Foot-and-Mouth Disease

Frequently Asked Questions AND Misconceptions

... for UK Vets and Farmers


  • This collection of "Frequently Asked Questions" was originally compiled during the 2001 UK Foot-and-Mouth Disease (FMD) outbreak, Spring 2001, and has been updated in September 2007 to reflect changes since 2001. These questions were asked by farmers, vets, electricians, receptionists, bankers, scientists, journalists and many other people from diverse walks of life. Although all the individuals had a great wish for accurate information, the overall level of knowledge tended to be basic and scanty (there were a minority of notable exceptions where people had an excellent grasp of the issues - particularly some journalists), whilst some people were working from entirely inaccurate information. This section (indeed the whole of the Wildpro FMD volume) aims to equip all those affected by Foot-and-Mouth Disease with the scientific background to the disease and the management options, and so to clarify some of the misconceptions that have arisen.
  • Information within Wildpro is entered under a strict policy that original sources are respected and referenced wherever possible. We strive to maintain a non-judgmental position, properly reflecting areas of difference in opinion and explaining the issues involved.
  • The information within this section has specifically brought together for UK Vets and Farmers, and the issues are discussed with respect to the UK situation. Comments refer specifically to the vaccines that would be used in the UK (should the current policy alter), and risk assessment and legislation information refers specifically to that of the UK Government.
  • The other sections within the Wildpro volume are written to be of relevance worldwide.

The following leaflets written by Defra provide useful information for the UK.

NOTE: These documents were current in England in September 2007. Please note that regulations may change over time and vary between countries. It is advisable to consult your relevant authority for current regulations in your country.


(For more detailed information and source references see: Quarantine and Disinfection, Literature Reports: Disinfection, Literature Reports: Quarantine, D322 - Fact Sheet 2 Biosecurity Preventing the introduction and the spread of foot and mouth disease, MAFF: Biosecurity - advice for cattle and sheep farmers, MAFF: Restocking Form A premises: A farmers guide, MAFF: Guidance on the Storage, Handling and Movement of Animal Manures and Slurries, MAFF: Silage and hay-making, and grassland management, during Foot and Mouth disease restrictions: guidance for farmers, MAFF: Measures to Allow Movement of Big Bale Silage within a Protection Zone, MAFF: Advice and precautions for zoos, wildlife parks etc)

What is the best way for farmers to protect their stock?

  • The best way for farmers to protect their stock and minimise further spread of the disease (particularly in an infected area) is by strict control of all movement (animals, people, vehicles and any materials) onto and off the farm, combined with rigorous disinfection. When moving items or people ONTO the farm, assume that the world outside is "infected" and the farm is "clean". When moving items or people OFF the farm, assume that the farm is "infected" and the world outside is "clean".

What are the important factors for disinfection?

  • For confidence that disinfectants will work to effectively kill FMD virus, they must:
    • be an approved disinfectant (see Defra Guidelines link above) and lists of approved disinfectants: for England (at W66.Aug07.w1), for Scotland (W672.Aug07.w1) and for Wales (W673.Aug07.w1)
    • never be mixed with one another. Disinfectants active against FMD virus are often acids or alkalis (which depend on their pH for their action against the virus) and mixing would prevent their action against the virus.
    • be used on clean surfaces (they are deactivated by organic matter, so it is important to remove mud, muck, milk etc. before using disinfectants, if they are to work properly)
    • be used at the correct concentration
    • have the right amount of detergent added (if appropriate)
    • be left in contact with the item to be disinfected for long enough

We wash our vehicles through a ford/splash every day. Does this clear the vehicles of the virus?

  • Washing vehicles through a ford or splash may remove gross contamination from your vehicle. However, it will not kill the virus and will not necessarily remove all the virus from your vehicle. Additionally, live virus may be carried downstream from the ford or water splash.

What are the main danger areas for persistent viral contamination on the farm?

  • The virus survives in the environment quite well, especially in dung and slurry, and can remain active inside buildings for long periods (months). The virus has spread through hay contamination and can remain active on pasture for some time. (see MAFF Guidelines link above)

What the best way to deal with substances that may be contaminated?

