A retrospective study of morbidity and mortality in captive Przewalski's horses (Equus przewalskii) between 1973 and 2021

Przewalski's horses (Equus przewalskii) were declared extinct in the wild in 1996, but reintroduction programmes initiated in 1997 have enabled the re-establishment of free-ranging populations. The maintenance of healthy captive populations remains essential to support these conservation efforts, yet systematic pathological investigations in captive Przewalski's horses are lacking. This study provides the first necropsy-based overview of morbidity and mortality in a captive European population. Pathology reports from 64 horses examined between 1973 and 2021 were reviewed retrospectively. Across these animals, 105 organ system (OS) lesions were recorded, reflecting multiple lesions in some individuals. Data extracted included signalment, season of death, euthanasia status, cause of death (COD), aetiology, affected OS and incidental findings. Infectious disease was the most common COD, accounting for 28.1% of cases (18/64), followed by trauma (21.9%; 14/64). The gastrointestinal tract was the most frequently affected OS, involved in 25.7% of all OS lesions (27/105), followed by the musculoskeletal (15.2%; 16/105) and respiratory (13.3%; 14/105) systems. Age- and sex-related patterns were evident. Geriatric deaths were predominantly female, adult deaths predominantly male and euthanasia more frequent in males. Neonatal animals were especially affected by respiratory lesions, while subadult animals showed notable vulnerability to extrinsic causes, including intoxications and trauma. Overall, infection, trauma and gastrointestinal disease emerged as the main health concerns in captive Przewalski's horses. The findings further suggest that management factors, including peripartum hygiene, social dynamics, diet and stress, may play an important role in morbidity and mortality. Targeted husbandry, improved health monitoring and standardized pathological reporting may help strengthen captive population management and support future reintroduction efforts.