Tick-Borne Encephalitis in Sheep, Romania

Salát, Jiřı́; Mihalca, Andrei Daniel; Mihaiu, Marian; Modrý, David; Růžek, Daniel

doi:10.3201/eid2312.170166

Cited by 26 publications

(14 citation statements)

References 8 publications

(8 reference statements)

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“…However, in single flocks in the same village seroprevalences between 0 and 43% were seen which confirmed the patchy pattern of TBEV [9]. Nearly the same differences between 2% (Mureş County) and 27.73% (Bihor County) seropositive sheep were found in Romania with a higher prevalence than in our investigated samples of 15.2% of all tested 519 samples in Romania [23]. A low overall seroprevalence was seen in Lithuanian domestic ruminants of 1.7% in eight out of 18 checked regions with high regional differences.…”

Section: Discussionsupporting

confidence: 82%

Tick-borne encephalitis virus (TBEV) antibodies in animal sera – occurrence in goat flocks in Germany, longevity and ability to recall immunological information after more than six years

et al. 2019

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BackgroundTBE is an important tick-borne viral zoonosis in Europe and some parts of Asia. Humans can become infected by tick bite and in some cases also by consumption of nonpasteurized raw milk and raw milk products from ruminants. Serological investigations of milking flocks can help to assess the risk of TBEV infection for humans. 735 blood samples from 50 goat flocks from four federal states of Germany were tested by TBEV-VNT to assess a potential risk for TBEV infection.There are some gaps in the knowledge about immunity in animals, for example with regard to the longevity of TBEV immunity. Two goats and two sheep were immunized and TBEV antibody titers could be detected for up to 7 years.Furthermore, nothing is known about a possible long-lasting immunological memory that could quickly be reactivated by an additional contact to TBEV. Seven years after the first immunization two goats and two sheep as well as two naïve goats and two sheep were boostered and TBEV antibody titers followed.ResultsOnly one sample in each of the three states was TBEV-antibody positive (VNT), albeit with low titers. However, in Baden-Württemberg seven samples were positive, among them four goats of the same flock.TBEV-antibody positive titers were detected in goats for up to 6 years and 10 months, in sheep for up to 4 years and 7 months.Seven years after immunization a clear immunological recall occurred in response to administration of one dose of vaccine in two goats and two sheep.ConclusionIt can be concluded that in the tested flocks the risk of an alimentary TBEV infection was low. However, in one single flock a considerably higher risk must be assumed.Antibody titers in goats and sheep can last very long after contact to TBEV, albeit at a low level. This should be taken into consideration in cases where the risk of an alimentary infection is assessed in a flock by serological investigations.The immunological recall gives rise to the suspicion that the immunological memory after a first contact to TBEV lasts for many years, probably lifelong.

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Section: Discussionsupporting

confidence: 82%

Tick-borne encephalitis virus (TBEV) antibodies in animal sera – occurrence in goat flocks in Germany, longevity and ability to recall immunological information after more than six years

et al. 2019

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“…Seroprevalence in the goat sera was 14.6%, but in the human sera, from goat owners in that region, there were no detectable TBEV antibodies. Sheep have also been used for identification of TBE risk areas in north-western Romania [42]. Serum from adult sheep was collected in five counties and TBEV was identified using virus neutralization test in 15.02% of sheep tested.…”

Section: Discussionmentioning

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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“…Seroprevalence studies on TBE in domestic animals in Europe have demonstrated that animals may serve as useful sentinels for detection of TBEV risk areas (Klauset al, ; Rieille, Klaus, Hoffmann, Peter, & Voordouw, ; Salat, Mihalca, Mihaiu, Modry, & Ruzek, ). In the present study, a total of 112 serum samples from five farms were analysed.…”

Section: Discussionmentioning

confidence: 99%

Tick‐borne encephalitis virus in cows and unpasteurized cow milk from Norway

Paulsen

Stuen

Neves

et al. 2018

Zoonoses and Public Health

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Tick‐borne encephalitis virus (TBEV) is recognized as the most important zoonotic tick‐transmitted virus in Europe. TBEV is mainly transmitted to humans through bites from TBEV‐infected ticks (Ixodes ricinus and Ixodes persulcatus). However, alimentary infection after consumption of unpasteurized milk and cheese from domestic ruminants has been reported. There is little information about TBEV in ruminants in Norway. The objectives of this study were to analyse unpasteurized cow milk for TBEV RNA and to study the presence of IgG antibodies to TBEV in the same animals. A total of 112 milk and blood samples were collected from cows from five different farms spread from southern to northern Norway. The milk samples were analysed by an in‐house reverse transcription (RT) real‐time polymerase chain reaction and confirmed by pyrosequencing. Serum samples were screened by a commercial enzyme‐linked immunosorbent assay and verified by a TBEV‐specific serum neutralization test. We found TBEV RNA in unpasteurized milk collected from farms in the municipalities of Mandal, Skedsmo and Brønnøy in 5.4% of the tested animals. Specific antibodies to TBEV were only detected in Arendal, where 88.2% of the tested animals were positive. Further studies on milk containing TBEV RNA should be performed to conclude if TBEV found in unpasteurized milk in Norway is infectious, which could be of great importance in a One Health perspective.

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Tick-Borne Encephalitis in Sheep, Romania

Cited by 26 publications

References 8 publications

Tick-borne encephalitis virus (TBEV) antibodies in animal sera – occurrence in goat flocks in Germany, longevity and ability to recall immunological information after more than six years

Tick-borne encephalitis virus (TBEV) antibodies in animal sera – occurrence in goat flocks in Germany, longevity and ability to recall immunological information after more than six years

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

Tick‐borne encephalitis virus in cows and unpasteurized cow milk from Norway

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