The domestic ferret is known to be affected by several distinct ferret health problems. Among the most common are cancers affecting the adrenal glands, pancreas, and lymphatic system. Viral diseases include canine distemper and influenza. Certain health problems have also been linked to ferrets being neutered before sexual maturity was reached. Certain colors of ferret may also carry a genetic defect known as Waardenburg syndrome. Similar to domestic cats, ferrets may also be affected by hairballs, or dental problems.
Adrenal disease, a growth of the adrenal glands that can be either hyperplasia or cancer, is most often diagnosed by signs like unusual hair loss, increased aggression, constant grooming of owner or other ferrets as well as themselves, difficulty urinating (caused by an enlarged prostate) or defecating, or agitation when urinating, and (in the case of females) an enlarged vulva. Signs of an enlarged prostate should be considered an emergency; even if the growth is benign, it can still cause a hormonal imbalance which can have devastating effects on the ferret's health.
Treatment options include surgery or cryosurgery to excise the affected glands, melatonin or deslorelin implants, which treat the symptoms but not the disease itself, and/or hormone therapy. The causes of adrenal disease are as yet uncertain, but speculated triggers include unnatural light cycles, diets based around processed ferret foods, and prepubescent neutering. It has also been suggested that there may be a hereditary component to adrenal disease.
Adrenal disease is usually detected during the spring or fall, as it affects the hormones that make the fur grow. When affected ferrets shed their winter coat, the fur does not grow back. The hair loss pattern is usually very specific for adrenal disease. It begins at the base of the tail and then continues up the back. Ferrets treated for adrenal disease may temporarily have severe hair loss as their bodies recover.
Insulinoma, a type of cancer of the islet cells of the pancreas, is the most common form of cancer in ferrets. It is most common in ferrets between the ages of 4 and 5 years but may also occur in younger ferrets. The growth of cancerous nodules on the lobes of the pancreas sometimes, but not always, leads to an increase in the production of insulin, which regulates the rate at which the ferret's body metabolizes blood glucose. Too much insulin causes blood sugar to drop, resulting in lethargy, seizures, and ultimately death. Symptoms of an insulinoma attack include episodes of lethargy, drooling, pawing or foaming at the mouth, high pitched screams, staring "blankly" into space, and seizures.
The exact cause of insulinoma is unknown. It is speculated that the diets of domestic ferrets are too far removed from the natural diets of their polecat ancestors, and include too much sugar or simple carbohydrates.
Treatment for insulinoma may include surgical excision of the cancerous lobes, pharmaceutical treatment with steroids that suppress the production of insulin, supplemental changes in diet (most often poultry-based baby food), or a combination thereof. Unfortunately, the growth of the tumors cannot always be completely stopped, and the ferret will sometimes have a recurrence of symptoms. In an insulinoma attack, a temporary remedy to stabilize the ferret is any kind of a sugary syrup, such as corn syrup or honey.
Lymphoma/lymphosarcoma is the most common malignancy in ferrets. Ferret lymphosarcoma occurs in two forms -- "juvenile lymphosarcoma", a fast-growing type that affects ferrets younger than two years, and "adult lymphosarcoma", a slower-growing form that affects ferrets four to seven years old.
In juvenile ferret lymphosarcoma, large, immature lymphocytes (lymphoblasts) rapidly invade the thymus or the organs of the abdominal cavity, particularly the liver and spleen. In adult ferret lymphosarcoma, the lymph nodes in the limbs and abdominal cavity become swollen early on due to invasion by small, mature lymphocytes. Invasion of organs, such as the liver, kidney, lungs, and spleen, occurs later on, and the disease may be far advanced before symptoms are noticeable.
As in humans, ferret lymphosarcoma can be treated surgically, with radiation therapy, chemotherapy or a combination thereof. The long-term prognosis is rarely bright, however, and this treatment is intended to improve quality of life with the disease.
Viral diseases | Epizootic catarrhal enteritis
Epizootic catarrhal enteritis (ECE) is a viral disease that first appeared in the northeastern US in 1994, is an inflammation of the mucous membranes in the intestine. The condition manifests itself as severe diarrhea (often of a bright green color), loss of appetite, and severe weight loss. The virus can be passed via fluids and indirectly between humans. Although it was often fatal when first discovered, ECE is less of a threat today.
Viral diseases | Ferret systemic coronavirus (FSC)
The coronavirus which causes ECE has a counterpart strain that has more systemic effects with a higher mortality rate. This systemic syndrome has been compared to Feline infectious peritonitis in cats.
Viral diseases | Aleutian disease virus
Aleutian disease virus (ADV) is a parvovirus discovered among mink in the Aleutian Islands in the early 20th century. In ferrets, the virus affects the immune system (causing it to produce non-neutralizing antibodies) and many internal organs, particularly the kidneys. There is no cure or vaccine for the disease, and ferrets may carry the virus for months or years without any signs.
Viral diseases | Canine distemper
Canine distemper (CD) is an extremely contagious virus that is considered always fatal. Being strict indoor pets does not necessarily protect ferrets, as owners may bring the virus home on their clothes or their shoes. The distemper virus is very short-lived in hot, dry weather, but may persist on hands or surfaces for much longer in cool, damp weather. The only protection against the virus is vaccination, but that is not without controversy as there have been reports, particularly from the USA, of ferrets going into anaphylactic shock after being vaccinated against CD. There is some anecdotal evidence that occurrence of a vaccine reaction is related to a low blood sugar level, and that feeding the ferret a sweet paste-type nutritional supplement shortly before the vaccination to raise the blood glucose has reduced the incidence of reactions.
