Wildcats are also threatened by interbreeding with feral cats
A vet has urged cat owners to neuter and vaccinate their pets against diseases in an effort to help protect Scotland's rare wildcat population.
Jane Harley, who is based in the Cairngorms National Park, said the species was at risk from picking up highly contagious conditions.
Her warning came ahead of a major conference on wildcats in Aviemore.
The park authority said it was the first step of a conservation project for the mammals.
It has been estimated that there are 400 wildcats, but their survival has been threatened by interbreeding with domesticated cats and diseases they could be carrying.
Ms Harley said: "I think that most people acknowledge that interbreeding is the biggest risk to wildcats, but many won't have considered the serious risk to wildcats from diseases, which can be prevalent in feral cats.
"The feline leukaemia virus, for example, is a highly contagious cat disease which can be vaccinated against.
"For those domestic cat owners who would like to play their part in protecting the wildcat, my advice is to have their pet cats neutered and ensure that all vaccinations are up-to-date."
Scottish Natural Heritage is supporting a year-long survey of the population.
Dr David Hetherington, ecology advisor at the park, said the area provided an important habitat for the animal.
He added: "However, the wildcat is important for the Cairngorms too and people here identify with the species' wild and untameable spirit, which is why it's used as an icon by local clans, villages, groups and businesses."