Agriculture
Current control measures providing a national livestock movement ban in Scotland.
FOOT AND MOUTH DISEASE
Veterinary Risk Assessment (No.11)
What are the risks of causing new outbreaks of FMD by lifting the current control measures that provide for a national ban on livestock movements, while retaining additional temporary movement controls where livestock pass through markets and shows?
Current position
Scottish ministers declared a restricted zone on 3 August in the following terms:
SCOTTISH EXECUTIVE - RURAL DIRECTORATE
DECLARATION OF A RESTRICTED ZONE
The Scottish Ministers being satisfied in accordance with article 37(1) of the Foot and Mouth Disease (Scotland) Order 2006 (SS! 2006/44) ("the Order") that there is confirmation of the disease on premises in Great Britain and that following a thorough epidemiological assessment and having consulted the Chief Veterinary Officer (Scotland) are of the opinion that despite the measures already taken the disease appears to be spreading, hereby declare -
1. That from 9 p.m. on 3 August 2007, the area described in schedule 1 below is a restricted zone ("the zone").
2. Terms defined in the Order have the same meaning in this declaration.
Signed:
Ian Anderson
Authorised to sign by the Scottish Ministers
Date: 3 August
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SCHEDULE 1
The zone comprises the territory of Scotland.
The Scottish Executive published a Veterinary Risk Assessment on 10 August 2007 which recommended that movement control measures should be removed from the outer Scottish islands and these were lifted on 12 August. Movement restrictions remained elsewhere in Scotland, but have recently been progressively relaxed under a strict licensing programme. This veterinary risk assessment describes the risks associated with removing the remaining national movement control measures in Scotland, while maintaining temporary movement controls measures where livestock pass through markets and shows. The risks associated with a resumption of livestock markets/shows are the subject of a separate veterinary risk assessment to be considered in association with this document.
Summary of the risk factors
Movements of livestock, personnel and equipment between farms during a FMD outbreak increase the risk of spreading infection to premises that were previously uninfected. The risk is that undisclosed or incubating infection will be carried to new locations. The last case of confirmed FMD was in Surrey on 6 August 2007. The important risk factors today, 22 August are:-
• There may be undisclosed FMD at farm premises because of "silent spread" of FMD by sheep, or the presence of susceptible livestock incubating disease, or where insufficient inspection and detection has failed to detect clinical disease.
• Subsequent mechanical spread of FMD virus - by livestock, people handling livestock (boots and clothing) and by vehicles/equipment, used in connection with handling susceptible livestock, can occur easily and rapidly where there are no movement controls to mitigate this risk.
The factors considered to be most responsible for increasing the risks are:-
• Movement of live animals onto farms delivered before the national movement ban came into force on 3 August 2007
• Poor disease detection in susceptible livestock that are not frequently or effectively inspected, or where there is ineffective implementation of the appropriate biosecurity precautions on farms.
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Summary of risk reduction factors
The possibility of undisclosed or incubating infection and its subsequent spread is mitigated by the following:
• The latest Defra epidemiology report, on the outbreak of foot and mouth disease in Surrey (published on 15 August), concludes that the risk of disease spread outside of the Surrey Protection and Surveillance Zones, or outside of the county of Surrey, is now considered to be very low: "the spread of infection to the rest of the country, through the movements of cattle, pigs, or silently-infected sheep, out of the PZ/ SZ during the risk period, is considered to be very low".
• Throughout the recent FMD outbreak in Surrey, there have been no reports of suspected disease in Scotland that have not been negated by veterinary inspection and no cases of FMD have been confirmed in GB since 6 August.
• The incubation period for the strain of FMD virus causing the Surrey outbreak is thought to be between 5 and 8 days, although the incubation for FMD can be up to 14 days. There have been 16 disease-free days throughout GB on 22 August 2007.
• Veterinary inspections and serosurveillance of livestock in the PZ and SZ have not identified any livestock exposed to, or infected by FMD.
• This strain of FMD in cattle and pigs has proved relatively straightforward to detect clinically and the general media interest in the FMD outbreak has raised farmer's awareness further.
