Rabies
There have been very few documented cases of rabies in ferrets. Althought they are certainly susceptible to rabies if bitten by a rabid animal, ferrets are usually kept in an environment where exposure to rabies is unlikely. However, there is always the risk of the ferret escaping and coming into contact with a rabid animal.
Until 1990 there was no approved vaccine against rabies, now there is and these vaccines are specifically for use in ferrets. It is recomended that healthy ferrets three months or older receive an annual vaccination and your veterinarian should be able to recommend a rabies vaccination schedule for your pet.