Thortveit et al.
Human seroprevalence of antibodies to tick-borne microbes in southern Norway
Ticks Tick Borne Dis. in press, doi.org/10.1016/j.ttbdis.2020.101410
Along the southern coastline of Norway, Ixodes ricinus ticks are widely distributed and Lyme disease is the most common tick-borne disease in this area. Additional tick-borne infections are detected in southern Norway: TBE virus, Anaplasma phagocytophilium. Babesia species and Rickettsia helvetica.
A study has been carried out to assess the seroprevalence of IgG antibodies to various tick-borne pathogens in an unselected Norwegian adult population (18 to 69 years of age) in Søgne, Vest-Agder county (west of Kristiansand). In January 2016, Søgne had 11,260 inhabitants and 7,424 were aged from 18 to 69 years. A total of 3571 inhabitants responded to the study invitation and serum samples from 3568 individuals were available for analyses. Mean age in this study was 48.2 years vs. 41.9 years in the whole Søgne population aged 18-69 years.
The seroprevalence of IgG antibodies to Borrelia burgdorferi sensu lato tended to increase with age (11.9% in the age group 18-29 years vs. 33.5% in the age group 60 to 69 years. The seroprevalence of IgG antibodies to A. phagocytophilium was 11.0%, to R. helvetica/conorii was 4.2% and to B. microti was 2.1%. There was a seroprevalence of IgG antibodies to TBE virus of 3.1% among all tested participants and of 1.4% among participants reporting no vaccination against TBE virus and/or yellow fever. Among individuals with serum antibodies to Borrelia the seroprevalence of IgG antibodies to the TBE virus was higher (2.0%).
The study indicates a high exposure to tick-borne microbes in the general adult population living in a coastline municipality in the southern most part of Norway. Vaccination against TBE virus has been reported by only 4.3% of respondents in this study.