by Susan Brown, DVM
*For the purposes of discussion we will refer to the virus that causes canine distemper as canine distemper virus (CDV) and the disease caused by the virus as canine distemper (CD).
Canine distemper (CD) is a contagious disease caused by a large RNA paramyxovirus. Families of animals that can become infected with CDV include Canidae (such as dogs, foxes, wolves and coyotes), Mustelidae (such as ferret, mink, weasel, skunk, badger and otter), Procyonidae (such as raccoons) and possibly some exotic cats, but not domestic cats. CDV can be transmitted to ferrets directly from infected animals of any of the species mentioned or through contact with infected material such as shoes or clothing. In other words, you can bring CDV home if you are in contact with infected material in places such as the woods a pet store or a breeding facility. Using a canine distemper vaccine that is not approved for use in ferrets can also transmit CDV. Canine distemper vaccines all contain live viruses that are altered to stimulate an immune response, but not cause disease, however there are some types that are safe to use in ferrets and some that carry risk of spreading the disease. The incubation period for CD is 7 to 21 days.
Signs of CD in the ferret may vary, but classically it starts with a mild conjunctivitis and green to yellow discharge from one or both eyes. A high fever of 104oF or more develops in a few days. The ferret may loose its appetite and become lethargic. The most prominent development is a reddening and thickening of the skin of the chin, lips and anal area. This progresses into thick crusting. In addition, the footpads become extremely thickened and hard. These lesions are classic signs of CD in the ferret and do not occur with any other disease of the ferret of which I am aware. Death is usually caused either by severe overwhelming secondary bacterial infections, because the CDV is causing serious inhibition of the immune response, or by central nervous system (brain) damage.
Other signs that can be seen include diarrhea and severe depression or bizarre behavior and seizures. The younger the ferret when it contracts the disease, the more quickly it will develop central nervous system signs. Some baby ferrets do not develop any skin lesions at all, but develop a sudden loss of appetite, high fever, seizures and death all within a few days.
There is no treatment for CD. If the ferret is severely affected it is best and most humane to consider euthanasia. Even severely affected ferrets can last for days in pain and discomfort. Occasionally a mild or moderately affected ferret can survive the disease. These ferrets have to be treated with antibiotics, supportive fluids, force feedings and lots of nursing care. It may be beneficial to give them serum from ferrets that have been properly vaccinated against CDV and may have antibodies to the disease. Some recovered ferrets suffer permanent effects from the skin, foot or brain damage that occurs during the disease. The ferret’s behavior may be altered significantly if the brain is affected.
As of 3/01 there is still only one USDA approved CDV vaccine for ferrets; Fervac-D produced by United Vaccine. Fortunately there is interest in developing alternatives so in the near future we will have other choices. But the following is a general discussion of the uses and problems with vaccinations no matter what the source.
There is no vaccination that is 100% effective in all pets. The reasons for potential vaccine “failure” include:
* The animal’s immune system does not respond properly to the vaccine for genetic, medical or other reasons and the appropriate level of protective antibodies does not form. * The vaccine was damaged either by being overheated or being reconstituted too long before its use. Vaccines have to be refrigerated up to shortly before use and used within 30 minutes of reconstituting. * An inappropriate vaccine for ferrets was used. There have been reported cases where CD was caused in ferrets by the use of an inappropriate vaccine. * It may take several days for the immunity to develop after a vaccination. For instance, if a ferret was vaccinated on day one and was exposed to the CDV on day 2 or 3, then he/she would not likely be protected from CD. In addition, baby ferrets need to have a series of vaccinations ending with one after 14 weeks of age to insure immunity for one full year. This is because the mother’s antibiotics that are passed through the milk can gradually destroy the effectiveness of the immune response in the baby. At 14 weeks, all the mother’s antibodies have been cleared from the young ferret’s body. Adult ferrets that have never had any distemper vaccinations in their lives need to initially have a series of two vaccinations two to three weeks apart to develop a strong immunity for a year.
At this time it is recommended to have your ferret vaccinated for CDV on an annual basis. However there is evidence that the immunity to CD may last up to three years. In future it may be feasible to test a ferret for its level of immunity prior to vaccinating on a yearly basis particularly where the risk of contracting CDV is low.
Ferrets at high risk such as those going to ferret shows, those with exposure to other species of CDV susceptible animals, those that travel and those in a breeding program where new ferrets are frequently added should probably be vaccinated routinely on an annual basis.
Unfortunately anaphylactic (allergic) reactions to CDV vaccine are occasionally seen with Fervac-D. Reactions occur in approximately 2 to 5% of ferrets vaccinated. Reactions can also occur with rabies vaccinations as well, but are uncommon. The reaction is most likely in response to a substance carrier liquid in which the CDV is preserved. The majority of reactions are not life threatening, but they can be uncomfortable for your pet and frightening to see. Rarely the reaction can be severe. Because we wish to avoid any serious health problems for you pet, we recommend the following guidelines when visiting your veterinarian for any vaccination.
* Allow enough time for your appointment to be able to wait for at least 20 minutes in the reception area after the vaccination to watch for adverse reactions. Most vaccine reactions occur rapidly. * Watch for signs of a reaction over the next 24 hours after vaccination which can include one or more of the following; weakness, rapid and shallow breathing, vomiting, diarrhea, depression, incoordination, collapse and/or a blue color to the gums. Streaks of blood may be present in the vomit or diarrhea. * Report any unusual signs to your veterinarian immediately.
The treatment for anaphylactic vaccine reaction depends on the severity of the condition and can
Include corticosteroids, antihistamines and fluid therapy. Most ferrets respond rapidly to treatment. Ferrets that have previously had a reaction to a vaccine may be pretreated with an antihistamine injection prior to receiving subsequent vaccines. This pretreatment is not necessary for ferrets that have never experienced a reaction.
The above is general veterinary information. Do not begin any course of treatment without consulting your regular veterinarian. All animals should be examined at least once every 12 months.
About the Author
Copyright 2001 – 2006 by Susan Brown, DVM.
Used with permission. All rights reserved