Foodborne zoonoses and control Flashcards
What is zoonoses?
- infections/ disease that are naturally transmitted between animals and humans
- 60% pathogens = zoonotic
- 75% of emerging infectious diseases have roots in zoonotic pathogens
What are FBDs?
- food borne disease
- acute illnesses that are associated with the recent consumption of food
- contain a pathogen/ toxin
What is the worldwide impact of foodborne disease?
- 2.5 million deaths/year from diarrhoeal disease
- 1.4 million cases of salonella - USA
- $35 billion loss to economy
- death of HIV patients
Difference between foodborne infection and intoxication?
- infection - caused by an infection of bacteria etc
- intoxication - toxin - more rapid onset
What are foodborne infections caused by?
- pathogenic microorganisms infecting food, entering the body and the reaction of the body tissues to the pathogen
- long incubation periods
- fever
`Symptoms of food borne infection?
- diarrohea
- fever
- sweating
- cramps
- nausea
- vomiting
- dehydration
What are the different types of food borne infections?
- bacterial e.g. Salmonella, E.coli, Listeria
- virus e.g. Hep A
- Mycotic e.g. Candida spp
- Parasitic - toxoplasma, protozoa, roundworms, tapeworms
Properties of Salmonella?
- G-ve
- rod shaped
- anaerobic
What are the 2 species in the genus (salmonella)
- S.enterica
- S.bongori - cold blooded
How many serovars does S.enterica have?
- 2,500
What are the 3 most common Salmonella causes of infections?
- S.enteritidis
- S. tymphimurium
- S. Dublin
Incubation period of Salmonella?
- 12-36 hours
How many organisms per gram do you need of Salmonella to cuase infection?
- 1,000 -> 1,000,000
How are Salmonella killed?
- commercial pasteurisation - 85 degrees for 15 mins/ 4 degrees
- not killed by freezing/ chilling carcasses
- survive in moist earth - 1 year
- in dry earth - 16 months
WHere do most outbreaks of salmonella come from?
- eggs (50.5%)
How are developing eggs infected with salmonella?
- transovarian transmission
What are the properties of Campylobacter and which are the important human pathogens?
- thermophilic - 41/42 degrees
- microaerophilic
- g-ve
- spiral rods
- C.jejuni and C.coli most important
Describe Camp outbreaks
- more sporadic
- rare
- but have low infectious dose
What is the reservoir and incubation period of Camp?
- reservoir - intestinal tract of poultry/wild birds
- incubation - 2-5 days
Symptoms of Camp?
- watery, bloody diarrhoea, nausea, vomiting, headache, fever, abdo pain
- self limiting
- mod to severe
In what groups in camp most common?
- 65+
- bowel cancer
- proton-pumps
What is the reservoirs and symptoms for Listeria?
- reservoir = plant material and soil
- 12.7% mortality
- flu like, abortion, septicaemia, meningoencephalitis
- incubation - 3-70 days
Properties of E.coli?
- only a few pathogenic strains
- O.157 - pathogenic
- linked to poorly cooked beef/ minced
- part of normal gut flora
- can be beneficial - Vit K
What does enteroinvasive E.coli cause (EIEC)?
- watery diarrhoea (bloody in under 10%)
- abdo pains, nausea, headaches, fever
- self limiting
- 18 hours median
- 10^8 bacterium needed
- lasts 2/3 days
What symptoms fo EHEC cause?
- causes haemorrhagic colitis
- bloody diarrhoea
- vomiting
- sometimes fever
- incubation: 3-4 days
- lasts 4-8 days - up to 13
- O157:H7
- hemolytic uremic syndrome (HUS)
What do Yersinia and Shigella cause?
- Yersinia - causes enterbacillae yersiniosis
- 4 shigella species - dysentry - can be food borne or person to person
How are food borne intoxications characterised?
- short incubation
- no fever
Categories of food borne intoxications?
- bacterial
- fungal chemical
- poisonous
- plant
How does S.aureus cause foodborne intoxication?
- G+ve, fac. anaerobe, non-spore forming cocci
- enterotoxins formed by the S.aureus (A,B,C,D,E)
Nature of the enterotoxins?
- temp stable
- pH stable
- enzyme stable - trypsin, chymotrypsin, renin, pepsin
- not sensitive to irradiation
How does S.aureus compete with other micoorganisms?
- poorly
- doesnt grow very well
- so normally in foods where all other microorganisms gone - cooking etc.
WHat are the vehicle foods and reservoirs for S.aureus?
- milk
- poultry
- meat
- shellfish
- eggs
- salad cereals
- veg
Reservoirs:
- mucous membranes of nasopharynx and skin
- some in air, water, dust, faeces
Disease symptoms of S.aureus?
- nausea, abdo cramps, vomiting, salivation
- 1-6 hours after ingestion of enterotoxin
- lasts for 24-72 hrs
Describe Bacillus cereus poisoning
- G+ve, spore forming rod
- produce heat stable toxins:
- emetic
- diaroheal:
- haemolysis BL
- non-haemolytic
What are the vehicle foods of Bacillus cereus?
- meat, eggs, dairy products
- cereals - if not cooked and not chilled then spores can germinate, bacteria and toxins produced
- re-heating does not kill toxins
- spores not killed
Symptoms of B.cereus in man?
- emetic syndrome
- nausea, vomiting, abdo cramps
- 1-6hrs after diarrohea
- diarrhoeal syndrome
- profuse diarrhoea
- abdo cramps
- tenesmus
- 8-16 hours after ingestion
What Clostridiums cause food poisoning?
- G+ve, spore forming rods
- C.perfringens and C.botulinum - severe
- C.difficile - antimicrobial chemotherapy - resistant
What is C.perfringens and what does it cause?
- g+ve, anaerobic, spore forming
- soil, dust, sewage, marine sediments
- spores can resist boiling for 4 hours
- ingest vegetative cells
- multiply in intestine and produce CPE
- CPE = heat labile - 60 degrees for 10 mins
- may be pre-formed - 1-2hours after
Vehicle foods for C.perfringens?
- meat, fish, veg, chicken, pork, fruits, spices
- cooking = heat resistant endospores
- cooling, warming - endospores germinate
- food cooked one day then eaten the next
- anerobic conditions increase this
- need to reach 10^7/8
Symptoms of C.perfringens?
- nausea, vomiting, diarrhoea, cramps
- 6-24 hours
- 1-2 days duration
- needs to reach 5 x 10^8 cells
What does C.botulinum cause?
- obligate, anaerobic, spore forming bacillus
- spores -> vegetative cells -> enterotoxins
- poorly canned/ bottled - honey
- enterotoxins - blocks synapses - paralysis and death
- Toxins - A, B, E, F, G
- spores - survive 120 degrees
- Heat liable toxins - 80 degrees for 10 mins
- resists action of gastric and intestinal juices
- any foods associated with anerobic conditions - cooked meats (canned), fermented foods
Symptoms of botulinum toxins?
- paralysis
- nausea
- double vision
- respiratory failure
- headache
- lack of fever
- great muscular weakness
- fatigue
- 60-100% mortality
duration of botulinum illness?
- 1-10 days
