Pet owners are being encouraged to vaccinate and neuter their cats to help save the Scottish wildcat.
The virus, known to cause the cat version of Aids, was discovered after wildlife experts from the University of Edinburgh Royal (Dick) School of Veterinary Studies and National Museums Scotland carried out postmortem examinations on 23 feral and hybrid cats from around Scotland.
One of the cases was detected in an area that has been identified as a priority zone for wildcat conservation.
A long-haired tabby found dead in a barn in Morvern in the Western Highlands was one of the animals to test positive for the virus.
Morvern is one of six places identified by Scottish Wildcat Action last year as a priority area for wildcat conservation. Although FIV is common in feral cats, these are the first known cases of the virus affecting hybrid cats in a wildcat priority area.
There is no vaccine for FIV. The infection is transmitted mainly when adult male cats fight and experts say neutering is key to tackling the disease.
Professor Anna Meredith, of the Royal (Dick) School of Veterinary Studies, said: “This find confirms pet owners must be encouraged to vaccinate and neuter their cats, particularly if they live in a wildcat priority area.
“Cats are susceptible to other illnesses, such as cat ’flu and feline leukaemia virus, and these can be common in feral cats too. This means the importance of vaccinating and neutering cats is at an all-time high as we continue to work together to save our Scottish wildcat.”