Cerebral listeriosis in an adult Freiberger gelding.

The research discusses a case of rare cerebral listeriosis in a Freiberger gelding (a type of horse), caused by Listeria monocytogenes infection, highlighting unique symptoms and subsequent diagnosis after necropsy and histopathology tests.

Case Details

• The study started with an adult Freiberger gelding showing severe neuronal symptoms that had suddenly appeared. Unfortunately, the horse collapsed within 24 hours of the onset of these symptoms and had to be euthanized for humane reasons.

Necropsy Findings

• Following the gelding’s euthanasia, a necropsy – a post-mortem examination – was conducted. This revealed multiple small brown to reddish foci, or spots, in the gelding’s brain stem and pons, areas that are crucial for basic physiological functions like breathing, sleeping, and heartbeat regulation.

Histopathology Results

• Through histopathological examinations, multiple areas in the horse’s brain were found to be inflamed with suppurative meningoencephalitis, a condition that involves pus-filled swelling in the brain and meningitis. In addition to this, microabscesses were spotted.
• Interestingly, the horse also had occasional intra-lesional, coccoid to rod-shaped bacteria residing in the brain’s affected lesions.

Identification of the Bacteria

• The discovered bacteria was immunohistochemically identified as a Listeria species. It was then further specified as Listeria monocytogenes, a bacterium that normally causes infection in humans and animals, via an in-situ hybridization-based commercial test system.

Overall Discovery and Insight

• This research importantly highlights a unique case of equine cerebral listeriosis in an adult horse, as cerebral listeriosis is commonly only reported in newborn animals.