  • After a farm has been infected, anything that cannot be disinfected properly must be burned or buried with the animals. Treatment/disposal of slurry will need to be undertaken. In the UK, EU guidelines must be followed (set out in ) have developed strict guidelines for disinfection of infected premises, for the treatment of manure and slurry, for making hay and bringing in and using of big bale silage. (see MAFF Guidelines link above)

How long should a farm be left empty before re-stocking?

  • When restocking, sufficient time must be left between cleaning and disinfection and restocking. Officially, a premises must be left at least 21 days following approval of full cleaning and disinfection before restocking. Initially it is advisable to re-stock with only a few animals to act as sentinels. A longer period before restocking may be suggested or required if the disease is persistent in the local area. If a farm becomes re-infected, the entire cleaning and disinfection process must begin again. It was suggested following the 1967-68 outbreak that a longer period be left before restocking where sheep were involved due to difficulties in clinical diagnosis. During the 1967-68 outbreak there were a number of cases of disease recurrence following stocking. These were thought to be due to either:
    • Infection from surrounding premises still with active virus infection (possibly airborne)
    • Active virus still being present on the farm premises (e.g. in hay).

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Spread of the Disease

(For more detailed information and source references see: Foot-and-Mouth Disease, FMD Virus, Literature Reports: FMDV Transmission, Literature Reports: FMDV Definitive Host Species, Literature Reports: FMDV Paratenic Host Species, Literature Reports: FMD Disease Duration to Recovery in Individual Animals, Literature Reports: FMD Incubation Period, Literature Reports: FMD Time Course / Persistence of Disease, Computer modelling)

How long is an animal infectious?

  • In livestock, after an animal becomes infected, the virus multiplies in the body for several days, and is released from a variety of body systems, including the lungs (air), mouth (saliva), skin (epithelium), urinary (urine), intestinal (faeces), mammary (milk) and reproductive systems (semen / vaginal secretions). This is the time that the animal is most infectious. After a few days the body begins to produce antibodies which then appear to minimise virus production and the virus infection "burns itself out" (usually a few days after antibodies first become active). At this point the infected animal is usually reported to stop producing enough virus to infect other animals. The chronic signs seen so frequently after FMD Virus infection (lameness, infertility, poor milk yield, weight loss) are due to damage done to the body in the early stages of viral multiplication before antibodies to the virus can be produced, and / or due to secondary infection.

What are the distances the virus can travel on the wind?

  • The distance virus can travel on the wind and still cause an infection depends on environmental factors such as humidity, wind speed etc., the amount of virus produced, and the type and number of potential hosts downwind of the virus-producing animals. The virus seems to travel particularly long distances over water (up to 250km/156 miles) has been reported) although not nearly so far over land. Pigs produce much more virus than do cattle or sheep, while cattle are the species most likely to be infected by breathing in airborne virus. A recent study indicated that small numbers of sheep or cattle (e.g. ten infected animals) would not be infective more than about 100 metres (110 yards) downwind and even for 100 cattle or sheep producing virus, only cattle would be likely to be infected as little as 700 m (half a mile) downwind. At the other end of the scale, 1000 fully infective pigs could theoretically infect cattle 300 km downwind. Cattle are the domestic species infected most easily by wind-borne virus (pigs are least likely to be infected by this route). Larger herds appear to be more likely to become infected by such virus, probably because they breath in a larger total amount of air and there is more chance that one of them will inhale an infective dose (once one animal is infected the virus will then multiply in that animal and quickly spread to the other animals in the herd).

How does the virus spread through so many farms and herds so quickly and can it establish itself permanently?

  • Animals with active infection, with or without clinical signs, are the major source of continuing spread of the virus. They can produce massive amounts of virus. Having multiplied in one animal's body the virus must find a susceptible host in order for FMD to continue to spread. The major route of spread within a herd or flock is by direct contact, e.g. infected animals breathing out virus and the animals next to them breathing it in. A major way in which the virus is spread from one farm to another is by animals which are not visibly diseased being moved. However indirect contact is also important (airborne spread between herds occurs less often). FMD can survive for some time in the environment, particularly when attached to animal debris, so long as it is not exposed to acid or alkaline conditions. In this way, FMD virus moves from the infected animal to the external environment and then on to another susceptible animal. It will then remain active in a region so long as there are a progression of susceptible animals, that is it will become endemic (particularly if wildlife become infected and spread virus between different farms or areas). New born animals may then become infected with FMD virus as they lose any antibody immunity gained from their mother, and other individuals may become infected as their natural immunity (caused by previous exposure to the virus) wears off.

