Item 5 Diagnostics – virus detection

Dr Simon Barteling presented 2 papers on the procedures for managing outbreaks, including biosecurity and vaccination. The first paper (Appendix 14) dealt with the problems of containment of disease on suspicious and outbreak farms. Principles and technologies developed for high-containment laboratories were discussed and, also whether they could be implemented on suspicious and outbreak farms in addition to the current bio-containment practices. For transport and rendering of infected carcasses a closed system was proposed with the rendering process starting already during transport.

The practicality of reducing the concentration of airborne virus in infected farms by spraying with acid solution or by the installation of high efficiency air filtration systems was discussed. It was pointed out that spraying water equivalent to a heavy rainfall shower was required to produce a significant reduction in airborne virus concentration. Using acid sprays in the same way might not be practical. However, the effects of an evapourable acid such as acetic acid is not known and might well be evaluated as well as the effect of citric acid spray on the FMDV presence on surfaces.

His proposal that the vaccination of animals on large suspicious or infected premises could assist disease control during an epidemic was also challenged since premises containing infected animals would be difficult to properly clean and disinfect and therefore efficient decontamination might be impossible. However, the present possibilities to use protective vaccination or suppressive vaccination must be kept open.

Dr Barteling’s second paper considered contiguous culling and, as an alternative, emergency vaccination (Appendix 15). Although the simplicity of the contiguous-cull has the advantage of rapid decision-making it has as a main disadvantage of the associated risk of further spread of the disease. The other drawback is the associated large number of animals that have to be culled and the environmental problems as well as the human dramas.

Emergency vaccination has the disadvantage that it takes time (organisation plus the 4-5 days before protection starts). The spread of disease during this time should be anticipated for estimating the size of the vaccination zone. When carried out by well-trained vaccinators, the risk of associated spread of disease can be minimised. Dr Barteling stated that the use of vaccination is very much hampered by concerns about the risk of (vaccinated) carriers and by the belief that “vaccination suppresses the symptoms but does not eradicate the disease”. Dr Barteling claimed that during the last 15 years of vaccination – when carried out with a qualified vaccine – campaigns were always successful and there were no indications of ongoing or re-occurring disease, he recommended that this belief does not hold true. Therefore, he concluded that the associated “punishment” on export trade should be discontinued.

During the discussion which followed Dr Barteling’s argument in favour of vaccination was disputed. Several participants pointed out that in the event of outbreaks vaccination alone will not control the disease - additional measures, including movement stand-still and zoo-sanitary procedures are essential.

In regard to the consequences for trade of vaccination not everybody agreed with Dr Barteling’s opinion that surveillance can be employed as effectively in a vaccınatıng country as ın an FMD-free non-vaccinating country even when supported by testing for antibodies against non structural proteins (NSP). However, when vaccination is carried out on a limited