Comparative Tick-Borne Encephalitis (Virus) Surveillance in Belgium 2009-2015: Experiences with Diagnostic Tests, Sentinel Species and Surveillance Designs

When it is not overtly affecting human beings, the Tick-Borne Encephalitis Flavivirus (TBEV) remains mostly unnoticed during its enzootic cycles within vectors and unaffected animal species. Until recently, Belgium was “presumed” free of this important neuro-pathogenic virus without any scientific substantiation. Nonetheless, Belgium is clearly at risk of Tick-Borne Encephalitis (TBE) emergence and incursions from endemic zones in the neighboring countries.

This comparative review paper describes 5 Belgian veterinary serological studies with enzyme-linked immunosorbent assays and seroneutralisation tests (ELISA/ SNT), in which several surveillance schemes were used (active/passive, risk-/ laboratory-/range-based) in classic TBE sentinel species (dogs, cattle, roe deer, wild boar). Additionally, passive syndromic surveillance in two medical laboratories resulted in inconclusive medical data. Details are given on the scientists’ experiences with available first/second line diagnostic tests and with the different surveillance methods/survey designs.

Each of the veterinary studies clearly demonstrated the presence of TBEV-specific antibodies in Belgian sentinels, sometimes even at high seroneutralisation (SNT) titers, while the medical data remain so far inconclusive, despite positive reactions of some patients in some TBEV-tests. These results have substantiated our suspicion of TBEV-presence in Belgium from 2010 onwards and have allowed sentinel comparisons based on “suitability criteria”. Furthermore, the studies have highlighted the need for further veterinary validation of commercial ELISA-tests in comparison to the gold standard SNT.

Author(s): Sophie Roelandt*, Vanessa Suin, Steven Van Gucht, Yves Van der Stede and Stefan Roels

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