Listeriosis is caused by the bacteria Listeria monocytogenes. The bacteria is present everywhere in the environment and survives well in moist soil for about one year. In domestic animals the disease is most important in ruminants and most seen during winter months when they are being fed silage.
As winter conditions persist, cattle producers often find themselves scraping the last silage out of pits and silos. This reality may raise the risk of listeriosis infections.
Listeriosis is usually acquired from feeding of poor quality or poorly fermented silage . . . infection almost always results from ingestion of the bacteria.”
Source: The Cattle Site, February 14, 2022. Link. Listeria has an affinity for the central nervous system, more specifically the brainstem, with encephalitis being the most common presentation. Animals suffering from Listeriosis can demonstrate a range of symptoms. In cattle and sheep, the condition is mainly seen as a nervous disease or encephalitis showing symptoms such as depression, head tilt, paralysis of facial muscles causing an inability to eat, and possibly death.