Occurrence of tick-borne encephalitis (TBE) virus in Berlin (West)

The main vector of Central European tick-borne encephalitis (TBE), the hard tick Ixodes ricinus, is very common in forests of Berlin (West) all of which are frequently visited nearby recreation areas. While the presence of the causative agent, a flavivirus, has been demonstrated in all districts of the German Democratic Republic (GDR) there has been no corresponding investigation concerning Berlin (West). In the present study, 4593 unengorged I. ricinus nymphs and adults were collected by the flag-dragging method in forest areas of Berlin (West) in 1978, 1979, and 1986 and virologically examined in 327 pools. One TBE virus strain was isolated from a pool of 5 females in 1978. In addition, 5 out of 15 sera taken from roe deer freshly shot in Berlin (West) were positive for hemagglutination inhibiting antibodies against TBE virus in 1984 indicating a previous infection. The titres were 1:10 (2 x), 1:20 (2 x), and 1:40 (1 x), respectively. Although clinical cases of autochthonic TBE in humans have not been found in Berlin (West) so far and the risk for people becoming infected by tick-bite seems to be small, our findings strongly suggest an at least sporadical presence of TBE virus in this area.