What are carrier animals and what role do they play in outbreaks?

  • The issue of carrier animals has been generally greatly over-exaggerated. Carrier animals are those individuals in which virus can be detected more than 28 days after infection. The virus has been recovered from the throat of Domestic sheep for up to nine months post infection and from Domestic cattle for 3 years. Numerous scientific experiments under biosecure conditions over the decades have failed to demonstrate transfer of virus from carrier livestock to susceptible animals. There is some epidemiological (field) evidence suggesting that carriers may be sources of infection for other livestock occasionally.

Which species other than cattle, sheep, pigs and goats can get and spread FMD?

  • A wide variety of species can be infected naturally with FMD, mostly cloven-hoofed animals such as deer and antelope but also hedgehogs and Asian elephants, among others; infection in humans is extremely rare. Hedgehogs with clinical disease develop severe foot problems and are unlikely to move long distances. Almost any animal - bird, mammal, insect etc. can spread FMD mechanically. Among wild animals, scavenging animals such as crows, seagulls, foxes and rats may be most likely to spread the virus in this manner, although movement of people and their vehicles is thought to play a much larger role.

Do small numbers of pet animals such as sheep really pose a risk to other animals?

  • FMD is transmitted by three main routes: direct contact between infected and susceptible animals, indirect contact (e.g. movement of infected milk or faeces from infected animals) and windborne spread. Small numbers of llamas, pet sheep and other ruminants are unlikely to become infected by windborne spread unless they are directly downwind of infected pigs and would be extremely unlikely to infect other animals downwind of them. A single pet pig on the other hand, might produce enough virus to infect cattle five kilometres downwind in good conditions for wind-borne spread.

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(For more detailed information and source references see: Vaccination Overview, Literature Reports: Vaccination Regimes, Literature Reports: Vaccine Developments, MAFF: Approach to Vaccination of Animals in Zoos)

Will vaccination work for a hill sheep flock where a few animals might not be found at the time of vaccination?

  • In order to protect a herd of animals against FMD virus it is not absolutely necessary to vaccinate 100% of the animals, although as many animals as possible in an area should be vaccinated. (To have herd immunity, 80 - 85% should be protected / immune). This should be easily achievable in the domestic sheep, pig, and cattle herds of infected areas within the UK since the vaccines can be distributed promptly and maintained under the optimal conditions to retain maximum activity (i.e. vaccines should be kept cool but not frozen).

Can animals carry FMD virus after vaccination?

  • Vaccinating an animal does not make it a carrier (the vaccine uses an inactivated (dead) virus). In vaccinated animals which have ALSO been exposed to FMD virus, samples taken from the back of the throat have been positive for virus infection in the days immediately after infection and it has been shown that they may pass virus to other animals for a few days after infection. Vaccinated animals may also become long-term carriers. However, there is NO evidence that vaccinated animals which become carriers pass infection to susceptible animals.

Is there a test that can distinguish between infected animals and vaccinated animals?

  • Both infected and vaccinated animals will produce antibodies which protect the animals from further attack by the virus. New serological tests which have been validated on tens of thousands of animals are reported to reliably distinguish between those herds which have been vaccinated and have had no exposure to virus, and those which have been exposed to virus and consequently developed antibodies. These tests are under consideration by the OIE, but at present ruminants with antibodies to FMD virus cannot be traded internationally and under the present regulations a country such as the UK, if using vaccination alongside stamping out, would not regain its FMD-free status until either three months after the slaughter of the last diseased or vaccinated animal or twelve months after the slaughter of the last diseased animal if vaccinated animals were not culled.

Can vaccination cause the virus to mutate or cause disease?

  • The vaccines that would be used in the UK are killed vaccines which are manufactured to very high safety standards. There is NO live virus in vaccines produced to European industry standards. Vaccination does not cause the virus to mutate and does not cause disease.

What are the vaccines and how are they given?

