http://www.defra.gov.uk/footandmouth/contingency/tree.pdf

 

 

DISEASE CONTROL STRATEGIES: FOOT AND MOUTH

DISEASE

A CONSULTATION PAPER

Introduction

1. This paper outlines the measures that may be taken to slaughter or

vaccinate animals in the event of an outbreak of foot-and-mouth disease

(FMD). It sets out the factors the Government will take into account in

deciding which strategy to adopt in order to control and eradicate the disease

in the future.

 

2. The EU Council Directive on FMD, 85/511 as amended, requires

slaughter of all susceptible animals on infected premises, and provides for

culling of susceptible animals on epidemiologically linked holdings (known as

dangerous contacts). This reflects the EU's policy of adopting "FMD free

without vaccination" status for all Member States, and is provided for in

Defra's FMD Contingency plan. The EU Commission is about to bring forward

revisions to the FMD Directive and the revised FMD Directive will be

discussed with stakeholders.

 

3. Beyond this basic strategy, which will apply in all cases, there are a

range of additional options and strategies potentially available depending on

the circumstances of a particular outbreak and on the scientific and veterinary

advice. These include: -

• emergency vaccination (either to live or to kill; within an area or in a

ring around an area);

• culling of other livestock exposed to the disease (e.g. premises under

virus plumes, contiguous premises); and,

• subject to passage of the Animal Health Bill, pre-emptive or ‘firebreak’

culling of animals not on infected premises or dangerous contacts or

necessarily exposed to the disease, in order to prevent the wider spread of

the disease outwith an area.

 

4. Since each disease outbreak is different and each has to be tackled at

speed and – inevitably – with imperfect information it is not possible to

prescribe in detail which strategy will be followed in advance of knowing the

circumstances of a particular outbreak. This calls for a flexible approach,

which recognises that different approaches may be needed in different

geographical areas or to deal with different species. Nevertheless, there is

clear advantage in reaching a view on the likely options for response in

advance. Accordingly, this paper and the enclosed "decision tree" seeks to

set out:

• The factors that would be taken into account in deciding what kind of

slaughter policy will be adopted.

• The factors that would be taken into account in deciding whether to use

vaccination and if so whether to vaccinate to live or kill.

 

5. The Government’s objective in tackling any fresh outbreaks of FMD will

be to eradicate the disease as quickly as possible and to maintain the UK’s

disease-free status. In doing so, the Government will seek to select a control

strategy which:

• minimises the number of animals which need to be slaughtered, either to

control the disease or on welfare grounds, and which keeps animal welfare

problems to a minimum;

• causes the least possible disruption to the food, farming and tourism

industries, to visitors to the countryside, and to rural communities and the

wider economy;

• minimises damage to the environment and protects public health;

• minimises the burden on taxpayers and the public at large.

 

VACCINATION POLICY

6. In responding to the FMD Inquiries the Government has made clear

that emergency vaccination will now be considered as part of the control

strategy from the start of any outbreak of FMD where measures additional to

the culling of infected animals and dangerous contacts are needed. The

Government also accepts that if emergency vaccination is used it should be

on the basis of vaccinate-to-live wherever possible.

 

7. EU legislation allows for the use of emergency vaccination in

circumstances where an outbreak of FMD threatens to become extensive in

the Member State concerned. In order for a vaccination strategy to be fully

effective there would need to be a concerted EU approach and a new

legislative framework at EU level. The Government will actively pursue with

the Commission the need for a new framework for the use of vaccination.

 

8. The decision to introduce vaccination is normally taken by the

European Commission in consultation with Member States, although Member

States can vaccinate and then seek the EU’s agreement later. Two types of

vaccination strategy are envisaged:

(i) "Protective Vaccination" (Vaccination to live)

(ii) "Suppressive Vaccination" (Vaccination to kill)

 

9. The Inquiries investigated in detail the issues involved in employing

emergency vaccination. Between them they highlighted a range of significant

questions that would need to be addressed, particularly as regards

vaccination to live, but concluded that once these were resolved, the option of

emergency vaccination to live should be the preferred approach. The

Government is committed to tackling these issues in consultation with all

interested parties so that it is in a position to trigger an emergency vaccination

campaign should the need arise. As part of this process it is essential to have

stakeholder support and the Government will engage in dialogue with a wide

range of stakeholders in order to achieve, so far as possible, a shared

understanding in advance of an outbreak of the factors which influence the

choice of control options. The Decision Tree is intended to assist this

process.

