Review: Sentinels of tick-borne encephalitis risk

Imhoff, Maren; Hagedorn, Peter; Schulze, Yesica; Hellenbrand, Wiebke; Pfeffer, Martin; Niedrig, Matthias

doi:10.1016/j.ttbdis.2015.05.001

Cited by 69 publications

(57 citation statements)

References 93 publications

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“…The geographical distribution of TBE displays a patchy pattern, with each patch representing a TBE focus. Human TBE cases, detection of TBEV in fieldcollected ticks, in ticks detached from humans, in birds or in animals, as well as in tissues and blood samples from mammals, are all used as golden standards to detect TBEV foci [12]. Since the prevalence of TBEV in the tick population is low and these methods are laborious and involve invasive interventions, there is a need for new and reliable surveillance techniques to identify new TBEV risk areas at an early stage.…”

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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“…Tick larvae and nymphs feed on small mammals including rodents, whereas adult ticks feed on larger animals, including deer. Although it is arguable whether ticks are the true reservoirs of TBFVs rather than a mammal, rodents are essential for virus transmission between feeding ticks and maintenance of the virus in nature [15,16]. Historically, reservoir host species have been defined by the identification of virus or virus-specific antibodies in wild-caught rodents with no apparent disease symptoms.…”

Section: Introductionmentioning

confidence: 99%

Interferon signaling in Peromyscus leucopus confers a potent and specific restriction to vector-borne flaviviruses

Izuogu

McNally²,

Harris

et al. 2017

PLoS ONE

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Tick-borne flaviviruses (TBFVs), including Powassan virus and tick-borne encephalitis virus cause encephalitis or hemorrhagic fevers in humans with case-fatality rates ranging from 1–30%. Despite severe disease in humans, TBFV infection of natural rodent hosts has little noticeable effect. Currently, the basis for resistance to disease is not known. We hypothesize that the coevolution of flaviviruses with their respective hosts has shaped the evolution of potent antiviral factors that suppress virus replication and protect the host from lethal infection. In the current study, we compared virus infection between reservoir host cells and related susceptible species. Infection of primary fibroblasts from the white-footed mouse (Peromyscus leucopus, a representative host) with a panel of vector-borne flaviviruses showed up to a 10,000-fold reduction in virus titer compared to control Mus musculus cells. Replication of vesicular stomatitis virus was equivalent in P. leucopus and M. musculus cells suggesting that restriction was flavivirus-specific. Step-wise comparison of the virus infection cycle revealed a significant block to viral RNA replication, but not virus entry, in P. leucopus cells. To understand the role of the type I interferon (IFN) response in virus restriction, we knocked down signal transducer and activator of transcription 1 (STAT1) or the type I IFN receptor (IFNAR1) by RNA interference. Loss of IFNAR1 or STAT1 significantly relieved the block in virus replication in P. leucopus cells. The major IFN antagonist encoded by TBFV, nonstructural protein 5, was functional in P. leucopus cells, thus ruling out ineffective viral antagonism of the host IFN response. Collectively, this work demonstrates that the IFN response of P. leucopus imparts a strong and virus-specific barrier to flavivirus replication. Future identification of the IFN-stimulated genes responsible for virus restriction specifically in P. leucopus will yield mechanistic insight into efficient control of virus replication and may inform the development of antiviral therapeutics.

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“…Although rodents have been confirmed as reservoirs and amplifying hosts for a number of tick-borne microorganisms [11, 12], their reservoir role has not been resolved in the case of rickettsiae. In our study, we found only 0.5% R. helvetica -infected A. flavicollis, whereas 4.9% of ticks attached to A. flavicollis , My.…”

Section: Discussionmentioning

confidence: 99%

“…Small rodents are important hosts for immature stages of ixodid ticks and are considered, e.g., as reservoirs of tick-borne encephalitis virus [11], Borrelia miyamotoi and “ Ca . N. mikurensis” [12] in Europe.…”

Section: Introductionmentioning

confidence: 99%

Molecular evidence of Rickettsia spp. in ixodid ticks and rodents in suburban, natural and rural habitats in Slovakia

et al. 2017

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BackgroundNatural foci of tick-borne spotted fever group (SFG) rickettsiae of public health concern have been found in Slovakia, but the role of rodents in their circulation is unclear. Ticks (Ixodes ricinus, Ixodes trianguliceps, Dermacentor marginatus, Dermacentor reticulatus, Haemaphysalis concinna and Haemaphysalis inermis) and tissues of rodents (Apodemus flavicollis, Apodemus sylvaticus, Myodes glareolus, Microtus arvalis, Microtus subterraneus and Micromys minutus) were examined for the presence of SFG rickettsiae and Coxiella burnetii by molecular methods. Suburban, natural and rural habitats were monitored to acquire information on the role of ticks and rodents in the agents’ maintenance in various habitat types of Slovakia.ResultsThe overall prevalence of rickettsial infection in questing I. ricinus and D. marginatus was 6.6% and 21.4%, respectively. Rickettsia helvetica, R. monacensis and non-identified rickettsial species were detected in I. ricinus, whereas R. slovaca and R. raoultii were identified in D. marginatus. Rickettsia spp.-infected I. ricinus occurred during the whole tick questing period. Rickettsia helvetica dominated (80.5%) followed by R. monacensis (6.5%). The species were present in all studied habitats. Rickettsia slovaca (66.7%) and R. raoultii (33.3%) were identified in D. marginatus from the rural habitat. Apodemus flavicollis was the most infested rodent species with I. ricinus, but My. glareolus carried the highest proportion of Rickettsia-positive I. ricinus larvae. Only 0.5% of rodents (A. flavicollis) and 5.2% of engorged I. ricinus removed from My. glareolus, A. flavicollis and M. arvalis were R. helvetica- and R. monacensis-positive. Coxiella burnetii was not detected in any of the tested samples. We hypothesize that rodents could play a role as carriers of infected ticks and contribute to the maintenance of rickettsial pathogens in natural foci.ConclusionsLong-term presence of SFG Rickettsia spp. was confirmed in questing ticks from different habitat types of Slovakia. The results suggest a human risk for infection with the pathogenic R. helvetica, R. monacensis, R. slovaca and R. raoultii.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2094-8) contains supplementary material, which is available to authorized users.

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Review: Sentinels of tick-borne encephalitis risk

Cited by 69 publications

References 93 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

Interferon signaling in Peromyscus leucopus confers a potent and specific restriction to vector-borne flaviviruses

Molecular evidence of Rickettsia spp. in ixodid ticks and rodents in suburban, natural and rural habitats in Slovakia

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