A case of BSE - also known as Mad Cow Disease - has been confirmed in a cow on a farm in Dumfries and Galloway.
Precautionary movement measures are in place on the animal's offspring and its "cohort", the Scottish Government said.
BSE (bovine spongiform encephalopathy) is a progressive brain disease and can't be treated.
People can become infected with the equally fatal human form (Creutzfeldt-Jakob disease) by eating the meat of a contaminated animal.
However, Food Standards Scotland said the animal hadn't entered the human food chain and there is no wider risk.
Investigators from the Animal Plant and Health Agency (APHA) are investigating the case, which was found due to regular BSE surveillance and control measures.
There was a major outbreak of BSE in the UK in the 1980s and 90s.
More than 184,000 British cows are estimated to have died from it between 1986 and 2015, and more than four million cattle were slaughtered.
Scotland's agriculture minister, Jim Fairlie, said authorities had "acted swiftly and decisively to protect the agriculture sector".
"The fact we identified this isolated case so quickly is clear proof that our surveillance system for detecting this type of disease is working effectively," he said.
"I want to thank the animal's owner for their diligence. Their swift action allowed us to identify and isolate the case immediately, minimising its impact on the wider industry."
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The outbreak at the end of the last century peaked in 1993 with about 1,000 cases per week and many countries banned British beef. The crisis is thought to have been caused by contaminated cattle feed.
Among BSE's symptoms are apprehension, nervousness, aggression, and kicking out while being milked, hence the colloquial term Mad Cow Disease.
(c) Sky News 2026: Mad Cow Disease case confirmed at Dumfries and Galloway farm
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