Lecture 2 Flashcards
- What is the main route of transmission for most bacteria?
- When does the gut microflora of animals start to establish and how is it established?
- Once established, what is the benefit of the microflora?
4.How can the gut microflora be disrupted? – Examples.
- Faecal-oral
- From birth – established maternally and environmentally.
- Prevents colonisation of harmful pathogens.
- Stress – eg parturition, weaning, diet change, mixing animals) – and antimicrobial therapy.
- What is an important source of salmonella?
- Contaminated feed.
How can feed become contaminated?
How can this be combatted?
From faecal matter from other positive animals e.g. birds/rodents when stored on the farm.
Importation of already-contaminated feed.
Statutory testing of animal protein for livestock feed
How can type of diet be a causing factor?
Diet-type affects shedding of E.coli O157. E.coli populations are higher in grain fed animals, and switching to grass/hay-based diet reduces E.coli O157 shedding into the environment.
What is a major source of Listeria monocytogenes on the farm?
Why does this happen?
How can it be prevented?
– How does this work?
What can be the result of an L. monocytogenes infection?
Silage
Improper preparation (where air is not properly excluded or excluded quickly enough.)
Proper silage production.
Low oxygen levels mean aerobic bacteria levels are low and lactic acid bacteria can proliferate with rapid fermentation. Lactic acid bacteria produce lactic acid and further eradicate harmful bacteria.
Abortion, encephalitis and septicaemia in cattle and sheep.
How can spread occur between animals?
Group housing.
Introduction of infected new animals.
Introduction of new animals increases stress and causes increased shedding in carriers.
Effect of age on pathogen spread.
Gut colonisation of E. coli O157 is easier in young cattle.
Biggest reservoir of salmonella spp found in grower pigs and finisher pigs, but younger animals over 8 weeks are mire likely to be clinically affected.
How can spread occur by birds, rodents and other animals?
Vehicles for spread within and between farms.
Mice carrying Salmonellae can shed 100 pellets in 24 hours – sufficient to infect an animal.
E. coli O157 isolated from gulls, geese, wild rabbits, rats, dogs, horses and deer – sharing farm land.
How can pathogens be spread through the environment?
Faecal oral route
But also a hygiene problem.
Pathogens can survive in non-animal habitats e.g. soil, faeces, bedding, wood, wood, brick, iron, steel, concrete.
Contaminated material is disseminated by dust, aerosols, wind and water (hosing, rain). – E. coli can survive in rain water and puddles for 6 weeks.
Humans are one of the biggest causes of spread around the farm e.g. if they don’t disinfect boots between pens etc.
How can spread in the environment be controlled by building design?
Good ventilation
Adequate drainage
Not leaking
Avoid build up of contamination around feeders and drinkers (Important source of E.coli O157 – can survive there for 4-5 months).
Stocking densities
Slatted floors generally dirtier than straw bedding but cleaner than solid floors.
How does animal waste contribute to pathogen spread?
How does abattoir waste contribute to pathogen spread?
Pathogens present in manure/slurry can survive for up to 3 months depending on the source of manure, temperature, aeration, drying, pH and manure composition. – important to mature slurry for more than 3 moths before spreading onto pasture.
Lairage, blood and gut contents. 2003 survey found Campylobacter and Listeria monocytogenes in wastes from red meat abattoirs.
On-farm control measures – good hygiene practices.
If disease diagnosed, correct procedures must be followed.
Operate all-in, all-out policy.
Disinfect pens between batches of animals.
Avoid mixing animals (avoid stress).
Use a reliable source of livestock (disease-free).
Disinfect vehicles used for transportation.
Train staff to disinfect boots and equipment and keep work clothes on site.
Restrict visitors.
Effective programme for control of vermin.
Regular cleaning of water troughs.
Store wastes for 3 months prior to spreading onto land.
Good feed management – reliable source, fermented feeds, pellet feed, feed testing. proper silage production.
Monitor stock for diseases and follow National Control Plans.
Vaccination – e.g. of layers and broilers against s. Enteritidis and S. Typhimurium.
Consequences of stress at transport and market.
Affects meat quality – use of glycogen in muscles.
Increase in catecholamine production.
– Reduces immune system so infected more easily and carriers can be reactivated.
– Reduces gut transit time so more faecal material excreted to the environment and therefore more pathogens in environment.
– Decreased gastric acid production so more bacteria can survive passage through GIT so more pathogens excreted into the environment.
Food withdrawal around time of slaughter. – Why? Consequence?
12-24hr prior to transport.
Done to reduce gut fill at slaughter, reduce level of faecal material carried, and avoid gut puncture and reduce faeces on the carcass.
Consequence = stress – High proliferation of coliforms, increased gut movement and increased bacterial shedding.
How can stress be kept at a minimum during transport?
Journey as short as possible.
Calm handling
Ventilation
Avoid unloading and re-loading, and unnecessary stop-overs where possible as it compounds the stress effect.
