Listeria moncytogenes


            Listeria moncytogenes is a disease causing, gram positive bacterium that causes a bacterial infection of the brain and central nervous system, called listeriosis.  Listeriosis in sheep is also called circling disease.  Pathogenesis affects not only sheep, but also humans and other animals as well.




          Listeria lives in many places in the environment, on plants and vegetation, soil, water, or in animal and human feces under the proper environmental conditions and pH.  Listeriosis is mainly caused by feeding improperly preserved or spoiled silage, or spoiled hay. 



Clinical Signs 

            The animal can show signs of confusion, walking in circles "circling", uncoordinated movements, inability to eat or drink, fever, and depression. You may also see drooping of the ears, protrusion of the tongue, holding of the head to one side of the body, and possible excessive salivation.   When animals begin to show these clinical signs and symptoms death can occur within a couple of days.  In sheep, listeriosis often times causes abortion at 12 weeks or later, encephalitis, and retained placentas.



Treatment and Prevention

          If any of the above symptoms are noticed early treatment is crucial.  It is important to call your veterinarian immediately, so that they can try to save the animal by treating with antibiotics.  If abortions are occurring in your flock, your veterinarian may recommend treatment with high levels of tetracyclines.  Prevention is also a very important aspect of this disease.  It is very important to prevent spoilage of any type of forage or silage.  Make sure that your silage is below a pH of 5.0 because the bacteria do not like an acidic environment.  Moldy corn silage should never be fed to sheep as well.  If an outbreak were to occur discontinue feeding silage, isolate affected sheep, and burn or remove the sheep carcasses dying from listeriosis. 

Prevent this disease by feeding good quality silage that has been cut and stored properly!



Health Concern

Listeriosis is a zoonotic disease so humans can contract this bacterium in many ways.  Immuno suppressed patients, pregnant women, and young children should be especially careful around sheep and lambs, but anyone can get listeriosis.





Reference to cite for sheep clip-art

 Other web sites for Listeriosis reference:




 Return Home