Rabies in Europe.

Since 1950 the type of rabies that has occurred in continental Europe has been maintained essentially in red foxes, in contrast to the type that prevailed at the start of the century, which was maintained in dogs. ' This difference in hosts is important. Even though both viruses are ofserotype 1, the fox virus is oflow infectivity for dogs, and vice versa. When one of these two species becomes infected with the heterologous virus it sheds little virus. Thus the transfer of fox rabies virus from an infected country to a rabies free country in Europe would not readily occur through dogs. ' The current strategy for controlling rabies in continental Europe is therefore to protect domestic animals by parenteral vaccination and to reduce the wildlife reservoir of the virus by oral vaccination of foxes (the main effort). 2 With this strategy terrestrial rabies could soon disappear from Europe (except for Turkey, where rabies is maintained in dogs). Nevertheless, in some countries rabies could still persist in bats and arctic animals. The Arctic fox is a host for another distinct rabies virus, and markers of this virus have been recognised in outbreaks among non-arctic animals, including the red fox, the raccoon dog, domestic dog, and perhaps wolf.3 Such outbreaks could maintain an epizootic (an epidemic in animals). The present red fox rabies epizootic of central Europe is thought to have started in 1939-40 at the Russian-Polish border and advanced mainly westwards stopping in eastern France in about 1982. The factors that influence the epizootic are the density of the fox population, its rate of turnover, and foxes' social behaviour.4 Changing numbers of foxes, as rabies decimates the population, account for the cyclic incidence of the disease. In autumn about 70% of the total population are young foxes, born in the spring of that year. This ensures a pool of susceptible animals for the propagation of infection. The red fox is responsible for 60 to 80% of all cases of rabies, and a further 10% of rabid wild animals share the fox's habitat (for example, deer, badger, and other small mustelids). Of domestic animals farm animals bear the brunt, followed by cats and dogs. Human cases are rare. For example, in Germany (including the former German Democratic Republic), a relatively heavily infected country, only two indigenous cases and one imported case were reported from 1977 to 1990.5 Previously, measures to control the infection combined vaccinating domestic animals with reducing the number of host species. Poisoning, trapping, and gassing of foxes, however, met with limited success, and the success of a field trial using oral vaccine therefore marks a milestone in the research into rabies.6 The aim of the trial was to immunise enough foxes to interrupt the chain of infection. Chicken heads were used as bait, and the vaccine was an attenuated live virus. A new bait (consisting of fat and fish meal) has since improved the seroconversion rate and facilitated mass production.7 At least a dozen European countries have now used oral vaccine to immunise foxes. In Turkey, the single European country where dogs make up most registered cases (and human cases are relatively more common), efforts have been made to supplement parenteral vaccination with oral vaccination so as to reach non-accessible dogs.8 The rabies that affects bats in Europe is serotype 4 (compared with serotype 1, responsible for rabies in red foxes dogs, and arctic animals). Cases in European bats have been recorded since 1954; from 1985 to 1991, 429 cases were reported from Denmark, the Netherlands, Germany, France, Poland, Czechoslovakia, and Spain. Nearly all cases occurred in the serotine bat. No programme for preventing rabies in bats exists. For patients exposed to rabid bats doctors should follow the usual postexposure guidelines, though all rabies vaccines are produced from serotype 1 strains.9 Postexposure treatment depends on the animal and the severity of injury that it causes. After local treatment of the wound one of several different combinations of vaccines or immunoglobulin (or both) may be given. '" Vaccines remain the most important method for preventing rabies in humans. To protect against rabies, a country that is free of rabies must ensure that any animal entering its territory is not carrying the virus. Controlling the entry of free living wild animals is virtually impossible, except in countries with insurmountable natural barriers. Island countries are not at risk-except from migratory bats. By contrast, the entry of domestic animals can be strictly controlled. Two ways exist of ensuring that such animals are not carrying the rabies virus. The first is to place the animals under observation and isolate them for a period equal to the maximum incubation period of rabies. This period varies from a few weeks to a few years, according to species. By imposing a quarantine period of six months, as does the United Kingdom, the risk ofan animal developing rabies after leaving quarantine is extremely low, although not zero. The second way is to verify that the animals have been immunised against rabies before being imported. This depends on a reliable vaccination certificate, preferably supported by the measurement of rabies antibodies. " Those