The public health importance of tick-borne encephalitis in Europe.

After an historical survey establishing the distinction between Russian spring-summer encephalitis, a serious disease with a high mortality rate caused by a virus spread by the tick Ixodes persulcatus, and the milder Central European encephalitis, which is spread by I. ricinus, the public health aspects of the latter disease are discussed. The factors affecting the incidence of the disease-tick population, role of rodents and insectivores, etc.-are considered. Only a small proportion of those infected develop clinical symptoms. Measures for the control of the disease include (a) vaccination of humans, (b) reduction of the tick population by cultivation of the land, by spreading the enemies of ticks and by dusting with insecticides, and (c) reduction of the infectivity of ticks by vaccination of domestic animals. It is concluded that, under the conditions prevailing in Central Europe, mass vaccination is not to be recommended, although those working regularly within a natural focus of infection should be vaccinated.