Emerging neurotropic tick-borne flavivirus infections in goats and wild ungulates in the Italian Alps

Recently a novel neurotropic tick-borne flavivirus (TBFV) was isolated from Alpine chamois with encephalitis and from attached ticks in the Austrian federal state of Salzburg and the Italian provinces of Piedmont and Lombardy, preliminarily characterized, and provisionally named Alpine chamois encephalitis virus (ACEV). However, several aspects of this newly described virus-including its host range and epidemiology-remain unknown. Therefore, surveillance was conducted in 2023 and 2024 in the Orobic Alps (Northern Italy) to investigate the circulation of this virus in wild and domestic ruminants and attached ticks, and to characterize clinical cases. Neurological cases in goats and chamois revealed meningoencephalitis by histopathology and tested positive for ACEV by RT-PCR and sequencing. Viral RNA was also detected in 5 out of 34 Ixodes ricinus ticks (15%) collected from an affected goat. In domestic goats, serological screening of animals from affected farms revealed TBFV antibodies in 16 out of 67 animals (24%), while antibodies were detected in 19 out of 1462 individuals (1.3%) sampled through broader wildlife surveillance, including 11 red deer, 7 chamois, and 1 roe deer. These findings provide evidence of active ACEV transmission at the wildlife-livestock-vector interface in the Italian Alps, highlight its clinical relevance in ruminants, and raise concerns for potential risk for human health through consumption of unpasteurized goat milk and goat milk products, emphasizing the need for integrated One Health surveillance.