Italy: tick-borne encephalitis found in a roe deer and a chamois

Tick-borne encephalitis (TBE) is an inflammation of the brain and/or its membranes caused by the tick-borne encephalitis virus (TBEV), and as the name suggests, it is transmitted by infected ticks.

It is known that roe deer (Capreolus capreolus) and chamois (Rupicapra rupicapra) rarely become ill after being bitten by a tick infected with TBEV, but they do develop antibodies against the virus. That is why they are very suitable as indicators to gain insight into the spread of the virus in a country (see https://dwhc.nl/en/2024/03/national-surveillance-of-roe-deer-2024/). Although rare, two cases of illness due to TBEV infection have now been described in Italy: in a roe deer in 2021 and in a chamois in 2023. Both showed neurological symptoms, including ataxia, frequent swallowing, incoordination, excessive salivation, repeated head movements, and muscle tremors. The roe deer was identified as a one-year-old female, while for the chamois no details about sex or age has been given. Both animals were in poor condition. Histologically, brainstem inflammation was found in the roe deer, accompanied by the presence of the virus in the brain. In the chamois, there was also evidence of brain inflammation and the presence of the virus was confirmed. Because test results for several other pathogens that can cause neurological symptoms were negative, it was determined that these two animals had tick-borne encephalitis.

Roe deer and chamois do not serve as reservoirs for the virus itself, but they do play an important role in the overall ecology of the virus because they are involved in the life cycle of ticks.

The Netherlands

In mammals with neurological symptoms and/or brain (membrane) inflammation examined by the DWHC, the tick-borne encephalitis virus has not yet been detected. There is therefore no evidence that roe deer in the Netherlands have become ill from the virus. However, antibodies against TBEV were found in the previous national roe deer surveillance (see https://dwhc.nl/2019/04/bloedonderzoek-reeen-teken-encefalitisvirus/). This research is currently being repeated (https://dwhc.nl/en/2024/03/national-surveillance-of-roe-deer-2024/). The RIVM website features a map showing where tick-borne encephalitis virus occurs in the Netherlands: https://www.rivm.nl/en/tick-borne-encephalitis.

More information about tick-borne encephalitis

About tick-borne encephalitis in humans: RIVM: https://www.rivm.nl/en/tick-borne-encephalitis

DWHC reports on tick-borne encephalitis: https://dwhc.nl/en/ziekten/teken-encefalitis/

A person can also become infected by drinking contaminated raw milk or eating contaminated raw-milk cheese, but this is a rare route of infection. Infected ticks are the main transmitters of TBEV.

Abbreviation
RIVM: National Institute for Public Health and the Environment