Tick borne encephalitis and West Nile Virus prevalence in Hamburg – TiboWeNi

Background: Part i: Over the past 20 years, the risk areas for tick borne encephalitis (TBE) have extended from Southern Germany to Northern areas. Hamburg is one of the only German states without a reported local infection. However, infections have been detected in the surrounding areas. A majority of infections (around 70–95%) have an asymptomatic course. These remain undiscovered and unnotified. Thus, also in Hamburg, TBE-infections may have remained undiagnosed and thus unnotified in the past years. In addition, disease awareness may be low among physicians and thus TBE cases may have been missed. In this study, we aim to conduct a TBE-seroprevalence study in healthy blood donors in Hamburg. Our objectives are to investigate TBE-antibody prevalence and potential protection rates through vaccination in Hamburg.

Part ii: West-Nile Virus (WNV) is a flavivirus which has classically circulated in the Tropics. The virus is mainly transmitted by mosquitoes between wild birds. Mosquitoes infected with birds can also transmit the virus to humans and other mammals (especially horses). Vectors are various mosquitoes. With migratory birds, WNV has travelled to areas in Europe around the Mediterranean Sea. In Southern Europe, it has been transmitted seasonally in summer for a long time and it can also hibernate locally. In 2018, a circulation of WNV in birds and horses was registered in Germany for the first time, and autochthonous human infections have also been notified in Germany since 2019. Mainly the Eastern Federal States and Berlin have been affected. The Culex mosquitoes, which are widespread throughout Germany, are considered the main vectors. Also in Hamburg, WNV has been in detected in several birds since 2018, and in 2022, a first WNV infection was diagnosed in a horse. For WNV, a majority of infections are asymptomatic in humans. Around 20% of infected persons, develop a febrile, flu-like illness. Around 1% develop a neuroinvasive form of the disease, in the form of a meningitis, or rarely an encephalitis. Approximately 5–10% of patients with a neuroinvasive West Nile disease die, especially the elderly and patients with a pre-existing cardiovascular condition or immunosuppression can develop a severe course. In this study, we aim to conduct a WNV-seroprevalence study in healthy blood donors in Hamburg. Our objectives are to investigate WNV-antibody prevalence in Hamburg.

Methods: This is a cross-sectional study. TBE infection-induced seroprevalence, WNV infection induced seroprevalence and TBE vaccination induced seroprevalence are determined in around 1,000 persons aged≥18 years living in the Metropolitan region of Hamburg and donating blood at the Zentralinstitut für Transfusionsmedizin (ZIT) in Hamburg in May 2023. At the Bundeswehr Institute for Microbiology/ National TBEV Consultant Laboratory, Munich, Enzyme-linked immunosorbent assays (ELISAs), Microneutralisation assays (mNAs) and Indirect immunofluorescence tests are performed and results are expected in November 2023.

Conclusion: With knowledge gained from this project, we aim to initiate awareness campaigns among physicians, especially primary care physicians, vaccinologists, and neurologists. Furthermore, information campaigns among the population can be performed about prevention measures (e.g. TBE-vaccination, tick prevention, mosquito bite prevention, mosquito control).

Publication History

Article published online:
10 April 2024