Public Health and Food Safety Flashcards
What is the main contributor of contamination of the carcass?
Hides during skinning
What are the 2 approaches to control carcass bacteria?
Clean up the final carcass (USA)
Control the level of contamination entering the abattoir, reducing levels on the inside and the outside of the animals (UK)
What does the enteric form of salmonellosis cause?
Inflammation of the ileum and is less severe. Recovery after 1 week with carrier state
What are the clinical signs of septicaemic form of salmonellosis?
Restless
Inappetent
Have fever
Watery diarrhoea
Bury in the straw
Have blue/red colouration on ears, limbs and back
What are the reservoirs of E.coli?
Beef and dairy cattle are important reservoirs, isolated from sheep, pigs, goats, horses and deer
How does E.coli affect animals and humans?
Asymptomatically carried in caecum and colon of animals. Pathogenic to man but not to animals
What is the infectious dose of E.coli?
Very low – 10-100 cells
What is the pathogenesis of E.coli?
Organism invades colon – mild non-blood diarrhoea to haemorrhagic colitis
What is the role of the gut microflora?
Gut microflora begins to establish from birth and is then stable and well-balances, preventing pathogen colonisation.
What disrupts the gut microflora?
Stress from parturition, weaning, diet change or mixing of animals, as well as antibiotic therapy disrupts the gut microflora and increases susceptibility
How can feed be a source of salmonella?
Feed can be contaminated with faecal material from other positive animals
What is the role of silage in disease for cattle and sheep?
If air is not properly excluded/excluded quickly, organisms such as L. monocytogenes proliferate. Silage is a major source of this organism on the farm. Causing abortion, encephalitis and septicaemia.
Why does age affect E.coli colonisation in cattle?
Gut colonization is easier in young cattle. Calves shed for 189 days, adults 100 days
How does age affect salmonella?
Biggest reservoir is growers and finishers. But younger animals, over 8 weeks, are more likely to be clinically affected
What are the control measures at transport, market and lairage?
- Keep stress to a minimum at all stages
- Ensure calm and proper handling
- Follow appropriate guidelines for transportation of animals
- Transporters to be cleaned and disinfected
- Holding pens to be regularly cleaned and disinfected, adding clean bedding
- Animals for slaughter to be clean and disease free
- Use best practice whenever possible
What are the 2 broad categories of aquatic animal production?
Capture fishery/wild catch from wild and freshwater
Aquaculture production
What are the systems used in aquaculture?
- Recirculation systems (closed)
- Open basins
- Sea based seed systems
- Rope cultivation
- Open-pen sea cages
- Combinations
What are the nutrient contents of fish?
- Fat – highly unsaturated and lots of phospholipids
- Carbohydrates – negligible, except 3% glycogen in molluscs
- Minerals – low but full range
Name 3 processes in spoilage of fish.
Enzyme action
Action of bacteria
Chemical action
How does enzyme action affect fish spoilage?
Breakdown of ATP: ATP > inosine > hypoxanthine (indicator)
How does bacterial action affect fish spoilage?
Reduction of trimethylamine N-oxide/fish molecule to trimethylamine. Breakdown of amino acids and formation of primary amines. Ammonia production.
How does chemical action affect spoilage of fish?
Fatty fish has oils oxidise and have rancid smell. Level of peroxide value and free fatty acid > index of quality.
How do fish eyes indicate spoilage?
After catch: convex, crystal clear cornea
Medium stage: flat/slightly sunken, some loss of clarity of cornea
Spoiled: sunken, cloudy, discoloured cornea
How do the gills indicate fish spoilage?
After catch: bright red or pink, clear mucus
Medium stage: flight loss of red colour and brightness
Spoiled: bleached and/or discoloured, thick slime
How does the skin indicate fish spoilage?
After catch: well differentiated colours, glossy, transparent slime
Medium stage: slight fading of colours, slightly milky slime
Spoiled: loss of colour, yellow, knotted slime
How is odour indicative of fish spoilage?
