Bluetongue serotype 3 (BTV-3) has been identified in three sheep moved to Gwynedd from the east of England.
This is the first time Bluetongue-3 has been found in Wales and follows BTV-3 cases being detected in the east of England over the last month.
Farmers are being urged to be vigilant for the disease and practice safe sourcing of livestock.
Bluetongue is caused by a virus that is primarily transmitted by certain species of biting midges. It affects ruminants (such as cattle, goats, sheep and deer) and camelids (such as alpacas and llamas).
Bluetongue does not affect people or food safety.
Further investigations are taking place on the farm affected to determine whether additional controls are needed.
The Deputy Chief Veterinary Officer Gavin Watkins said:
“The cases identified in Gwynedd are from animals bought into Wales.
“We will apply measures to stop disease spreading from these three sheep, and our aim remains to keep Wales free of bluetongue.
“It is important to talk to your vet, and practice safe-sourcing of livestock to protect our herds and flocks and keep any further disease out of Wales.
“I would urge all farmers and others who keep ruminants and camelids to be vigilant for the signs of Bluetongue and to report any suspect cases to APHA immediately.
“We have been raising awareness of the disease with vets and industry and appreciate their help in communicating the risks to animal keepers in Wales.”