Antibodies to Tick‐Borne Encephalitis Virus in Human Sera from the Western Coast of Norway

Abstract

Sera from 341 individuals living in the distribution area of the tick Ixodes recinus were tested for tick‐borne encephalitis (TBE) antibodies by HAI and gel diffusion. Kaolin treatment was unreliable for the removal of non‐specific HAI inhibitors. Seven sera positive after this treatment were shown to be negative after acetone extraction/flotation centrifugation. The antibody prevalence rate was 19.6%. Seventy‐one % of the sera had titres > 40. The prevalence rate decreased with age. Some sera with low HAI titres could be confirmed by a sensitive Ouchterlony technique, while some with high titres could not, even after ten‐fold concentration. Clinical information obtained retrospectively regarding patients with high antibody titres revealed some cases consistent with a TBE virus infection. Antibody prevalence rates indicate that TBE virus is more active than Uukuniemi and Kemorovo group virus in tick‐infested areas. Mixed foci of these viruses have been indicated by serological findings and virus isolations.

Tick bites in healthy adults from western Norway: Occurrence, risk factors, and outcomes

“…Traavik and co-workers found evidence of tick-borne encephalitis-like virus in the western counties of Sogn og Fjordane and Hordaland in studies of animals and humans in the 1970s (Traavik, 1973;Traavik et al, 1978;Traavik, 1979). However, there is evidence that these findings represented other flaviviruses (Gao et al, 1993;Haglund, 2002).…”

Seroprevalence of antibodies to tick-borne encephalitis virus and Anaplasma phagocytophilum in healthy adults from western Norway

“…However, a case of TBE-seropositivity in a red dear in the county of Møre and Romsdal, just north of Sogn and Fjordane, has recently been reported [5]. Traavik and co-workers found evidence of tick-borne encephalitis-like virus in this part of Norway in studies of animals and humans in the 1970s [6][7][8]. However, there is evidence that these findings represented other flaviviruses [9,10].…”

“…Traavik and co-workers reported in the 1970s that antibodies to TBEV were prevalent in animals and humans from the western coast of Norway, and five isolates from ticks were obtained [6][7][8].…”

Louping-Ill Virus Serosurvey of Willow Ptarmigan (Lagopus Lagopus Lagopus) in Norway

“…Cross-reactivity between LIV and TBEV can occur (Mansfield et al 2011;Klaus et al 2014), and cross-reactivity may also occur with other closely related flaviviruses. The existence of other flaviviruses in wildlife in Norway has been suggested by Traavik (1979) and Traavik et al (1984), who hypothesized that flaviviruses transmitted by mosquitos could explain seroreactivity against TBEV outside the known range of sheep tick. A candidate could be West Nile virus, a mosquito-borne flavivirus that can cause fatal infections in bird species within the same subfamily (Tetraoninae) as ptarmigan (Clark et al 2006;Nemeth et al 2017).…”