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FMD Culling and Disposal of Carcasses:

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Introduction and General Information

In the face of an outbreak of Foot-and-Mouth Disease in a country where the FMD Virus does not usually occur, and in some endemic areas, culling ("stamping out") is an important part of foot-and-mouth disease (FMD) control operations. The main aim of culling is to remove virus sources (infected animals) from the environment, which will reduce the risk of further animals becoming infected and getting the disease.

Culling is the killing of animals for management purposes. It is a serious responsibility and those undertaking this task must ensure that the welfare of the animal is not compromised. Most countries have Animal Welfare legislation which specify issues associated with the humane destruction of animals and it is important that this legislation is consulted and respected. In addition there are considerable risks posed to those undertaking the culling operation and it is essential that relevant Health and Safety legislation is considered and complied with.

In the UK some of the relevant Legislation that must be consulted include:

  • Animal Protection Acts / Animal Health and Welfare Acts
  • Health and Safety Acts

It is widely recognised that the time from detection of diseased animals to slaughter and disposal should be minimised for effective disease control and it is generally recommended that all animals with FMD should be slaughtered and disposed of rapidly, within twenty four hours of diagnosis, to reduce the time over which animals are producing and releasing virus, and thus reduce the transmission of disease. (B495.6.w6 -full text provided, J3.148.w5, J3.156.w4, J18.49.w1, J21.69.w1, J35.127.w1)

Factors which may prevent culling and disposal within this time frame include:

  • Large number of animals requiring culling and disposal if there are: (J112.25.w3)
    • Large numbers of affected herds.
    • Large numbers of herds requiring culling due to presence of dangerous contact animals in the herd.
    • Blanket "contiguous cull" policy.
    • Increased problem if large livestock units are involved (J35.134.w2).
  • Delay in confirmation of disease
  • Delay in valuation (J35.134.w2).
  • Lack of appropriate means of disposal:
    • Lack of burial sites.
    • Insufficient material for burning.
    • Insufficient manpower/machinery.
    • (J35.134.w2).
  • Environmental pollution considerations (J112.25.w3) such as:
    • Level of water table.
    • Smoke from carcass pyres.
    • (V.w23)
  • Manpower, machinery and logistical constraints on culling and carcass disposal; these problems are more likely if large numbers of animals must be culled. (B495.6.w6 -full text provided)
  • Public reaction to large-scale culling, and possible legal injunctions (B495.1.w1 - full text provided, J112.25.w3, V.w23).

It must always be remembered that the main reason for culling is to remove the source of infection and that culling alone is unlikely to be effective in preventing the spread of the virus. For "stamping out" of FMD, culling must be used alongside other disease control measures, such as:

  • Strict movement restrictions (quarantine)
  • Disinfection

In terms of disease control, which aims to reduce animal/production losses, an effective culling policy is a balance between preventing production and spread of the virus in infected animals and the losses incurred through any "stamping out" procedures. If the virus is likely to multiply and spread beyond the capacity of the authorities to implement a "stamping out" policy, then additional control measures must be considered, such as:

  • Vaccination. (B495.6.w6 -full text provided, B495.9.w9 - full text provided, J35.167.w2)

The Gowers Committee and the Northumberland Committee in response to Foot-and-Mouth Disease outbreaks in the 1950's and 1960's noted the essential role of a slaughter policy in the control of FMD but also recognised the emotional costs of such a policy through the following statement:

"We wish to make it clear at the outset that we are not among those who regard stamping-out [the slaughter policy] with complacency. We sympathise with the widely expressed view that it is a crude and primitive way of dealing with a disease. We know what a harrowing duty it is for the officers of the Ministry who have to carry it out. We recognise the mental anguish it may cause to those who suffer its consequences, and the shattering disaster, not computable in terms of money, that it may bring to a farmer who has to see the work of a lifetime destroyed in a day." (D36.Paragraph 175)

Culling operations should be designed to minimise the spread of disease while avoiding unnecessary slaughter. 