A ferret with partial immunity to distemper can be exposed to canine distemper and go through an incubation period of up to six weeks before showing signs of infection, as compared to a few days in an unvaccinated animal. Signs can include runny nose, discharge from the eyes, fever, up to , and severe malaise, followed by development of changes in the skin including discoloration and thickening of the nose (a pink nose will develop an orange coloration), measles-like sores on the chin and belly, and thick crusting of the pads of the feet (hyperkeratosis). The discharge is highly contagious to other unvaccinated ferrets and canines. If the ferret survives the initial acute phase of the disease, they will die within a few weeks from a progressive and incurable neurological infection, progressing to severe epileptic seizures and death.
Viral diseases | Influenza
Influenza, essentially the same disease and same agent that occur in humans, is caused by an othomyxovirus that can be passed from ferrets to humans and from humans to ferrets. Ferrets have served as experimental animal models in the study of influenza virus. Smith, Andrews, Laidlaw (1933) inoculated ferrets intra-nasally with human naso-pharyngeal washes, which produced a form of influenza that spread to other cage mates. The human influenza virus (Influenza type A) was transmitted from an infected ferret to a junior investigator, from whom it was subsequently re-isolated. The virus usually affects the nasal epithelium but can cause pneumonia. Signs include anorexia, fever, sneezing, nasal and ocular discharges and usually spontaneous recovery in 4 days or less. Antibiotic use can prevent complicating secondary bacterial infections.
A common ailment which can be fatal in ferrets is foot rot, a form of fungal infection which attacks the feet and sometimes spreads to the tail. It initially appears as a small, yellow, scab-like infection. If untreated, it can cover the feet, and later the entire body. Foot rot is normally caused by poor cage hygiene, i.e., excessive feces accumulation.
Like many other carnivores, ferrets have scent glands near their anuses, the secretions from which are used in scent marking. Ferrets recognize other individuals from these anal gland secretions, as well as the sex of unfamiliar individuals. Ferrets may also use urine marking for sex and individual recognitions.
Males, if not neutered, are extremely musky. It is considered preferable to delay neutering until sexual maturity has been reached, at approximately six to eight months old, after the full descent of the testicles. Neutering the male will reduce the smell to almost nothing. The same applies for females, but spaying them is also important for their own health. Unless they are going to be used for breeding purposes, female ferrets will go into extended heat and a female that will not mate, without medical intervention, can die of aplastic anemia. It is possible to use a vasectomised male to take a female out of heat.
Due to speculation on the possible effects of the photoperiod effect on the ferret's adrenal gland, some owners prefer to house their pets outdoors in sheds, and not indoors.
Male ferrets may be chemically castrated using a deslorelin implant, which lasts for at least a year. Males with a deslorelin implant are less aggressive to other males compared to males castrated surgically.
Congenital sensorineural deafness
A high proportion of ferrets with white markings which form coat patterns known as a blaze, badger, or panda coat, such as a stripe extending from their face down the back of their head to their shoulder blades, or a fully white head, have a congenital deafness (partial or total) which is similar to Waardenburg syndrome in humans. Ferrets without white markings, but with premature graying of the coat, are also more likely to have some deafness than ferrets with solid coat colors which do not show this trait. Most albino ferrets are not deaf; if deafness does occur in an albino ferret, this may be due to an underlying white coat pattern which is obscured by the albinism.
In humans, Waardenburg syndrome leads to higher instances of reproductive disorders and a reduced life expectancy; these phenomena have been reported by some ferret owners, but as of 2016, there is no scientific evidence correlating these findings with congenital sensorineural deafness. Except for albinism, the genetics of coat color in ferrets is not known, and the genes that cause deafness have not been identified.
Owners may not easily identify deafness in their ferret; affected ferrets may have behavioral or training problems, or may have greater than usual social conflict with other ferrets. A ferret's hearing can be tested by a brainstem auditory evoked response test, with the ferret under general anesthesia.
Hairballs can occur in ferrets, but are not readily expelled by vomiting like the way cats deal with them. One or more hairballs in a ferret may lead to loss of appetite and subsequent weight loss. A hairball may enter the intestine and cause a life-threatening obstruction. Ferrets typically replace their coats twice a year, and at that time require brushing to remove loose hairs before they can be ingested, and possibly administration of a hairball remedy as a preventive. Artificial lighting or administration of certain medications may alter the normal spring and fall seasonal coat changes in the ferret.
Tartar and dental abrasion
Dental calculus (tartar) is a hard substance formed on the teeth from the mineralization of plaque. Dental tartar primarily comes from wet food which get stuck to the teeth for extended periods of time. Tartar can be avoided by ferrets eating raw meat, bones and preferably whole prey. The biomechanics of consuming meat and bones will keep the teeth clean. Left to itself, tartar may lead to gingivitis which in turn can lead to a dental abscess, bone loss, infections which may spread bacteria through the bloodstream to internal organs and lead to death if not treated. Tartar can be removed either mechanical or by ultrasound at a veterinarian (this usually involves anesthesia), a small toothbrush can also be used as a preventive measure if one is unable to feed the animal with raw meat. Tartar can be prevented by feeding raw food or giving specially made gelatin treats for ferrets.
Dental abrasion or tooth wear is common in ferrets, and is caused by mechanical wear of the teeth. Eating manufactured dry food (kibble) will erode (due to the hard and extremely dry kibble) the carnassial teeth of the ferret, the wear from the eating kibble can become significant with old age (after three to five years). If teeth are overly ground down, a ferret cannot use them as scissors to eat raw meat. Tooth erosion eventually affects a ferret's ability to eat solid food. Dental abrasion can also be caused by excessive chewing on fabrics or toys, and cage biting. If the ferret engages in these activities a lot, it might be a sign of boredom, and more stimulating activities (such as play) should rectify the situation.