Listeriosis is commonly known as 'circling disease', as circling in one direction is caused by the effect it has on the sheep's brain.

Other symptoms include fever, lack of appetite, red tissues around the eyes, usually with blindness, and depression.

Due to a partial paralysis of the face, affected animals may also have a droopy ear, drooping eyelid, and saliva running from limp lips on one side of the face.

Listeria bacteria are commonly found in the paddock environment and in the intestinal tract of healthy animals.

Listeriosis can also be caused by feeding sheep with mouldy or spoiled hay or silage.

Roughly one quarter of late term abortions in sheep are caused by listeriosis, with campylobacter and toxoplasmosis being the other common causes of abortion in sheep.

Unfortunately, listeriosis is not treatable as clinical signs are usually not identified until the end stage of the disease.

If faced with an outbreak of listeriosis, it's critical to find and remove the source, and in the event of an abortion outbreak, move the other pregnant ewes to another paddock.

Listeriosis is potentially a zoonotic disease; therefore, it may be transmitted to humans.

Pregnant women and people who have weakened immune systems are also at risk.

Good hygiene, such as wearing gloves and washing hands, should always be implemented, particularly when handling aborted lambs.

It's important to remember, adult sheep showing neurological signs, staggering gait, constant trembling or persistent itchiness, are eligible to be autopsied for the national TSE Surveillance program with a producer incentive of $100 for each sick sheep sampled.

For further advice, please contact your local veterinarian or Agriculture Victoria veterinary or animal health officer, or in NSW your Local Land Services.