A Systematic Review on the Prevalence of Tick-Borne Encephalitis Virus in Milk and Milk Products in Europe

Background: Tick-borne encephalitis virus (TBEV) is one of the most significant zoonotic diseases in Europe. It primarily spreads through the bites of infected ticks and, less frequently, through consumption of raw milk and dairy products from viremic domestic ruminants. Aims: Assess the prevalence of TBEV or anti-TBEV antibodies in milk and milk products from domestic ruminants in Europe. Materials and methods: Systematic literature review adhering to the JBI methodology, and reported following the PRISMA framework. Results: From the 16 included scientific articles, we extracted 35 data collections (31 on raw milk and 4 on raw milk cheese); studies focused on cow (n = 15), goat (n = 11) and sheep milk (n = 5), goat (n = 3) and cow/goat cheese (n = 1). Fifteen data collections involved individual milk and 16 bulk milk samples. The estimated prevalence of TBEV in individual raw milk and cheese was 6% and 3%, respectively. TBEV prevalence in bulk milk was very heterogeneous, with most values either 0% or 100%. Discussion: Although published research on TBEV transmission to humans through milk and dairy products in the EU countries is limited, our results highlight the potential infection risk for consumers. The variable prevalence reported in the studies may reflect the focal nature of TBEV. Conclusion: Studies on unpasteurised dairy products from domestic ruminants can be valuable for the detection of TBEV presence in a geographic area, even when human cases are not reported. Thanks to the ease of sample collection, their testing could be adopted in monitoring plans on TBEV.