Progress and setbacks in the oral immunisation of foxes against rabies in Europe.

The oral immunisation of foxes has led to a substantial decrease in the number of rabies cases in Europe. Between 1989 and 1994 the prevalence of rabies in animals was reduced to less than 20 per cent of the 1989 level in countries which had been conducting oral immunisation campaigns since 1992 or before. Since 1978 more than 73.7 million baits have been spread over an area of 4-9 million km2. However, large areas have not yet been declared rabies-free, so the economic and public health benefits stemming from the reduced prevalence of rabies have so far remained marginal. Setbacks have occurred which have slowed the progress of vaccination, particularly towards the end of the 1980s and during the early 1990s. The reasons for the territorial differences in progress are discussed and the factors which have contributed to greater success in vaccination campaigns are identified. Unfortunately, the many positive and negative experiences with oral immunisation of foxes in Europe have resulted in only a limited number of scientifically validated recommendations for strategies to be applied under the different ecological and epidemiological conditions in Europe. Solutions have not yet been found to questions such as the duration of vaccination campaigns, the level of surveillance during and after campaigns and the appropriate countermeasures to compensate for the obvious increase in the density of the fox population.