Foot and Mouth Disease: Veterinary Risk Assessment and Protocol for Rights of Way Closure
In the event of an outbreak of FMD, what is the risk of causing further outbreaks if rights of way are open to the public?
Summary of Risk Assessment
Great Britain is classified as FMD free, in the event of a new introduction of disease, there is a risk that persons using rights of way could cause further outbreaks. Infection may result from contaminated persons or accompanying animals arriving at the right of way and subsequently passing on infection to livestock or by persons or accompanying animals becoming contaminated while using the right of way and passing infection to livestock then or at a later time.
The factors considered to be most responsible for increasing this risk are:
- contact with infected premises or premises where animals have been exposed to the risk of infection prior to arrival at a right of way
- contact with livestock prior to arrival at a right of way
- failure to disinfect footwear prior to arrival at a right of way
- proximity of rights of way to livestock areas, including infected premises and premises where animals have been exposed to the risk of infection
- presence of accompanying animals
- failure to limit access for persons or accompanying animals from rights of way to livestock areas failure to limit access by livestock to rights of way, resulting in deposits of faeces, urine, milk etc.
- contact with livestock while in locality of a right of way
- contact with surroundings (including pasture and foliage) while in locality of a right of way
- meteorological and environment conditions which influence virus survival
- failure to disinfect footwear after leaving locality of a right of way
- contact with livestock after leaving locality of a right of way
- contact with surroundings (including pasture and foliage) after leaving locality of a right of way
Of these, the major factors are:
- proximity of rights of way to livestock areas, including infected premises and premises where animals have been exposed to the risk of infection
- contact with livestock prior to arrival at a right of way
- contact with livestock while in locality of a right of way
- contact with livestock after leaving locality of a right of way
- failure to limit access for livestock to rights of way, resulting in deposits of faeces, urine, milk etc.
Summary of Risk Management options and rationale
This section identifies ways in which the risks which have been identified can be managed, taking no account of whether the management options are practical or proportionate to the level of risk. Theoretical risk management options include:-
i. Closing all rights of way over land which may be grazed by livestock,
making public access a criminal offence.
ii. Closing rights of way only in areas where the risk of FMD virus being
present is greatest
iii. Preventing or discouraging access by those who keep or handle susceptible livestock in the course of their work, and so are most likely to have been exposed to and contaminated by FMD virus.
iv. Permitting access but encouraging the public
- to wear clean clothing and footwear so that they do not introduce infection to an area;
- to avoid walking amongst livestock, and, in particular, NEVER to handle or touch animals, and
- to use any disinfectant footbaths or pads which the landowner may choose to provide.
Regulating access in accordance with the likelihood that infected animals or their products may be encountered. The risks are greatest on Form A and Form D premises, but entry and exit to and from these are already controlled by statute. Elsewhere the risk diminishes with distance as follows:
- within the protection zone, normally an area of 3km radius around any Infected Premises in an Infected Area
- within an Infected Area outside any protection zone
within a Controlled Area - where no FMD controls are in force.
In addition to geographical factors, risk may diminish with time. Virus viability on pasture is limited and is dependent on meteorological conditions. Virus survival during the summer months is limited by warmer, drier weather. Meteorological conditions will be more favourable to virus survival on pasture during the winter months.
Recommended action
i. FMD virus may be introduced to previously uninfected premises in many ways: by airborne spread; by the movement of infected animals, feed or bedding; and by the movement of people, vehicles or equipment contaminated with the virus. Transmission by people has been recorded on many occasions, but those responsible have generally had close contact with animals on infected, and then on uninfected, premises. It is theoretically possible that persons using rights of way who had not had direct contact with infected animals could carry infection to previously uninfected animals, although there is no evidence that this has actually happened and the risk, if any, is small in comparison to other transmission risks.
ii. Even small risks can be further diminished by appropriate action, but the cost may outweigh the benefit. There is a balance to be struck between the need to control FMD and the damage that controls do to other important industries, such as tourism. Draconian action may be unnecessary and inappropriate, particularly if universally applied.
iii. There is no veterinary justification for closing all rights of way and preventing all public access to land. A more measured response, which takes account of both public perception and of the real risk, is required. The latter is the product of many factors, including the prevalence of infection in an area, the presence or absence of susceptible livestock, and the density of the livestock if present.
