Reconsidering the classification of tick-borne encephalitis virus within the Siberian subtype gives new insights into its evolutionary history

Kovalev, Sergey Y.; Mukhacheva, Tatyana A.

doi:10.1016/j.meegid.2017.09.014

Cited by 100 publications

(78 citation statements)

References 20 publications

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“…TBEV has traditionally been divided into three genetically distinguishable subtypes: Western European TBEV transmitted by Ixodes ricinus, and Far Eastern and the Siberian TBEV, predominantly transmitted by I. persulcatus [4]. In addition, two new subtypes have recently been proposed, these being the Baikalian and the Himalayan subtypes [5,6]. The virus is maintained in small mammal-tick cycles, whereas human infection is a viral dead end for further transmission [7].…”

Section: Introductionmentioning

confidence: 99%

Revealing new tick-borne encephalitis virus foci by screening antibodies in sheep milk

et al. 2020

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Background: Tick distribution in Sweden has increased in recent years, with the prevalence of ticks predicted to spread towards the northern parts of the country, thus increasing the risk of tick-borne zoonoses in new regions. Tickborne encephalitis (TBE) is the most significant viral tick-borne zoonotic disease in Europe. The disease is caused by TBE virus (TBEV) infection which often leads to severe encephalitis and myelitis in humans. TBEV is usually transmitted to humans via tick bites; however, the virus can also be excreted in the milk of goats, sheep and cattle and infection may then occur via consumption of unpasteurised dairy products. Virus prevalence in questing ticks is an unreliable indicator of TBE infection risk as viral RNA is rarely detected even in large sample sizes collected at TBE-endemic areas. Hence, there is a need for robust surveillance techniques to identify emerging TBEV risk areas at early stages.Methods: Milk and colostrum samples were collected from sheep and goats in Örebro County, Sweden. The milk samples were analysed for the presence of TBEV antibodies by ELISA and validated by western blot in which milk samples were used to detect over-expressed TBEV E-protein in crude cell extracts. Neutralising titers were determined by focus reduction neutralisation test (FRNT). The stability of TBEV in milk and colostrum was studied at different temperatures. Results:In this study we have developed a novel strategy to identify new TBEV foci. By monitoring TBEV antibodies in milk, we have identified three previously unknown foci in Örebro County which also overlap with areas of TBE infection reported during 2009-2018. In addition, our data indicates that keeping unpasteurised milk at 4 °C will preserve the infectivity of TBEV for several days. Conclusions:Altogether, we report a non-invasive surveillance technique for revealing risk areas for TBE in Sweden, by detecting TBEV antibodies in sheep milk. This approach is robust and reliable and can accordingly be used to map TBEV "hotspots". TBEV infectivity in refrigerated milk was preserved, emphasising the importance of pasteurisation (i.e. 72 °C for 15 s) prior to consumption.

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Section: Introductionmentioning

confidence: 99%

Revealing new tick-borne encephalitis virus foci by screening antibodies in sheep milk

et al. 2020

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“…TBEV-Eur is carried mainly by Ixodes ricinus ticks in central and north-eastern Europe, whereas TBEV-Sib and -FE are found mainly in Ixodes persulcatus ticks in an area reaching from north-eastern Europe to the Russian Far East, China and Japan [1]. Recently, new subtypes of TBEV (Himalayan and Baikalian) have been characterized [2,3].…”

Section: Introductionmentioning

confidence: 99%

Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland

Smura

Tonteri

Jääskeläinen

et al. 2019

Emerging Microbes & Infections

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Number of tick-borne encephalitis (TBE) cases has increased and new foci have emerged in Finland during the last decade. We evaluated risk for locally acquired TBE in the capital region inhabited by 1.2 million people. We screened ticks and small mammals from probable places of TBE virus (TBEV) transmission and places without reported circulation. The TBEV positive samples were sequenced and subjected to phylogenetic analysis. Within the study period 2007-2017, there was a clear increase of both all TBE cases and locally acquired cases in the Helsinki area. The surveillance of ticks and small mammals for TBEV confirmed four distinct TBEV foci in the Helsinki area. All detected TBEV strains were of the European subtype. TBEV genome sequences indicated that distinct TBEV lineages circulate in each focus. Molecular clock analysis suggested that the virus lineages were introduced to these foci decades ago. In conclusion, TBE has emerged in the mainland of Helsinki area during the last decade, with at least four distinct virus lineages independently introduced into the region previously. Although the overall annual TBE incidence is below the threshold for recommending general vaccinations, the situation requires further surveillance to detect and prevent possible further emergence of local TBE clusters.

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“…Phylogenetic studies based on the E protein revealed three TBEV subtypes: European (TBEV-Eu), Siberian (TBEV-Sib) and Far-Eastern (TBEV-FE). However, two potential new subtypes were described: Himalayan (TBEV-Him) and Baikalian (TBEV-Bkl) [ 19 , 20 ]. During the last decades, the incidence of TBE has been fluctuating annually with a general upward trend in several European countries (reviewed in [ 21 ]).…”

Section: Tick-borne Encephalitis Virusmentioning

confidence: 99%

Tick-Borne Encephalitis Virus: A Quest for Better Vaccines against a Virus on the Rise

et al. 2020

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Tick-borne encephalitis virus (TBEV), a member of the family Flaviviridae, is one of the most important tick-transmitted viruses in Europe and Asia. Being a neurotropic virus, TBEV causes infection of the central nervous system, leading to various (permanent) neurological disorders summarized as tick-borne encephalitis (TBE). The incidence of TBE cases has increased due to the expansion of TBEV and its vectors. Since antiviral treatment is lacking, vaccination against TBEV is the most important protective measure. However, vaccination coverage is relatively low and immunogenicity of the currently available vaccines is limited, which may account for the vaccine failures that are observed. Understanding the TBEV-specific correlates of protection is of pivotal importance for developing novel and improved TBEV vaccines. For affording robust protection against infection and development of TBE, vaccines should induce both humoral and cellular immunity. In this review, the adaptive immunity induced upon TBEV infection and vaccination as well as novel approaches to produce improved TBEV vaccines are discussed.

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Reconsidering the classification of tick-borne encephalitis virus within the Siberian subtype gives new insights into its evolutionary history

Cited by 100 publications

References 20 publications

Revealing new tick-borne encephalitis virus foci by screening antibodies in sheep milk

Revealing new tick-borne encephalitis virus foci by screening antibodies in sheep milk

Recent establishment of tick-borne encephalitis foci with distinct viral lineages in the Helsinki area, Finland

Tick-Borne Encephalitis Virus: A Quest for Better Vaccines against a Virus on the Rise

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