Cervids as sentinel-species for tick-borne encephalitis virus in Norway - A serological study.

Katrine M Paulsen,Erik G Granquist,Carlos G Neves,Åshild K Andreassen,Karin Stiasny,Snorre Stuen,Mara Rocchi,Ellie Laming,Knut Madslien,Rose Vikse,Benedikte N Pedersen

doi:10.1111/zph.12675

Abstract

Tick-borne encephalitis virus (TBEV) is the causative agent of tick-borne encephalitis (TBE). TBEV is one of the most important neurological pathogens transmitted by tick bites in Europe. The objectives of this study were to investigate the seroprevalence of TBE antibodies in cervids in Norway and the possible emergence of new foci, and furthermore to evaluate if cervids can function as sentinel animals for the distribution of TBEV in the country. Serum samples from 286 moose, 148 roe deer, 140 red deer and 83 reindeer from all over Norway were collected and screened for TBE immunoglobulin G (IgG) antibodies with a modified commercial enzyme-linked immunosorbent assay (ELISA) and confirmed by TBEV serum neutralisation test (SNT). The overall seroprevalence against the TBEV complex in the cervid specimens from Norway was 4.6%. The highest number of seropositive cervids was found in south-eastern Norway, but seropositive cervids were also detected in southern- and central Norway. Antibodies against TBEV detected by SNT were present in 9.4% of the moose samples, 1.4% in red deer, 0.7% in roe deer, and nil in reindeer. The majority of the positive samples in our study originated from areas where human cases of TBE have been reported in Norway. The study is the first comprehensive screening of cervid species in Norway for antibodies to TBEV, and shows that cervids are useful sentinel animals to indicate TBEV occurrence, as supplement to studies in ticks. Furthermore, the results indicate that TBEV might be spreading northwards in Norway. This information may be of relevance for public health considerations and supports previous findings of TBEV in ticks in Norway.

Highlights

Tick-borne encephalitis virus (TBEV) is a vector borne disease that cause tick-borne encephalitis (TBE) in humans and animals
It is estimated that TBEV is one of the most important neurological pathogens transmitted by tick bites in Central and Eastern Europe, as well as Russia, with significant impact on the public health (Ruzek et al, 2019)
This study identified one seropositive red deer along the western coast of Norway, an area where TBEV has been documented in ticks (Paulsen et al, 2015)

Summary

Introduction

Tick-borne encephalitis virus (TBEV) is a vector borne disease that cause tick-borne encephalitis (TBE) in humans and animals. The virus is widespread throughout Europe and consists of five known subtypes: European, Siberian, Far Eastern, Baikalian and Himalayan (Dai, Shang, Lu, Yang, & Xu, 2018; Dobler, Gniel, Petermann, & Pfeffer, 2012; Kovalev & Mukhacheva, 2017). The main vectors for transmission of TBEV in Eurasia are the Ixodes ricinus and Ixodes persulcatus. It is estimated that TBEV is one of the most important neurological pathogens transmitted by tick bites in Central and Eastern Europe, as well as Russia, with significant impact on the public health (Ruzek et al, 2019). A rapid increase in the incidence of TBE has been observed in many European countries where TBE is endemic, simultaneously with the emergence of new foci (Jaenson, Hjertqvist, Bergstrom, & Lundkvist, 2012; Ruzek et al, 2019; Suss, 2011)

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