After catch: sharp, sea-like, iodine like, metallic
Medium stage: slightly fishy, cut grass, shellfish-like, musty, garlic, lactic acid
Spoiled: stale cabbage-water, sour drains, wet matches, ammoniacal, trimethylamine
How is fish spoilage reduced/prevented?
- Chilling – short term preservation
- Freezing – long term preservation, effective for retaining flavour, colour and nutritive value
- Drying/salting
- Canning
- Controlling autolytic enzymatic spoilage by gutting
Where is bacteria on fish?
Fish meat is sterile. Bacteria are on skin, gill entrances, intestines
What is microflora of water a determinant of?
Determinant of bacterial types and numbers on fish
How does cold and warm water affect fish contamination?
Cold water will have less contamination than warm water
Why are molluscs at high risk of contamination?
They are filter feeders
What residues are tested in fish as a legislative requirement?
- Heavy metals
- Antibiotics
- Malachite green – treatment of external fungal and protozoal diseases
- Organophosphorus pesticides
- Organochlorine pesticides
- Ivermectin – treatment of external and internal parasites
What is vibrio parahaemolyticus/vulnificus and how does it cause food poisoning?
Halophilic organisms isolated in finfish, shellfish, and crustaceans. Oysters main culprit due to warm water and high contamination. Causes vomiting, diarrhoea, fever/chills are usually self-limiting
What does leptospira icterohaemorrhagiae cause food poisoning?
Rat urine contamination of fish farm feed sheds
How can those with deficiencies suffer histamine/scombroid poisoning?
Spoilage bacteria convert it to histamine. Diaminooxygenase degrades ingested histamine. Those with deficiencies can suffer histamine poisoning.
What are the symptoms of initial histamine poisoning due to scombroid poisoning?
Very rapid onset. Initial facial flushing and sweating, burning peppery taste sensations in mouth and throat, dizziness nausea and headache
What are the symptoms of progressed histamine poisoning?
Progresses to facial rash, hives oedema, short term diarrhoea and abdominal cramps
What are the symptoms of severe histamine poisoning?
Severe results in blurred vision, respiratory stress and swollen tongue
How do you get ciguatera fish poisoning?
Eating reef finfish containing ciguatoxins derived from dinoflagellates
What are the symptoms of ciguatera fish poisoning?
Myriad of GI, neuro and cardiovascular symptoms
How is ciguatera fish poisoning prevented?
- Difficult to prevent, toxin is odourless and tasteless
- Toxins are not removed by cooking or freezing
- Avoid eating large reef fish, large predatory reef fish and their viscera
What is Anisakis simplex/herring worm?
Parasitic nematodes
- Pseudooterranova decipens – cod or seal worm
- Contracaecum species
- Hysterothylacium species
How do you get Anisakis simplex/herring worm?
Ingested raw or undercooked finfish or squid
What is the pathogenesis of Anisakis simplex/herring worm?
Worm coughed up/vomited/manually extracted > burrow into the gut wall and occasionally penetrate > attract eosinophils > form granuloma around worm > appendicitis like pain > normal host response eliminates worm, usually no more than 3 weeks post ingestion
What is Diphyllobothrium latum?
Broad tapeworm with human DH
What does Diphyllobothrium latum cause?
- Mostly asymptomatic
- Can cause megaloblastic anaemia
How can Diphyllobothrium latum be prevented?
Adequately freezing or cooking fish will kill the parasite
How do you get shellfish poisoning?
Shellfish concentrate toxins in their tissue. No specific treatment and ordinary cooking/freezing does not elimate toxin
What are the toxins produced shellfish?
Paralytic shellfish poisoning (PSP)
Neurotoxic shellfish poisoning (NSP)
Amnesic shellfish poisoning (ASP)
Diarrheal shellfish poisoning (DSP)
How are eggs designed so that they have a shelf life of 21 days?
