Mathews-Martin et al.
Exposure of cattle to tick-borne encephalitis virus in the historical endemic zone in north-eastern France. BMC Vet. Res. 2024;20(1):228. doi:10.1186/s12917-024-04079-8

In France, the first case of Tick-Borne Encephalitis (TBE) was reported in 1968. Since then, the number of reported cases remained low for many years until recently, when the number of cases increased, and new TBE foci were detected.

An alimentary TBE outbreak in 2020 prompted an assessment of the risk of food-borne TBE cases. A seroprevalence study was conducted in cattle (aged 21 months to 21 years) in an endemic area in north-eastern France (Alsace-Lorraine). The TBE seroprevalence was high, with 57.6% of cattle testing positive using a micro-neutralisation test (MNT). Seroprevalence did not increase with age, indicating that natural immunity (antibody persistence) may not last a lifetime in the absence of new contact with the TBE virus. Some seropositive sera were also detected in western France, an area previously presumed to be TBE-free.

In contrast to the MNT, commercial ELISA kits had relatively low sensitivity, particularly when the level of neutralising antibodies was below 1:40. The authors concluded that cattle of any age were highly exposed to the TBE virus in the center of the French historical endemic region, at an unexpected level considering the reported human incidence in France. When using cattle sera for further studies to assess exposure to the TBE virus, the screening strategy will be crucial, and the MNT may be preferred over ELISA kits.

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