Foodborne Dz And Outbreak Investigation Flashcards
Origins of food borne hazards
> e.coli
- present in water, cattle act as reservoir (manure infects)
campylobacter
- in environment introduced in broilers houses
listeria
- envirment contamination (steel pipes drains etc.)
Give egs. Foodborne illness caused by biological, chemical and physical hazards
> Biological
- animal, human or envirment origins
Chemical and physical eg. Dioxins and mycotoxins transmissable by food of animal origin
Which food borne dz has highest mortality rates?
Listeria (proportionally)
> but the public health impact is a function of the fatality rate and the incidence of infection
Which is the highest number of cases impact pathogens of foodborne dz (UK)
- campylobacter over half
- norovirus
Outline FSA priority list of foodborne diseae from the 2010-2015 action plan
> campylobacter > listeria > e. Coli > salmonella > norovirus > clostridium perfringens
Which food group has the highest risk of food borne disease per serving
Poultry (compared to cooked vegetables)
- eggs
- red meat
- sea food
- milk
- other dairy lowest risk
Sources of campylobacter
- endemic in animals (poultry, cattle, sheep, pigs)
- sources food and nonfood eg. Untreated water
Clinical signs campylobacter
- incubation period 2-5d
- d+ and abdo pain
- self limiting in 10d
- rare sequalae : Guillan Barre syndrome
How does seasonal incidence of campylobacter change ?
- seasonal peak late spring and summer (maybe d/t flies? Not known)
- mirrored by humans (sometimes this proceeds the poultry rise!!)
Aim of FSA 2010-2015 wrt campy?
Decrease numbers of highly contaminated chickens from 27% to 10%
> hasn’t happened!!!
How can campylobacter tried be managed?
- NB even doing these things risk of campy infection is VERY HIGH*
> on farm - biosecurity fly screen, feed and water additive, vax, genetic resistance
> farm level management or husbandry - thinning or partial depopulation strong risk factor for flock colonisation
> slaughter and processing - campy+ flocks cross contaminate at abbattoir , slaughter last
> freezing/hot water/chemical decontamination
> consumer - cook properly, avoid cross contamination
Second most common cause of food borne dz in UK?
Salmonella
- and most common pathogen causing food borne OUTBREAKS across the WHOLE EU
- cf. campy which causes sproadic cases NOT outbreaks
Trend of salmonella case
Decreasing but still high (s. Enteridis poultry)
Clinical signs salmonella
- incubation period 12-48hrs
- VD+ abdo pain and fever
- self limiting 3-5d
Which sero are of salmonella exist?
- s. Dublin cattle
- s. Diarizonae sheep
- s. Typhimurium pigs
> s. Enteridis POULTRY most successful cause of decrease in salmonella cases
Where is salmonella a hazard?
- raw egg (mayonnaise, ice cream)
- eggs contaminated before shell is formed
- pasteurisation destroys
Hazards milk and milk produce
- TB
- Brucella
- Salmonella
- Campylobacter
- Listeria monocytogenes
- Staph aureus
- Bacillus spp.
Which hazards in raw milk are destroyed by heat treatment
- TB
- brucellosis
- salmonella
- campylobacter
Give 3 pathogens that may pose a risk despite heat tx of milk
- listeria monocytogenes
- staphylococcal aureus
- bacillus spp.
Sources listeria monocytogenes
- infected animals
- environment
- silage
- BIOFILMS in food processing environment
Infective dose of listeria and risk foods
> low
- raw milk
- chilled ready to eat foods (long shelf life when chilled, no need to cook before eating)
- sandwiches
- pate
- soft mould rippened cheese
- cooked sliced meats
- smoked salmon
Does heat Tx destroy listeria?