Shell outside has pores to allow gas exchange, sealed waxy cuticle, inside there are antimicrobial proteins in the albumin, albumin is very low in iron (essential to bacterial growth), yolk contains glucose (where things grow).
Why are eggs not washed in the UK?
Cuticle provides protection. If eggs are washed, the cuticle can be replaced by soap, wax, oil or cactus juice and so must be refrigerated afterwards
What is the main form of salmonella?
Salmonella enterica serovar typhimurium
What are the vehicles of infection of eggs?
Raw or undercooked egg
When is the greatest risk of death of salmonella?
Risk of death is up to 3 times greater in year post-infection
How does poultry system type affect prevention of salmonella?
Options are more limited in extensive systems, as intensive systems there is not enough time for immune system to develop for vaccination before they are selling/slaughter weight. Vaccination will protect all systems in egg layers.
How do enriched cages affect poultry susceptibility to salmonella?
Enriched cages = increased cortisol to adapt to surroundings = shed more salmonella = less good immune system, shuts down T cell signalling = physiologically different birds.
How is salmonella enteritidis in chickens different to other salmonella forms?
Does not stay in the gut. Migrates to oviduct and colonises the ova. Eggs are freshly contaminated in the yolk. Once in the oviduct, it will cause inflammation, causing more ova to be released and more eggs produced.
How does salmonella enteritidis affect chickens?
Subclinical
What is done with eggs from infected flocks?
Cannot go directly for human consumption
If you produce eggs on a commercial basis, what must you do?
Take samples
When do flocks not need testing?
- All production is for private domestic use
- The premises has fewer than 350 hens and supplies the consumer direct – farm gate or local retailers
How many species of bees are there?
- 7 species of honeybee. Apis mellifera is the most common species in the UK
What is infant botulism?
The only real public health concern with bees. Clostridium botulinum spores. Rare bacterial infection
What are the clinical signs of infant botulism?
Constipation, muscle weakness, difficulty eating and breathing
How can infant botulism be prevented?
Honey should not be given to infants less than 1 year of age
What is the national surveillance scheme for honey sampling?
Testing for residues of banned substances (e.g. neonicotinoids), contaminants and authorised vet meds.
What is varroa mite in bees?
Major cause of colony collapse – high economic losses worldwide. Spreads viruses as a vector
What is the pathogenesis of varroa mite?
- Attaches to the bee body
- Sucks haemolymph
- Varroosis
What is the main defence against varroa mite?
Pyrethroid insecticide
Resistance now widespread
What are the 2 forms of foulbrood?
American foulbrood – paenibacillus larvae – a spore forming bacterium
European foulbrood – melissococcus plutonius – non-spore forming bacterium that survives in wax
What is the pathogenesis of American foulbrood?
Fatal, no cure. Infection when larvae ingest spores during feeding > germinate in larvae guts, replicate to high numbers > very resistant and long lasting spores
What is the main cause of spread of American foulbrood?
Beekeeping practices and adult bees
How is American Foulbrood controlled?
Destruction of infected hives and irradiation of contaminated equipment
What is the pathogenesis of European foulbrood?
- Larvae become infected after ingesting food contaminated with the bacteria.
- Replicate in the mid gut of larvae
- Compete for food, larvae starve
- Infection can be present for years without complete destruction of colony
How is European foulbrood controlled?
Destruction of heavily infected hives, antibiotic treatment possible, shook swarm/transfer of bees to new combs.
How is AFB and EFB distinguished?
EFB is a stress disease, unlike AFB
What are the characteristics of colony collapse disorder?
- Complete absence of adult worker bees
- No dead bees visible around the hive
- Live queen
What are the potential causes of colony collapse disorder?
- Pathogens
- Climate change
- Pollution
- Pesticides – neo-nicotinoids insecticides are banned in the EU
- Wax moths
- Mobile phone signals
What are the factors causing decline of bees in the UK?
- Climatic conditions
- Increased prevalence of pests/disease
- Pesticides cause bees to have very erratic and disorientated movement and area unable to find way back to hives.
