Surveillance of endemic foci of tick-borne encephalitis in Finland 1995–2013: evidence of emergence of new foci

Abstract

The geographical risk areas for tick-borne encephalitis (TBE) in Finland remained the same until the beginning of the 21st century, but a considerable geographical expansion has been observed in the past 10 years. In order to support public health measures, the present study describes the number of laboratory-confirmed TBE cases and laboratory tests conducted and the associated trends by hospital district, with a particular emphasis on the suspected geographical risk areas. An additional investigation was conducted on 1,957 clinical serum samples throughout the country taken from patients with neurological symptoms to screen for undiagnosed TBE cases. This study identified new TBE foci in Finland, reflecting the spread of the disease into new areas. Even in the most endemic municipalities, transmission of TBE to humans occurred in very specific and often small foci. The number of antibody tests for TBE virus more than doubled (an increase by 105%) between 2007 and 2013. Analysis of the number of tests also revealed areas in which the awareness of clinicians may be suboptimal at present. However, it appears that underdiagnosis of neuroinvasive TBE is not common.

Prevalence estimation of tick-borne encephalitis virus (TBEV) antibodies in dogs from Finland using novel dog anti-TBEV IgG MAb-capture and IgG immunofluorescence assays based on recombinant TBEV subviral particles

“…Similar ELISA results (seroprevalence of 30.4%) were obtained for dogs from Bornholm, Danish Island in Baltic Sea (Lindhe et al, 2009). The high percentage of seropositive dogs is likely explained by situation of most important foci in the archipelago regions of the country due to an optimal ratio of temperature and humidity allowing tick co-feeding, as compared to continental parts of Finland (Tonteri et al, 2015). However, there is evidence of new foci accumulating, and is likely that if the mean annual temperatures continue to increase, as predicted, it is likely that both the population of ticks and TBE foci will continue to spread northward (Perez Vera et al, 2014).…”

EAN consensus review on prevention, diagnosis and management of tick‐borne encephalitis

“…The incidence of TBE in European countries including Russia is shown in Fig. 1 [1,6,12,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. Austria is a country with decreasing annual incidence to 1/100 000 due to vaccination; however, the occurrence of TBE is higher in unvaccinated tourists and Austrians [3,9,37].…”

High tick abundance and diversity of tick-borne pathogens in a Finnish city

“…Because the prevalence of TBEV in I. ricinus is typically 0.5-2% in Finland (Jääskeläinen et al 2010(Jääskeläinen et al , 2016, it is not unexpected that we did not find that pathogen in the relatively small subsample (157 ticks) that was extracted for RNA. The large archipelago around Turku and the Åland Islands are known risk areas for TBE (Tonteri et al 2015). According to the National Infectious Diseases Register (which is maintained by the National Institute for Health and Welfare), approximately 10-20 people contract TBE in Turku or nearby areas every year (Tonteri et al 2015), in spite of the relatively high vaccination coverage against TBE in these areas.…”

“…The large archipelago around Turku and the Åland Islands are known risk areas for TBE (Tonteri et al 2015). According to the National Infectious Diseases Register (which is maintained by the National Institute for Health and Welfare), approximately 10-20 people contract TBE in Turku or nearby areas every year (Tonteri et al 2015), in spite of the relatively high vaccination coverage against TBE in these areas. Furthermore, as TBE cases have emerged and novel TBEV foci have been found in new areas (Tonteri et al 2015;Jääskeläinen et al 2016;Sormunen et al 2018), the possible current or future presence of TBEV in the city of Turku cannot be overlooked.…”