This document was produced by MAFF as a specific response to the FMD outbreak in the UK in 2001 and was made available on their website. Risk Assessments and specific recommendations related to the conditions in the field at the time and should be viewed in this context as they may not be applicable to outbreaks occuring under different circumstances.
Foot and mouth disease
27 March 2001

MAFF: Veterinary Risk Assessment No.7: What is the risk of feral wild boar becoming infected with FMD and subsequently causing new incidents of FMD in domestic livestock?

1. Summary of major risks identified in full assessment

The presence of a population of feral wild boar which are potentially susceptible to infection with FMD from Infected Premises or premises where unrecognised infection is present, pose a disease risk to other domestic livestock. Breeding populations of feral wild boar are currently recorded as present in Great Britain, on the East Sussex/Kent border and in West Dorset. Small numbers of escaped animals may be present elsewhere around wild boar farms that are located throughout the country.

Factors considered to be the most responsible for increasing this risk are:

• proximity of feral wild boar populations to Infected Premises
• proximity of feral wild boar populations to livestock on other premises
• proximity of feral wild boar to pig farms in particular
• failure to provide adequate perimeter security to livestock premises
• failure to provide adequate separation between feral wild boar and other livestock
• species of initially infected livestock, with pigs typically producing the greatest amount of respiratory aerosol whilst alive
• stage of pathogenesis of disease in livestock on an Infected Premises at the time of slaughter
• failure to minimise time between confirmation of disease and slaughter of domestic livestock
• failure to disinfect and dispose of domestic livestock carcases after slaughter
• failure to detect FMD infection in domestic livestock
• number and population density of infected feral wild boar populations

2. Summary of risk management options

1. There are few practical ways of managing the risks posed by feral wild boar. It is fortunate that there is no carrier state, making any long-term problem unlikely.

2. Boar populations can be controlled by shooting, or by cage trapping followed by destruction. Shooting is likely to increase dispersal (and so spread the risk), and should be avoided if possible. Trapping requires prebaiting and the provision of suitable traps. It would take many months and complete removal of the population might not be achieved. Traps are also susceptible to interference and may attract animal rights activists onto the land.

3. Exposure of the wild boar population to FMD virus can be minimised by:

1. Ensuring rapid diagnosis, slaughter and destruction of livestock on Infected Premises, so limiting virus production
2. Ensuring effective preliminary disinfection immediately after depopulation
3. Preventing wild boar access to farm buildings and fields. Good housekeeping will limit food availability, and electric fencing is an effective deterrent to most feral wild boar (but not to the sex-crazed).

4. Exposure of susceptible domestic livestock to infected feral wild boar can be minimised by:

1. Reducing or eliminating the wild boar population
2. Keeping feral wild boar and domestic livestock as far apart as possible and preventing direct contact with domestic pigs in particular. Outdoor pigs are at greater risk than those that are housed.

3. Recommended action

The only practical measures that can be taken are:

1. To minimise virus production on infected premises by rapid diagnosis, slaughter and destruction (in hand for other reasons),
2. To ensure that food (including, for example, pig carcases) is not available to encourage wild boar visits
3. To encourage good perimeter security, especially around outdoor pig units. Electric fences are reported to be effective.
4. To house sows in outdoor enterprises whilst on heat, to avoid al fresco service by feral wild boar.

If FMD were to be confirmed in an area where feral wild boar herds are known to be present, cage trapping and serological sampling of the boar could be considered as part of the procedure leading to removal of the Infected Area restrictions.

Contributors:

Dr A Donaldson IAH, Pirbright Laboratory
L Gallagher Risk Research Dept, VLA
Dr A M Garland Special Adviser, IAH, Pirbright Laboratory
Dr M Heydon FRCA
Dr P Kitching IAH, Pirbright Laboratory
C Livesey Risk Research Dept, VLA
K C Taylor Veterinary Consultant
Dr M Wooldridge Head of Risk Research Dept, VLA, Weybridge