What are microbial criteria?
Set of microbiological indicators used to determine whether a specific food lot is acceptable (safe) or not. Used to indicate the required microbiological status of raw materials, ingredients and end-products at any stage of the food chain
What is food safety objective?
Maximum frequency and/or concentration of a microbiological hazard in a food at the time of consumption.
What is performance objective?
Maximum frequency and/or concentration of a hazard in a food at a specific step in the food chain before the time of consumption that provides or contributes to an FSO or ALOP.
What is performance criteria?
Effect on the frequency and/or concentration of a hazard in a food that must be achieved by the application of one or more control measures to provide or contribute to a PO or an FSO
What are the 2 types of microbial criteria?
Food Safety Criteria – assess the safety of a product or a batch of foodstuffs
Process Hygiene Criteria – assess the hygiene of the production process
How can sampling in red meat abattoirs be carried out?
Excision method
Sponge swap
What is excision method when sampling in red meat abattoirs?
Sterile cork border scores the surface tissue and removed using a sterile scalpel. Can only use this method for the determination of PAC and Enterobacteriaceae.
How are poultry carcasses sampled?
Neck skin sampled by excision – 5 samples per session (1 sample = 3 skins). Sampling carried out after carcasses have been chilled for 1.5 hours.
How are processed meats sampled?
5 samples from a single batch need to be collected and tested each week
What happens if microbial criteria are failed to be met?
Failure to meet Food Safety Criteria = FBO should not place the foodstuff on the market, product may need to be recalled
Failure to meet Process Hygiene Criteria – the product can be placed on the market but production process needs to be reviewed
What are the methods of rapid sampling in food premises?
- Swabbing methods for contact surfaces in abattoirs
- Protein detectors
- ATP bioluminescence
- VerifEYE screening of red meat carcasses for chlorophyll (= gut spillage)
What are the sources of food contamination in meat?
Guts of animals can contaminate the outside of the animal transferred to the carcass during dressing
What are the sources of food contamination in dairy?
Contamination during milking > pasteurisation problems > contamination post-pasteurisation
How are rodents and birds a source of food contamination?
Carrying bacteria in faeces; shedding into food areas
How are food handlers a source of food contamination?
Organisms carried naturally on the skin, in the nose, poor personal hygiene; handling of foods
How are utensils and equipment a source of food contamination?
Cross-contamination between foods and surfaces; proper cleaning not carried out
How is processing a source of food contamination?
Extra ingredients added to foods, airborne contamination
How is soil a source of food contamination?
Contamination from vegetables
How is water a source of food contamination?
Non-potable water used for washing
How is the environment a source of food contamination?
Bacteria are ubiquitous
What are the intrinsic factors of microbial growth in foods?
Food structure, types/levels of nutrients, antimicrobials, aw, pH and buffering capacity, redox potential
What are the extrinsic factors of microbial growth in foods?
Temperature and humidity of storage, atmosphere
What are the processing factors of microbial growth in foods?
Physical treatment, chemical treatments, increase in microbes
What does the growth of microorganisms in food cause?
Chemical changes. Yeasts produce chemicals quicker than bacteria due to cell volume = quicker spoilage.
What are some substances in food that are naturally inhibitory to microorganisms?
Lysozyme – egg white, milk
Lactoperoxidase system – cows milk
Eugenol - cloves
Allicin - garlic
Allyl isothiocyanante - mustard
Thymol - sage, oregano
What are some antimicrobials are produced by bacteria?
Lactic acid
Bacteriocins
Antibiotics
Hydrogen peroxide
How are foods preserved based on water activity?
Lowering the aw will increase the lag phase, decreases growth rate, size of final population and spore germination. Below 0.50 microbes will not proliferate
How are foods preserved based on pH?
Lowering the pH of the food below that which will support microbial growth
How are foods preserved based on freezing?
Cannot grow on frozen foods stored below -12°C. Slow spoilage due to enzyme systems remaining active.
