poultry). Most likely an effect of environmental conditions. Raise in human cases sometimes precedes raise in chickens
How will a decrease in the highest level Campylobacter contamination from 27% to 10% in 2015 affect human Campylobacter cases?
estimated to reduce Campylobacter food poisoning by 30% (30,000 cases/year)
Methods - reduce campylobacter
- ON FARM: biosecurity (fly screens), feed and water additives that reduce risk of colonisation, vaccination, genetic resistance.
- MANAGEMENT/HUSBANDRY: thinning or partial depopulation has been identified as a strong risk factor for flock colonisation
- SLAUGHTERING AND PROCESSING: Campylobacter positive flocks –> contaminated chicken products (from same bird and cross-contamination). Logistic slaughter (campylobacter negative flocks slaughtered first).
- Freezing, treating with hot water, chemical decontamination
- ROLE OF CONSUMER: adequate cooking and avoid cross contamination
What is the second commonest cause of foodborne illness across the EU?
Salmonella
- generally decreasing trend, but still most common pathogen causing food-borne outbreaks across EU (S. enteritidis = poultry)
CS - salmonella
- incubation 12-48h
- diarrhoea, vomiting, abdominal pain
- fever
- self-limiting within 3-5d
Vehicles - salmonella
- poultry, eggs, deserts (products made with raw eggs - mayonnaise, ice cream)
- 4-5% chicken contaminated at retail (not current estimates)
What salmonella spp cause dz in livestock?
- Cattle: S. dublin
- Sheep: S. diarizonae
- Pigs: S. typhimurium
SOurces - listeria monocytogenes
- infected animals
- environment
- silage
- biofilms in food processing environment
- low infective dose
Vehicles - listeria monocytogenes
- raw milk
- chilled ready to eat food (prepacked sandwiches, pate, soft mould-ripened cheese, cooked sliced meats, smoke salmon)
CS - listeria monocytogenes - humans
- incubation typically 3-4w, can be up to 90 days
- non-invasive (flu-like symptoms, often asymptomatic)
- invasive: abortion, meningoencephalitis in children/ elderly/ immunocompromised
How is the risk of L.monocytogenes in milk reduced?
- WHO states: pastuerisation is a safe process which reduces the # of L.monocytogenes occurring in raw milk to levels that don’t pose an appreciable risk to human health
- ensure proper pasteurisation
- avoid post-pastuerisation contamination (Listeria can thrive in cool and damp food processing environments such as floor drains)
- consumer behaviours
- provision of food to vulnerable groups (especially as many aren’t responsible for meeting their own food needs)
- industry compliance/enforcement (target high risk businesses, prevent contamination from equipment and the environment and prevent growth to dangerous levels through product formulation and shelf-life restricion)
Outline Bacillus cereus in milk and milk products
- produces spores that survive pasteurisation
- grows at 5 degrees
- produces toxin
Ways to minimise risk of B.cereus
- proper refrigeration
- dairy products normally spoil before B.cereus contamination is sufficient to cause illness
Outline S.aureus food poisoning
- d/t enterotoxins formed in the food
- outbreaks associated with cheese, when milk was contaminated after pasteurisation
- food handlers can be asymptomatic carriers of S.aureus.
List hazards in pork
- Salmonella
- Yersinia enterocolitica
- Hepatitis E
- Campylobacter
- Trichinella
- Aeromonas (spoilage pathogen)
Describe Yersinia enterocolitica
- v common in pigs, normally causes little or no dz
- from USA
Vehicles - Yersinia enterocolitica
- pork (undercooked pork products)
- others: untx water, unpasteurised milk
Yersinia in people
- usually resolves on own
- can be more severe in young and elderly
Outline hepatitis E
- increasing # human cases
- processed pork products as risk factor
- high prevalence in pigs in UK, seroprevalence as 92.8% and prevalence infection is 5.8%
Highest risk category - hepatitis E
- male humans >45 years old (overrepresented)
- unknown why
What hazards are in beef?
- E.coli 0157
- aeromonas (spoilage pathogen)
- prions (BSE)
- Clostridium perfringens
Vehicle - E.coli 0157
- undercooked minced meat
- direct contact with open farms
CS - human E.coli 0157
- low infection dose ( haemolytic uraemic syndrome (HUS), renal failure, death
Contrast E.coli and Salmonella
Infection (e.coli) rare c.f. campylobacter but dz can be severe for affected individuals
Hazards - fish and shellfish
- hepatitis A virus
- norovirus
- Vibrio spp (raw seafood - oysters)
- environmental contaminants
Risk management - norovirus
Options before and after harvesting:
- RELAYING: shellfish are harvested from a contaminated area and moved to a clean area for at least 2 months
- DEPURATION: shellfish are placed in tanks of clean recirculating seawater tx by UV radiation for at least 42h. More effective in removing bacteria than norovirus
List hazards in honey
- Clostridium botulinum
- Environmental contaminants
- Antimicrobial residues
Outline botulism
- extremely potent
- C. botulinum: ubiquitous in soil, sediments, water
- growth of pathogen required under anaerobic conditions
Name 2 ‘process hazards’
- S. aureus
- C. perfringens
Give examples of chemical hazards in foods
- INDUSTRIAL POLLUTANTS: heavy metal, halogenated hydrocarbons (e.g. dioxins)
- AGRICULTURAL CHEMICALS: insecticides, herbicides, fungicides, fertilisers
- GROWTH PROMOTERS: hormone-like GP, antimicrobial-like GP (both banned in EU)
- VET MEDS: antimicrobials, antiparasitics
- NATURALLY OCCURING TOXINS: biogenic amines, mycotoxins, algal toxins, plant toxins
- FOOD ADDITIVES: sensory additives, meat conservation, packaging
How do shellfish get contaminated?
faecal material from sewage and surface water can contaminate shellfish production areas where oysters and other shellfish which filter large volumes of water can accumulate pathogenic viruses and bacteria
Vehicles - botulism
- home-canned vegetables, meat, fish
- fermented bean, fish
Describe clinical botulism in humans
- incubation time 12-36h
- tx: antitoxin
- fatal outcome possible
Describe S.aureus as a ‘process hazard’
- intoxication
- common source of bacteria are food handlers
- bacteria contaminates product and produces toxin
- high risk products: custards, whipped cream
Describe C. perfringens as a ‘process hazard’
- intoxication
- present in environment and raw meat
- inadequate temperature control during cooking may allow spores to germinate and bacteria to grow
- high risk products: stew, long, slow-cooking
What hazards accumulate in the food chain?
- heavy metals, halogenated hydrocarbons, inseciticides (DDT)
- toxicity mostly chronic (carcinogen, teratogen)
- recommended minimum levels (WHO/FAO) monitored by UK FSA and DEFRA. Recall if higher levels found.
What surveillance does the VMD do?
for veterinary medicines and environmental residues
