The Chief Veterinary Officer for Wales has confirmed Avian Influenza H5N8 in a back yard flock of chickens and ducks on a premises near Pontyberem, Carmarthenshire.
Prior to confirmation it was decided to cull the birds on strong suspicion of disease.
A 3km Protection Zone and 10km Surveillance Zone have been put in place around the infected premises to limit the risk of the disease spreading and as part of the wider surveillance and disease control measures.
The UK Chief Veterinary Officer has declared a Prevention Zone to help protect poultry from a strain of Avian Flu in Europe.
The Government Chief Vet has declared a Prevention Zone introducing enhanced biosecurity requirements for poultry and captive birds, helping protect them from a strain of avian flu circulating in mainland Europe.
The zone covers England and will remain in place for 30 days until 6 January 2017. Declarations have also been made by the Scottish Government and Welsh Government. It does not include Northern Ireland.