  • Vaccines should always be used as detailed by the manufacturer. The vaccines, which all use killed not live virus, are designed for use in domestic cattle, sheep and pigs and work fast and well in all these species. The vaccines come in two forms - "oil emulsion" (given by intramuscular injection and used in cattle, sheep and pigs) and "aluminium hydroxide - saponin" (given by subcutaneous injection and used in cattle and sheep). In emergency situations high potency vaccines may be used which increase the speed and level of protection. Immunity begins to develop a few days after a single vaccine dose and for one-off Emergency Vaccination with a high potency vaccine (with all susceptible animals being vaccinated), one dose may be considered sufficient. With conventional lower potency vaccines, or if the risk of exposure to FMD Virus was considered likely to be long-standing, a second booster dose may be recommended after 2-4 weeks and again at 6 months (usually pigs and cattle) or 1 year (sheep). (In endemic regions regular booster vaccinations are used). The precise vaccination regime to be recommended would depend on the species to be vaccinated, the vaccine used and the level of risk of exposure to the virus.

Can the vaccines be given to zoo animals?

  • There is a long history of zoo animals of many different susceptible species being vaccinated, for example within continental Europe. Whilst it is likely that the vaccines would provide protection to non-domestic (wild) susceptible species, they are not tested in these species and as a result it is not known whether they reach a strong immune status after vaccination. As the "oil emulsion" preparation can be given by intramuscular injection, it could be administered by dart.

Can free-living wild animals be vaccinated?

  • Vaccinating free-living susceptible wild animals (e.g. deer and wild boar) would be impractical. Unlike rabies, there is no oral vaccine for FMD and injecting e.g. all the wild deer, even using dart guns, would not be possible. However, vaccinating farm livestock in an area would protect wild animals indirectly by reducing the amount of virus in the area and decreasing the risk of spread from wild to domestic animals.

Are there enough vaccines to vaccinate all Domestic animals in the UK?

  • Vaccines are usually made to order in an emergency situation, with protection for the specific virus strain. Vaccine could be made available extremely quickly from the emergency antigen banks to start emergency vaccination in the UK of animals in high-risk areas. It would be physically impossible to vaccinate the whole population of UK livestock in one or even a few days and more vaccine could be made available to complete the vaccination programme. Enough virus antigen of the correct type to protect animals against the type of FMD virus causing this outbreak is held in the EU Emergency Vaccine Bank and the International Vaccine Bank to produce 5.5 million cattle-doses (11 million sheep doses) of highly potent emergency vaccine.

Who makes the vaccines and how does one get permission to use a vaccine?

  • There are three major vaccine manufacturers in Europe, Merial Animal Health Ltd., Bayer, and Intervet. In the UK, the use of vaccines is strictly restricted by law. In addition, the UK Government must give written notification to the European Commission before it can implementing a vaccination programme. 

What is the EU Policy on vaccination?

Would we still need to cull animals if we vaccinated?

  • Vaccination alone is not enough to control and eliminate FMD. However, vaccination used alongside the slaughter of infected and in-contact animals, quarantine and disinfection would reduce the number of animals becoming infected and could greatly reduce the amount of culling needed to eliminate the disease.

Will vaccinating stop us exporting meat or livestock for several years?

  • No. Vaccination, alongside "stamping out" of infected animals and "dangerous contact animals", quarantine and disinfection is widely recognised as allowing the disease to be brought under control in an area more quickly. Under the present rules for international trade, FMD-free status and the export of meat and livestock could re-start just six months after the last infected animal was slaughtered, if proper tests were carried out. If vaccinated animals were also slaughtered, FMD free status could be regained as early as three months after the last diseased or vaccinated animal was slaughtered. This is set out in Terrestrial Animal Health Code Sixteenth Edition: Chapter 2.2.10 Foot and Mouth Disease and Appendix 3.8.7 Surveillance (Office International des Epizooties)

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Computer Models and Changing Policy

(For more detailed information and source references see: Use of Models of Airborne Spread for Foot and Mouth Disease, Control Options for Stopping FMD Virus Spreading - Use of Epidemiological Modelling, Assessing the Costs (Actual and Potential) and Consequences of FMD and its Control)

Are Computer models of FMD spread worth using?

