SMALL MAMMAL HEALTH SERIES By Susan Brown, DVM

GENERAL INFORMATION

In the spring and summer the fleas will be out in force again and these pesky little parasites afflict many of our pets, including ferrets. In some areas of the country, fleas are a year round problem. In this paper we will take a look at how fleas can safely be controlled in ferrets using the products available on the market. Remember to always check with your veterinarian first before using any new product on your pet to ensure its safe use.

Fleas of one of the following species, Ctenocephalides felis, Ctenocephalides canis, or Pulex irritans, can affect dogs, cats, rodents, rabbits, ferrets and many other animals. The adult flea lives on the host long enough to acquire its blood meal and lay its eggs. The flea also spends time in the surrounding environment laying more eggs and waiting for its next victim. Adult fleas live about 3 to 4 months and the entire life cycle from egg to adult can take as little as two weeks. These fleas can also feed on humans, although we are not their preferred host. Some pets (as well as some humans) develop an allergic skin reaction to the flea's saliva resulting in scabs, sores, intense itching and hair loss. * It is important that flea control be aimed at removing the fleas both from the pet as well as from the environment or the fleas will not be eliminated.

There are a variety of flea control products on the market today and the list will get longer as we hopefully find less and less toxic means of controlling insect pests. Some products are used only on the pet and some are used only as environmental controls and should not come in direct contact with the pet. I would like to point out that none of the products that are covered in this paper (as of this writing) are officially (USDA) approved for use in the ferret. Therefore, if you use any of these products it will be at your own risk. Some veterinarians require your signature on a release form before using a nonUSDA approved product so that there is a clear understanding of client responsibility in case of an adverse reaction. In addition, the drug companies that produce these flea control drugs are not liable for the product's use outside of the recommended species and should not be held responsible if a problem occurs. It is highly unlikely that any of these products will acquire official USDA approval for use in ferrets because the process is extremely time consuming and expensive. The information in this article is based on my own experience as well as that of several other exotic animal veterinarians and does not represent scientifically produced data. As mentioned, always check with your veterinarian before trying any new product to insure that it can be used safely on your individual pet.

Ferrets have fairly thick skin, but medications can still cause a localized dermatitis or be absorbed directly through the skin and cause an internal toxic reaction. In addition, if the ferret can reach the area where the product is applied, he/she may lick the product during grooming activities and ingest toxic amounts of the material. Whenever you use a new product on your pet, please observe him /her closely for 24 hours following application for signs of toxicity. Some signs to look for include redness of the skin, intense scratching, lethargy, depression, loss of appetite, diarrhea, excessive salivation, tremors, seizures and loss of consciousness. If you observe any of these signs, wash the product off the ferret immediately, using mild soap and copious amounts of water, and call your veterinarian for further instructions. Keep all flea products and soaps away from the ferret's eyes, ears and mouth.

Do not use flea collars on ferrets for any reason. Not only is the material in the collar often toxic but contact with the collar can cause serious skin irritation. In addition, the ferret can get the collar wedged over the lower jaw if they tried to chew it off or he/she could choke to death if the collar gets caught on something in the environment.

The ferrets at greatest risk of developing a toxic reaction to even a “safe” product include those that are under 3 months of age, are ill, have hair loss and thinning of the skin, in a poor nutritional state or on on medication.

A successful flea control program has to include control of the parasite on the pet as well as the environment. Do not forget that ALL the pets in the household need to be taken into account when determining what products to use.

FLEA CONTROL PRODUCTS

Here is the list of the more common flea products available and our recommendations regarding their use.

Organophosphates -(malathion, ronnel, fenthion, cythionate, dichlorovos, neguvon, etc.) *These are highly toxic chemicals, to humans as well as pets, which are either applied to the skin or are used in the environment. They kill the flea on contact, but are also absorbed through the skin into the internal organs of the pet. Toxic reactions are common and are related to damage to the nervous system. THESE PRODUCTS ARE NEVER RECOMMENDED FOR TOPICAL USE IN FERRETS.

Carbamates - (sevin, carbaryl) - These are topical insecticides that are less toxic than organophosphates and do not accumulate in the internal tissues of the pet. They kill the flea on contact. Resistance by fleas is common (it doesn't kill all the fleas). Although many of these products have been used on ferrets, toxic reactions occasionally occur, and we recommend avoiding their use. If you must use one of these products, only as directed by your veterinarian, and use a powdered product that has less potential for absorption through the skin than a spray or shampoo. Watch closely for reactions, particularly in those high-risk animals as described above.

Pyrethrins (natural and synthetic) - This chemical is derived from chrysanthemums and is one of the least toxic of the topical insecticides to the pet. It kills the flea on contact, however resistance by fleas is common. Although pyrethrins are fairly safe, some of the other additives in the flea spray or powder may not be and these additives can cause toxic reactions. Read the label carefully to know what you are buying. I would have the same recommendations for pyrethrins as I do for carbamates with the comment that of the insecticides, pyrethrins are safer to use overall.

D-Limolene - This topical insecticide is a natural citrus extract. It dissolves the waxy coating on the flea causing its dehydration and death. Although fairly non-toxic in dogs, there have been reports of severe adverse reactions in cats and rabbits. They appear to be fairly safe to use in ferrets.

