Parasitism ---------- Most of the external parasites of domestic dogs and cats (fleas, mange mites, ear mites, etc.) can cause disease in ferrets. Less is known about the ferret's susceptibility to the more common internal parasites (roundworms, etc.) of dogs and cats. Protozoan (one-celled) parasites, also shared by dogs and cats (especially Giardia and Coccidia), can cause intestinal disease among ferrets. Periodic fecal (stool) examinations should be performed by your veterinarian to check for such parasites. Appropriate treatment can then be given, if warranted.