Epizootic Haemorrhagic Disease Virus (EHDV) Infection in Red Deer (

Epizootic haemorrhagic disease virus serotype 8 (EHDV-8) emerged in southern Europe in 2022-2023, but clinical and pathological characterization in free-ranging wildlife remains limited. This study investigated EHDV-8-associated morbidity and mortality in wild ruminants in a 2023 outbreak in Sierras de Cazorla, Segura y Las Villas Natural Park (Jaén, Andalusia, Spain). Moribund animals demonstrated a consistent acute neuro-respiratory syndrome characterized by weakness, ataxia, nystagmus and severe dyspnoea with frothy oral discharge. On the carcasses of 39 red deer, two fallow deer, and one mouflon, necropsy was performed and subsequently histopathology and a real-time polymerase chain reaction (RT-PCR) on the collected samples. Gross lesions included marked pulmonary oedema, tracheal foam and widespread congestion, while histopathology revealed lymphoid depletion, pulmonary haemorrhage, vascular injury and renal tubular necrosis. All animals tested positive for EHDV-8 with low RT-qPCR cycle threshold values, indicating high viral loads. This series provides the first confirmed clinical, pathological, and molecular evidence of EHDV-8 infection in fallow deer and mouflon in Europe. The observations demonstrate that EHDV-8 causes a peracute systemic haemorrhagic disease in susceptible wild ruminants and underline the importance of integrated wildlife surveillance and timely diagnostic sampling during peak vector activity.