  • It should be remembered that Foot-and-Mouth Disease can be extremely severe and produce acute suffering with or without producing long-standing chronic illness. 
  • Aside from the need to cull for disease control purposes, culling may sometimes be the best option on welfare grounds to prevent unnecessary suffering.
  • It is important to consider other methods of control which minimise the number of animals which must be culled. (B495.9.w9 -full text provided)
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Which animals to cull in an outbreak

Because of the highly contagious nature of foot-and-mouth-disease virus (FMDV), and because animals are known to release large amounts of virus into the environment before starting to show clinical signs (up to five days before for cattle and sheep, as long as ten days for pigs), it is usual in FMD-free countries to cull not only those animals with clinical disease (lesions) but also all "in-contact" animals.
  • The reason for culling "in-contact" animals is that there is a high chance that these animals will already be infected and may already be producing virus and releasing it into the environment. This policy, i.e. the slaughter and burial or burning of all affected and in-contact susceptible livestock on an affected premises is also known as "stamping out" (J3.131.w1).

If more than one species of animals are present on a premises, due to the fact that pigs produce more virus than other species, affected pigs should be slaughtered first, then cattle, then sheep, and of animals not yet showing clinical signs, pigs should be slaughtered first (J35.127.w1).

DIFFERENT CULLING POLICIES

  1. "Stamping out"
    1. Slaughter all other susceptible affected and Dangerous Contact Animals (e.g. animals on the same farm, animals which were at the same market, animals which were transported in same lorry immediately after it has been used for infected animals, or tended by the same stockman immediately after tending infected animals).
      • Note: Rapid culling of animals on dangerous contact premises (i.e. of animals on other premises likely to have been infected due to direct or indirect contact with known infected animals) is important. However, tracing may be difficult if livestock keepers are non-cooperative, for example due to misconstruing the motives of those asking about movements. Additionally, contact tracing requires determination of the length of time for which a farm has been infected, which may not be straightforward. (B495.6.w6 -full text provided)
  2. Partial slaughter
    1. Slaughter only clinically affected animals.
    2. This policy may be used in countries in which prophylactic vaccination is practised.
    3. "Stamping out" i.e. "total slaughter" is not considered economically feasible when FMD is prevalent in an area (J3.131.w1).
  3. "Vaccinate and cull" policy
    1. As part of "stamping out" operations, a "vaccinate and cull" policy is sometimes recommended and one variation ("damping-down" emergency vaccination) is described in the Strategy for Emergency Vaccination against Foot and Mouth Disease (FMD) Report of the Scientific Committee on Animal Health and Animal Welfare (European Union) (D35.w1 - full text available).
    2. This policy aims to reduce production and spread of the virus over the time required to carry out the cull and dispose of carcasses. See: "Dampening-down" Vaccination for Foot-and-Mouth Disease
    3. Vaccinating in the infected area would be expected to slow down the rate at which herds became infected, reducing the number of outbreaks per day and therefore making it easier to ensure that culling and disposal of stock on all premises where clinical disease was diagnosed could be carried out rapidly (within 24 hours).
    4. From an export-sparing viewpoint, "vaccinate and cull" would not increase the time period before a return to "FMD free" status, and may be expected to decrease this interval since the outbreak would be brought under control faster if vaccination stopped spread of the disease.
  4. No cull or culling for welfare purposes only:
    1. This policy is used in some regions where the disease is endemic and FMD control policies aim to limit rather than eliminate the disease.
  5. Extended Cull:
    1. An Extended Cull involves killing animals which are not yet infected but may become infected thereby allowing the virus to spread. The extent and range of the cull will be decided by the relevant authority.
    2. In some situations it may be decided that there is a large chance (high risk) in the short-term that the virus is likely to multiply in animals on adjacent/nearby farms.
    3. This risk may be made worse if:
      • The animals have close contact with infected animals in next door fields - most likely at the start of an outbreak, as once the disease is known to be present efforts are generally made to prevent such contact, keeping animals in well-separated fields.
      • Wind-borne virus is a factor. It has been shown that FMD Virus may be transported considerable distances (up to 150 miles across the sea in exceptional conditions) on the wind, although the distances for which the virus is transported in sufficient quantities to cause infection are usually much shorter than this.
      • Some animals become infected and excrete virus without showing enough outward signs of infection to be noticed and diagnosed. The virus can then pass between many individuals and spread without the farmer realising. Sheep have been frequently noted to be affected in this way.
    4. In the 2001 Outbreak in the UK, two forms of Extended Cull policies were implemented:
    5. Decisions as to which properties (and therefore animals) should be included in such an "extended cull" should be made on the basis of a scientific/veterinary risk assessment that:
      • The animals to be culled have been / will be infected.
      • The animals to be culled pose a risk to other animals further from the properties known to be infected.
    6. The risk assessment needs to take into account the factors which affect the likelihood of the animals being infected, including:
      • The distance between the animals known to have the disease and those on adjacent/nearby properties.
      • The types of animals involved (pigs produce the largest amounts of virus likely to be transported on the wind, while cattle take in large quantities of air through breathing and are most likely to become infected by wind-borne virus).
      • Computer model predictions of the likely rate of spread, particularly the movement of the virus plume.
      • Local circumstances (B494.10.w10 - full text provided)
      • The actual disease in the field, which may differ from the disease in models (J3.159.w). 
    7. It may be more appropriate to target high-risk farms, such as: (B495.9.w9 - full text provided)
      • large farms (particularly large dairy farms);
      • close proximity to an Infected Premises;
      • species mix of animals;
      • possibility of spread (particularly the direction of airborne virus plumes).
    8. NOTE: Descriptive modelling carried out following the 2001 epidemic in the UK showed that the outbreak peaked before the Extended Cull control measures were instigated, that longer distance spread continued after they were instigated, and that the novel culling strategies were not effective or efficient in disease control (as indicated by various measures, including the low areal attack rates for contiguous premises and the very small number of IPs identified among the farms culled under these strategies), while the traditional policies, focusing on rapid slaughter of animals on IPs, strict biosecurity, and tracing and veterinary assessment of Direct Contacts (including contiguous premises, where appropriate) from the IPs, were effective and efficient (J3.154.w4, J3.155.w3, J3.155.w4, J3.156.w3, J3.156.w4).
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Accommodation and transport of animals awaiting culling

