Dr. Murai Éva szerk.: Parasitologia Hungarica 24. (Budapest, 1991)

relatively high CSF level. As we have only few patients who receive ceftriaxone monotherapy, we could not collect enough data for statistical analysis. In the present circumstances we do not think of Rocephin as a first choice of treatment. A similar conclusion was drawn by Neu (109). Ticks, borrelia isolation and prevention At least 20 different diseases are transmitted to humans by ticks (38), the commonest being Lb (139). The primary vectors of the etiologic agent of Lb are hardbodied ticks belonging to the genus Ixodes. Ixodes dammini, I. scapularis, I. pacificus, I. dentatus, I. persulcatus and, in Europe, /. ricinus are the main vectors. Although other blood sucking insects have also been incriminated in the transmission of Bb, there are no epidemiological data to support this theory. Lb is becoming more prevalent because of the increased exposure of humans to infected ticks. Humans may be attacked by ticks even indoors after the pets have carried the ticks inside. During their two-year life cycle, ixodid ticks develop through four stages of growth, namely egg, larva, nymph and adult. Each stage (except egg) feeds only once upon blood from a host animal. In the U.S.A. the white footed mouse (Peromyscus leucopus) is a particularly important host. In Europe, several small rodents are considered as a natural host of Bb. As natural hosts of ticks, birds play an important role in spreading ticks in new areas. All stages feed on humans. Sixty per cent of ticks collected in Shelter Island, a highly infected area, contained Bb (18). In the Swiss Plateau an infection rate of 36% was found (19). On well-kept lawns, near the homes of Lyme disease patients a tick prevalence of approximately 1 per m

2 was found. Thirty-three per cent of nymphs and 55% of the adult ticks contained spirochetes (35). Thirty-four per cent of Ixodes persulcatus ticks examined in the Leningrad area was infected by Bb (69). In the most severely infected region of Germany 40% of the ticks harboured spirochetes (164). Similar prevalence was found in other parts of Europe (138). In contrast, less than 1% of ticks contains the tick-borne encephalitis virus, even in the hyperendemic regions (124). We have dissected only 31 Ixodes ricinus ticks: six (16%) of them contained spirochetes. Light and electron-microscopic examination, IFA and Western blot analysis proved that the isolated strains are the causative agents of Lb. Both strains that could be studied (Mk5 and Mk6) showed the characteristic 41 kDa flagellar and the 60 kDa common bacterial antigens. Only a faint band was demonstrated in the region of 32 kDa OspA, which is typical of the American isolates. The 35 kDa OspB was missing, typically of the European strains (162). Our data are not sufficient to judge the Hungarian infection rate but very probably it is similar to the European situation. The direct fluorescent technique was reported to be better for detecting Bb in ticks (118). In our hands, dark field microscopy and cultivation were more successful than the former method. Haemaphysalis ticks are seldom infected (20, 79), so our failure to find specimens harbouring borrelia is not surprising.