 

Protective Vaccination (Vaccination to live)

10. This strategy would be considered:-

• where veterinary and scientific advice is that an outbreak could not be

contained by stamping out of Infected Premises and Dangerous

Contacts alone;

• where a defined category of animals could be identified for protection,

either in geographical or species terms;

• to protect zoo animals and rare breeds collections as recommended by

the Royal Society;

11. More generally, this option is likely to carry advantages where the

population density of susceptible animals is high; where pigs are the main

species involved; where there is a high risk of airborne spread; where the

origin of the outbreak is unknown; where incidence is rising rapidly, and

where the distribution of outbreaks is widespread.

 

Suppressive Vaccination (Vaccinate to kill)

12. This strategy could be considered where the number of animals to be

culled is likely to exceed the available disposal capacity. In those instances,

animals in defined areas would be vaccinated first and slaughtered only as

disposal capacity became available. It could also be used where there is an

urgent need to reduce the amount of virus circulating in an area and reduce

the risk of spread beyond that area.

 

STAMPING OUT POLICY

13. EU Directive 85/511 lays down the minimum measures Member States

must take against FMD. The Directive requires slaughter of all susceptible

animals on infected premises, and provides for culling of susceptible animals

on epidemiologically linked holdings, as well as depopulation of holdings

where FMD is suspected.

 

14. UK legislation allows for slaughter of:

• Animals affected or suspected of being affected with FMD.

• Animals which are believed to have been exposed to FMD infection.

 

Animals affected or suspected of being affected

15. When the State Veterinary Service (SVS) is made aware of suspicion

of foot and mouth disease in animals they will arrange for a veterinary

investigation to be undertaken.

 

16. The decision to slaughter will be based either on the results of

laboratory tests carried out on samples arising from animals suspected of

being affected with disease, or on convincing clinical evidence of disease. In

an area considered to be free of disease, except in exceptional

circumstances, it is likely that disease will be confirmed on laboratory results.

However, once disease has become established in an area it is likely that

cases will be confirmed on clinical grounds alone in order to ensure animals

are slaughtered quickly.

 

Animals which are believed to have been exposed to infection

17. Animals may be slaughtered if they are believed to have been exposed

to infection. In these cases, animals will be subject to a veterinary inquiry to

determine if, in the opinion of the Veterinary Inspector, they have been

exposed.

 

18. Animals that are believed to have been exposed to infection are known

as Dangerous Contacts. This can include animals on contiguous premises. As

virus can be excreted by such animals prior to the development of obvious

and identifiable clinical signs, it is important that they are culled as soon as

possible to stop virus production and hence spread of disease. A decision to

slaughter will be taken by the veterinary inspector based on information

gathered during the inquiry and account will be taken of levels of biosecurity.

The action that we take will depend on a risk assessment. Where it is

believed that the likelihood is that exposed animals are at an high risk of

becoming diseased they will be slaughtered. Where that risk is lower and

there are the resources to observe the animals, they will be restricted and

observed. So our action depends not only on the degree of risk but our ability

to mitigate the risk by having available the necessary resources to observe

animals regularly and our ability to detect early disease in exposed animals

and take immediate action should disease occur.

 

19. Animals can be exposed to infection by many routes. The following list

is not exhaustive and the relative importance of each will depend on a number

of factors:

a. Direct contact with infected animals

b. Airborne Spread

c. Movement of a live animal

d. Movement of a person

e. Movement of vehicles

f. Movement of equipment or other materials

g. Movement of animal products

h. Movement of feedstuffs or bedding

i. Movement by wildlife or non-susceptible vector

 

To prevent the spread of disease

20. A third type of slaughter policy is proposed in the Animal Health Bill.

This is culling "to prevent the spread of disease", e.g. to create a ‘firebreak’.

Such a cull might be required in order to protect areas of high livestock

density, either as an addition to emergency vaccination or, in some cases,

instead of it. The species and geographical area of the cull would have to be

carefully assessed.

 

21. If the Bill becomes law, the Government is committed to using the new

slaughter powers only where this is justified by the circumstances and on the

basis of sound veterinary, epidemiological and scientific advice. That means

in particular that a risk assessment will be made of the possibility of disease

spreading. It will include those animals that are judged to be at lesser risk of

infection but which, should they become affected, would present a very

significant risk to the farming and livestock community more generally. It is in

these cases that effective preventative action may be necessary to safeguard

the wider public interest. The steps that would be undertaken before the

decision is reached include:

a) identify a group of animals that could contribute to spread of disease.

