Ferrets with chronic kidney failure drink and urinate much more than normal. When the disease is advanced, they lose weight. Relatively simple blood tests indicate the extent of kidney damage. These animals need a good quality diet, constant access to fresh drinking water and careful attention to dental health. Drugs, such as sulfas that compromise kidney function, should be used with caution. Any disease or situation that causes dehydration can be life threatening.
Older ferrets may become blind due to retinal atrophy or cataracts. Retinal atrophy is probably not inherited in ferrets: it may be caused by nutritional deficiencies. The eyes appear normal to the casual observer. Cataracts, on the other hand, give the eyes a characteristic pearly appearance and are usually hereditary. There is no effective treatment other than surgery, which is rarely attempted. Blind ferrets enjoy a normal life if you don't rearrange the furniture in their play area.
Cardimyopathy causes the heart muscle to thicken until it is so stiff that it cannot contract properly and is unable to pump enough blood to the body. You will notice your ferret tires easily after even gentle exercise and breathes rapidly all the time. Cardiomyopathy can be diagnosed early with an X-ray and echocardiography. The cause has not been determined, but nutritional deficiencies may contribute. Medication will extend the life of the ferret, but will not stop the course of the disease, which is usually fatal less than a year after diagnosis.
Other common diseases in older ferrets include: lymphosarcoma, a cancer of the lymph glands; adrenal gland tumors, a common sign of which is hair loss; and insulinoma disease, pancreatic tumors that produce excess insulin.