TECHNIQUE

"Damping-down" Vaccination for Foot-and-Mouth Disease (Disease Investigation & Control - Treatment and Care)

Summary Information
Type of technique Health & Management / Disease Investigation & Control / Treatment & Care / Techniques:
Synonyms and Keywords Suppressive vaccination
Description

'Dampening down' or 'suppressive' emergency vaccination is vaccination carried out within the protection zone, in a known foot and mouth disease infected area where it is considered that there is an urgent need to reduce the amount of virus circulating and the risk of spread beyond the area.

It could also be described as "ring vaccination and cull", with the outer edge of the ring being relatively close to the centre of the outbreak, e.g. to or just past the outer limit of the "protection zone".

  • Such a policy involves a separate team(s) of people, not those required for the slaughter and disposal operations, who would vaccinate animals inside the area considered to be infected.
  • The usual disease control measures (including stamping out) as laid down e.g. in LEU6 - COUNCIL DIRECTIVE 2003-85-EC of 29 September 2003 on Community measures for the control of foot-and-mouth disease should be continued irrespective of when vaccination commences.
  • Inspection of the animals on a farm must always precede vaccination and if the animals were found to have clinical signs of FMD vaccination would not proceed on that premises; culling operations would start.
  • The team(s) might work from the centre of the area outwards, or concentrate first on pig farms (since pigs excrete larger amounts of virus into the air than do cattle, sheep etc.).
    • The holdings should be selected for vaccination according to risk ranking with the highest priority being given to the vaccination of pigs, the species which has the greatest potential for the dispersion of plumes of airborne virus and environmental contamination downwind. (D35.w1 - full text available)
  • Stamping out procedures should continue and would be applied to the vaccinated animals. (D35.w1 - full text available; LEU6 - W19.Sept07.w1).
  • Culling of vaccinated herds, even those which showed no signs of disease, would avoid the risk that any of the herds could be infected subclinically and be carrying the virus.
  • The aim of such a policy is to reduce the amount of virus excreted by animals and thereby reduce the amount of virus in the environment and the risk of windborne spread out of the immediate infected area.
  • N.B.
  • 1) From an export-sparing viewpoint, "vaccinate and cull" would not increase the time to the return to "FMD free" status, and may be expected to decrease this time since the outbreak would be brought under control faster if vaccination stopped spread of the disease.
  • 2) It has been argued that with modern serological tests, which enable vaccinated non-infected animals to be distinguished from vaccinated infected animals, herds or flocks which have been vaccinated and not shown any signs of disease should not be slaughtered automatically but should be tested first and spared if found not to be infected. This would increase the time taken to return to FMD-free status. 
    • The OIE Terrestrial Animal Health Code Sixteenth Edition Chapter 2.2.10 - Foot and mouth Disease [Text available in Wildpro], states that a vaccinated area can be considered free of FMD:
    • "3 months after the slaughter of all vaccinated animals where a stamping-out policy, emergency vaccination and serological surveillance are applied in accordance with Appendix 3.8.7."; or
    • "6 months after the last case or the last vaccination (according to the event that occurs the latest), where a stamping-out policy, emergency vaccination not followed by the slaughtering of all vaccinated animals, and serological surveillance are applied in accordance with Appendix 3.8.7., provided that a serological survey based on the detection of antibodies to nonstructural proteins of FMDV demonstrates the absence of infection in the remaining vaccinated population." (B493.2.2.10.w1)
Appropriate Use (?)
  • As a measure to assist pre-emptive slaughter (stamping-out) particularly where there is a high density of animals in the area, in the following circumstances:
    • a high density of animals (especially pigs);
    • an overwhelming of the capacity to kill and dispose of carcasses within a short time period,
    • poor infrastructure,
    • inadequate manpower
    • or delayed stamping out.
  • Outbreaks in areas containing high densities of susceptible animals and inadequate resources of manpower or rendering plants for the slaughter and disposal of animals or outbreaks involving a predicted risk of airborne virus spread beyond the protection zone.(D35.w1 - full text available):

  • Indications for the use of an emergency vaccination programme within the EU would be if a large number of the following criteria applied to an outbreak (D35.w1 - full text available):

    • High population density of susceptible animals
    • Significant number of pigs involved
    • Evidence of movement of potentially infected animals or products out of the protection zone
    • High predicted airborne spread of virus from infected premises
    • Suitable vaccine available
    • Widespread distribution of outbreaks
    • Suitable vaccine available
    • Unknown origin of outbreaks
    • Incidence slope of outbreaks rising rapidly
    • Widespread distribution of outbreaks
    • Strong public reaction to total stamping out policy
    • Acceptance of regionalisation after vaccination.
  • Council Directive 2003/85/EC (29th September 2003) gives the following statements regarding the use of emergency vaccination in EU member states the following criteria for implementation of emergency vaccination (W19.Sept07.w1 - full text included):

