Tick-borne encephalitis virus (TBEV) can be transmitted alimentarily through contaminated dairy products, yet the mechanisms by which the virus survives the digestive tract remain poorly understood. In this study, we investigated the stability of TBEV in milk under simulated gastrointestinal conditions. While milk is known to preserve viral infectivity at low temperatures, our results demonstrate that in the gastric environment and at physiological temperature, it exerts a destabilizing effect, significantly reducing TBEV viability. All major milk fractions-whey, casein, and lipids-contribute to this effect. This highlights the necessity for rapid transit of virus-containing milk through the stomach to avoid inactivation. Conversely, in the intestinal environment, milk protects TBEV from bile salt-mediated inactivation, allowing viral persistence in the upper small intestine. Casein was identified as the primary protective component counteracting bile salt disruption. These findings offer new insights into how milk can simultaneously act as a transmission vehicle and modulator of TBEV stability, advancing our understanding of alimentary infection routes and their implications for public health.

Department of Experimental Biology Faculty of Science Masaryk University Brno Czechia

Laboratory of Arbovirology Institute of Parasitology Biology Centre of the Czech Academy of Sciences Ceske Budejovice Czechia

Laboratory of Emerging Viral Infections Veterinary Research Institute Brno Czechia

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