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Thread: Flea resistance to Frontline?

  1. #1
    Staff - Birds LindaD's Avatar
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    Default Flea resistance to Frontline?

    Dr. Gus

    We've had a lot of trouble this year with fleas among our rescue kittens. They obviously come in with fleas. Our protocol is to treat with Capstar and then work to keep the flea population down, sometimes retreating with Capstar to kill the adult fleas at regular intervals. When the kittens are old enough they are treated with Frontline. However, most of the kittens still have fleas and Frontline doesn't seem to be doing the job anymore. Is this due to resistance to the active ingredient in Frontline? What are you using in your practice? A vet that did a big S/N clinic for us recommended using Prometrix. Do you have any experience with it and does it work better than Frontline? This vet commented that it is a lot cheaper than Frontline and she found it seemed to work better. I was not familiar with the active ingredient in this product and it seems to have been approved recently (I used to work as a consultant helping companies register products).

    Comments welcome!

    Linda

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    Staff - Veterinary DrGus's Avatar
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    Never heard of Prometrix, no hits on either Google or Bing.

    I discussed this recently with the world's foremost expert on flea control. His lab at Kansas State does all the testing for the various manufacturer's flea products and he works for the state, not the companies, so he has no bias one way or the other. Basically, two things are involved with a perceived resistance to Frontline.

    First, Frontline's competitors are spreading the rumor concerning resistance. In fact, however, these competitors have been trying to breed Frontline resistant fleas for some time and have been unable to do so. The mechanism of action of Frontline makes resistance very, very, VERY unlikely to ever occur.

    Second, a combination of a much worse flea season, the flea life cycle, the way topicals like Frontline work, and a failure to treat the environment.

    The flea life cycle isn't quite what we used to think. When the adult flea hatches out of its little coccoon 3-8 weeks after the egg was dropped, it searches for a host dog or cat. Once it hops on the pet the flea never leaves; the pet is a dead end host and the flea stays on the animal until the flea dies of old age. Fleas don't hop back into the environment, they don't hop from pet to pet, they stay put. Males and females take an initial blood meal in 1-3 minutes, breed, and the female starts dropping eggs off the pet in about 24 hours. The pet walks around like a giant salt shaker dropping flea eggs all over the house/yard, starting the 3-8 week life cycle all over again.

    The key to flea control is treating the environment because that is where every single flea on a pet came from.

    The way topicals like Frontline work is by contact. The flea contacts the treated hair, the drug percolates through the exoskeleton of the flea, and then kills the flea. With Frontline this can take up to 24-48 hours for the flea to die, depending on whether you are in the first two weeks after application or the second two weeks. So even though the Frontline is killing 100% of the fleas within two days of hopping on the animal, you will see those fleas running around on the pet, biting the pet, for that period of time.

    If there are no fleas in the environment, after 48 hours the pet will be flea free. If you see fleas after 48 hours the only possible source is the environment, so you know that is where your problem lies.

    There are several ways to approach the problem, in no particular order.

    -- treat the environment (house/yard) aggressively, repeatedly. Keep in mind that if you even have one pet who goes outside, all of your pets in the house are effectively outdoor pets as far as flea control (and disease exposure) are concerned. If you don't control the environment, nothing will control the fleas on the pet when the flea season is particularly heavy.

    -- you can apply Frontline every 2 weeks. This ensures that all fleas die in less than 24 hours, before the female starts dropping eggs. Frontline Plus has an egg hatch inhibitor for eggs that are dropped in the second two weeks of the month, but it's more effective to stop the eggs completely. Frontline Plus every 2 weeks carries no toxicity concerns and is a very safe approach. Never try to stretch Frontline past 4 weeks, you will have viable eggs dropped after 4 weeks and will start the 3-8 week life cycle all over again.

    -- you can use Capstar every day. Not very practical, but since it is a systemic product, not a topical, the fleas ingest the drug with the first blood meal and are all dead in 15-30 minutes of the initial bite.

    -- do what we recommend in our hospital. In cats, we prefer Revolution over Frontline Plus for several reasons. It is applied like Frontline but is absorbed into the bloodstream and therefore is a systemic, not a topical drug. Like Capstar, the first bite kills the flea within minutes, unlike Capstar one application lasts one month. Revolution has one drawback vs Frontline Plus and several benefits. The drawback is that it give no tick control at all, Frontline is the only effective tick killing product on the market. But ticks tend not to be such a big deal in cats; Lyme disease, a terrible problem in dogs in our area, has never been diagnosed in a cat. Benefits of Revolution over Frontline Plus are that Revolution also treats ear mites, treats two intestinal parasites, and most importantly prevents heartworms in cats without having to give anything by mouth!

    So with Revolution one gives up tick control, but picks up immediate flea kill, heartworm prevention, ear mite and intestinal worm control, a good tradeoff in a cat. Because of the serious problem with tick borne diseases in dogs we still recommend Frontline Plus and Heartgard Plus for dogs.

    --
    Dr. Gus

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    Staff - Birds LindaD's Avatar
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    Wow! Thanks! I got the name wrong -- it's Promeris by Fort Dodge. Senior moment?

    Anyway, it's good to know that treating every 2 weeks can be done with Frontline. That may be a way to break the cycle for as soon as we bring in kittens, we usually have fleas as well. We try to give Capstar as soon as they come in, but if they are very young, the options for treatment are limited. And Capstar is quite expensive to give very often.

    I'm going to forward your response to all our foster parents and perhaps we can break this cycle. Revolution may be a good option since our fosters usually have ear mites and intestinal parasites as well.

    Thanks

    Linda

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    Staff DianeP's Avatar
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    Thanks for your excellent response, Dr. Gus!
    Diane and Cicero - Sr. Manager
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    Quote Originally Posted by DrGus View Post
    ... Frontline's competitors are spreading the rumor concerning resistance. In fact, however, these competitors have been trying to breed Frontline resistant fleas for some time ...
    the mind boggles .. that's appalling.

    but thanks for the information, Dr. Gus.

    .m

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