Listeriosis is a sporadic bacterial infection of the brain due to Listeria monocytogenes. The infection results in encephalitis and occasionally causes abortion or systemic infection.
Listeriosis usually occurs in cold climates or conditions, especially if there is a history of feeding spoiled silage. It is therefore unlikely to occur in export animals. If it does it will be in assembly points in winter.
Animals with encephalitis become dull, uncoordinated, develop a head tilt, walk in circles, become recumbent and usually die within one to two days of onset. Goats may survive for several days. There may be severe inflammation of one or both eyes. At necropsy, membranes at the base of the brain may be cloudy. If this history and signs are present and there is no middle ear abscess, one can be reasonably confident of listeriosis. Confirmation depends on histopathology and culture.
Laboratory confirmation requires specimens of cerebrospinal fluid and sections of brain, liver, spleen and kidney, chilled for bacteriology; and the brain in buffered formalin for histology.
Treatment with antibiotics (procaine penicillin, oxytetracycline, or erythromycin) may be attempted but is rarely effective unless initiated very early. The brain damage will not repair.
Avoid feeding spoiled silage in winter if possible.