Mad cow disease has been found on a United Kingdom farm for the first time since 2015, raising concern that some countries may move to limit imports of British beef.
Scottish beef was officially declared risk-free from BSE a year ago for the first time since 1996.
He said: "While it is important to stress that this is standard procedure until we have a clear understanding of the disease's origin, this is further proof that our surveillance system for detecting this type of disease is working".
Sheila Voas said: "Sad to have confirmed a case of BSE in Aberdeenshire this morning, but good surveillance system is proved to work well".
Farmers concerned about their cattle are being urged to seek advice from a vet immediately.
It can be passed on to humans in the food chain, causing a fatal condition called variant Creutzfeldt-Jakob disease (vCJD).
Ewing added: "Be assured that the Scottish government and its partners stand ready to respond to any further confirmed cases of the disease in Scotland".
BSE was first discovered in the United Kingdom back in 1986, when more than 180,000 were infected with the disase when it was at its height - peaking in 1993 with nearly 1,000 new cases per week, with 4.4 million slaughtered as part of the eradication programme.
Ian McWatt, director of operations at Food Standards Scotland, noted that there are "strict controls in place to protect consumers from the risk of BSE" and that officials remain vigilant.
The real impact of this case will be that Scotland is nearly certain to lose its status as an area with negligible BSE risk, which could affect whether importers buy British beef.
"Liaising closely with other UK Chief Veterinary Officers and Government and agencies all working together". Though it is not directly transmitted between animals, "its cohorts, including offspring" will now be destroyed in line with European Union requirements, the Scottish government said.
Strict controls were introduced to protect consumers after the link was established in 1996.