Food-Borne Transmission of Tick-Borne Encephalitis Virus—Spread, Consequences, and Prophylaxis

Abstract

Tick-borne encephalitis (TBE) is the most common viral neurological disease in Eurasia. It is usually transmitted via tick bites but can also occur through ingestion of TBEV-infected milk and dairy products. The present paper summarises the knowledge of the food-borne TBEV transmission and presents methods for the prevention of its spread. The incidence of milk-borne TBE outbreaks is recorded in central, eastern, and north-eastern Europe, where Ixodes ricinus, Ixodes persulcatus, and/or Dermacentor reticulatus ticks, i.e., the main vectors of TBEV, occur abundantly. The growing occurrence range and population size of these ticks increases the risk of infection of dairy animals, i.e., goats, sheep, and cows, with viruses transmitted by these ticks. Consumers of unpasteurised milk and dairy products purchased from local farms located in TBE endemic areas are the most vulnerable to alimentary TBEV infections. Familial infections with these viruses are frequently recorded, mainly in children. Food-transmitted TBE can be monophasic or biphasic, and some of its neurological and psychiatric symptoms may persist in patients for a long time. Alimentary TBEV infections can be effectively prevented by consumption of pasteurised milk and the use of TBEV vaccines. It is recommended that milk and dairy products should be checked for the presence of TBE viruses prior to distribution. Protection of dairy animals against tick attacks and education of humans regarding the epidemiology and prophylaxis of TBE are equally important.

Comparison of Extraction Methods for the Detection of Tick-Borne Encephalitis Virus RNA in Goat Raw Milk and Cream Cheese

“…A second TBEV transmission pathway to humans is via the consumption of raw milk and raw milk products (Lickova et al, 2021 ; Buczek et al, 2022 ). When TBEV-infected ticks feed on cows, sheep and goats, the animals can become viraemic and for a few days the virus can be excreted into the milk (Muhd Radzi et al, 2015 ; Rodrigues et al, 2019 ).…”

“…For example, TBEV could be detected for up to 5 days in the blood and for 3–8 days in the milk of goats after infection (Muhd Radzi et al, 2015 ; Rodrigues et al, 2019 ). As TBEV infection in goats is largely asymptomatic, it is often difficult to identify animals potentially releasing the virus into the milk (Buczek et al, 2022 ). In goat raw milk, the virus was described to be stable for up to 24 h at 4 °C and 22 °C (Offerdahl et al, 2016 ).…”

“…After consumption of raw milk by humans, the virus can therefore reach the duodenum without losing its infectivity, causing infection and disease (Balogh et al, 2012 ). Several outbreaks of TBE after consumption of raw milk or raw milk products have been reported from Hungary, Austria, Estonia, Slovakia, Czech Republic, and Germany (Salat & Ruzek, 2020 ; Lickova et al, 2021 ; Buczek et al, 2022 ). For example, a large outbreak involving 27 patients, which could be linked to consumption of goat raw milk sold in a supermarket, was described in Estonia in 2005 (Kerbo et al, 2005 ).…”

Bearing the Burden of Tick-Borne Encephalitis in Europe, 2012-2020: Rising Cases, Future Predictions and Climate Change

“…4 The main route of infection in humans is through a tick bite, while contracting the infection via consumption of infected unpasteurised dairy products is less common. 5 There is still no specific antiviral therapy to combat TBE. Mainstay options are supportive or, in severe cases, require hospitalization in intensive care units with ventilatory support.…”

“…What are the current vaccination recommendations of Tick Borne Encephalitis in Europe? 5. What are the steps we can take to raise awareness of the increasing incidence and burden of Tick Borne Encephalitis?…”