    Article 50 Decision on introducing emergency vaccination
    1. It may be decided to introduce emergency vaccination where at least one of the following conditions applies:
    (a) outbreaks of foot-and-mouth disease have been confirmed and threaten to become widespread in the Member State where such outbreaks have been confirmed;
    (b) other Member States are at risk due to the geographical situation of or the prevailing meteorological conditions in relation to reported outbreaks of foot-and-mouth disease in a Member State;
    (c) other Member States are at risk due to epidemiologically relevant contacts between holdings on their territories and holdings keeping animals of susceptible species in a Member State where there are outbreaks of foot-and mouth disease;
    (d) Member States are at risk due to the geographical situation or the prevailing meteorological conditions in a neighbouring third country where there are outbreaks of foot-and-mouth disease.
  • The rational from a disease-control point of view for vaccinating prior to culling is that vaccinated animals, even if not yet fully protected against the disease will be less severely infected and produce less virus, therefore reducing the amount of virus in the environment and the rate of spread of the disease.
  • 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 cull-and-disposal of stock on all premises on which clinical disease was diagnosed could be carried out rapidly (within 24 hours).
  • Culling of vaccinated herds/flocks would avoid any risk of vaccinated animals becoming carriers and possibly spreading disease to non-vaccinated animals in the future.
Notes
  • The OIE Terrestrial Animal Health Code Sixteenth Edition [Text of Chapter 2.1.10 - Foot and mouth Disease available in Wildpro], Chapter 2.1.1., states that a vaccinated area can be considered free of FMD 3 months after slaughtering of the last vaccinated animal where stamping-out, serological surveillance and emergency vaccination are applied. (B493.2.2.10.w1)
  • A detailed report at the end of a vaccination campaign must contain fundamental information about the number and the species of vaccinated animals, the holdings, if clinical signs were detected on holdings, the actions taken, and the number of doses of vaccine used. (D35.w1 - full text available)
Complications/ Limitations / Risk Disease control considerations:
  • Increased risk of disease spread associated with increased contact between animals and personnel involved in vaccination. (J3.131.w1, J16.22.w1).
  • During the period immediately after vaccination (14 days following the vaccination of cattle and 7 days following the vaccination of pigs), virus transmission may occur from vaccinated animals to susceptible animals in contact with them (Donaldson and Kitching 1989; Salt et al. 1998).(D35.w1 - full text available)
  • Identification and traceability of every vaccinated animal must be guaranteed (e.g. ear tagging or notching).(D35.w1 - full text available)
  • Some animals may be in the early incubation stages of FMD at the time when they are vaccinated, and a small proportion may become carriers (D36.Para124). Ruminants, including cattle, with or without developing clinical disease, and including animals which have been vaccinated and then been in contact with live FMD virus may carry live FMD virus in the pharynx, for up to three years (cattle), nine months (sheep), less than nine months (goats). (J42.118.w1). However, good-quality vaccines, if given a sufficient length of time prior to exposure to live virus, may reduce the incidence of the development of the carrier state in vaccinated animals (W18.Apl01.sib1). 

Economic considerations:

  • Immediate costs associated with vaccination (D35.w2).
  • Extended loss of export trade from the vaccinated zone, due to export restrictions on seropositive animals, related to the problems of identifying carriers (J3.131.w1).
  • Need to ensure vaccinated animals were not moved outside the vaccinated zone except under special licence (J3.131.w1).
  • "Possible generation of a surplus of meat" (J3.131.w1).
  • "There are no fully validated serological tests to distinguish between antibody produced by vaccination and that resulting from recovery from infection." (J42.118.w1).

Safety considerations:

  • Risk of stress, particularly to highly pregnant animals, during gathering and handling for vaccination (D36.Para200).
  • Hazards to both animals and humans in trying to gather animals in inclement weather such as fog or snow (D36.Para200).
Equipment / Chemicals required and Suppliers
  • Vaccine. An emergency vaccine should be a vaccine of high potency containing antigen of a strain which is antigenically appropriate. It should provide a sufficient level of protection after the application of a single dose. However, if the field strain is antigenically different from the available vaccine strain and there is no alternative strain available it may be necessary to implement a second round of vaccination.
    • Formulated foot and mouth disease emergency vaccines (inactivated antigens being stored as concentrates over liquid nitrogen) must have been validated as potent vaccines.
    • The response to an initial vaccination depends on the dose of antigen used. High potency vaccines are essential for use in emergency situations (J16.22.w1).
    • High potency is essential (at least 6 PD50 E.P.) to achieve rapid development of immunity and a broad antibody response in vaccinated animals. Therefore, in circumstances when there is a lack of homology between a field virus and the vaccine strain then the broader response induced by a highly potent vaccine can compensate in part for the lack of antigenic homology.
    • High-potency vaccines can protect cattle and pigs within a few days (e.g. by four days after vaccination) (J70.12.w1, J70.16.w2).
    • Oil-adjuvanted inactivated vaccines should be used whenever possible since they can be expected to produce an acceptable immune response in all foot and mouth disease susceptible species, whereas aluminium hydroxide adjuvanted vaccines are effective in ruminants but not in pigs.
    • The vaccine strain used should be as homologous as possible with the field strain; diagnostic procedures on FMDV isolates should include the provision of information about the degree of relationship to vaccine strains.
    • Non-structural proteins should not be present in the vaccines because this could interfere with differential diagnostic tests. Batches must be tested to verify this.
    • (D35.w1 - full text available)
  • Cold chain facilities must be available for the storage and distribution of vaccine so that it is, at all times, kept under cool temperature conditions, as specified in the European Pharmacopoeia .(D35.w1 - full text available)
Expertise level / Ease of Use Vaccination teams and equipment. A sufficient number of well trained vaccinators and the required equipment to ensure the rapid administration of vaccine to the animals must be immediately available according to prior contingency planning.
Cost/ Availability
  • Sufficient vaccine would be needed to vaccinate all animals within the designated vaccination area.
  • Suitable concentrated inactivated FMDV vaccines are stored in vaccine banks such as the International Vaccine Bank at Pirbright and the European Vaccine Bank.
  • Emergency vaccines held in highly concentrated form in virus banks (e.g. at Pirbright) contain large numbers of vaccine doses and vaccines may be made available by 48 hours following request. (J70.12.w1).
Legal and Ethical Considerations
Author Debra Bourne
Referee Suzanne I Boardman
References

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