James, Good questions!! 1)Lyme disease---I have never seen or heard of a case of Lyme disease in a ferret. Part of this is because most ferrets spend a limited time outdoors and exposure to ticks are limited as a result. We have seen a large number of cases of Lyme disease and Rocky Mountain Spotted Fever in the past couple of years in our practice. These are both spread through ticks and can be potentially fatal if not diagnosed and treated. 2)Heartworm Disease--This is a blood parasite which is spread through mosquitos. Dogs are very susceptible, and as a result are tested yearly and placed on a monthly preventitive. Ferrets are also susceptible and if they spend time outside you should consider monthly medication to prevent this fatal disease. Since ferrets are so small it only takes 1-2 heartworms to cause the signs of heart failure associated with heartworm disease. Dr Weiss Potomac Animal Hospital 301-299-1412 [log in to unmask] [Posted in FML issue 1159]