Not all but enough to render it safe
- post-pasteurisation contamination main risk
Listeria Clinical signs and Risk management listeria monocytogenes
> CS
- incubation period LONG ~1month
-non-invasive: flu like symptoms/asymptomatic
- invasive: abortion, meningioencephalitits in children elderly and immunocompromised
risk management
- only causes illness in limited subset of population (target at risk groups)
- industry compliance and enforcement (listeria widespread in environment but need to minimise growth to harmful levels)
- consume food in date
Why is bacillus cereus a risk
- produces spores that survive pasteurisation
- it grows at 5* and produces a toxin
> need proper refrigeration - usually spoils milk before toxin produced so not often consumed
Why does staph aureus cause problems?
- post pasteurisation contamination from asymptomatic carrier worker people
- staphylococcal enterotoxins formed in food are consumed
Hazards in pork
- salmonella
- yersinia enterocolitica
- hepatitis e
- campy
- trichinella
- aeromonas (spoilage pathogen)
Yersinia in pigs
- very common in pigs asymptomatic
- undercooked pork
- other vehicles untreated water and unpasteurised milk
> in humans usually resolves on its own but more severe young and elederly
How has hepatitis E incidence changed? Likely source?
- massively increased numbers native humans over last few years
- Pigs very often carriers
- ^ risk of hepatitis E with processed pork consumption
- makes over 45 years old over represented
Hazards in beef
> e.coli 0157 - feacal contamination mince meat > aeromonas (spoilage) > prions (BSE) > clostridium perfringens
E. Coli 0157 clinical signs and infective dose needed
- low dose needed
- VD+ abdo pain
- haemorrhage colitis
- most severe children and the elderly
- haemolytic uraemia syndrome(HUS)
- renal failure and death
Vehicles for E.coli infection and therefore risk management strategies
- undercooked mince meat
- direct contact open farms
- prevalence in cattle up to 20%
> prevention - farm biosecurity
- slaughter hygiene
Hazards in fish and shellfish
> hepatitis A
norovirus
- raw seafood eg. esp oysters (virus not destroyed as not cooked)
vibrio spp.
- raw seafood eg. esp oysters (virus not destroyed as not cooked)
environmental contaminants
why do shellfish pose a health risk?
- filter large volumes of water, accumulate pathogenic viruses and bacteria
Risk management shell fish
- relaying (moved to clean area of water for min 2 months before harvest)
- depuration (placed in tanks of clean re-circulating sea water tx with UV radiation min 42hrs)
> this is v effective for bacteria, less so for viruses
Hazards in honey
- clostridium botulinum
- environmental contaminants
- antimicrobial residues
Why should children not consume honey?
Potential for clostridial botulinum spores to grow in intestinal tract of very young children
Are all foodborne dz zoonotic?
- not all foodborne illness is zoonotic
- not all zoonoses are foodborne
Infectious dose, pathophysiology of botulism
> extremely potent low dose needed
- c. botulinum ubiquitous in soil, sediments, water etc.
- growth of pathogen ANAEROBIC conditions only
- home canned or fermented stuff
Clinical signs botulism in humans. Tx?
- incubation time 12-36hrs
- tx: antitoxin
- can be fatal
> infant botulism if bacteria colonises large intestine
Give 2 “processing” hazards
> staph aureus
- on food handlers
- produces toxin
- high risk products: custard, whipped cream
clostridium perfringen s
- present in environment and raw meat
- inadequate temperature control during cooking -> spores can germinate and bacteria can grow
- high risk products: stew, long, slow cooking
egs. chemical hazards in food
- heavy metals
- halogenated hydrocarbons
- insecticides
- fertilisers
- hormone like GP/antimicrobial GP
- biogenic amines
- MYCOTOXINS
- meat conservation
- packaging
> see table for more egs./
Which hazards can accumulate in the food chain? How are these monitored/controlled?
- heavy metals, halogenated hydrocarbons, insecticides (DDT)
- toxicity mostly chronic (carcinogens, teratogens)
> max levels (WHO/FAO) monitored by UK FSA and DEFRA
> recall of products if higher than max allowed (eg. Dioxins in pork)
> VMD statutory residue surveillance for vet medicines and environmental residues