What are the 2 methods of preserving foods based on high temperatures?
Pasteurisation
Sterilisation
How does bacteria get into milk?
Udder infection – depends on pathogens present on the farm
More likely a contamination during milking – dirty udder/cluster/pipes, inadequate parlour cleaning, contaminated water source
What tests are carried out on milk?
Residues - antimicrobials
Somatic cell counts
Bactoscan
Total bacteria count
Fat and protein
Routine statutory disease surveillance (brucella abortus)
Elective disease surveillance (Johnes, neospora, IBR, BVD)
Name the 2 markers of hygienic milk production.
Bactoscan
SCC
What do bactoscans measure?
Identifies live and dead bacteria.
Regulation 853/2004 says milk with more than 100,000 cfu/ml is not suitable for human consumption
What do SCC measure?
A marker of subclinical mastitis and so a marker of hygienic management of cow housing, less a marker of hygienic production.
What diseases can you catch from raw milk?
Campylobacter
Salmonella
E.coli
Q fever
Listeriosis
Leptospirosis
Bovine TB
Why is it important for milk products to be clean?
Many milk products are made using bacteria for fermentation so if we already have bacteria in the milk, it can outcompete the bacteria that are used to make these products, so important for milk to be clean for this reason too.
What causes black spots in cheese?
Remnants of teat sealants
What can give milk a taint?
Herd level issues with ketosis
What is the vet’s role in farm assurance schemes?
- Policy level informing standards
- Enforcing standards
- Supporting farmers to meet standards
- Trusted advice source when it comes to consumer purchasing behaviour
What information does food labelling include?
- Nutritional information
- Place of origin
- Place of processing
- Marketing claim
- Retailer policy
- Production system
- Assurance scheme
What are the BVA 7 principles to evaluate farm assurance schemes?
- Lifetime assurance
- Welfare at slaughter
- Veterinary involvement
- Behavioural opportunity
- Responsible use of antimicrobials and other medicines
- Animal health and biosecurity
- Approach to sustainability and the environment
What are the roles of APHA?
- Ensuring farmed animals in the UK are healthy, disease free and well looked after
- Manage outbreaks of notifiable disease
- Regulate trade of endangered species
- Ensure that dairy hygiene and egg production standards are met
What are the roles of the VMD?
- Marketing Authorisations for vet medicines
- License manufacturers and wholesalers
- Monitor Suspected Adverse Reactions
- Run statutory residue testing scheme
- Policy on veterinary medicines
What is the role of the Food Standards Agency?
- Advises public and government on food safety, nutrition and diet
- Monitoring of food and enforcement of compliance with animal welfare and food safety legislation
- Abattoirs – constant supervision
What are the aims of the Food Standards Agency?
- Reduce food borne illness
- Reduce chemical contamination of food
- Make it easier to choose a healthy diet
- Enable consumers to make informed choices
What are the task undertaken by an environmental health officer?
Waste control
Pest control
Animal welfare
Housing
Nuisance
Food premises licensing and inspection
Enforcement of food hygiene regulations
What are the tasks undertaken by an animal welfare officer?
Market inspections
Animal transport
Identification
Trades descriptions
Animal movements
Cleansing and disinfection
Farm visits
What is disease surveillance?
Monitoring trends and levels (incidence/prevalence) of disease agents within animal and human populations.
What are the aims of disease surveillance?
- To warn potential outbreaks
- To give advanced warning of emerging problems
- To implement control measures on a more global scale
Which international organisations are involved in disease surveillance?
World Health Organisation of the United Nations
Food and Agriculture Organisation of the United Nations
World Organisation for Animal Health
What is SAVNET?
Small animal veterinary surveillance network
What are the aims of SAVNET?
- Monitor disease trends and highlight appropriate interventions
- Identify populations at risk and monitor treatments and outcomes
- Provide data resources
- Improve general public awareness of small animal diseases and prevention
- Provide a route to clinical benchmarking for vets in small animal practice
