Olivieri A, et al.
Emerging neurotropic tick-borne flavivirus infections in goats and wild ungulates in the Italian Alps. Ticks Tick Borne Dis. Published online April 10, 2026. doi:10.1016/j.ttbdis.2026.102643
Recently, a novel neurotropic tick-borne flavivirus was isolated from Alpine chamois with encephalitis and has been provisionally named Alpine chamois encephalitis virus (ACEV) (Snapshot 8/2025). Surveillance has been conducted in the Orobic Alps in northern Italy to investigate the circulation of this virus in wild and domestic ruminants and attached ticks, and to characterize clinical cases.
Goats infected by ACEV began exhibiting neurological signs such as ataxia and hyper-excitability. Post-mortem findings included, among others, massive tick infestation, hepatic dystrophy, cholestasis, and focal areas of cerebral hyperaemia. Histopathology of the brain revealed severe diffuse chronic lympho-histiocytic meningoencephalitis. Immunohistochemical analysis revealed neuronal positivity for tick-borne flavivirus (TBFV). Five of 34 Ixodes ricinus specimens collected from infected animals tested positive by TBFV RT-PCR, and positive samples were successfully sequenced, confirming infection by ACEV.
Screening of the first affected goat herd revealed evidence of TBFV circulation, as 16/67 animals were TBFV ELISA-antibody positive.
TBFV antibodies were also found in red deer, chamois, and roe deer, but the serological assay applied may not reliably discriminate between infections caused by TBE virus and other closely related tick-borne flaviviruses.
Phylogenetic analyses revealed that ACEV is more closely related to Louping Ill virus (LIV) than to the European subtype of TBE virus. The sequences clustered in a well-defined monophyletic clade together with Spanish goat encephalitis virus (SGEV), distinct from LIV strains, supporting classification of ACEV together with SGEV as a novel viral subtype, provisionally termed the goat and chamois encephalitis virus subtype within the Orthoflavivirus loupingi.
The findings of this study highlight the clinical relevance of active transmission of the newly identified virus at the wildlife–livestock–vector interface in the Italian Alps and raise concerns about a potential risk to human health through the consumption of unpasteurized goat milk and goat milk products.