Biosecurity livestock Flashcards
What is biosecurity?
‘The combination of all the different measures implemented to reduce the risk of introduction and spread of disease agents’
The prevention of disease-causing agents entering or leaving any place where they can pose a risk to farm animals, other animals, humans, or the safety and quality of a food product. The same principles apply
within the farm, preventing disease spreading between animals and
groups.
Importance of biosecurity
Fundamental to disease prevention and control Prevent and control endemic and exotic diseases Aims to reduce the infection pressure on the livestock Reduce the need for treatments (antimicrobials etc) Reduce morbidity and mortality
Considerations in biosecurity planning
- Prevent or minimise contact between sources of infection and susceptible animals
- Reduce the infection pressure (we cannot keep animals in sterile conditions)
- Focus on high-risk transmission routes
- Consider probability of transmission and frequency of occurrence
- Larger herds or flocks are more at risk – biosecurity must improve with farm size
External biosecurity
bio-exclusion – aims to keep pathogens out of the herd, farm, region, country
Internal biosecurity
– bio-management – aims to prevent the spread of pathogens within a herd or flock
Why is livestock disease important?
Disease reduces production = reduced farm income
Protein output losses Reduced weight gain Reduced yields
Stock & genetic losses
Disease increases costs
Treatment costs – medicines, vet bills
Increased labour – time spend on treatment and care
Disease affects … animal welfare, consumer perception, pride in the job Zoonoses – human health implications – also a cost involved
The triad of disease causation
Environment
Host
Agent
The triad of disease causation
Host
Characteristics:
• Age • Prior exposure • Susceptibility • Co-infection • Immune response
Interventions:
• Treat, isolate • Immunize • Nutrition
The triad of disease causation
Agent pathogen
Characteristics:
• Toxicity, virulence, infectivity • Susceptibility to antibiotics • Ability to survive outside body
Interventions:
• Eradicate • Genetically modify
The triad of disease causation
Environment
Characteristics:
• Climate • Physical structures • Population density • Social structure
Interventions:
• Housing quality • Sanitation, water • Preventive services
Transmission of infection
Possibilities:
Horizontal – direct or indirect between animals
Vertical - from one generation to the next – hereditary or congenital
- Hereditary – carried in genome of parent e.g. avian leukosis virus (Retrovirus) - Congenital – present at birth, acquired in utero e.g. paratuberculosis (Johne’s)
Routes of infection: entry points
How can infectious agents enter the host? Oral - ingestion
Respiratory system - inhalation
Skin
Mucous membranes – oral, eye, vaginal Iatrogenic – needles, rectal examination
Disease transmission routes - exits
Transplacental Faeces Urine & venereal contact, uterine discharge Milk Skin, esp. on feet Ocular discharge Nasal discharge, aerosols, droplets Oral (saliva, vomit (not cattle), bites)
Modes of pathogen transmission
• Contact – direct or indirect – some pathogens do not survive well outside host; others can survive in environment for a long time
• Airborne – infectious aerosols – very small particles < 5μm – suspended and potentially carried long distances – very good penetration of alveoli in lungs
• Droplet – common for respiratory pathogens – suspended in larger particles > 5μm – fall to ground faster – more often trapped in mucous of respiratory
epithelium
Fomites
– contaminated ‘things’ – boots, buckets, water troughs, lorry wheels
Vectors
e.g. flies, midges, mosquitoes (mechanical or biological)
Airborne transmission
For successful airborne transmission:
1. Pathogen needs to be aerosolised
2. Must remain infectious in the aerosol
3. Must gain entry to susceptible host tissue
Humans – Tuberculosis, chicken pox, measles
Livestock – Foot and Mouth Disease virus, Mycoplasma hyopneumoniae
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Droplet transmission
- Definition: ‘The transmission of diseases by expelled particles that are likely to settle to a surface quickly, typically within 3 feet (1 metre) of the source.’ (Fernstrom & Goldblatt, 2013)
- Overlaps with airborne at short distances, but these droplets much less likely to travel longer distances
- Implications at pen and fence boundaries
Biosecurity in transport - legislation
• The Transport of Animals (Cleansing and Disinfection) (England) (No. 3) Order 2003 (as amended)
‘Cleansing and disinfection in relation to the transport of hoofed animals and poultry
3.—(1) This article shall apply in relation to the transport of— (a) hoofed animals, other than horses ……
(3) The user of any means of transport which has been used to transport any animal, or anything which may give rise to a risk of transmission of disease, shall, as soon as reasonably practicable and not more than 24 hours after the journey is completed, ensure that it and any equipment are cleansed and disinfected in accordance with Schedule 2 …’
Biosecurity at markets
- Cleansing and disinfection – during and after sales
- State movement controls – bTB restrictions on farms
- Sick animals should not come to market
- Inspection on entry
- Isolation – including separate sales for accredited stock
- The unseen infections – mixing animals - BVD, Johne’s, bTB, IBR, Maedi- Visna etc.
