A 14-year-old warmblood mare developed progressive neurological signs including ataxia, nystagmus, impaired mental status as well as decreased cranial nerve reflexes, and finally went recumbent. Postmortem examination and histology revealed severe chronic active multifocal suppurative meningoencephalomyelitis with multifocal fibrinoid degeneration and necrosis of the vessel walls, multiple microabscesses and pyogranulomas. Additionally, there was mild multifocal necrotising to pyogranulomatous hepatitis and moderate multifocal suppurative to pyogranulomatous interstitial nephritis with fibrinoid degeneration of the vessel walls. Routine diagnostic procedures did not reveal any viral or bacterial aetiology; however, listerial enrichment with subsequent matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis and 16S rRNA sequencing confirmed infection with Listeria monocytogenes. Listeriosis is uncommonly reported as a cause of sepsis in foals and rarely in adult horses. Furthermore it is rarely reported causing meningoencephalitis in foals as well as in adult horses. To the authors’ knowledge, this is the first case of meningoencephalomyelitis most likely due to septic distribution in an adult horse.
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Contributors MH drafted the manuscript and performed the postmortem examination. EP-B performed the microbiological investigations and proof-read the manuscript. CF performed the virological investigations and proof-read the manuscript. KF performed and supervised the clinical and laboratory investigations and proof-read the manuscript. CH performed and supervised the histopathology and proof-read the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.
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