Listeriosis in Small Ruminants: A Review

Listeriosis is a bacterial disease caused by different Listeria species; among these Listeria monocytogenes being the most pathogenic species to small ruminants. The other two species, the so called Listeria ivanovii and Listeria innocua are less frequently implicated in disease of animals. Listeriosis is most prevalent during spring and winter seasons. Soil contamination and ingestion of contaminated silage are the primary modes of transmission. Poor quality silage, a pH greater than 5.5 is commonly implicated and accounts for listeriosis often being referred to as “silage disease”. Both host management and the pathogen itself has different contributions for the occurrence of the disease. The clinical manifestations of listeriosis in small ruminants are usually severe and include abortion, meningoencephalitis and neonatal septicemia. The great effect of listeriosis in small ruminants and cattle is due to the consequence of severe damage on brain. Those diseases affecting the nervous system such as rabies, gid (coenurosis or sturdy), scrapie and pregnancy toxemia should be differentiated from listeriosis. Silage feeding should be discontinued if an outbreak of listeriosis is confirmed. In the case of abortion, isolation of aborting does and ewes from their offspring reduces further infection of the dam. The recommended drugs used for treatment of listeriosis include Oxytetracycline, penicillin-G and Dexamethasone.