When animals are awaiting culling they should be assumed to be highly infectious and efforts should be directed at minimising viral spread. Whenever possible they should be maintained where they are prior to slaughter. This minimises the chance of spreading Foot-and-Mouth Disease by moving the animals. Keeping the animals inside buildings may help to decrease the amount of virus released into the air outside (some will be trapped in the building) and therefore reduce the risk of transmission to other properties.

Movement of animals within an Infected Premises from the time of diagnosis to slaughter should be minimised, although movement may be necessary to bring the animals into an area where slaughter can be carried out in safe hygienic conditions, preferably in an area with an impervious substrate (ground surface).

Animals which are already showing clinical signs are likely to be lame and every effort should be made on welfare grounds to avoid transporting these animals and to provide them with soft bedding until they can be humanely killed.

If transport to a place of slaughter is necessary, every precaution must be taken to reduce the risk of this transport spreading the disease (J249.91.w2). This includes disinfection of vehicles, minimising the distance to be moved, and moving straight from a farm to the place of slaughter, not moving between farms.

The risk factors associated with the transport of animals to another site for disposal have been set out in Veterinary Risk Assessment No.6: What is the risk of causing new outbreaks of FMD by moving sheep directly from "Farm A" (on which animals have been exposed to the risk of infection by proximity to an infected premises, or in some other way) to an alternative place of slaughter, and from there to a further place for disposal? [Formerly available on the MAFF Website] (W32.Apl01.sib7).

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Techniques of culling animals

