# Epizootic Haemorrhagic Disease Virus (EHDV) Infection in Red Deer (Cervus elaphus), Fallow Deer (Dama dama) and Mouflon (Ovis orientalis musimon) in South-Eastern Spain: Implications for Wildlife Health and Ruminant Disease Ecology

## TL;DR

A 2023 outbreak of EHDV-8 in wild ruminants in Spain showed rapid, fatal disease in red deer, fallow deer, and mouflon, highlighting the need for wildlife and veterinary monitoring.

## Contribution

First confirmed clinical and molecular evidence of EHDV-8 in fallow deer and mouflon in Europe.

## Key findings

- EHDV-8 caused peracute systemic hemorrhagic disease in wild ruminants with high viral loads.
- Clinical signs included neuro-respiratory symptoms like ataxia, nystagmus, and severe dyspnea.
- Gross and histopathological findings included pulmonary edema, lymphoid depletion, and vascular injury.

## Abstract

In 2023, veterinary field teams investigated an outbreak of acute morbidity and mortality in free-ranging wild ruminants in a national park in Andalusia (Spain). Forty-two carcasses were examined. A consistent peracute clinical picture was observed. Affected animals demonstrated marked weakness, ataxia, and eye tremors, as well as difficulty breathing, often with frothy oral discharge. On postmortem examination, blood and key organs (e.g., spleen, lung and lymph nodes) were collected for comprehensive pathological evaluation. Presumptive diagnosis of epizootic haemorrhagic disease virus (EHDV) was established based on observed symptoms, clinical findings, and gross pathology observations. Infection with EHDV was confirmed using a real time-polymerase chain reaction on blood and tissues. Positive cases occurred in red deer (Cervus elaphus), fallow deer (Dama dama), and mouflon (Ovis orientalis musimon). To our knowledge, this series provides the first confirmed EHDV infections in fallow deer and mouflon. These observations demonstrate that EHDV can cause rapidly progressive, fatal disease in wild ruminants following its detection in southern Europe. Practical implications for veterinary and wildlife health services include prompt field triage, safe carcass handling, rapid laboratory testing, and coordinated monitoring of wildlife, livestock and biting midges during late summer and early autumn.

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.