A single outbreak of highly pathogenic avian influenza of the H5N8 type was isolated on a farm near Villiers.
According to the South African Poultry Association, the strain of the virus has its origins in Europe and has been infecting European poultry for more than a year.
In May, it was isolated in Zimbabwe. The disease is spread primarily by water fowl that carry the disease in the highly pathogenic form, the association said.
The affected farm was near the Vaal River, and it was likely that the disease is present in other parts of South Africa in wild water birds, especially ducks.
The public is requested to report any sightings of high levels of large wild bird or backyard chicken mortalities, the association urged.
The farm has been isolated and culling of the birds on the affected site has commenced. Some 28 000 birds are to be culled. The Mpumalanga Veterinary Authority is on the farm, assisting with quarantine implementation, culling and disinfection of the farm.
This strain has been found not to be dangerous to humans and the birds affected are a very small percentage of the total South African chicken flock. At this stage there is a very limited impact on chicken supply.
As this is the first time the disease has been found in South African poultry, the association is monitoring the situation very closely.
According to Agri SA, avian influenza is a notifiable disease in terms of the Animal Disease Act, 35 of 1984.
The H5N8 strain of avian influenza, which is believed to be transmitted by wild migratory birds, has already wreaked havoc in the poultry industry in Zimbabwe, where hundreds of thousands of commercial birds have already had to be culled, Agri SA said.