Karen L. Rosenthal, DVM, MS, Diplomate ABVP-Avian
It is estimated that over 8 million pet ferrets live in the United States. They are said to be the third most popular pet in the United States. Ferrets are a commonly used research animal for such disciplines as infectious and neoplastic diseases. They are also used for hunting, mainly in Great Britain. They have been domesticated for over 2000 years.
Ferrets, Mustela putorius furo, are in the order Carnivora and the family Mustelidae. Their anatomy is very similar to other carnivores. Males are larger than females. Ferrets have poorly developed sweat glands and do not tolerate hot weather when no protection is offered. Ferrets have a very long trachea with 60-70 tracheal rings. The gastrointestinal tract lacks a cecum, appendix, teniae coli, and an ileocolonic sphincter. Male ferrets have a prostate gland but in neutered ferrets, it is usually atrophied. Ferrets in the United States rarely live more than 7 years but potentially they can live up to 12 years of age.
Ferrets are born in the spring and summer. They become sexually mature in their first spring. Most ferrets in the United States are neutered before six weeks of age. Adult neutered females weigh between 600 to 900 grams and adult neutered males weigh between 800 to 1100 grams. Females are jills, males are hobs, and young are kits.
Supervise pet ferrets when they are free in the house. When owners are not home, keep ferrets in a cage or secure enclosure Also, provide a "den" area. Ferrets will use a litter box like cats but are not always "perfect" in this regard. Protect ferrets from heat and predators when kept outdoors.
Ferrets are carnivores and require a diet high in protein and fat and low in fiber. The exact nutritional requirements of pet ferrets are not yet known and feeding recommendations are extrapolated from mink. Feed ferrets either a high quality kitten food or a high quality ferret food. Dry food is highly recommended. It is assumed that canned food increases the likelihood of dental tarter.
In their relatively short life, ferrets develop numerous diseases and annual visits to the veterinarian are essential. Older ferrets should be seen twice a year. Vaccinate ferrets for canine distemper virus and rabies virus. Historically, the canine distemper virus vaccine that was widely used was Fromm-D. It was an egg-propagated modified live canine distemper virus. It was never approved for use in ferrets but experience proved it to be both safe and efficacious. Fromm-D is no longer manufactured but has been replaced by a vaccine called Galaxy-D by Schering-Plough, that is made in a primate cell line. The efficacy and safety of this vaccine in ferrets appears to be good, again from experience. There is a modified live vaccine produced by United Vaccines (Madison, WI) called Fervac that is the only USDA approved vaccine for use in ferrets for protection against canine distemper virus. There are anecdotal reports of anaphylactic vaccine reactions associated with the use of this vaccine. If this occurs, treat the ferret with oxygen, fluids, epinephrine, steroids, and antihistamines. Killed vaccines are not recommended due to a lack of long lasting immunity. Canine or ferret cell propagated vaccines are not recommended as they may induce distemper. Vaccinate ferrets at 6 to 8 weeks of age and then every 3 to 4 weeks until 16 weeks of age and then yearly. A rabies virus vaccine, Imrab, is approved for ferrets as a subcutaneous injection. Give this vaccine at 3 months of age and then annually. Check local government regulations first. Ferrets are not susceptible to feline distemper or feline leukemia virus. There is also no evidence to vaccinate ferrets with the Bordetella vaccine.
Client education regarding pet ferrets is very important. Include in a handout for the owner, information about vaccines, common diseases, and how to hold and groom a ferret. Show owners how to scruff their ferret. If a female ferret is intact, encourage neutering. Ferrets are induced ovulators and prolonged estrus results in anemia and thrombocytopenia which can be fatal.
There are very few instruments and supplies that veterinarians need to obtain that they do not already have for their dog and cat patients if they are going to start seeing ferrets. Obtain a gram scale for accurate weight assessment. Also, small needles, catheters, and blood collection tubes are essential to obtain quality results.
