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Perspective:  Ring Vaccination -  Common Sense ?

Stephen M. Apatow
Director of Research and Development 
Humanitarian Resource Institute Biodefense Reference Library
Foreign Animal and Zoonotic Disease Center
Eastern USA: (203) 668-0282   Western USA: (775) 884-4680

The objective is eradication of an FMD outbreak. 

In the "old" days in the UK with very local facilities, most outbreaks were only a few farms -- 5 to <20 say.

If your 'index' case is either the first or second to go down you are in real luck. We frequently found it was the 4th to 7th affected so some spread had already occurred, though usually limited to neighbours.

In the new scenario:

"The cause for the concern was associated with the index case in the UK (Essex abattoir) was some 20 days after the putative start which combined with the disease getting into a sheep market gave it a tremendous advantage -- silent host, massive refluxing of flocks & sheep from one end of England to the other."  -- Martin Hugh Jones

According to statistics presented on ProMED-mail: Foot & mouth disease - UK (62) :

On March 27 (approximately one month after the index case) the number of known infected farms diagnosed as of that date in the epidemic was 707 with 342 infected premises that had not yet been detected.

In this scenario, the question arises should a ring or a protective' vaccination programme been implemented to: 

(1) Decrease the number of infections and thus the production of large quantities of virus particles and shedding  into an environment where they can infect other animals. 

(2) Protect susceptible animals and  'dampening down' to reduce virus spread by reducing the number of susceptible animals, assisting a pre-emptive slaughter policy in places where poor infrastructure, inadequate manpower, delayed stamping out or other factors resulted in insufficient capacity to dispose of carcasses, and to reduce the severity of direct economic losses from the outbreak.

Note: Emergency vaccine is a high-potency preparation designed to elicit a rapid immune response. Animals vaccinated with emergency vaccine are protected within about 4 days of vaccination, which protection lasts about 6 months. Emergency vaccines may be used in a 'ring' or 'protective' vaccination programme (susceptible animals on holdings around an outbreak are vaccinated to protect them against aerosol infection), or 'dampening down'. 'Dampening down' is the vaccination of a chosen group of animals at risk from an outbreak . --

This strategy was successful in the Netherlands, allowing meat exports to Europe to be re-established.  According to Martin Hugh Jones "the Europeans had good warning and in spite of errors caught it very quickly and stopped it dead. If they had not been warned to look for FMD and be alert, I suspect that FMD would have ravaged Europe just as it has the UK." 

This strategy was said to be impossible during the initial phase of the UK outbreak for the following reasons:

1. The EU (and therefore the United Kingdom) and other countries wishing to maintain FMD-free status are required to attempt to bring an FMD outbreak under control by using a 'stamping out' policy (swift slaughter and disposal of infected herds and contacts) before considering vaccination. Only if an outbreak threatened to become extensive or affect particularly valuable livestock is consideration would be given to 'emergency' vaccination as an additional control measure. 'The control measures for foot-and-mouth disease laid down in Directive 85/511/EEC are aimed at eradicating the disease as quickly as possible by stamping out of infected, contaminated or in-contact herds, applying strict movement controls on animals of susceptible species and products derived from such animals and surveillance in the affected area to substantiate prior to lifting the control measures the absence of virus circulation' (2001/257/EC, 31.3.2001). Provision is made for emergency vaccination 'where the disease expands'. 

2. Due to the number of infected farms in late March and the expectation that there were more yet to be discovered, classical ring vaccination was not considered a feasible option because of insufficient supplies of vaccine and vaccinators to achieve this quickly.

So, the UK could not simply decide to vaccinate against FMD: the EU, the International Vaccine Bank (of which the UK was a founding member) and the OIE all either recommend or require that 'stamping out' be used to control or eliminate FMD. The UK could expect to receive permission to use vaccination to control an FMD outbreak only if the 'stamping out' policy had demonstrably failed, or if particularly rare animals were at risk. The UK did in fact apply for permission to vaccinate, and received it on the 30 March 2001. After noting that the UK had not only initiated a 'stamping out' policy, but also the pre-emptive killing of susceptible animals in close proximity to infected or suspect holdings, taking into account the density of the livestock population and the exigencies of carcass disposal, the Commission Decision permitted vaccination of bovine animals over 1 week of age in the counties of Devon and Cumbria subject to certain conditions. --

Statistics: 8.28.2001: (Guardian) Foot and mouth flare-up spreads:Effectiveness of  'stamping out' policy which included the pre-emptive killing of susceptible animals in close proximity to infected or suspect holdings:

Animals Slaughtered as of 8.26.2001:  3,768,000
Total number of affected Premises: 9124

[Revised Estimate (The Telegraph - UK): 10,849,000 animals culled]

The question remains, If OIE policy allowed a strategy of ring vaccination in the case of widespread distribution of infections due to the movement of animals, sufficient vaccine and vaccinators were available to implement ring vaccination combined with a pre-emptive slaughter policy, could spread into the wildlife (deer) have been prevented, affected premises decreased, impact on rural industries and tourism minimized, and as in the Netherlands the outbreak controlled and exports reestablished?

If the answer to this question is yes, then countries need to develop contingency plans (especially in the light of agroterrorism) which encompass sufficient vaccine stores and vaccinators for rapid response to a scenario which, as illustrated during early stages of the UK outbreak, could affect 1000 infected premises, thus increasing the odds for the restoration of FMD free status in a 3 month time frame objective.

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