This would be based on

• epidemiological modelling,

• consideration of local factors

• determination of which species involved

• determine geographical area involved;

b) consider if any exemptions could be allowed based on husbandry or

other criteria, e.g. genetic value

c) determine the rules for inclusion of animals at the boundaries of that

area

d) analysis of risks, cost and benefits

e) publish an outline of the reasons why such a cull is needed.

22. Any decision to use the wider powers of slaughter provided in the

Animal Health Bill would be taken in the light of an overall assessment of the

risks, costs and benefits in a given situation. This could include not only risks

of transmission but also social and economic risks that would arise if effective

and timely action were not taken. The Government would justify its decision to

use the slaughter powers, explaining the veterinary, epidemiological and other

relevant factors that had been taken into account.

 

UK DECISION TREE FOR CONTROL STRATEGIES

FOR FMD

 FMD DECISION TREE - FACTORS TO BE CONSIDERED

(Warmwell cannot reproduce the diagram.  It can be seen on DEFRA's site  here: http://www.defra.gov.uk/footandmouth/contingency/tree.pdf

 

 

Each decision on the tree is taken on the basis of a number of factors. The

decision matrix has been based on a USDA paper but has been adapted to

take account of the fact that any disease control strategy in the UK must take

account of the relevant EU framework.

In using the decision tree, the following factors should be taken into account

at each decision point. Modelling – economic & epidemiological – will be

used to assist in identifying trigger points.

At decision box 1: can disease be eradicated by stamping out (of

Infected Premises and Dangerous Contacts)?

All outbreak and mitigation factors need to be considered at this point in

deciding whether stamping out will eradicate the disease. However at the

start of an outbreak information on many of these factors will be incomplete

and this may not be available until well into the outbreak. Decisions may

need to be revisited as more information becomes available.

Outbreak factors

• Time from introduction of infection to detection (epidemiology);

• Contact rate: type of farms; direct and indirect movement and distance

of movement; efficacy of movement controls;

• Host or species affected – the species affected and species at risk

(manifestation of clinical signs leading to early recognition): domestic

livestock only – whether disease is in pigs, cattle or sheep; game

farms/zoos – how effective would isolation methods be; wildlife.

• Status of outbreak – estimation of the extent of the geographical

distribution of FMD and duration of epidemic: number of affected

herds; number of foci of infection; rate of spread. Use of

epidemiological models.

 

• Environmental: livestock density and distribution; livestock

management; casual access – network of roads, etc; physical barriers;

climate – does it favour airborne spread?.

Mitigation factors:

• Physical resources: slaughter capacity; transportation capacity;

disposal capacity. Incineration - max 1000 tonnes per week (2000

bovines or 20,000 sheep or 10,000 pigs approx.) Rendering - max

15,000 tonnes per week

• Human resources: emergency response system ie are there sufficiently

trained staff for stamping out and to maintain movement controls; what

are the epidemic projections.

• Socio-political factors: EU Directive 85/511 requires slaughter of all

susceptible animalson Infected Premises and provides for culling of

susceptible animals on epidemiologically linked holdings (known as

Dangerous Contacts); public opinion; industry acceptance; other

affected sectors eg. tourism.

• Economic considerations: compensation; value of exports and value of

other affected sectors eg tourism – a cost benefit analysis of loss of FMD

free status versus stamping out (cost-benefit analysis of different

scenarios to be commissioned)

Decision Box 2: is vaccination permissible and possible?

2. Physical resources to be considered:

• Vaccine strain availability – there are 7 strains of FMD antigen kept by

the International Vaccine Bank to which the UK has drawing rights of

500,000 doses for each. In addition we have purchased 15.4M doses

of 01 Manisa antigen from Merial. The UK is currently taking steps to

procure a range of vaccines for the strains which IAH, Pirbright advise

as presenting the greatest risk to the UK at the moment. In addition,

the EU Vaccine Bank holds a range of antigens for emergency use.

• Vaccine doses available – there is currently enough 01 Manisa antigen

to vaccinate cattle in the England & Wales. The 500,000 doses of

each of the other main FMD strains would be sufficient to complete

vaccination within a defined area.

