The role of small rodents and hedgehogs in a natural focus of tick-borne encephalitis.

The role of small rodents and hedgehogs in the circulation of tick-borne encephalitis in natural foci in the Tribec region of Czechoslovakia has been studied. Isolation of virus from the blood of Apodemus flavicollis, Clethrionomys glareolus and Erinaceus roumanicus, as well as the demonstration of antibodies in the sera of these mammals and of A. sylvaticus, Microtus arvalis and Sciurus vulgaris, showed that these mammals had been in contact with the virus in recent years. The proportion of positive sera was low, ranging from 4% to 11% for A. flavicollis in various parts of the Tribec region. In a study of the elementary focus at Jarok, it was found that the frequency of antibodies was considerably higher in hedgehogs than in small rodents; this may be due to the longer life-cycle of the former, which makes the probability of reinfection greater. Clearly, the hedgehog and the small rodents studied are important hosts of ticks and reservoirs of tick-borne encephalitis virus in the Tribec region.