Ron Hines DVM PhD 4/24/06

You may want to read a companion article to this one, Vaccinations To Give Your Ferret. Distemper that ferrets occasionally contract is actually a disease of dogs. The form of distemper that cats contract will not infect ferrets. Although dogs often recover from distemper, the disease is usually fatal in ferrets. Ferrets that contract distemper have been exposed to a dog that was incubating the distemper virus or recently recovered from infection. Young, unvaccinated dogs in a rural setting are the principal carriers of the distemper virus. The odds that a household ferret that never leaves the home will contract distemper are very very low.

The distemper virus does not survive long in the environment. Sunlight and drying quickly kill the virus, as do common household disinfectants. In my youth working at a veterinary hospital, I saw many cases of distemper every week. But it has become a rare disease in urban America because so many dogs are now vaccinated and immune to the disease. Distemper incubation time in ferrets is a week to ten days. Infected dogs shed this virus to ferrets primarily through their respiratory secretions. The virus is usually transmitted through a sneeze or a cough when the inquisitive pets meet. After it enters the ferret the virus multiplies in the lymphatic tissue surrounding the respiratory tract.

Symptoms Of Distemper
When ferrets contract distemper, the first signs are loss of appetite, lethargy and depression. Fever, skin rash and a clear to pussy eye and nose discharge soon follow. The characteristic rash of distemper in ferrets is present on the chin and between the rear legs. Many ferrets develop a dry cough, which soon becomes a moist cough as secondary bacterial pneumonia develops. Their eyes and nose become caked with brownish crusts and scabs. After this respiratory phase of the disease, the distemper virus invades the ferret’s nervous system causing twisted neck, cross-eyed gaze, muscular twitching, convulsions and incoordination. Some ferrets develop brown tarry stools and diarrhea. In some, the skin of the foot pads thicken and harden.

Early in the disease, distemper can be confused with human influenza to which ferrets are also susceptible. One can try to support ferrets, sick with distemper, with antibiotics and intravenous fluids but there is little chance of their survival. Ferrets usually die 12-14 days into the diseases. A few will appear to be on the road to recovery only to develop nervous deterioration several weeks to months later. Although there is no effective treatment for ferrets that contract distemper, vaccines on the market are very effective in preventing the disease. I give the first distemper vaccine at 6-8 weeks of age. Booster vaccinations are then given at 10-12 and 14-16 weeks of age. Immunity in ferrets, as in dogs, is almost certainly longer than a single year. So yearly vaccinations are probably unnecessary. I vaccinate my own ferrets every three years. If your ferret will be exposed to young, unvaccinated dogs, vaccination every second year might be more appropriate until we have some scientific data on the length of vaccine immunity.

Vaccine
There are three distemper vaccines available for use in ferrets in the United States. The oldest on the market is Fervac-D produced by United Vaccine Co. in Madison, Wisconsin (800 283-6465) especially for use in ferrets.

The second vaccine is Galaxy-D marketed by Schering-Plough in Kenilworth, New Jersey (800 521-5767). Many practitioners used this vaccine to vaccinate ferrets before Fervac-D became available and have returned to using it now. Although it is not approved by the FDA for use in ferrets, it has proven safe and effective.

The Third and newest vaccine is the one that I now recommend. It is Purevax-D produced by Merial in Iselin, New Jersey (888 637-4251). Purevax-D is a recombinant DNA vaccine manufactured especially for ferrets. Since it consists of purified antigen it does not contain components that might set off an anaphylactic reaction.

Distemper Vaccine Reactions and Anaphylaxis

Anaphylaxis refers to a sudden and severe allergic reaction that causes a crisis in many body systems. It occurs in all species of mammals as well as in human beings. Some signs of this reaction are hives (urticaria), swelling (angioedema), a sudden drop in blood pressure (hypotension) and difficulty breathing due to swollen air passages (bronchospasm). Anaphylaxis is an immunologic event in that portions of the immune system are responsible for all the events that occur. The immune system of ferrets and other animals contain memory cells that recognize things foreign to the body. To gain immunologic memory the body must be exposed to the agent once, to know it, and then a second time to remember it. Because of this the ferret’s first distemper shot never causes a problem and its second or third vaccination may not either.

When the ferret is exposed to the vaccine a second or third or fourth time the foreign protein (antigen or allergen) causes the release of dangerous mediator chemicals called histamines, leukotrienes, prostaglandins and tryptase. The ferret’s blood cells that are responsible for the release of these chemicals are called basophils and mast cells. These four chemicals cause the smooth muscle within the respiratory and digestive tract to contract and smooth muscle surrounding the blood vessels to relax. Blood vessels also begin to leak. This causes the respiratory distress and shock-like drop in blood pressure characteristic of anaphylaxis in ferrets. Histamine released into the skin causes the hives we see frequently in dogs and humans undergoing an anaphylactic reaction. In people, the most common cause of anaphylaxis are antibiotics, peanuts and bee stings.

When I was using Fervac-D to vaccinate ferrets, I became very familiar with untoward reactions associated with the vaccination. Within two minutes or less following vaccination, the ferrets would often salivate and begin to hyperventilate. They would often void their urine and bowels. Some turned blue. I saw so many reactions that I began giving all ferrets a small (0.2ml) dose of chlorpheniramine maleate or benedryl antihistamine about twenty minutes before giving the vaccine. I never let ferrets leave the office until thirty minutes after receiving a vaccination.
Ferrets that show any signs of an impending vaccine reaction immediately receive an injection of epinephrine and oxygen via a face mask.

These acute allergies or anaphylactic reactions are due to the ferret’s body becoming sensitized to ingredients in the vaccine. It is not the actual virus protein, needed to immunize the ferret, that causes the reaction but other ingredients used in the propagation of the distemper virus or used to preserve the vaccine.

If your ferret ever experiences a vaccine reaction, insist that it receives an antihistamine injection 20 minutes before its next vaccination or, if your lifestyle does not bring the animal in contact with dogs and distemper, consider forgoing the vaccinations entirely. I have never seen or heard of distemper occurring in a ferret that received a single distemper vaccination in its life.

Recently, recombinant feline omega interferon has become available in Europe and Japan. This product seems to have anti-viral properties in dogs as well as cats. It would be interesting to try the product early in ferrets suffering from distemper since no other treatment has proven effective..

The vaccines that have traditionally prooved safe in ferrets are all produced from the Onderstepoort and Lederle strain of distemper virus.
I stopped using United Vaccines ferret distemper vaccine, Fervac-D because so many animals went into shock after it was given. The Company told me this was not so. Call them and ask if they have reformulated the vaccine so it is now safe.
When they do give it, many vets give only a half-dose because it seems to protect the ferret just as well but cause less reactions. There is also rumor that giving the vaccine in the hip is safer than giving it at the shoulder. I know of no rational to support this claim.
The best distemper vaccine for ferrets was Galaxy-D. It was sold by Solvay Corporation. It was not labeled for ferrets because the cost of obtaining FDA approval for use in ferrets was more than the profit they made selling the vaccine. However, Solvay wasn't making enough money selling this vaccine so they sold the patent to Schering-Plough (possibly Fort Dodge).
See if your vet can call these Companies for advice. If none are available at this time, try to find a catalog vaccine that is marketed to mink farmers.

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