• Vaccination strategy – including position of rare breeds/zoos, etc.

• Vaccination logistics – this will be covered by the revised Viper

Chapter. A 1-dose strategy is more likely to be used where the policy

is vaccinate-to-slaughter as it saves on resources (human and vaccine)

but results in vaccine being used off-label. A 2-dose strategy (followed

by a booster at 6 months) would be necessary for a vaccinate-to-live

strategy.

• Vaccine distribution – vaccine would be procured centrally and

distributed via vaccination centres (see revised Viper chapter).

• Laboratory capacity/ability to distinguish vaccinates from infected –

Laboratory capacity exists to do testing but there are currently no

internationally recognised standards for NSP testing. The Government

accepts that the validation of NSP (non-structural protein) tests is a key

area. There are a variety of NSP tests at differing levels of validation.

There are currently a number of research projects in the UK, Europe and

America and many of the European groups are partners in a European

Union Concerted Action project on FMD diagnosis. The main limiting

factor for the validation of such tests is the availability of suitable panels of

sera, especially from vaccinated and then challenged animals. Defra is

supporting research into this area. In addition, the Government also

accepts that there is a need to develop accepted strategies for

surveillance after vaccination. Indeed, this is something that the OIE has

under consideration.

• Time – Whether there would be enough time for vaccination to

completed before spread of infection would depend on the

epidemiological projections during the outbreak. Need for modelling

input.

 3. Human resources to be considered:

• Emergency response system – need to have sufficient numbers of

vaccinators available. The revised Viper Chapter 3A will deal with

recruitment and training of vaccinators.

• Movement controls are a recognised part of any UK control strategy.

Specific restrictions will apply on movement of vaccinated animals and

products from vaccinated animals within the vaccination zone as laid

down by EU. There will be welfare considerations in establishing a

vaccination zone. Need sufficient staff to monitor movement controls.

NSP tests are only reliable on a herd basis so herd integrity will need to

be maintained pending testing.

• Epidemic projections – different for each outbreak.

4. Socio-political factors to be considered:

• Available legislation – Powers to vaccinate exist. Any decision to

vaccinate would have to be agreed by the EU (last year there was a

Decision allowing the UK to vaccinate in Cumbria and Devon).

• Public opinion – there needs to be a communications plan that should

be communicated to stakeholders in advance. Need active

engagement with stakeholders especially on FSA advice on safety and

to clarify any labelling issues.

• Industry opinion – Stakeholders to be kept involved in developments

connected with the issue of vaccination ie FMD Directive, changes to

the OIE Code. Stakeholder involvement (should be all inclusive) and

agreement would be important in any decision to vaccinate.

5. Economic considerations to be considered:

• Cost of vaccination – the cost of purchasing 15.4M doses of 01 Manisa

antigen was £3.5 million (including VAT). There are also costs of

storage and formulation to be taken into account. There is also a cost

of the UK continuing to be a member of the International Vaccine Bank.

The cost of vaccination equipment, training and employing staff as part

of a vaccination campaign also needs to be costed into the equation.

• Value of exports – versus benefit to wider rural economy and tourism.

• Regionalisation – whether there would be regionalisation within the UK

would depend on the outbreak. EU legislation requires vaccination zones

to be clearly defined.

Decision Box 3: is the exit strategy "vaccinate to live"?

6. Physical resources to be considered:

• Slaughter capacity – vaccinate to live is likely to reduce pressure on

slaughter capacity whereas as vaccinate to slaughter would lead to

higher numbers for slaughter than a stamping out policy (the Dutch

experience). Capacity would need to be able to cope with slaughter of

vaccinates and slaughter of infected livestock in a vaccinate-toslaughter

scenario.

• Disposal capacity – The higher numbers generated by a vaccinate to

slaughter policy may result in disposal becoming a limiting factor. A

vaccinate to live policy would not cause disposal problems but there

would be implications for products from vaccinated animals entering

the food chain. And movement controls imposed on vaccinates

• Controls on products from vaccinated animals - Under EU rules,

products from vaccinates would need to be kept separate from nonvaccinates.

