Meteorological and environmental factors associated with the exposure to tick-borne encephalitis virus (TBEV) in cattle, north-eastern France, 2018-2019.

Tick-borne encephalitis virus (TBEV) is a severe neurological disease that can be transmitted to humans through the bites of infected ticks or the consumption of unpasteurised dairy products from infected but asymptomatic ruminants. The recent detection of food-borne cases in France is a rising concern, since the production and consumption of raw milk cheese is common. There is limited data available on seroprevalence and factors associated with the exposure to TBEV of domestic ungulates in Europe, and to date, such data are not available in France. A total of 4,483 cattle sera were collected between 2018 and 2019. We used principal component analysis and spatial random forest modelling to explore meteorological and landscape predictors and their relationships with seroprevalence levels. TBEV antibodies were detected in cattle across the region, with an overall apparent seroprevalence of 7.5% (95% CI 6.7-8.3%). The highest seroprevalence was observed in the southern Vosges Mountains, reaching 72.5%. Cattle exposure was higher in areas where the annual land surface temperature was below 12 °C, mixed forest coverage exceeded 25%, and pastures located within 50 m of wooded areas covered more than 3%. This study represents the first large-scale serological survey of TBEV in cattle in France, revealing that TBEV is widespread in north-eastern France and extends beyond the distribution of TBE human cases. The main factors identified as influencing cattle exposure can be used to predict the risk of TBEV food-borne transmission. Further research is needed to fully understand this risk in France, including investigations into breeding and cheese practices.