Recover
are available for diseases such as FMD, based on antibody types produced by field virus but not by the vaccine (antibodies against non-structural protein) or for HPAI through the use of non-homologous vaccines (i.e. a vaccine containing a virus with a different N protein than the field virus). In both of these cases, vaccinated animals that have also been infected with the field strain can be identified and so removed. Clearly, the use of a DIVA strategy needs to be decided before vaccination commences because of the need to select the correct vaccine, and so this should have been part of the planning process. It should be noted that using a DIVA strategy requires substantial resources. An alternative might be the use of unvaccinated sentinel animals or birds to detect disease in vaccinated groups. In the absence of a DIVA strategy, it can be difficult to know how to deal with vaccinated animals if there is a requirement to have a population that is free of antibodies as an essential part of demonstrating freedom. This is a major reason for not using vaccines unless control cannot be achieved without doing so. If there is no possibility of a DIVA strategy and it is certain that vaccination prevents infection as well as clinical disease, it will be important to identify animals at the time of vaccination. This does not need to be an individual identification (although this is preferable), but some form of permanent mark. It may also be desirable to introduce known uninfected and unvaccinated animals into a vaccinated population as sentinel animals that can then be closely monitored over at least the known maximum incubation period for disease, and blood sampled at a given time after this period to demonstrate a lack of sero-conversion and exposure. Alternatively, if strategic vaccination has been used as part of the control programme, it may prove desirable to maintain strategic vaccination if there is still a high risk of a new incursion of the disease, for example from a neighbouring country. If neighbouring countries are free of infection, stopping vaccination programmes altogether can be considered, diverting the resources that have been devoted to the vaccinations to enhanced early warning activities and intensified surveillance. In this way, preparedness for the disease recurrence will be maintained at a high level and any disease breakdowns can be detected and eliminated quickly, either by a short, sharp targeted vaccination campaign or by eradication procedures. If the latter strategy is followed, it should be possible to declare provisional freedom from the disease after a suitable period following the cessation of vaccination. After further periods, declarations of freedom from the disease and finally from infection may be made to OIE. This is subject to demonstrated evidence of a high level of clinical surveillance, the carrying out of well-planned serological surveys giving negative results and follow-up on false positive results. At the stage where searches are being made for the last possible pockets of infection, consideration could be given to offering monetary or other forms of reward to people reporting a clinical episode of what might be the disease in question with a larger offering if the reporting leads to actually finding the disease. However, the advantages and disadvantages should be carefully evaluated before embarking on this course.
Declaration of official recognition of animal disease status Recommended standards for epidemiological surveillance in order to obtain official recognition of animal disease status have been laid down by OIE for bovine spongiform encephalopathy (BSE), rinderpest and FMD. To obtain OIE’s recognition, the applicant country
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