• There are ongoing statutory controls to reduce the spread of undetected disease, including the pre-existing 6 day standstill periods applying to all farms in England and Wales and the 13 day standstill periods in Scotland, introduced after the 2001 FMD epidemic
• The rapid introduction of the Restricted Zone measures prevented almost all movements of susceptible animals since the evening of Friday 3 August 2007, notwithstanding the recent relaxations under a strict licensing regime.
• Biosecurity standards can reasonably be expected to be higher as a result of the publicity generated by the current outbreak in Surrey.
• Although extensively kept sheep are not always closely or frequently inspected, extensively kept sheep are much less likely to come into contact with, and propagate FMD virus.
Tracing / Epidemiological information from Surrey:
• No FMD susceptible animals were moved off the two infected premises in Surrey during the risk period. There were 31 movements of susceptible livestock from the PZ during the risk period, approximately half of which were direct to slaughter and none of which were moves to Scotland or the north of England.
Epidemiological Modelling work at the University of Edinburgh partner in the Centre of Excellence in Epidemiology.
There have only been a limited number of animal movements from England and Wales to Scotland during the summer, as supported by preliminary modelling results from the University of Edinburgh partner in the Centre of Excellence in Epidemiology, and there are no reports on SAMU of any movements of sheep from Surrey into Scotland since 16 July 2007. The significant elements of the recently commissioned work include;
• No direct movements of susceptible livestock from a 20 km zone around the two infected premises (IP) in Surrey to Scotland since 16 July (as recorded on the SAMS / ALMS / CTS databases.
• Twelve movements of susceptible livestock indirectly to Scotland from premises within a 20 km zone around the two IPs. All premises have been visited and the resident livestock declared free of FMD by a veterinary inspector at that time. Three other premises in Scotland that were subsequently discovered to have received indirect movements of livestock (while conducting the original 12 visits) were also inspected and the livestock found to be free from clinical signs of disease.
• A "time to detection" analysis has been conducted that indicates that, if there is a case of FMD in Scotland that currently lies undetected, and assuming an average four week time to detection period, the probability of failing to detect that case of FMD will have fallen to zero on around the 23 August (subject to confirmation and final analysis).
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CONCLUSIONS
It can be concluded that the current risk of there being a case of undetected or incubating disease in susceptible livestock in Scotland is now "very low" - defined by EFSA as "very rare if present, but cannot be excluded". The veterinary consensus is that the risk of having a case of FMD in Scotland now approaches the background level of persistent risk that is ever present between relatively infrequent epidemics.
Undetected or incubating disease arising from the Surrey outbreak cannot be ruled out however, because it is not possible to quantify and eliminate all the possible risk factors. For example, there are no available data on the frequency of movements of people and vehicles from Surrey to Scotland and the very small unquantifiable risk of further cases cannot therefore be entirely eliminated.
SUMMARY OF THE RECOMMENDED ACTION
The weight of current evidence supports a conclusion that (a) is it increasingly unlikely for there now to be a case of undisclosed or incubating FMD disease in Scotland originating from the Surrey outbreak and (b) that national livestock movement controls could now be lifted in Scotland, subject to certain safeguards. Movement conditions in the inner Scottish islands should now match the outer Islands and pig movements can return to pre-outbreak rules, including a 20 day standstill within the pyramid systems of controls
The remaining very low risk of new cases of FMD in Scotland is not however negligible - for the reasons stated. The consequences of missing a case of FMD would be very serious, and greatest if undetected livestock moved through a livestock market or an agricultural show, thereby negating the rapid and successful control of this outbreak to date. It is therefore recommended that a separate veterinary risk assessment is conducted to deal separately with the risks from livestock markets/shows. If the national movement controls are lifted, livestock will be able to move across the entire length of Scotland. The very low residual risk of spreading previously undetected infection could be further mitigated by the temporary employment of a 20 day movement standstill on locations receiving susceptible livestock.
Veterinary Division
Rural Directorate
Scottish Executive
22 August 2007
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