Pet ferrets are easy to restrain. During most of the physical examination, use minimal restraint. If more restraint is needed, scruff the skin on the neck of a ferret. Always warn the clients before you do this. If a ferret is very difficult to restrain, you can use isoflurane anesthesia. Rarely are injectable anesthetics used or needed in ferrets for tranquilization. They may be used for anesthesia induction. Isoflurane is safe and well tolerated in ferrets. One technique that is often used is the "Nutrical" technique. The ferret is offered Nutrical from a syringe or finger and while it is pre-occupied eating, an examination can take place.
Always use the same approach to the physical examination so important aspects are not overlooked. Examine the oral cavity for ulcerations and broken teeth and dental calculus. Check the ears for ear mites. Palpate peripheral lymph nodes well as lymphosarcoma is a common disease. Auscultate the heart and lungs using a small stethoscope. Listen to the entire thoracic area as murmurs are common. Palpate the abdomen as organomegaly and gastrointestinal diseases are frequently encountered. In females, note the size and discharge, if any, from the vulva. Evaluate the integument for hair loss or thinning and skin masses.
Venipuncture and blood collection may seem daunting at first but improve with practice. It is important to have the correct tools. Use the jugular vein when a large volume of blood is required. For small blood volumes, use the saphenous or cephalic vein. Use small gauge needles for cephalic and saphenous venipuncture. For jugular venipuncture, use a 25 gauge needle on either a 3 or 1cc syringe. For the experienced ferret practitioner, the cranial vena cava can be a preferred site in which to perform venipuncture. This is not recommended if you are inexperienced with pet ferrets. It takes practice to do this procedure with little chance of harm to the ferret. It is necessary to have appropriately sized blood tubes available such as microtainers. Injections are much like that in other mammals. Give subcutaneous injections along the dorsum. Administer intramuscular injections in the semitendenosus and semimembranosus or the lumbar muscles. Give most intravenous injections in the saphenous or cephalic veins
Give parenteral fluids in ferrets either intravenously, subcutaneously, or intraosseously. Usually, administer a physiologically balanced solution. Very commonly, ferrets need the addition of dextrose to their fluids. Give fluids at a rate of 50-75 ml/kg/day. Increase the fluid rate to compensate for losses and dehydration. Commonly, catheters are placed in the cephalic, jugular, or saphenous vein. Use small gauge catheters (24-26 gauge) and immobilize the ferret with anesthesia. Pre-puncture the skin with a 22 gauge needle to allow easier catheter placement. Use jugular vein catheters when it is important to have central venous access. Typically, though, jugular catheters are not placed in ferrets because ferrets seem to object to the tape around their neck and become depressed. Reserve intraosseous catheterization for severely ill ferrets when venous catheterization is not possible. You may need to use a needle as small as 25 gauge in order to not damage the bone. Sites of intraosseous catheterization include the proximal tibia or greater trochanter of the femur. Subcutaneous fluids are given along the dorsum. It is difficult to place a substantial amount of fluids in this space as it is small and appears painful to the ferret.
Pills are very difficult to administer to ferrets; liquid medications are easier. You cannot easily put a pill in a ferret's mouth nor hide it in food. Therefore, most oral medications given to ferrets are either in liquid form or compounded into liquid form. It is possible to try to hide pills or liquids in Nutrical or some other thick paste. Liquids can be given by syringe to the ferret. This includes medication and feeding formulas. For anorexic ferrets a variety of feeding formulas can be used including meat baby food, human liquid calorie supplements, a home-made gruel, or even cat/dog food blenderized to fit through a syringe.
Neoplasia is seen frequently in pet ferrets. Common ferret neoplasms include lymphosarcoma, pancreatic beta cell tumors, adrenal gland tumors, and cutaneous mast cell tumors. Common gastrointestinal diseases include obstructions and epizootic catarrhal enteritis. Heart disease is also a common disorder of pet ferrets in the United States.