Listeria can also cause abortion, diarrhea and speticemia. It is commonly referred to as Circling disease and silage is often the source of the listeria, but it can also be found in hay, or even on sheep grazing pastures. The most common clinical signs are a sheep that walks in circles and has one half of the face paralyzed. The affected ear and lips on one side of the face will hang, often the sheep is drooling and the eyelid on the affected side will droop and the eye will also water causing the cheek to be wet. Finally, after only one or two days the sheep will be found down and be paddling and unable to rise on its feet.
Treatment is dismal at best.
Very early treatment with high doses of penicillin will save some animals. Listeria organisms are commonly found in the soil which has been contaminated with manure of apparently normal carrier animals. When making silage it is very difficult to complete the job without some soil contamination. If the silage is not properly packed tight to exclude oxygen, or the pH of the silage is not low enough the Listeria will multiply in these small pockets. Sheep that are cutting teeth such as newborn lambs, yearlings and mature ewes will have the greatest incidence via the bacteria getting in the tooth socket and following the facial nerve to the brain.