& Management / Disease
Investigation & Control / Treatment
& Care / Techniques:
||Vaccination of susceptible animals over a
wide geographical area, such as a country, in the face of an outbreak of
|Appropriate Use (?)
- In order to control the disease without slaughtering excessive numbers of livestock
- To reduce the risk of the disease spreading into areas with large populations of
wildlife in which the disease might then circulate.
- If FMD became endemic in a wildlife population, control of the disease in that
population might require the eradication of that wild population. this may be
difficult/impossible, and may not be publicly acceptable.
- If FMD became endemic in a wildlife population, control of the disease in domestic
livestock would require ongoing (routine/prophylactic) vaccination of livestock and/or the
setting up of barriers to prevent contact between domestic livestock and wild animals.
- Both the EU Strategy for Emergency Vaccination and the Northumberland Report (The Report
of the Committee of Inquiry on Foot-and-Mouth Diseases 1968) make it clear that if
emergency vaccination programmes are not implemented rapidly, and FMD becomes widespread,
regional or national vaccination (mass vaccination) may be the only remaining option for
the control of the disease.
- "If an analysis of
parameters gives a result which supports a programme of protective emergency vaccination
then the programme must be implemented without delay. It is emphasised that if
decision-making and the required actions are delayed and as a consequence the initiative
is lost and the disease becomes widespread, then the only remaining option may be a
programme of either regional or national vaccination." (D35.w1)
- "If, as would happen in the event of a
large number of scattered outbreaks, large areas of the country and large numbers, say
fifty per cent of animals were involved in ring vaccination, then general prophylactic
vaccination would probably become inevitable." (D36.Para207).
Vaccinated animals are protected against FMD. They will not usually
develop the disease. This means that:
- They will not develop the clinical signs of FMD.
- No loss of milk output
- No weight/condition loss
- No loss of growth rate
- No deaths of young animals
- No loss of draught power
- No welfare problems associated with severe disease
- No secondary infections of lesions
- No prolonged convalescence of recovered animals.
- They will not excrete large quantities of virus which could infect other
animals; the total amount of virus in the environment will be reduced. (J70.12.w1)
- However, low level excretion may occur with subclinical
infection if infected prior to fully developing protection, but much less than with full
- However, may still develop carrier state if exposed to
virus (ruminants, not pigs) with slight risk of passing virus to other animals.
- N.B. Number of carrier animals decreases with time. (J19.73.w1).
- Reduced numbers of farms on which FMD occurs (J3.102.w6).
- Except where used as part of a "vaccinate and cull" policy
around infected areas, livestock which have been vaccinated do not need to be culled.
- Meat, milk and other animal products from vaccinated animals may
enter the human food chain as usual. and other
- There are no risks to human health health from FMD vaccines
(which are inactivated vaccines) entering the food chain (W32.Apl01.sib1).
- The loss of genetically valuable stock and rare breeds, including e.g.
hill sheep which are particularly adapted to their local area, is avoided. (D35.w2)
- The loss of income to farmers associated with loss of stock due to either
infection on the premises or extended culling is avoided, along with the costs to the
government of compensation.
- The costs and environmental risks associated with disposal of carcasses
following culling operations may be greatly reduced.
- Movement restrictions may be lifted within a relatively short time
following the end of the period in which exposure to infection may occur (e.g. two or
three weeks) (J21.23.w1)
- Could be useful to prevent virus entering populations such as gated or hefted
upland/moorland sheep and susceptible wildlife populations (e.g. deer) in upland areas
where domestic and wild species share habitat (D35.w2).
- FMD in the wild deer population could be a source of infection for domestic livestock.
- Vaccination of wild deer would be very difficult or impossible, however vaccinating
livestock would reduce the risk of the disease being passed to deer and therefore the risk
of the disease being passed back from deer to susceptible livestock.
- "FMD-free" status may be regained 12 months after the last case
of FMD even if the vaccinated animals are not slaughtered (D35.w2).
- The option to use emergency vaccination was
retained by the European Union when routine vaccination was abandoned after 1991, and
stores of highly concentrated vaccine were set up to allow the rapid use of emergency
vaccination if required.
- Concentrated inactivated FMDV antigens may be stored at ultralow temperatures which
allow stable storage for several years and formulation of vaccine when required (J70.16.w2).
|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,
- 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).
Difficulties in differentiating between animals which have been
vaccinated and those which have been infected.
- Vaccinated animals will have antibodies to FMDV.
- Tests usually used for detecting antibodies to FMDV cannot give
information as to whether an animal has been vaccinated (but not infected) or infected
(whether or not it has been vaccinated).(J42.118.w1).
