Rapport de cas Mononuclear pleocytosis and meningoencephalitis caused by Listeria monocytogenes in an adult horse.

Clinical disease caused by infection with Listeria monocytogenes is rare in adult horses, and there is a paucity of ante-mortem clinicopathologic changes for this species reported in the literature. Confirmatory diagnosis is difficult and often requires post-mortem sampling of the brainstem. This report details a case of meningoencephalitis caused by Listeria monocytogenes in an adult American quarter horse gelding presenting with central neurologic signs. Pre-mortem analysis of the cerebrospinal fluid revealed a mononuclear, primarily lymphocytic, pleocytosis, which is a reported finding in other species with listeriosis. Post-mortem histopathologic changes of the brainstem were characteristic of listeriosis, and infection was confirmed with immunohistochemical labeling and bacterial culture. Key clinical message: Listeriosis should be included as a differential diagnosis in neurologic horses with mononuclear pleocytosis identified on cerebrospinal fluid analysis.
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