Listeria (L.) monocytogenes is widely distributed in the environment, but also has the ability to cause serious invasive disease in ruminants and humans. This review provides an overview of listeriosis in ruminants and discusses our insufficient understanding of reservoirs and possible cycling ofL. monocytogenes between animal and human hosts, food and the environment. It indicates gaps in our knowledge of the role of genetic subtypes in L. monocytogenes ecology and virulence as well as risk factors, in vivo diagnostics and pathogenesis of listeriosis in ruminants. Filling these gaps will contribute to improving the control of L. monocytogenes and enhancing disease prevention. As the prevalence of listeriosis in ruminants in Switzerland is likely to be underestimated, propositions concerning improvement options for surveillance of listeriosis in ruminants are provided. Summary Listeria (L.) monocytogenes is widely distributed in the environment, but also has the ability to cause serious invasive disease in ruminants and humans. This review provides an overview of listeriosis in ruminants and discusses our insufficient understanding of reservoirs and possible cycling of L. monocytogenes between animal and human hosts, food and the environment. It indicates gaps in our knowledge of the role of genetic subtypes in L. monocytogenes ecology and virulence as well as risk factors, in vivo diagnostics and pathogenesis of listeriosis in ruminants. Filling these gaps will contribute to improving the control of L. monocytogenes and enhancing disease prevention. As the prevalence of listeriosis in ruminants in Switzerland is likely to be underestimated, propositions concerning improvement options for surveillance of listeriosis in ruminants are provided.

Brain disease is an important cause of neurologic deficits in small ruminants, however few MRI features have been described. The aim of this retrospective, case series study was to describe MRI characteristics in a group of small ruminants with confirmed brain disease. A total of nine small ruminants (six sheep and three goats) met inclusion criteria. All had neurologic disorders localized to the brain and histopathologic confirmation. In animals with toxic-metabolic diseases, there were bilaterally symmetric MRI lesions affecting either the gray matter (one animal with polioencephalomalacia) or the white matter (two animals with enterotoxemia). In animals with suppurative inflammation, asymmetric focal brainstem lesions were present (two animals with listeric encephalitis), or lesions typical of an intra-axial (one animal) or dural abscess (one animal), respectively. No MRI lesions were detected in one animal with suspected viral cerebellitis and one animal with parasitic migration tracts. No neoplastic or vascular lesions were identified in this case series. Findings from the current study supported the use of MRI for diagnosing brain diseases in small ruminants.

Listeria rhombencephalitis is caused by infection with Listeria monocytogenes and is associated with a high mortality rate in humans and ruminants. Little is known about the metabolic changes associated with neurolisteriosis in particular and infectious central nervous system (CNS) diseases in general. The purpose of our study was to investigate the metabolic changes associated with listeria rhombencephalitis in small ruminants (goats and sheep) as a model for inflammatory CNS disease by 1H high‐resolution magic angle spinning nuclear magnetic resonance (1H HR‐MAS NMR) spectroscopy of brain biopsies obtained from the brainstem and thalamus. Statistical analysis revealed distinct differences in the metabolic profile of brainstem biopsies, the primary location of listeria rhombencephalitis with moderate or severe inflammatory changes. N‐Acetylaspartate (NAA), N‐acetylaspartylglutamate, choline, myo‐inositol and scyllo‐inositol were decreased, and glycine, phosphocholine, taurine and lactate were increased, in the diseased group (n = 13) in comparison with the control group (n = 12). In the thalamus, which showed no or only mild inflammatory changes in the majority of animals, no statistically significant metabolic changes were observed. However, trends for metabolic alterations were partly the same as those found in the brainstem, including NAA, choline and lactate. This may be an indicator of metabolic changes occurring in the early stages of the disease. Therefore, further research with a larger number of animals is needed to evaluate the presence of subtle metabolic changes associated with mild inflammatory changes in the thalamus. In conclusion, 1H HR‐MAS NMR investigation of listeria rhombencephalitis identified brain metabolite changes, offering new insights into the disease pathophysiology.

Background: Listeria rhombencephalitis, infection of the brainstem with Listeria monocytogenes, occurs mainly in humans and farmed ruminants and is associated with high fatality rates. Small ruminants (goats and sheep) are a large animal model due to neuropathological similarities. The purpose of this study was to define magnetic resonance imaging (MRI) features of listeria rhombencephalitis in naturally infected small ruminants and correlate them with histopathology. Secondly, the purpose of this study was to compare the results with MRI findings reported in humans.Methods: Twenty small ruminants (13 sheep and 7 goats) with listeria rhombencephalitis were prospectively enrolled and underwent in vivo MRI of the brain, including T2-weighted, fluid attenuation inversion recovery, and T1-weighted sequences pre- and post-contrast administration and postmortem histopathology. In MRI, lesions were characterized by location, extent, border definition, signal intensity, and contrast enhancement. In histopathology, the location, cell type, severity, and chronicity of inflammatory infiltrates and signs of vascular damage were recorded. In addition, histopathologic slides were matched to MRIs, and histopathologic and MRI features were compared.Results: Asymmetric T2-hyperintense lesions in the brainstem were observed in all animals and corresponded to the location and pattern of inflammatory infiltrates in histopathology. Contrast enhancement in the brainstem was observed in 10 animals and was associated with vessel wall damage and perivascular fibrin accumulation in 8 of 10 animals. MRI underestimated the extension into rostral brain parts and the involvement of trigeminal ganglia and meninges.Conclusion: Asymmetric T2-hyperintense lesions in the brainstem with or without contrast enhancement can be established as criteria for the diagnosis of listeria rhombencephalitis in small ruminants. Brainstem lesions were similar to human listeria rhombencephalitis in terms of signal intensity and location. Different from humans, contrast enhancement was a rare finding, and abscessation was not observed.

No abstract