- Also, seropositive animals (not including pigs, as these do not become
carriers) are excluded from international trade. (J42.118.w1).
- If no vaccination is used, or ring vaccination followed by slaughter of
vaccinated animals and serological surveys show an absence of FMD antibodies, "free
from FMD" status can be regained after three months from the last outbreak. (J42.118.w1).
- If vaccination is used, "because serology cannot detect carrier
animals and because FMD can infect immune animals and cause sub-clinical disease in partly
immune animals, it is acknowledged that FMD may circulate undetected in a vaccinated
- Therefore, if vaccination is used, "free from FMD" status
cannot be regained until two years after the cessation of vaccination (if vaccinated
animals are not slaughtered). (J42.118.w1).
- However, recently-developed serological (blood) tests
are able to distinguish between animals which have been vaccinated against FMD and those
which have actually been infected with foot-and-mouth disease virus. (J69.20S2.w1,
2) Possibility of vaccinated animals becoming carriers
(following undetected mild/subclinical infection, or without ever developing a general
infection) and then infecting unvaccinated animals.
- Ruminants, 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).
- Carrier animals may represent a risk of initiating further outbreaks of
- Epidemiological evidence suggests that carriers do sometimes transmit
virus to susceptible animals in close contact with them.
- Experimentally, it has been possible to prove transmission of virus from
carrier animals only very rarely.
- The factors which determine whether or not virus in the throats of
carrier animals infects other animals are not known.
- Detecting carrier animals is not easy.
- Testing for carrier status requires sampling cells and mucus from the
pharynx (back of the throat) using a probang cup. Virus is only excreted some of the time
and often at low levels. Sensitivity of testing is probably 50%, that is, about 50% of
carriers, tested on one occasion, would NOT be detected.
- However, this can be improved by repeated sampling (J42.118.w1).
- PCR techniques may be used to detect carriers using probang specimens: these are
potentially more sensitive than detection using tissue culture (J35.148.w1)
- There is no blood test to detect carrier animals; there is the
possibility that vaccinated animals may occasionally become carriers without developing
antibodies to the virus.
- However, used on a herd basis it should be possible to
distinguish by blood tests between vaccinated herds in which the virus has circulated (and
in which there might be carriers) and those which have never encountered the virus (in
which there cannot be any carriers). (J69.20S2.w1).
3) Need for definite identification of vaccinated animals.
- Vaccinated animals would need to be marked, to avoid the mixing of
potentially carrier animals with the seronegative population (J70.12.w1).
4) Perceived public health risks from meat, milk etc. from vaccinated animals.
- N.B. There are no risks to human health
from FMD vaccines (which are inactivated vaccines) entering the food chain (W32.Apl01.sib1).
- Meat from animals vaccinated against FMD is commonly eaten in many countries, including
countries which are free from FMD. There are no labelling requirements to indicate that
the animal was vaccinated against FMD any more than to indicate that it was vaccinated
against any of a range of other diseases.
|Equipment / Chemicals required and Suppliers
- Emergency mass vaccination is best carried out using high-potency vaccines which give
effective vaccination within a short time (a few days).
- 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 vaccines can protect cattle and pigs within a few days (e.g. by four days
after vaccination) (J70.12.w1,
- Sufficient vaccine would be needed to vaccinate all animals within the designated
- Suitable concentrated inactivated FMDV vaccines are stored in vaccine banks such as the
International Vaccine Bank at Pirbright and the European Vaccine Bank.
- Commercial vaccines, less highly concentrated, may also be used; however a second dose
of vaccine must be given after 3-4 weeks.
|Expertise level / Ease of Use
- Basic training required for carrying out vaccination correctly and to recognise the need
biosecurity measures, particularly disinfection, to minimise the risk of vaccination teams
spreading virus from one premises to another.
- A higher level of training would be required in and around an Infected Area to ensure
that vaccination teams fully understood the risks of transferring FMD virus between
premises and the importance of disinfection between premises as for Ring Vaccination and
Protective Emergency Vaccination..
- In an Infected Area, inspection of the animals on each premises by a veterinarian prior
to the start of vaccination of the herd/flock would be important to detect clinical FMD,
as with Ring Vaccination, "Damping-down" Emergency Vaccination and
"Protective" Emergency Vaccination.
- Sufficient vaccine to complete an emergency mass vaccination programme, or stored
antigen from which vaccine may be prepared, may not be available immediately.
|Legal and Ethical Considerations
||The use of vaccination may be restricted
legally within a region or country.
||Suzanne I Boardman
J35.148.w1, J42.118.w1, J69.20S2.w1,
- LEU1, LEU3,
, LEU6 - full