Z O O E C O . O R G

Tick-borne encephalitis in Norway

Skarpaas, Tone (1); Sundøy, Anders (2); Bruu, Anne-Lise (3); Vene, Sirkka (4); Pedersen, Judith (1); Eng, Per Gunnar (5); Csángó, Péter A (1)

(1) Dept Clinical Microbiology, Vest-Agder Central Hospital, Kristiansand, Norway;
(2) Dept Internal Medicine (Inf.), Vest-Agder Central Hospital;
(3) Dept Virology, National Institute Public Health, Oslo;
(4) Dept Virology, Swedish Institute for Infectious Disease Control (SMI);
(5) Chief medical officer, Tromøy, Norway.

E-mail: tone.skarpaas@vas.no
 

Introduction

The first reported patient with tick-borne encephalitis (TBE) in Norway became ill in 1998 and the second patient had TBE in the autumn 1999. Both had visited the island Tromøy, Aust-Agder county as tourists preceding their disease (1,2). Subsequently, we intensified the search for TBE antibodies in cases of encephalitis. Seroprevalence studies were carried out in our district.
 

Material and methods

Sera from persons with encephalitis were tested for TBEV IgM and IgG antibodies with EIA tests (Enzygnost, Dade Behring; µ-capture IgM, SMI; Progene Immunozyme IgG) and a neutralization test. In 1999 we studied 98 sera positive for Borrelia antibodies from persons in Aust- and Vest-Agder counties with regard to TBEV IgG antibodies (3). In 2000 we studied 126 stored specimens from 1997–2000 of persons living on Tromøy for TBEV IgG antibodies.
 

Results

We report 3 new cases of TBE: 2 had encephalitis in Sep–Oct 2000. The 3rd patient, with antibodies to TBEV found by retrospective testing, had the disease in Aug 1997. This is probably the first reported case of TBE in Norway.

None of the three patients had been outside the country in the weeks preceding disease. Summary of clinical pictures: Age 42-67 years. Prodromal phase with fever, headache and muscle pain. Manifestation phase with fever, headache, nausea and vomiting. One person had visual disturbances, another had reduced consciousness. 2 out of three were hospitalized. All three patients recovered after 4–6 weeks.
 

Summary of laboratory parameters

Serum: CRP 10–30 mg/l, moderate leucocytosis, neg. for antibodies to Mycoplasma pneumoniae, antibodies to B.burgdorferi in low titers in one patient. TBEV IgM and IgG detected, rise in titer with neutralization test. CSF (2 patients): leucocytes 29–39x106/l, protein 610–625 mg/l, PCR neg. for entero-, VZV and HSV. Retrospective study of sera from 1997–2000 of persons from Tromøy showed the presence of IgG to TBEV in 3 of 126 (2,4%), while in 1999, IgG antibodies to TBEV were found in 0,3–0,4 % of persons mainly from other areas of the Agder counties (3).
 

Conclusions

Three new cases of TBE from persons living in Aust- and Vest-Agder counties are reported. This study reports the first TBE case diagnosed in Norway, in a person living on Tromøy who had the disease in August 1997. Four out of the first 5 Norwegian cases with TBE visited Tromøy the last few weeks before falling ill, 3 as tourists. Our seroprevalence studies indicate that Tromøy may have a higher incidence of TBE than the rest of Aust- and Vest-Agder counties. Our results confirm that TBE occurs in the coastal area of southern Norway.
 

References

  1. Blystad H, Bruu AL, Mehl R, Moen EW. Første meldte tilfellet av sannsynlig innenlandsk smittet skogflåttencefalitt (TBE) i Norge. MSIS 1999; 27: 17.

  2. Ormaasen V, Brantsæter AB, Moen EW. Tick-borne encephalitis in Norway. Tidsskr Nor Lægeforen 2001; 121: 807-9

  3. Skarpaas T, Csángó P, Pedersen J. Skogflåttencefalitt (TBE) på sørlandet. MSIS 2000; 28:09.