Abstract
BackgroundBy using animal sera as sentinels, natural TBEV foci could be identified and further analyses including investigations of ticks could be initiated. However, antibody response against TBEV-related flaviviruses might adversely affect the readout of such a monitoring. Therefore, the cross-reactivity of the applied TBEV serology test systems – enzyme linked immunosorbent assay (ELISA) and virus neutralization test (VNT) – as well as the longevity of TBEV antibody titres in sheep and goats were investigated in this study.ResultsCross-reactivity of the TBEV antibody test systems with defined antibody-positive samples against selected members of the Flaviviridae family (e.g. Louping ill virus, West Nile virus) was observed for Louping-ill-positive sera only. In contrast, the commercial West Nile virus (WNV) competitive ELISA showed a high level of cross-reactivity with TBEV-specific positive sera.To assess the longevity of TBEV antibody titres, sera from two sheep and two goats, which had been immunized four times with a commercially available TBEV vaccine, were tested routinely over 28 months. In three of the four animals, TBEV-specific antibody titres could be detected over the whole test period.In addition, sera from the years 2010 and 2011 were collected in flocks in different villages of Baden-Württemberg and Thuringia to allow re-examination two to four years after the initial analysis. Interestingly, in most cases the results of the former investigations were confirmed, which may be caused by steadily existing natural TBEV foci.ConclusionCross-reactivity must be taken into consideration, particularly for TBEV serology in regions with a prevalence of Louping ill virus and for serological testing of WNV by cross-reactive ELISAs. Furthermore, over-interpretation of single TBEV-positive serological results should be avoided, especially in areas without a TBEV history.
Highlights
IntroductionBy using animal sera as sentinels, natural TBE virus (TBEV) foci could be identified and further analyses including investigations of ticks could be initiated
By using animal sera as sentinels, natural Tick-borne encephalitis (TBE) virus (TBEV) foci could be identified and further analyses including investigations of ticks could be initiated
Four out of five Louping ill virus (LIV)-antibodypositive sheep sera reacted positive in the TBEV-enzyme linked immunosorbent assay (ELISA) as well as in the TBEV-virus neutralization test (VNT)
Summary
By using animal sera as sentinels, natural TBEV foci could be identified and further analyses including investigations of ticks could be initiated. TBE virus (TBEV) circulates between ticks and hosts in geographically strictly limited natural foci, which can range in size from large to very small. Seroconversion without specific clinical signs of TBE has been described in some animal species such as cattle and small ruminants [11,19,20]. Clinical cases of TBE in ruminants are very seldom; one case of a mouflon (Ovis ammon musimon) for example has been reported from Austria [21]. These animals are of significant public health relevance. TBE in humans caused by virus-infected milk has occurred in many countries, in the last ten years in Hungary, Austria and Estonia [26,27,28]
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