Ctenocephalides felis, the cat flea, is the most common flea that affects ferrets and other house pets. However, ferrets that are allowed to go outside may go down holes that have been occupied by wild animals, such as groundhogs, rabbits, and squirrels, and can acquire different species of fleas. Fortunately, all fleas are susceptible to the same treatments.

Fleas bite and suck blood from the wounds they make, causing anemia. They cause itchy skin and sometimes allergies that make the hair fall out. Ferrets are such small animals that they can be seriously debilitated by a heavy flea burden. It is easy to prove to yourself that fleas ingest blood. Simply comb out of the animal's coat some of the black fecal droppings left by the fleas, and sprinkle them on a damp paper towel. Immediately the paper will turn red with the pet's partly digested blood. Some species of fleas transmit bubonic plague in the south western United States.

When your pets have been infested for a while, most of the fleas will be in your house, not on the animals. Any flea control program has to kill not only fleas on all pets that spend any time in the house, but also everywhere the animals can go. The most intense effort should be concentrated on the areas where the ferrets, cats, or dogs sleep. Eggs will hatch into larvae in these areas.

Larvae eat the droppings of mature fleas for about 2 weeks, then spin cocoons and become pupae. Inside the cocoons, the pupae metamorphose into juvenile fleas that emerge in 3 or 4 weeks as a new generation of mature fleas. Each female flea may produce 50 or 60 eggs a day, increasing the population of young fleas in your house exponentially within 6 weeks of the first adult flea's arrival. In the comfortable temperature of your home, flea eggs hatch in about 4 days. In the cooler temperatures of the basement or garage, they may remain dormant longer. This is an important point to remember when planning flea control strategy.

Killing only adult fleas, for instance, by a once-a-week bath or dip, will eventually control the problem in a northern climate, but it will take months. Fleas do not survive the winter outside, and pets are given a chance to be flea-free after the first killing frost, but in temperate climates, it is much more difficult to eliminate fleas from your house because there is a plentiful supply of them outside.

Because fleas can cause serious health problems, every effort should be made to eliminate them. If you have cats or dogs that habitually go outside, they will continually carry fleas back into the house in temperate seasons. If the ferret is allowed to play in the same areas as the cat or dog, it will quickly be infested. Using commercial cat litter containing fine cedar and softwood chips helps to keep fleas out of the ferret's cage without using other types of chemical control. Cedar-softwood cat litter is not toxic for ferrets, and no allergic reactions have been reported. Keeping the ferret's cage at least 18 inches off the floor will also prevent fleas getting near the ferret, as long as cats do not have the opportunity to jump up on top of the cage. However, if the ferret gets out of the cage for exercise, this advantage is lost.

Flea control chemicals

Pyrethrins, which are relatively safe even on baby kits, act as flea repellents and kill adult fleas. Products containing pyrethrins are available in many forms including powders, sprays, and towelettes (Flea Halt Towelettes^®) that can be wiped over the animal.

Imidacloprid blocks nerve transmission in adult fleas, immediately killing them. The familiar trade name is Advantage^® (Bayer). Advantage is also available as a topical liquid that can be applied to the skin once a month. It then spreads to the rest of the animal's skin, and is resistant to the effects of water in the form of rain, swimming, or baths. It kills larvae as well as adults, so is able to bring a heavy infestation of fleas under control fairly quickly. It has no effect on the eggs in the environment, of course, and they will continue to hatch, so the flea problem is not solved until all eggs have hatched and the adults contact the pet and the Advantage. If used monthly, this treatment will probably also control ear mites. It is not labelled for use in ferrets, but to my knowledge, no adverse effects have been reported.

The disadvantage to using these chemicals alone is that they do not affect the flea eggs. Eliminating all the intermediate stages in the life cycle (eggs, larvae, and pupae) required several weeks of intense effort, and preventing re-infestation of the house meant constant vigilance. In the last few years, flea control has become much easier because of new types of chemicals on the market that interrupt the life cycle of the flea. The new chemicals are safe for humans and even very young animals because they mimic hormones or enzymes that are present only in insects. They include lufenuron, Precor, and Nylar.

Lufenuron (pronounce loo-fen-your-on) is an insect developmental inhibitor. Its familiar trade name is Program^® (Novartis). Program is available in an oral suspension for cats that may be used to dose ferrets on a body weight basis once a month. Be aware that this product, like all other flea control products, is not labelled for ferrets. The manufacturer has no responsibility for any adverse effects that may result from treating animals other than those named on the label. To my knowledge, no reactions have been reported in treated ferrets.

Lufenuron is absorbed by the treated dog, cat, or ferret, and biting fleas get a dose of it with their blood meals. The eggs of treated fleas are damaged so that they do not hatch. This prevents the ordinarily rapid increase in numbers of young fleas in your house, but has no effect on the adults that are already there. The life span of an adult flea is at least a few months. If Program alone is used as flea control for animals that are already infested, it will take several months to eliminate all fleas from the house, because adult fleas are not affected. Program works best as a preventive, or in combination with other products that kill adult fleas on the animal and in the environment. Remember that all pets must be treated or there will be a constant source of fertile eggs hatching.

Precor and Nylar are insect growth inhibitors which can be found in products formulated for use on carpets and animal bedding. Some products are available which can be used directly on the animal and contain both a growth inhibitor and an insecticide; these include Bio Spot^® for Cats with Flea Halt Towelettes (Nylar and pyrethrin). Growth inhibitors have no effect on people or pets, and they do not kill adult fleas, but they prevent the flea eggs from hatching and the larvae from pupating and turning into adults. Using the combination of a separate growth inhibitor with an insecticide that kills adults brings a flea problem under control very quickly compared to the old methods of bathing, dipping or spraying the pet, and using sprays, bombs, or powders in the house for several months. Best of all, the new chemicals are much safer for animals and people.

It is possible to use traditional flea products to control fleas on ferrets, but they do not like to be sprayed and must be held firmly or scruffed to get a thorough treatment. Most are not fond of baths either, and the once-a-month treatment with either Advantage, Bio Spot with Flea Halt Towelettes, or Program is very much simpler and safer than any of the traditional methods. Although ferrets are very resistant to the toxic effects of insecticides, many people and cats are not.

Organic products that are relatively, but not absolutely, non-toxic are available to kill fleas. The most popular and probably most effective is D-limonene, a citrus product that both repels and kills adult fleas. It is applied in the form of shampoos that have a pleasant citrus odor. However, D-limonene is not nearly as effective as Advantage or Bio Spot for Cats at killing adult fleas, and will not bring a heavy infestation under control without using some other form of treatment, such as growth inhibitors.

If you have any pets that go outside, all animals in the house will need to be treated during the warm months to prevent fleas infestation. If either Advantage, Bio Spot with Flea Halt Towelettes, or Program is used as a preventive, very few fleas will be found in the house, and it will probably not be necessary to use other chemicals to control eggs and larvae.

To speed up the elimination process, remove all fabric bedding from the ferret's cage or nest and wash it. The litter box in the cage should be emptied and cleaned as usual. Cage cleaning and then treating with Precor or Nylar makes a huge difference in the number of eggs and larvae that will develop into adults.

It is very difficult to treat every part of the house that a ferret can access, so it is still important to vacuum thoroughly to pick up eggs, pupae, and larvae from ferret trails. The vacuum cleaner bag should be changed frequently, and sealed in a plastic bag before disposal in case it contains live and fertile fleas.