SA Health says the bug was discovered during routine testing by the manufacturer, O'Brien's Meats.

It says there have been no reported cases of the disease linked to consumption of the meat so far.

"O'Brien's is working to remove any potentially affected product from supply today," SA Health spokeswoman Karen Ferres said.

The affected ham has been available for sale at various Foodland, IGA and other independent butchers and continental delicatessens.

It is sometimes sold loose, so may have no distinct packaging.

"While many people exposed to Listeria often have only mild illness it can be more serious in at-risk groups, so all South Australians at-risk should avoid eating the product," Ms Ferres said.

"As a precaution, we recommend anyone who has purchased any of the listed O'Brien's leg ham to not eat it and either return it to the place of purchase, or discard it."

The ham has been available for sale since December 2020 with use-by dates of March 24, April 1 and April 6.

Listeriosis starts with flu-like symptoms such as fever, chills, muscle aches, nausea, and sometimes diarrhoea.

People can start experiencing symptoms within a few days, but they can take up to six weeks to appear after eating contaminated food.

Australian Associated Press