Biosecurity livestock

Question 1

What is biosecurity?

Answer 1

‘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.

Question 2

Importance of biosecurity

Answer 2

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

Question 3

Considerations in biosecurity planning

Answer 3

1. Prevent or minimise contact between sources of infection and susceptible animals
2. Reduce the infection pressure (we cannot keep animals in sterile conditions)
3. Focus on high-risk transmission routes
4. Consider probability of transmission and frequency of occurrence
5. Larger herds or flocks are more at risk – biosecurity must improve with farm size

Question 4

External biosecurity

Answer 4

bio-exclusion – aims to keep pathogens out of the herd, farm, region, country

Question 5

Internal biosecurity

Answer 5

– bio-management – aims to prevent the spread of pathogens within a herd or flock

Question 6

Why is livestock disease important?

Answer 6

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

Question 7

The triad of disease causation

Answer 7

Environment
Host
Agent

Question 8

The triad of disease causation

Host

Answer 8

Characteristics:
• Age • Prior exposure • Susceptibility • Co-infection • Immune response
Interventions:
• Treat, isolate • Immunize • Nutrition

Question 9

The triad of disease causation

Agent pathogen

Answer 9

Characteristics:
• Toxicity, virulence, infectivity • Susceptibility to antibiotics • Ability to survive outside body
Interventions:
• Eradicate • Genetically modify

Question 10

The triad of disease causation

Environment

Answer 10

Characteristics:
• Climate • Physical structures • Population density • Social structure
Interventions:
• Housing quality • Sanitation, water • Preventive services

Question 11

Transmission of infection

Answer 11

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)

Question 12

Routes of infection: entry points

Answer 12

How can infectious agents enter the host? Oral - ingestion
Respiratory system - inhalation
Skin
Mucous membranes – oral, eye, vaginal Iatrogenic – needles, rectal examination

Question 13

Disease transmission routes - exits

Answer 13

Transplacental Faeces
Urine & venereal contact, uterine discharge
Milk
Skin, esp. on feet
Ocular discharge
Nasal discharge, 
aerosols, 
droplets
Oral (saliva, vomit (not cattle), bites)

Question 14

Modes of pathogen transmission

Answer 14

• 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

Question 15

Fomites

Answer 15

– contaminated ‘things’ – boots, buckets, water troughs, lorry wheels

Question 16

Vectors

Answer 16

e.g. flies, midges, mosquitoes (mechanical or biological)

Question 17

Airborne transmission

Answer 17

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
25

Question 18

Droplet transmission

Answer 18

• 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

Question 19

Biosecurity in transport - legislation

Answer 19

• 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 …’

Question 20

Biosecurity at markets

Answer 20

• 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]

Question 21

Foot and Mouth Disease - UK in 2001

Answer 21

‘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.’

Question 22

Abattoir lairage biosecurity

Answer 22

• Necessity for ante-mortem animal health checks
• Cleansing and disinfection of vehicles and crates
• Lairage hygiene – meat hygiene
• Animals not returning to farm

Question 23

Feed mill biosecurity

Answer 23

• 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

Question 24

External biosecurity – purchasing policy

Answer 24

• 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)

Question 25

External biosecurity – transport

Answer 25

• 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

Question 26

External biosecurity – incoming feed/water

Answer 26

• 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

Question 27

External biosecurity – visitor policy

Answer 27

• 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

Question 28

External biosecurity – local environment

Answer 28

• 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)

Question 29

External biosecurity – vermin, birds, insects

Answer 29

• 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

Question 30

Internal biosecurity – disease management

Answer 30

• 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

Question 31

Internal biosecurity – farm hygiene

Answer 31

• 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

Question 32

Salmonellosis in pigs

Answer 32

• 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

Question 33

Salmonellosis - control and prevention

Answer 33

• 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

Question 34

Rodent control

Answer 34

• Rodents can shed millions of Salmonella bacteria in their droppings – control an ongoing challenge on pig farms.
• Also eat feed and damage electrical wiring.

Question 35

Sheep farm biosecurity - challenges

Answer 35

• 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)

Question 36

Flock health security

Answer 36

Five levels of flock security:

1. No flock health security – infectious diseases common and costly
2. Flock health security – general reduction in introduction of disease
3. Flock health security + specific disease targeting – prevention plus steps towards eradication
4. Flock health scheme with strict adherence – structured eradication, monitoring and certification of disease-free status
5. Specific pathogen free flock – experimental flocks or high genetic merit free of specific pathogens (e.g. scrapie)

Question 37

Sheep – external biosecurity - purchases

Answer 37

• 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.

Question 38

Sheep - external biosecurity

Answer 38

• 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

Question 39

External biosecurity – diseases to consider with sheep

Answer 39

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

Question 40

Sheep – internal biosecurity

Answer 40

• 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

Question 41

Considerations in biosecurity planning

Answer 41

1. Prevent or minimise contact between sources of infection and susceptible animals
2. Reduce the infection pressure (we cannot keep animals in sterile conditions)
3. Focus on high-risk transmission routes
4. Consider probability of transmission and frequency of occurrence
5. Larger herds or flocks are more at risk – biosecurity must improve with farm size

Question 42

Cattle purchase as a risk factor for bTB

Answer 42

• 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

Question 43

Why do farmers buy cattle?

Answer 43

• 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

Question 44

Contact chains – moving cattle

Answer 44

‘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.’