Open session of the standing technical committee of the EUFMD- 2004

limits) need to be defined, for example 0.2% between herds and 5% within herds. However defining a scientifically justifiable lower limit for prevalence which requires to be detected is more controversial; here the question is –“at what lower level would there be no virus circulation?”

He recommended that field data should be used to better define the design level prevalence. He indicated that goals need to be defined for test validation; fixed values for required DSe and Dsp are not useful; and that consensus is needed about the levels of “design prevalence”.

Discussion The use of concept of circulating infection was discussed. A move to the use of “circulation” was seen by some as a simplistic attempt to avoid the problem of carrier animals and detection of low prevalences. However since sustainable, continuous transmission sufficient to maintain an epidemic (“circulation”) is likely to leave far more evidence in the form of recovered, antibody positive animals, the relative ease of testing for circulation has some potential advantages.

There was general agreement that: 1. The disadvantages and advantages of a move from the current surveillance objectives, to adopting the “absence of circulation” objective after emergency vaccination in normally unvaccinated populations, needs to be clearly set out.

2. The issue of low target prevalence is stumbling block to progress on defining acceptable levels of PVS, and therefore the EUFMD Commission should explore alternatives.

3.4.2 Post-vaccination serosurveillance (PVS) for presence of FMD infected animals Dr Paton outlined the paper prepared with Dr De Clercq and Dr Dekker (Appendix 8), which would be presented in full at the Open Session. The Closed Session was an opportunity to air some of the issues for which the Group would need to propose solutions if doubts about the feasibility of PVS were to be assuaged. Following the Brescia workshop, the DSn and DSp of NSP tests are now far better known and can be applied to model the application to detection of infected farms. The paper raised several significant concerns, and proposed several possible solutions. One issue is that of testing small herds for absence of infection. One solution considered would be to not vaccinate small herds, but this could operationally objectionable to some stakeholders.

Discussion The effort of the authors to define the problems and possible solutions was widely appreciated.

However, some issues raised were not seen as major problems by all members. Dr Haas considered the risk posed by false negative animals in small herds would in principle not be different for such animals between small and large herds. Dr Greiner suggested there would be statistical methods applicable to defining small herds, and grouping of small herds.

Conclusions 1. The small herd problem requires further study to determine if there are guidelines that can be useful to decision makers in the application of vaccination.

2. The problems which require value judgments by policy makers should be clearly set out.

3. The existing Brescia WS data should be sufficient to undertake case studies and scenario modelling to better define the impact and feasibility of surveillance options.

4. The level of complexity in the scenario modeling needs to be defined and may require a new dedicated project to undertake.

Recommendations 1. The Group should identify the problems that may be addressed by technical means, that may be addressed by redefinition of existing standards, and those where higher level policy decisions are needed.

2. A working Group is needed to address the small Group problem (Action: Matthias Greiner, Aldo Dekker, Kris De Clercq and David Paton; Dr Greiner kindly developed a paper relating to this for the Session report – Appendix 9).

3. Attention to the issues for FMD free countries in regaining FMD free status when emergency vaccination is applied must be addressed when changes to the OIE Code and surveillance guidelines are under development or considered for adoption.

4. The OIE Code and surveillance guidelines require re-examination and a WG continues to be required to identify possible Code or guideline changes.

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