- Record keeping – animal identification - tracing – [BSE largely drove cattle id in EU; FMD in 2001 drove individual sheep id]
Foot and Mouth Disease - UK in 2001
‘The FMD epidemic in the UK in 2001 occurred almost entirely in sheep in a country that had been FMD-free, without vaccination for a considerable period of time and where the industry was of a highly complex nature involving dealers, markets and movements.’
Abattoir lairage biosecurity
- Necessity for ante-mortem animal health checks
- Cleansing and disinfection of vehicles and crates
- Lairage hygiene – meat hygiene
- Animals not returning to farm
Feed mill biosecurity
- 2003 feed-borne outbreak of Salmonella Cubana occurred in Sweden as a result of contamination in an animal feed plant
- Salmonella Cubana was detected in 49 out of 77 pig farms having received possibly contaminated feed
External biosecurity – purchasing policy
• Do you really have to buy in pigs? The benefits of a closed herd
• Introducingnewgenetics(gilts,boars),herdexpansion,replacements,
‘bed and breakfast’/rearing arrangements
• Pigsorsemen(fresh/frozen):respectiverisks
• Sources–Trustedhealthstatus?Tested?Incomingfrequency(feweroccasionsbetter)
• Quarantined–facilityonfarm.Vaccines?Atleast4weeks(butPRRSandPCV26-8wks;M. hyopneumoniae 8-10 wks)
External biosecurity – transport
- Pig transport vehicles – major risk – loading bay on perimeter ideally
- Pig carcasses – storage and then collection by a renderer
- Slurry/manure – Access from the perimeter if possible
External biosecurity – incoming feed/water
• Feed lorries should not enter the farm – siting of feed bins on perimeter
• Feed quality – concentrate pasteurisation at mill
• Straw bedding – Salmonella (birds, rodents), avian TB,
ringworm
• Water supply? Contaminated wells, biofilms in pipes and header tanks
External biosecurity – visitor policy
• Regular workers v Occasional visitors (e.g. vets)
• Humans can act as mechanical vectors to transmit
infection – footwear, clothing
• Proven examples – transmissible gastroenteritis virus (TGE), Escherichia coli, Classical Swine Fever
• Humans can also pass influenza and methicillin-resistant Staph. aureus to pigs
• Shower policy on high health farms; 24/48 hrs pig-free on some units too
External biosecurity – local environment
- Location – pig density? New farm – consider carefully
- Nearest neighbour - aerosol transmission risk, esp. <2km • Passing traffic – near road, abattoir
- Wild animals – wild boar risk in mainland Europe (ASF)
External biosecurity – vermin, birds, insects
• Vermin control is a never-ending (but essential) task on a pig farm! See Meerburg & Kijlstra (2007): https://onlinelibrary.wiley.com/doi/full/10.1002/jsfa.3004
• Wild birds have also been associated with carriage of pathogens onto pig farms, but control is very difficult
• Insects such as the common housefly (Musca domestica) and beetles can carry pathogens onto and around pig
farms
Internal biosecurity – disease management
• Farm health plan with vet – a working document
• Diagnostics, isolation of sick animals, treatment protocols, vaccination
considerations
• Colostrum – quality and quantity – essential and underestimated
• Avoid returning ‘poor doers’ into younger aged batches
• Needle use and medicine storage (expiry dates, storage conditions)
• Piglet management – cross-fostering and equipment use
• All-in, all-out principle (farrowing house, weaners, fatteners)
• Housing conditions – ventilation (pathogens, dust levels, ammonia), temperature, stocking density
Internal biosecurity – farm hygiene
• Cleansing and disinfection policy in pig housing
• Detergents and disinfectants – correct
concentration.
• Examine the potential for the farm workers to carry infection from one shed/age group to another (esp. older to younger)
• Equipment hygiene, clothing, boots, boot dips, separation
• Farm dogs and cats as mechanical and biological vectors
Salmonellosis in pigs
- Infection often inapparent and endemic – subclinical
- Clinical – diarrhoea, septicaemia
- Any age, most common weaners and growers • Serotypes found in pigs are zoonotic
• Genus Salmonella has > 2500 serotypes
• Most common serotypes in UK pigs in 2017:
S. Typhimurium (30%); 4,5,12:i (30%); 4,12;i (28%)
• Entry into herds – breeding stock, feed, fomites, rodents, wild birds
• Oro-faecal transmission – long survival in dust
• Carriage in tonsil and terminal ileum – shedding can be intermittent
Salmonellosis - control and prevention
- Hygiene - all-in all-out housing and disinfection • Isolation of affected pigs
- Rodent control
- Exclude birds (outdoors impossible?)