“Natural” flea control products - None of these products will effectively kill fleas, but rather act as repellents to keep the fleas away from the pet. Some products are added to the pet's food such as garlic, Brewers yeast and sulfur which are absorbed by the body and may alter the “taste” or smell of the pet's skin acting to repel the fleas. Products used only topically include pennyroyal oil, linalool, melaleuca oil, lavender oil, citronella oil and lemon oil. Adverse reactions to these products are rare and can be the result of using more than recommended amounts or by ingestion of a product intended strictly for topical use. Although these products can be helpful, we don't generally recommend using any of these products as an effective means of total flea control in the ferret. If you do choose to use them, please observe for any toxic reactions and use environmental flea control to further reduce the flea population.

In the last few years there have been several new products on the flea control market for dogs and cats. These include Program, Advantage and Frontline. They have a different approach to flea control that is less toxic to both the pets and their human companions. However, remember that none of these products have been officially approved for use in ferrets. However all of them have been used by ferret owners on their pets in various parts of the country and the world and so far the reports of toxicity are uncommon. I believe from what I have seen so far that these are the products that will be the safest and most effective to use in most pets. I would suggest that if you have a serious flea problem that you discuss the use of one of these products with your veterinarian.

Program - (active ingredient is luferon - produced by CIBA Animal Health) - This product is an insect growth regulator which interferes with the development of normal chitin which is the hard outer shell of the flea, and thus results in the death of the immature flea. It is not an insecticide and does not kill the adult flea, but rather prevents the immature fleas from reaching maturity so that over time the fleas in the household die out. The product is given orally as a pill once a month. The dose used in ferrets is 1/2 of a cat dose (45mg). It appears to be a very safe drug in all animals in which it has been used. Rare side effects might include vomiting, lethargy, diarrhea, itchy skin or loss of appetite. It may be necessary to use it initially with an adulticide or insecticide product until the flea population in the household is under control. There is about a 6 to 8 week lag period between starting with Program and the reduction of adult fleas on the pets.

Advantage - (active ingredient is imidacloprid - produced by Bayer) - This is a flea adulticide that kills on contact. It interrupts nerve transmissions in the flea resulting in paralysis and death. It kills 98-100% of the adult fleas within 24 hours of application and thus kills female fleas before they have a chance to lay eggs. Advantage is not absorbed into the blood stream or internal organs. It is applied topically and spreads as the animal moves to the entire skin area at the level of the hair roots. Bayer indicates that it has been tested on ferrets, chinchillas, rabbits and guinea pigs, but it is not officially approved for use in these species. The dose used in ferrets ranges from one half to a full cat dose applied once a month. It is important to prevent the pet or its cagemates from licking the material while it is wet. Bathing or excessive exposure to water can reduce the effectiveness of the product and it may have to be reapplied more frequently in these cases. This product can stain furniture and remove the finish from some materials if there is contact with the wet product. Advantage and Program can be used together.

Frontline - (active ingredient is fipronil - produced by Rhone Merieux Companion Animal Products) - This is an insecticide from a new family called phenylpyrazoles. It kills 96% of adult fleas in 2 hours on contact and 100% of adult fleas in 24 hours. In addition, it kills 100% of ticks within 48 hours, and most die before they can attach. Program and Advantage do not kill ticks. Sunlight, bathing and water do not affect the effectiveness of this product. The toxic action of fipronil is very specific to invertebrates such as insects and arthropods, and apparently does not affect mammals. It is applied directly to the skin with a spray or as a spot type application and is reapplied monthly. It has been used in ferrets at one half to the full cat dose. This product can also be used in conjunction with Program. I am not aware of any reports of toxic reactions in ferrets using this product but we have also not seen it used extensively. Since the safety is still being tested, use the product with caution and careful observation.

Environmental controls - The best environmental control is a clean environment. Vacuum frequently and either throw out the bag each time or use a carbamate or pyrethrin insecticide sprinkled inside the vacuum bag to kill any accumulated fleas. In addition wash the pet's bedding at least once a week in hot soapy water. Steam clean the carpeting a few times a year to kill parasites of all types. Boric acid salt coats the fleas and their larva and removes the moisture from their bodies and thus kills them. You can use boric acid salt products on the floors and carpets once or twice a year to kill fleas. There are pest control companies that can apply this product for you. Boric acid salt products should never be used directly on the pet and pets as well as humans should be protected from the dust during application in the environment. For flea control in the yard you can purchase nematodes, which are microscopic worms found in some gardening catalogs, that eat immature fleas and eggs. These nematodes have to be maintained in a moist area. In addition, ants love to eat fleas and their families and you might want to think twice before destroying all the ant nests in your yard. For very serious infestations, either inside or out, it may be necessary to use insecticide foggers or environmental sprays which contain a variety of ingredients including growth-inhibiting hormones. I recommend trying to avoid these products unless absolutely necessary and under the supervision of your veterinarian because most of them are toxic to some degree in mammals

In conclusion, remember that you must control the fleas on all the pets in the household and the environment as well. With several options available you should be able to be “flea-free” this year!

revised 3/08/01

Date Published: 3/8/2001