Current Knowledge on Tick-Borne Encephalitis Virus Interaction with Ticks: Acquisition, Dissemination, and Persistence.

Tick-borne encephalitis virus (TBEV) is a major arthropod-borne flavivirus responsible for severe neurological disease in humans across Europe and Asia. It is maintained in nature through complex interactions within ticks and between tick vectors, vertebrate hosts and environmental factors. This review summarizes current knowledge on TBEV-tick interactions, focusing on virus acquisition, dissemination, vector competence, and long-term persistence within tick vectors. TBEV is acquired by ticks during blood feeding on viremic hosts or through co-feeding transmission under experimental conditions. Transovarial transmission has also been reported, as indicated by the detection of infected larvae in nature, although its efficiency appears to be low and variable. Following ingestion, TBEV infects and replicates in the tick midgut before dissemination via the hemolymph to secondary tissues, including the salivary glands and reproductive organs, which are essential for viral persistence and transmission. Vector competence and capacity vary between tick species and are shaped by intrinsic and extrinsic factors. Although transstadial transmission and transovarial transmission contribute to long-term virus maintenance, their efficiency is generally low and variable. In vitro models, including tick cell lines, have provided valuable insights into virus-tick interactions. Nevertheless, important knowledge gaps remain, particularly in understanding early events at the tick-host interface and mechanisms underlying viral dissemination and persistence within ticks.