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The epidemiological criteria of the present sylvatic rabies epizootic are shown using the situation in the Federal Republic of Germany and its neighbouring countries as an example. It is demonstrated that the fox plays the leading role in transmitting the disease to other animal species and remains the main vector in the epizootic. Mustelids are of secondary importance. Cervides, rodents and domestic animals are of no concern in the spread of rabies. Rabies control measures have to be aimed at the population reduction of but one species, the fox, since the frequency of rabies among this species is primarily dependent on the population density. Other wild carnivores especially badgers should be spared. Intensified shooting of foxes as a single control measure has proven ineffective. According to the results obtained in Central Europe, the gassing of fox dens, where applicable, has proven to be the best single measure regularly resulting in a decrease of rabies cases. In individual instances this has led to a complete extinction of rabies. The oral immunization of foxes is not yet regarded as acceptable; large-scale success with this method is not to be expected.

Since spring 1983 a field trial to immunize foxes by the oral route against rabies has been carried out in a heavily infected area of Hessen measuring about 1,500 km2. The vaccine strain SAD B 19, produced by the Federal Research Institute for Animal Virus Diseases at Tübingen and filled into 2 ml aliquots, was inserted into chicken heads and distributed by forest rangers in the trial area, 15 baits per km2. Up to the present day five baiting campaigns, two per year in spring and autumn, have been completed and in all 110,000 vaccine baits additionally marked with 150 mg tetracycline were layed out. Four baitings have been previously evaluated. With the exception of some rabies cases on the border to the unvaccinated region in the northwest, rabies was reduced impressively. A secondary outbreak in the region of Hausen/Kiedrich, caused by an extremely high density of the fox population, was eradicated by increasing the baits to 25 per km2. The number of rabies cases, which amounted to 238 within 15 months prior to the vaccination trial, went down from 38 in the first 6 months to 6 cases after the fourth baiting. As innocuity control 2,273 wild and domestic animals from the vaccination area were examined for the presence of the vaccine virus. The results were always negative indicating that rabies strain SAD B 19 had not established an infective cycle in wildlife. As could be shown by the marker studies, an average of 78 per cent of the foxes (variation of the baitings from 62 per cent to 82 per cent) had taken up one or more baits. Seroconversion had been achieved in 65 per cent of the foxes (variation from 43 per cent to 70 per cent) as demonstrated by the presence of neutralizing antibodies. From experiences in Switzerland it can be expected, that rabies will be extinguished, if 50 per cent of the population are successfully immunized. This value has been surpassed in the field trial in Hessen. These very promising results have led to the project of an enlargement of the vaccination area to 12,000 km2. The neighbouring states of Rheinland-Pfalz and Nordrhein-Westfalen have joined in this effort, which has started in autumn 1985 with a new artificial vaccine bait developed at the Tübingen research institute.

The field trial for the oral immunization of foxes against rabies in the Federal Republic of Germany began in 1983 and since the end of 1985 has had the specific goal of the elimination of rabies in large interdependent areas of that country. To meet this goal it was necessary to develop methods for the large-scale production of the SAD (Street Alabama Dufferin) clone B19 vaccine as well as to develop a bait that could be mass-produced (the Tübingen fox bait). It has been shown that after a single vaccination campaign in the field approximately 75% of the fox population is immune to rabies and that after one or two repeated campaigns vaccination in many areas could be discontinued. Participation in the field trial in circumscribed border areas was extended to Italy in 1985 and to Austria, Luxembourg, Belgium, and France in 1986. For the first time, through the use of oral immunization, a method for the elimination of rabies is available that is effective, safe, inexpensive, and practical. Further, this method meets the requirements of animal-protection societies, does not interfere with the preservation of endangered species, and therefore represents a significant political factor.

Rabies statistics for 1950-81 were studied to investigate regional differences in the occurrence of rabies in the Federal Republic of Germany. At the level of Landkreis (administrative unit with a mean area of 1013 km(2)), four basic patterns of rabies incidence were identified: insignificant occurrence, low undulations, intermittent peaks, and high oscillations. The distribution of these four epidemiological patterns of rabies was geographically localized. Insignificant occurrence of rabies was found almost exclusively on land under 100 m above sea level with less than 10% forest cover. High oscillations in rabies occurrence were found most often in areas over 200 m above sea level with an average of at least 35% forest cover.