Ferrets are carnivores and naturally hunt rabbits and other rodents. They can be fed good quality cat food when kept as pets, as well as commercially available ferret diets.
Common diseases of ferrets include Canine Distemper Virus (which they can be vaccinated against), human Influenza (so they can spread this to ourselves), and Aleutian Disease (caused by a Parvovirus). They can also be affected by mites, worms and fleas and can develop hormonal problems too.
It is advisable to neuter ferrets, especially females as they can be prone to high oestrogen levels which can cause bone marrow suppression and eventually lead to death!