This may raise practical problems for the processing

industry. The post vaccination controls that would have been required

had vaccination gone ahead are set out in Commission Decision

2001/257/EC of 30 March 2001. Meat from vaccinated animals would

have had to be heat treated during the first 30 days following

vaccination and then deboned and matured for 24 hours for a period of

12 months from vaccination or from the last confirmed case of the

disease in the vaccination zone. For a period of 12 months milk from

vaccinated animals would have had to be pasteurised; in the first 30

days following vaccination pasteurisation would be required within the

vaccination zone unless otherwise authorised in exceptional

circumstances. There are practical problems in meeting these

standards for pig and sheep meat. The taking of semen, ova and

embryos from vaccinated animals would have been forbidden.

Vaccinated cattle would not have been permitted to move out of the

vaccination zone for 12 months, except under licence to slaughter.

May create an internal dual market for livestock and products

• Time – If a vaccinate to slaughter policy was followed it would be more

cost-effective to cull after the first dose of a 2-dose strategy. Vaccinate

to live would probably require a 2 dose strategy followed by a booster

at 6 months.

• Identification: individual identification of livestock is important so that

either one can ensure that all vaccinates are killed or products from

vaccinates are correctly treated. Currently very difficult for anything

other than cattle.

7. Human resources to be considered:

• Emergency response system – we would need to consider whether we

had the necessary staff to complete a vaccinate to live policy eg

vaccinators for 2 dose strategy. For a vaccinate to slaughter policy,

we would need to consider whether we had the necessary staff ie.

slaughtermen.

• Epidemic projections. As above.

8. Socio-political factors to be considered:

• Available legislation – The AHA allows for emergency vaccination as

does EC 85/511. The AH Bill will allow for slaughter of vaccinates and

for payment of compensation for slaughter of vaccinates.

• Public opinion – Public are likely to support a vaccinate to live policy

and this would be in line with Follett and Anderson Inquiry

recommendations. Labelling for vaccinated products is an issue which

needs to be resolved through discussion with stakeholders.

• Industry acceptance –possible pressure from trade, and other Member

States, to slaughter vaccinates to regain FMD free status. Need to

engage industry stakeholders.

9. Economic considerations to be considered:

• Cost of vaccinate to slaughter – include the costs of vaccination (Box

4) plus the cost of slaughter and disposal of all vaccinates.

• Compensation – Cost of compensation for slaughtered vaccinates

would substantially increase overall costs of epidemic.

• Value of exports versus benefit to wider rural economy.

• Regionalisation – As for Box 2.

At decision box 4: are there additional culling strategies that are

permissible and possible?

In some circumstances culling additional to DCs and IPs maybe the optimal

solution based on a risk assessment. This culling could take a number of

forms – contiguous premises (where these are judged to have been exposed

to infection) or preventive culling where scientific and veterinary advice is that

this will prevent further spread of disease outwith the area. In choosing

between these and other additional forms of culling a number of factors will

need to be taken into account:

10. Socio-political factors to be considered:

• Available legislation – control options are provided for under existing

legislation. Others –notably pre-emptive (or preventive) culling of

animals not exposed to FMD infection in order to get ahead of the

disease and stop it spreading – are proposed in the Government's

Animal Health Bill and are not yet law. Better powers of entry to

vaccinate are also included.

• public opinion - contiguous and 3km culls were controversial aspects of

FMD 2001;

• industry opinion – there was some resistance to the contiguous cull.

11. Economic considerations to be considered:

• compensation – additional culling may significantly increase the

amount paid in compensation.

• value of exports & other economic costs particularly in the wider

countryside and for tourism – cost-benefit analysis (see Decision Box

1). There are extra costs involved in additional culling.

• Regionalisation – would regionalisation of the UK or England be

feasible?

At decision box 5: are resources available for additional culling

strategies?

The prime concern is whether adequate resources exist to accommodate the

anticipated number of additional livestock in addition to those slaughtered

under stamping out.

12. Physical resources to be considered:

• slaughter capacity – does the capacity exist to slaughter animals under

the stamping out policy and additional culling;

• transportation capacity – does the transport capacity exist to remove

animals from farm for disposal under an additional culling scenario;

• disposal capacity - does the capacity exist to dispose of animals under

the stamping out policy and additional culling in environmentally

acceptable ways;

• time ie are there sufficient resources to permit additional culling before

such livestock develop FMD; identification of all premises included in

an additional cull.

13. Human resources to be considered:

• emergency response system ie are there sufficiently trained staff to

carry out an additional culling policy without adversely impacting on

other key control policies i.e. enforcing movement controls, etc;

• what are the epidemic projections – epidemiological modelling of high

risk groups.