Methods used for culling animals during an FMD outbreak should be capable of dispatching large numbers of animals in a short time, with due consideration for the welfare of the animals being slaughtered.
  • It is essential that whatever the method used, it should be carried out by people who are fully proficient in its use, and preferably under veterinary supervision.
  • It is essential that the method used, both for handling and killing, should be humane and fully effective and that all animals are confirmed dead prior to disposal of carcasses.
  • Adequate properly trained personnel (i.e. experienced slaughtermen for culling and experienced stockmen for handling animals) must be available to minimise delay and to ensure humane slaughter.
  • Particular consideration should be given to the requirements for humane culling of young animals (e.g. lethal injection for lambs and piglets) and animals in the late stages of pregnancy.
  • Consideration should be given to the use of sedatives before slaughter, particularly with animals likely to be nervous, aggressive or frightened.
  • The safety of persons carrying out culling must be considered when dealing with potentially dangerous animals such as bulls and boars.
  • Animals should be confined prior to slaughter, preferably in a suitable building, otherwise a stockade, screened by suitable materials such as tarpaulins, and a crush should be constructed.
  • Consideration should be given to the problems of removing large animals from buildings after the onset of rigor mortis.
  • When slaughtering cattle, bulls should be slaughtered first.
  • The method of choice for the slaughter of cattle is captive bolt followed by pithing.
  • The method of choice for the slaughter of sheep is captive bolt followed by pithing. Lambs should be euthanased by lethal injection.
  • The method of choice for the slaughter of pigs is longbolt captive bolt followed by pithing. Piglets should be euthanased by lethal injection.

The Northumberland Report (Report of the Committee of Inquiry on Foot-and Mouth Disease 1968 Part Two) recommended the use of a captive-bolt pistol followed by pithing, whenever possible. A rifle could be used as an alternative in exceptional circumstances where the use of a captive-bolt pistol was not possible. Dart guns could be used by people properly trained to handle such equipment if required for the administration of tranquillising drugs to allow handling for slaughter.

It is important to ensure that sufficient captive bolt pistols are available to be used in rotation, avoiding overheating which may be a problem when these pistols are used repeatedly and rapidly for long periods.

(D37.Para121, D37.Para124, D37.Para125, D37.Para222.52, J64.21.w31, J64.21.w32, W18.Apl01.sib1).

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Risk Assessment / Checklist for Live Firing on Cull Sites

Some authorities may use live firing for culling purposes when other options are not available. In view of the serious risks associate with this procedure, authorities may require a risk assessment to be completed prior to live firing taking place.

IF THE RESPONSIBLE AUTHORITY REQUIRES A SPECIFIC RISK ASSESSMENT TO BE COMPLETED, THIS MUST TAKE PRECEDENCE.

This should be undertaken by a person who has the experience of firearms and is authorised on his/her firearms certificate to use firearms to slaughter animals. Where risks are intolerably high, or significant points identified in the list below cannot be suitably addressed, other methods of culling should be implemented.

The points below represent the types of risk assessment questions asked for live-firing procedures for culling purposes during the UK 2001 FMD outbreak.

FACTORS TO BE ADDRESSED

  • Has adequate time been set aside for planning?
  • Are all personnel properly briefed as to roles and responsibilities?
  • Has there been liaison with the on-site Animal Health Officer / Veterinary Officer?
  • Have the areas of responsibility and arcs of fire been clearly defined?
  • Has a sterile area been created around the site to prevent unauthorised access?
  • Are the following all in place at the site:
    • safe backstop?
    • Steps to avoid ricochet?
    • Prevention of public intrusion?
    • Consideration of other possible sources of danger / causes of injury?
  • Have safety officers been appointed and deployed?
  • Are there satisfactory light levels?
  • Has the area beyond backstop been considered, both near and far distance, regarding the potential for danger/injury caused by discharge rounds?
  • Are there arrangements to ensure that staff do not work excessive hours?
  • Have all persons to be used as marksmen experience and authorisation on their firearms certificates?
  • Are adequate rest periods planned?
  • Are there monitoring arrangements for staff welfare?
  • Are weapons and ammunition suitable for the animals to be culled?
  • Are weapons / ammunition kept secure when not in use?
  • Have all personnel adequate hearing protection during live firing?
  • Are there measures to prevent eye injuries through exposure to chemicals, weapons and/or animal debris - eye protection to be provided and worn?
  • Injury / wounding caused by livestock:
    • Have all personnel been briefed to stop firing and make weapons safe if someone is injured?
    • Is there adequate First Aid provision on site?
  • Is the Officer in charge aware they have overall responsibility for the site?
  • Have the police been informed of the time and site of the shooting for their information?
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Carcass disposal and implications

The rapid, effective disposal of carcasses is a vital part of FMD disease control. It is well recognised that rapid slaughter without rapid disposal of carcasses is much less effective. Although the production of virus stops once the animal is dead, virus can still be released into the environment until the carcass is properly disposed of.

