Rhombencephalitis Caused by Listeria monocytogenes in Humans and Ruminants: A Zoonosis on the Rise?

Abstract

Listeriosis is an emerging zoonotic infection of humans and ruminants worldwide caused by Listeria monocytogenes (LM). In both host species, CNS disease accounts for the high mortality associated with listeriosis and includes rhombencephalitis, whose neuropathology is strikingly similar in humans and ruminants. This review discusses the current knowledge about listeric encephalitis, and involved host and bacterial factors. There is an urgent need to study the molecular mechanisms of neuropathogenesis, which are poorly understood. Such studies will provide a basis for the development of new therapeutic strategies that aim to prevent LM from invading the brain and spread within the CNS.

Figure 1

Cow with rhombencephalitis due to Listeria monocytogenes infection. The cow has problems with swallowing (note the feed below her head) and shows increased salivation, facial paralysis with drooping of left ear and upper eyelid, courtesy of Dr. Mireille Meylan, Vetsuisse Faculty, University of Bern.

Figure 2

Recumbent goat with rhombencephalitis due to Listeria monocytogenes infection. The animal has a head-tilt and pleurothotonus; its right ear is drooping.

Figure 3

Rhombencephalitis in a sheep: Brainstem at the obex region with multiple microabscesses and perivascular cuffing (arrowhead). Microabscesses involve the hypoglossal nucleus (XII), its intracerebral root (arrows), and the reticular formation (RtF). Hematoxylin & Eosin stain (H&E), bar  = 740 μm.

Figure 4

Rhombencephalitis in a sheep: Microabscesses with central bacterial colonies aligned along an axonal tract within the reticular formation (medulla oblongata). H&E, bar  = 100 μm.

Figure 5

Rhombencephalitis in a sheep: necrotic neuron (asterisk) with intraneuronal Listeria monocytogenes (arrow) in a microabscess of the medulla oblongata. H&E, bar  = 13 μm.

Figure 6

Rhombencephalitis in a sheep: intraaxonal Listeria monocytogenes (arrows) within a microabscess of the medulla oblongata. H&E, bar  = 13 μm.