iv. Viable virus is most likely to be picked up on premises which have been recently infected or exposed to the risk of infection by human, animal, or animal product movement, or by proximity. Premises on which infection is suspected or has been confirmed, or on which animals have been exposed to the risk of infection, are subject to restrictions which prohibit entry or exit except under licence. Restrictions on individual premises may remain in force for many months, particularly on premises where full cleansing and disinfection is not carried out for any reason. The risk that persons using rights of way will come into contact with FMD virus on premises on which final cleansing and disinfection has been completed is very small, and even on premises where it has not, there is virtually no risk from walking on the land (as opposed to through yards or buildings) after a sufficient period of time has elapsed.
v. Even on premises that are not subject to Form A or Form D restrictions, infection may be present but unrecognised. The risk is greatest in premises situated in the PZ of an Infected Area, less in Infected Areas outside PZs, much less in Controlled Areas, and least where there are no restrictions or where restrictions have been lifted.
vi. Whatever the status of an area there is only a very small risk that persons using rights of way who have not recently handled or been in direct contact with susceptible livestock will introduce infection from elsewhere, or spread infection from one premises to another. The risk is greatest on land close to an Infected Premises on which FMD has recently been confirmed and diminishes with time. A high density of livestock increases the likelihood of contact between persons using rights of way and animals, and so increases any risk of transmission.
vii. The single most effective method of reducing any risk posed by persons
using rights of way is to ensure that they have not handled or been in
contact with susceptible livestock before or during their visit. Enforcement
of such a condition is not practicable but it is reasonable to suppose
that most people using rights of way will respect the interests of the
community at large by taking precautions, which will minimise the risk
of spreading FMD.
viii. It is extremely unlikely that people using rights of way will come
into contact with viable FMD virus. The risk of transmission by these
persons from one farm to another is therefore very small. The following
action can be justified:
Allow public access to all paths and rights of way, but publicise and
seek the co-operation of persons using rights of way in observing the
following precautions intended to protect the disease - free status of
the area:
- start your walk wearing clean footwear and clothing;
- do not approach, touch or handle livestock;
- keep dogs on a lead wherever there are livestock;
- take any waste, including food, home; and
- use any disinfectant footpads or baths which the landowner provides.
ix. Even when area restrictions are lifted, individual premises may remain under restriction for much longer than is necessary to control the risk that persons using rights of way may come into contact with viable virus and carry infection to other premises. Virus survival on land at any time of the year is unlikely to extend beyond the date when final cleansing and disinfection of the premises is completed or more than three months from the date of preliminary cleansing and disinfection if this is sooner.
x. Entry to and exit from restricted premises is normally permissible only under licence but there is statutory provision for this requirement to be discontinued or modified. It is therefore feasible to allow rights of way on restricted premises to reopen whilst other restrictions (such as that which prevents restocking) remain in force.
xi. It is therefore recommended that:
In the event of an outbreak, rights of way should be closed within the Protection Zone, normally the area within a 3km radius of an infected place. In exceptional circumstances, following a veterinary risk assessment, the area may be larger than this in order to control the spread of disease. Such circumstances might arise, for example, where it is believed that conditions have allowed windborne dissemination of virus in high concentration over a large area. Rights of way should remain closed until the protection zone restrictions have been lifted. This will normally be when the Infected Area restrictions are lifted.
Rights of way which only cross the land of restricted premises should be reopened as soon as the completion of final cleansing and disinfection has been certified. However, rights of way which pass through farmyards and buildings should be temporarily diverted, but if this cannot be done, they should remain closed until supervised restocking has been completed and restrictions lifted.
If full cleansing and disinfection is being undertaken but has been delayed then rights of way which cross the land only may be reopened 3 months after the preliminary cleansing and disinfection. However, rights of way which pass through farmyards and buildings should be temporarily diverted, but if this cannot be done, they should remain closed until supervised restocking has been completed and restrictions lifted.
If full cleansing and disinfection is not being undertaken at all then rights of way which cross the land only may be opened 3 months after the preliminary cleansing and disinfection. However, rights of way which pass through farmyards and buildings should be temporarily diverted, but if this cannot be done, they should remain closed until the restrictions are lifted.
Page last modified:
November 16, 2006