  • Computer models of FMD spread can provide useful information to assist decision making. It is important to use the best, most accurate models of FMD spread available, which allow for different species (including wild species) producing and being exposed to virus, different methods of spread (direct / indirect contact, airborne) and different environmental conditions. Models are only as good as the data entered into them and good surveillance information, giving data showing the present extent of infection in wild as well as domestic animals is necessary for models to give accurate forecasts. It is also important to remember that answers from computer models, however sophisticated, should never be used as the sole means of making major decisions. Computer models can assist in making a professional judgement, but must never replace that judgement.

If vaccination works, why can't we just get on and vaccinate?

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Laboratory Tests

(For more detailed information and source references see: Diagnosis, Surveillance & Carriers, Literature Reports: FMDV Detection and Identification, Literature Reports: FMD Detailed Clinico-Pathological Findings)

What samples are needed for the diagnosis of FMD?

  • FMD is usually diagnosed by detecting virus or virus antigen. The best sample for this is material from fresh lesions, because this contains large amounts of virus and positive results can be confirmed just a few hours after the test is set up at the laboratory. Antigen can also be detected in samples of milk and of whole heparinised blood, in the early stages of infection. The sample most useful for detecting virus in subclinically infected sheep (and in carrier animals) is cells and fluid (oesophageal -pharyngeal fluid sample) taken from the back of the throat using a metal cup on a rod - a probang cup. Just a nasal swab is needed for a new test which has recently been developed but is not yet used in the UK. As the disease progresses and the animal's immune system responds the amount of virus decreases (some may be left in the back of the throat (pharynx area) of carriers). In the later stages of disease and after the period of clinical signs, clotted blood samples are taken and the serum separated for the detection of antibody.

How are cases of FMD confirmed and how long does this take?

Cases of FMD are usually confirmed by the detection of virus or virus antigen in samples taken from mouth or foot lesions, although blood and milk may also be used. If there are large quantities of virus in samples from lesions, confirmation using an ELISA (to detect the presence of virus antigen) may take only a few hours once the sample has reached the laboratory and been set up. However, if the initial test results are negative, attempts will be made to grow the virus in tissue culture cells to increase any virus present before re-testing, and this may take several days.

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Environmental Damage

(For more detailed information and source references see: Quarantine and Disinfection, Literature Reports: Disinfection, Environment Agency: Advice on the use and disposal of disinfectants, Environment Agency: Guidance on ash disposal arising from Pyres and mobile incinerators, Environment Agency: Licensed Landfill Sites that are Suitable for the Disposal of Carcasses, Environment Agency: Advice on disposal of manure, slurry and dirty water, Environment Agency: Risks From BSE Via Environmental Pathways)

What are the effects of disinfectants used in FMD control on the environment?

Disinfectants are chemicals which kill organisms that cause disease. They can also kill useful, valuable and / or rare organisms. Hence our rivers and waterways, and thereby our water sources for human use, can be seriously damaged by disinfectants. Care should be taken with their use and their disposal. The Environment Agency states on their website that "All disinfectants pose a potential pollution risk, particularly to rivers, streams and their associated wildlife, and those with a phenolic content can be particularly persistent. Sensible precautions, however, will minimise the risks."

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Wildlife and Pets

(For more detailed information and source references see: Wildlife, Zoos, Pets and other Animals, Literature Reports: FMDV Definitive Host Species, MAFF: Advice and precautions for zoos, wildlife parks etc, MAFF: Approach to Vaccination of Animals in Zoos)

Does FMD affect any UK wildlife species?

FMD virus is highly infective and all cloven-hooved animals appear to be susceptible, including deer and wild boar. Severe disease has also been reported in hedgehogs in Britain. Numerous other animal species have been infected experimentally with FMD virus, including cats, dogs, rats, mice, moles and water voles, but it would appear that for many species infection occurs only as a result of massive virus exposure or if injected with the virus.

Would it be possible to control the disease in wild animals?

Control of any disease in wild animals is difficult once it becomes established. Many wild animal populations are too widely dispersed for the virus to pass to sufficient new animals, so that FMD would be likely to die out in the population over a period of time. However, FMD has been known to persist in wild animal populations, including for a period in deer, and to return from wild populations into domestic stock. The best way to control disease in wild populations is to stop the disease getting into the population in the first place.

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