- Pasteurised feed - try to prevent feed contamination
- Treat cases (AMR concerns) and cull chronically-affected animals
Rodent control
- Rodents can shed millions of Salmonella bacteria in their droppings – control an ongoing challenge on pig farms.
- Also eat feed and damage electrical wiring.
Sheep farm biosecurity - challenges
- Hosie & Clark (2007): ‘Most UK sheep farmers take no animal health precautions either when introducing purchased animals to their flocks or at farm boundaries’
- Bellet et al. (2015): ‘Although most veterinarians believed that they provided a good service, they also believed they did not see their (sheep) clients sufficiently often, nor that their clients were aware of the services they could offer’ (PVM 122, 381-388)
Flock health security
Five levels of flock security:
- No flock health security – infectious diseases common and costly
- Flock health security – general reduction in introduction of disease
- Flock health security + specific disease targeting – prevention plus steps towards eradication
- Flock health scheme with strict adherence – structured eradication, monitoring and certification of disease-free status
- Specific pathogen free flock – experimental flocks or high genetic merit free of specific pathogens (e.g. scrapie)
Sheep – external biosecurity - purchases
- Purchase policy – buy in minimum possible
- Rams – consider health status of source flock – accredited?
- Breed own replacement ewes?
- Advanced fertility services – embryo transfer and laparoscopic AI
- Avoid markets if possible – source directly from farm
- Never buy sheep of unknown origin - examine before purchase
- Quarantine on arrival at farm (at least 4 weeks) – testing, treatments and vaccinations – health plan policy
- Be very mindful of anthelmintic resistance.
Sheep - external biosecurity
• Visitors to the farm – vets, shearers, dippers, scanners
• Incoming feed supplies
• Sheep contact at farm boundaries – fencing, common grazing, stray sheep • Dogs – hills, public rights of way – fouling:
Tapeworm Taenia multiceps oncospheres in dog faeces – ingested by sheep as intermediate host – ‘gid’ – cysts in brain/spinal cord
Tapeworm Taenia hydatigena oncospheres – cysticercosis in sheep liver – abottoir condemnations common
Tapeworm Taenia ovis oncospheres – cysticercosis in sheep muscle (often heart) – abattoir condemnation
External biosecurity – diseases to consider with sheep
Sheep scab Enzootic abortion of ewes (EAE) Footrot Maedi Visna (MV) Ovine pulmonary adenocarcinoma (OPA) Border disease Caseous lymphadenitis (CLA) Paratuberculosis (Johne's disease) Anthelmintic-resistant worms
Sheep – internal biosecurity
• Toxoplasma gondii is the second most common cause of abortion in sheep in UK (after EAE)
• Oocysts from cat faeces are ingested on feedstuffs
• Causes multifocal necrotic foci on placenta and
foetal organs – liver, brain – leads to abortion
• Need to protect sheep feed to reduce chances of contamination by cats
• Toxoplasmosis is a zoonosis
Considerations in biosecurity planning
- Prevent or minimise contact between sources of infection and susceptible animals
- Reduce the infection pressure (we cannot keep animals in sterile conditions)
- Focus on high-risk transmission routes
- Consider probability of transmission and frequency of occurrence
- Larger herds or flocks are more at risk – biosecurity must improve with farm size
Cattle purchase as a risk factor for bTB
- Looked at farm-level risk factors for long-duration bTB breakdowns
- 2016-2018 period – case-control study design
- Purchase of infected animals strongest association with these long outbreaks
- Mainly beef fattening herds buying in cattle
Why do farmers buy cattle?
• Research based on interviews with cattle farmers in N. Ireland • SVEPM conference, Dublin 2014
• Various reasons for attending and buying cattle in markets:
- Wide choice of animals all in one place
- Can judge the value better
- Spontaneous purchases
- If it’s in the market, assume it must be bTB-free - Enjoy bidding for cattle
- Social aspects – meet other farmers
Contact chains – moving cattle
‘In addition to the established role of markets as a ‘mixing pot’ for highly transmissible diseases while animals are on site, here we emphasize their part in facilitating the dispersal of animals to many premises from one source farm, thereby potentially amplifying the spread of fast and slow-spreading diseases alike.’
