Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 29-30. (Budapest, 1997)

inhibition test internationally accepted in the diagnosis of flavivirus infections is performed, and occasionally ELISA, virus neutralisation test, and virus isolation are also made use of. The early (IgM) type antibodies usually appear already in the first few days after the onset of clinical symptoms, and the rising level of IgG antibodies can also be detected by testing paired sera. Since the introduction of preventive vaccination (and especially since 1991 when the vaccine or, more recently, vaccines have been available to anybody without any restriction), vaccinations are being carried out also in periods when the risk of infection is high. This practice may be a source of diagnostic problems. This is the reason why in a total of

275 cases during the past 5 years virological examination failed to yield interprétable results, partly because of the deficiency of the data provided, partly because of the limitations of the methods available. Interpretation of the tests was impeded by the fact that the patients had received some type of preventive vaccination against TBE already earlier. During the test, it could not be decided whether the antibodies detectable in the serum sample resulted from vaccination or perhaps from wild virus infection. Patients getting over a wild virus infection acquire lifelong immunity, while those vaccinated do not. The use of other methods may be necessary in persons who have been vaccinated against some other flavivirus disease (yellow fever). It is therefore important to stress that in specific cases the lack of adequate data supply may render the serological diagnosis impossible. TREATMENT As the disease is autonomous, only palliative treatment is possible. By the time the diagnosis can be established, the clinical symptoms which are to be prevented have already developed. The viruses have already invaded the cells of the central nervous system, the majority of which will be destroyed together with the virus. Thereafter the number of viruses will usually decrease rapidly. Several authors have achieved good results with dehydrating treatment combined with the use of steroids, while others could not corroborate these findings. Steroid treatment is justified by the observation made in animal experiments that the time of death coincides with the appearance of antiviral antibodies. Assisted respiration and the administration of anticonvulsive drugs may occasionally be necessary. EPIDEMIOLOGY The only areas in Europe where the occurrence of TBE has not been demonstrated are the Benelux countries and the Spanish peninsula. Before the introduction of preventive vaccination, in numerous countries (e.g. in Austria) TBE was the commonest CNS disease of inflammatory origin, which it still is in countries like Slovenia where extensive vaccination has not yet been accomplished (Cizman and Jazbec 1993). In recent years, the number of recognised TBE cases has markedly increased in Poland (Zabicka 1996), and the disease has appeared in France as well (Collard et al. 1993). The number of cases diagnosed in Hungary had doubled by the 1980s as compared to the 1970s; however, this probably resulted from the improvement of diagnostic techniques (Ferenczi and Molnár 1991). In Hungary, primarily the Transdanubian region and the Northern mountain range are endemically infected areas. TBE virus is transmitted to humans by Ixodes ticks. Therefore, the epidemiology of TBE depends basically on the prevalence of Ixodes ticks,