Spraying of carcasses with an appropriate effective (approved) disinfectant immediately after slaughter and placing plastic bags over the heads and feet of carcasses immediately after slaughter have both been suggested as ways to reduce shedding of virus from the carcass into the environment before disposal.

Removal of carcasses from buildings may be difficult due to rigor mortis and bloat. Rapid removal of carcasses from buildings following slaughter minimises this problem.

It has been recognised for many years that the increasing size of livestock units makes disposal of animals on-site difficult. It is generally accepted that disposal at alternative sites involve an attendant risk of virus dissemination, as well as requiring a potentially huge operation.

(J35.127.w1, J35.134.w2, D37.Para128, D37.Para216, W18.Apl01.sib1).

The possible methods of carcass disposal include:

  • Burial on-site. See: Burial of Carcasses for Foot-and-Mouth Disease for detailed information
  • Burning - open bonfire on-site. See: Burning of Carcasses for Foot-and-Mouth Disease for detailed information
  • Burial off-site: This may take place for example in commercial landfill sites (B495.9.w9 - full text provided). This involves an increased risk of spread of virus compared to on-site disposal. See: Burial of Carcasses for Foot-and-Mouth Disease for detailed information)
  • Incineration: Incineration decreases the risk of air contamination from burning carcasses, but has a limited capacity (B495.9.w9 - full text provided, J3.151.w6) and there is an increased risk of spread of virus if animals or carcasses must be transported to the incinerator.
  • Rendering: Rendering has commonly been considered an option to be used only when alternative options have been ruled out. However, in areas of high human and livestock density, it may become the only option available. Rendering decreases the risk of air contamination from burning carcasses, and was recommended for the disposal of cattle carcasses, particularly those over 36 months old, during the UK outbreak in 2001, due to the potential, extremely small, risks of BSE spreading due to burial or burning. However, the capacity of local (even country-wide) rendering plants is unlikely to be sufficient if a large number of carcasses require disposal and there is an increased risk of spread of virus if animals or carcasses must be transported to the incinerator. (B495.9.w9 - full text provided, J3.151.w6, W32.Apl01.sib1)
  • Napalm: Napalm (jellied gasoline) has a bad reputation. However, the use of modern napalm formulations for the disposal of carcasses could potentially allow the burning of large numbers of carcasses very rapidly. Its use would also reduce the time required for pyre construction and the need for large quantities of conventional fuels such as coal, wood and straw. (W27.24March01.sib1, W27.14March01.sib1, W33.30May01.sib1)

In the UK, advice from the Environment Agency following the 2001 FMD epidemic, to the Royal Society Infectious Diseases in Livestock Inquiry was a preference for, in order, rendering; commercial incineration; disposal in licensed landfill sites; on-site burning; and on-site burial. This order was based on both risk to the environment and risks to human health. (Infectious Diseases in Livestock [Royal Society Inquiry Report] B495.9.w9 - full text provided)

Note: 

  • There are risks of FMD Virus being spread if there is inadequate biosecurity by either those carrying out the culling or personnel involved in disposal. (B495.9.w9 - full text provided)
  • The risk factors associated with the transport of carcasses to another site for disposal were set out in Veterinary Risk Assessment No.6: What is the risk of causing new outbreaks of FMD by moving sheep directly from "Farm A" (on which animals have been exposed to the risk of infection by proximity to an infected premises, or in some other way) to an alternative place of slaughter, and from there to a further place for disposal? [Formerly available on the MAFF Website] (W32.Apl01.sib7).
  • Maintaining high levels of biosecurity is more difficult if large numbers of premises need to be slaughtered out rapidly, for example with extended cull policies. (B495.9.w9 - full text provided)
  • Without adequate biosecurity, culling and disposal operations may be ineffective or even become counterproductive. (B495.9.w9 - full text provided)

Additionally, there are risks that that wild animals which can act as mechanical transporters of the virus will be displaced from infected premises by culling and cleansing operations, and may transport the disease to other farms. (B495.9.w9 - full text provided)

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Authors & Referees

Authors Dr Debra Bourne MA VetMB PhD MRCVS
Referee Suzanne I Boardman BVMS MRCVS

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