Tickborne encephalitis (TBE) is endemic in virtually all
countries in central and eastern Europe. It is caused by several closely related
but distinct flaviviruses. Three subtypes are recognised at present: a Far-Eastern
subtype, a Siberian subtype and a European subtype. The Siberian subtype is
associated with Russian spring-summer encephalitis and is transmitted predominantly
by the tick Ixodes persulcatus
, whereas the European subtype causes
central European encephalitis and is transmitted by Ixodes ricinus
The clinical spectrum of acute TBE ranges from symptoms of mild meningitis
to severe meningoencephalitis with or without myelitis . The incubation
period of central European tickborne encephalitis is seven to 14 days .
Onset is generally biphasic. The first phase involves a non-specific influenza-like
illness with fever, headache, nausea, and vomiting, lasting about a week.
After a period of remission lasting a few days, the fever returns with aseptic
meningitis or encephalomyelitis. The case fatality rate is 1-5% and about
20% of survivors have neurological sequelae. Residual motor defects are
Russian spring-summer encephalitis is more serious, with a more acute illness
and a case fatality rate of about 20%. Up to 60% of survivors are left with
neurological sequelae, including flaccid paralysis.
Vaccination using licensed vaccines is the only real way to prevent TBE.
Two commercially available vaccines are used in Europe: new versions of
Encepur produced by Chiron Behring, Germany and FSME-IMMUN by Baxter, Austria.
The conventional vaccination schedule consists of 3 doses at Day 0, 1-3
months and 9-12 months after the second dose.
After 30 years of development, both vaccines are now available in adult
and paediatric formulations that cause few adverse side effects.
Encepur is licensed for rapid immunisation at days 0, 7 and 21, and this
provides protection two weeks after the second dose of vaccine. The FSME-IMMUN
rapid schedule involves two vaccine doses given two or three weeks apart.
This two dose rapid schedule is only recommended for immunisation protection
over the summer months because, unlike the Encepur schedule, its protection
is only optimum for six months.
TBE trends in the Czech Republic
The population of the Czech Republic is near 10 million. In 2003, the approximate
incidence of tickborne encephalitis was 5.9 per 100 000 population. Incidence
is higher in regions south of Prague near the city of Ceske Budejovice.
There has been constantly high incidence near the town of Pilsen in the
western part of the Czech Republic. Recently, TBE foci have been identified
in the northern part of the province of Bohemia. In the east of the country
there hass been a high incidence near Olomouc. Clinical cases of TBE are
notified from April until November every year (Figure 1).
Figure 1. Seasonality of TBE in the Czech Republic by
particular months. Source: EPIDAT, (the Czech national database), by permission
of C. Benes, National Institute of Public Health, Prague
Figure 2. TBE incidence in the Czech Republic 1965-2003.
Source: EPIDAT, by permission of C. Benes, National Institute of Public
Since 1970, the incidence of TBE has changed twice: during the 1980s, incidence
fell by about 30% compared to previous levels, but in 1993 incidence doubled
to its present level, about 50% above its pre-1980 level  (Figure 2).
No single factor can adequately explain the rising incidence of the disease
in the Czech Republic. The changing weather pattern in the past few years
is a possible factor. The average annual temperature in the Czech Republic
increased very slightly from 1970, but then much more markedly from 1989
, and rainfall patterns have also changed, possibly affecting tick survival
and development rates. Changes in the geographical distribution of Ixodes
ricinus have been observed, with ticks appearing at higher altitudes
in mountains than in earlier years [Dr. Daniel, National Institute of Public
Health, Prague, personal communication, 2004] .
There is no direct support from state institutions to target residents
in areas of high endemicity for vaccination. There is partial financial
support for vaccination of children and adolescents under the age of 18
across the whole country (with reimbursement of a single dose of vaccine),
but childhood cases tend to recover spontaneously. Private companies immunise
employees who work in forests.
The risk of acquiring TBE has been evaluated in two published studies from
the United States (US)  and Austria . In Kosovo, the risk for members
of a US military unit that trained in a highly endemic area was evaluated.
The TBE virus infection rate was 0.9/1000 man-months of exposure. For an
unvaccinated tourist staying for 4 weeks in a highly endemic province of
southern Austria (Steiermark/Styria), the risk of acquiring TBE was 1/10
000 man-months of exposure . Based on total numbers of tourist overnight
stays in Austria during the summer season, about 60 travel-associated cases
of clinical TBE could be expected to occur among holidaymakers after their
stay in Austria.
Effective and protective inactivated vaccines are available, inexpensive
and have been licensed in the Czech Republic for more than 10 years. Visitors
to the Czech Republic and other endemic areas should consider three factors
before deciding on whether to be vaccinated: length of stay, place of residence
(urban or rural), and whether or not they intend to visit high risk areas
(in the Czech Republic, this would be the south, and parts of western Bohemia).
Vaccination is recommended for those travellers who intend to stay longer
than three weeks, who intend to visit rural areas in endemic regions, or
who plan to camp.