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May 24, 2012 at 6:00 AM

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From the archives: Veterinary Q&A on flea control

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Leroy, a 3-year-old goldendoodle, was medicated and had his neck shaved after he had a reaction to a topical flea-prevention medication. Photo by Jean Lange-Mollmann

This post originally ran on Tails of Seattle pet blog on June 8, 2011.

A reader sent us a note about her 3-year goldendoodle, named Leroy. To help prevent fleas, his owners purchased an over-the-counter, topical flea-control medication and administered it on the top of the dog's neck as indicated on the package. The next day Leroy was noticeably uncomfortable and having trouble staying still. Within a week, the dog had developed bloody lesions on the neck site and was clearly in pain. They took him to the vet, and he had to be sedated so the flea-control medication could be scrubbed off. The dog was put on antibiotics, pain killers and steroids, his owners said, and he recovered in about two weeks.


Veterinarian Jeffrey F. Duke, left, and Christina Karimi-Naser, a vet technician, below, from Pilchuck Veterinary hospital in Snohomish answer today's questions about flea control.

Question: Are any over-the-counter flea-prevention meds safe on dogs and cats? Are they species-specific? Do dog products only work on dogs and cat products on cats?

Answer: There are a multitude of over-the-counter flea products available for dogs and cats. Most, however, are insecticides (a type of pesticide) that can be toxic for your dog or cat.

Pesticides are designed to damage the nerve system of insects, and will have a similar effect on mammals, sometimes leading to convulsions and seizures. Less serious toxicities may be seen, such as vomiting, diarrhea and weakness.

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Cats tend to be much more sensitive to pesticides. By far, the worst reaction we see is when a product intended for use in dogs is applied -- even in small amounts -- to cats. These pets often arrive at our emergency facility unconscious, hyperthermic and having seizures, and end up in intensive care, sometimes for days, to recover.

Fortunately, effective flea control has evolved greatly over the years, and we now can avoid using pesticides on our pets, in our homes and in our yards. Michael Dryden, the world authority on flea biology and control, goes so far as to say that "all modern flea control methods involve interfering with flea reproduction."

These options, called insect growth regulators (IGR) or insect growth inhibitors (IGI), first appeared more than 15 years ago as products to be applied in the home and now come in pill or topical form, often given/applied monthly, for pets. IGRs are not pesticides.

Question: How do these flea products specifically kill the fleas? Are they safe?

Answer: IGR products prevent fleas from maturing by inhibiting the development of chitin. (Chitin is necessary for the formation of the hard outside skin, or cuticle, of an adult flea. Adult fleas cannot exist without chitin.) These products have no effect on humans or dogs and cats because mammal tissues have no chitin.

Compared with pesticides, which are largely composed of chemicals that affect the nervous system of mammals and insects, this is a much safer and very effective alternative.

Another positive feature is it will only affect the insects on our pets. When we apply pesticides in our indoor and outdoor environments to try to control fleas, we also kill many other insects. Because insects are a natural part of our world, and our intention is to focus our control on those that act as parasites on our pets, the random removal of other insects ends up with an unintended impact on the environment.

Also, by not using an OTC pesticide on your pet, you will be preventing family members from being exposed to pesticides unintentionally when they touch the family dog or cat.

Oral medications like Program and Sentinel, and even topical Revolution, are not pesticides and will not cause this unintended exposure. Program and Sentinel are based on their IGR composition for effective flea control. Revolution acts to kill fleas and stop development of immature fleas, similar to an IGR. Both Revolution and Sentinel happen to control many internal parasites, like worms, and Revolution is also effective at killing ticks.

Question: What are safe options to keep fleas out of my house?

Answer: Because fleas are parasites that prefer to spend all their time on your pets, treatment strategies discussed above should control the problem without the need to treat the indoor or outdoor environment. This saves expense, is more environmentally safe and will prevent many disease problems related to flea parasites.

Bottom line: The safest approach to flea treatment is prevention. The safest and most effective prevention is to avoid pesticides and use monthly flea-prevention medications that now are available by prescription from your veterinarian.

Question: If my dogs or cats are mainly indoor animals, do I have to take the same precautions?

Answer: Keeping in mind that the indoor environment is the most common place for fleas to replicate year round, any pet that comes in contact with other pets or areas where wildlife spend time, even their own yards, should be on flea prevention.

Interestingly, often people assume their cats are not affected by fleas because they don't see them scratching. The truth is that cats typically are not overt scratchers, so they often address their own flea infestations by normal-appearing grooming behaviors.

Question: Do I only need to use flea medication during flea season?

Answer: One common misunderstanding in our area is that fleas are a seasonal problem. That is true only in the sense that they are a problem in Western Washington during all four seasons!

Our mild and humid weather allows for a dozen fleas to become 2,000 fleas in one month. It is critical to realize that fleas are much easier to prevent than treat. Once you have an infestation in your home, that means that for every adult flea you see, there are 20 fleas in pre-adult stages as pupae, larvae and cocoons.

Also know this: There is nothing that will kill the cocoon stage of fleas. They will have to emerge as adults and bite your pet before they can be controlled. This is one reason why yearround prevention is so much more effective than waiting to try to treat the problem.

Question: Can a pet be too young or too old for the medications?

Answer: All medications for flea prevention have label directions that need to be followed. Over-the-counter pesticide products tend to be toxic to young pets, but some prescription flea medications can be used as early as 4 weeks of age.

Question: What kinds of diseases do fleas carry? What kinds of medical problems can they cause? Are they simply an annoyance or are they a danger to my pet?

Answer: Besides causing skin irritations, and sometimes severe allergic reactions in our pets, fleas also are a source of other diseases for pets and humans.

Tapeworms are a common infection for dogs and cats with fleas because the flea is an intermediate host for the Diplydium tapeworm. Many specialists believe the bacteria that caused cat scratch fever in people is carried and transmitted through the flea from one cat to another.

There may be other bacterial and viral infections that are transmitted by fleas from pet to pet and from pet to people.

Dr. Jeffrey F. Duke and Christina Karimi-Naser

Jeffrey F. Duke, DVM, is head of Pilchuck Veterinary Hospital's small-animal department in Snohomish. He grew up in Oregon and received his veterinary degree from Oregon State University in 1984. He joined Pilchuck the same year as a large-animal veterinarian, but by 1987 shifted to small animals. His areas of special interest are surgery, both soft tissue and orthopedic, and small-animal reproduction.

Christina Karimi-Naser is a veterinary technician at Pilchuck Veterinary Hospital in Snohomish. She has more than 15 years of experience at veterinary practices located in Oregon and Washington.

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Next: Other pests and parasites Pacific Northwest pet owners need to be aware of.

Read earlier Q&A columns here.

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We use Cedarcide and have had NO problems. Safe for everyone. Smells better than the... MORE

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