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Tick
Borne Encephalitis
 Related
to yellow fever, dengue fever and Japanese encephalitis virus.
Is caused by several species of ticks living in Central and
Eastern Europe and parts of Asia. Tick activity starts when
soil temperature rises to 5-70C in March or April and ends
in Fall.
In
Mediterranean countries ticks are more active November-January.
Ticks are worse in wet summers and mild winters.
The risk of infection from specific tick bites ranges from
1:200-1:900.
People
at highest risk of being bitten include agriculture/forestry
workers, hikers/ outdoorsmen and collectors of berries and
mushrooms.
These
ticks attach to humans at hair-covered portions of the scalp,
ears, arms, knee joints, and hands and feet.
CLINICAL SYMPTOMS:
- Incubation 2-28 days
- Biphasic symptom
1st Stage (viraemia): fever, headache, myalgia and leuko and
thrombocytopenia for 1-8 days. Latency stage then occurs lasting
1-33 days before the
2nd stage. - 2nd Stage Up to 25% of cases develops meningitis,
meningo-encephalitis, and transmyelitits. Case fatality rate
of 1-5%. Paresis in acute stage- (3-23%) usually involves
shoulder or hemiparesis and may sometimes involve cranial
nerve pulses.
SYMPTOMS:
- Mild disease (55%) meningeal/encephalitis.
- Moderate (37%) moderate meningeal symptoms.
- Severe (8%) severe encephalitis.
DIAGNOSIS:
- 1gM Elisa on serum (acute)
- Confirmation requires acute and convalescent serum to check
for immunity check serology.
TREATMENT: Gammaglobulin and Corticosteroids do not
appear to work well. Strict bed rest and observations recommended
LONG TERM SEQUALAE:
- Prolonged hospital stay.
- 50 days- 40% still on sick leave.
- 40% of patients had chronic residual symptoms.
DIVERSITY OF LONG TERM SYMPTOMS:
Include neuropsychiatric symptoms (memory loss, stress intolerance,
decreased concentration), balance, dysphagia, hearing, headache,
and paresis. Negative prognostic factors include middle to
high age and the severity of the acute phase.
3 CLINICAL COURSES:
1) Full recovery in 3 months.
2) Prolonged clinical return with neuropsychiatric and neurological
problems.
3) Residual paresis.
In epidemic areas, TBE is one of the most important causes
of viral CNS infections. Case fatality and severe effects
still is very low (0.5-5%).
TICK BORNE ENCEPHALITIS VACCINE:
1) Common in Austria/Germa ny/Balkan. Invented in 1971 by
Dr Kunz.
2) Indicated for long-term residents.
3) Short-term travelers? May consider if significant exposure.
4) Recommended for endemic areas in the Alps
5) People receive 90%protection after the 2nd dose.
6) Vaccine not available in North America but can be specially
ordered
TBE VACCINATION FOR TRAVELLERS:
1. Consider epidemology of travelers and the disease. Austria
has 84% of the population vaccinated. Goal is to have no more
than 5-10 hospitalizations per year. Vaccination occurs in
schools. Travelers to Austria, Western Europe should consider
vaccination if they plan to be outside even including stays
in urban parks.
2. Schedule: Day 0 1st, day 14-90 2nd, and 10-12 mos 3rd .5ml
for adults and .25ml for children <12 yrs. Boost every 3 yrs.
3. Alternative for travelers arriving into Central /Western
Europe. If a person is at a very high risk at exposure the
TBE vaccine is available upon arrival at many European clinics.
Compiled June 2001
1. 8th ISTM meeting in Austria
2. Lecture by Dr. Kunz
3. Baxter monograph on TBE.
Tick Borne Encephalitis links
Patient.uk http://www.patient.co.uk/showdoc/27000510/
Travelhealth,co.uk http://www.travelhealth.co.uk/diseases/tick_encephalitis.htm
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