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Pyrethrin-based flea preventative not working

Posted by ritaweeda (My Page) on
Fri, Jun 1, 12 at 7:20

For the first time we are seeing fleas on our dog. We've been using a pyrethrin-based product. It has kept her flea-free for a year but isn't working anymore. We last treated her a week ago. Since it isn't working is it ok to use a different medication on her with fipronil, or do we have to wait another 3 weeks? I heard on the radio that the fleas may become resistant to one type of chemical and you might have to switch to another, but don't want to do something that will hurt the dog.


Follow-Up Postings:

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RE: Pyrethrin-based flea preventative not working

There is definitely resistance to pyrethroids and pyrethrins in the flea world. However, saying that, 90% of the time when I hear clients say the product is 'not working' it is because the flea problem is so overwhelming that the pet is constantly getting a new population of fleas on it from the environment, and the product is actually working... just not as instantaneously as the client wants (sadly there is no such instantaneous flea killing product on the market). This is particularly common with Frontline as it takes an average of 48 hours from initial exposure to death, making owners very frustrated when they see fleas still running around on their dogs. All those fleas, as soon as getting on the dogs, will die (nearly 100% effective, and true resistance to a product like Frontline or Advantage are extremely rare)... the fleas just don't know it yet (and neither do the owners). Revolution is also equally effective but it can take up to 4 days for flea to die after exposure. It WILL die. But it takes a bit. This can still be true with the pyrethroid products, too, though those have been around for well over 30-40 years and true resistance has been proven... so determining lack of effect versus overwhelming repopulation with pyrethroids is very difficult.

Anyway, since all fleas look alike, it is hard to track individual fleas to see if they are all dying or not, or are they just being replaced by new fleas? Studies done on fleas have often involved vet students (free slave laborers, in other words) actually tagging individual fleas (Not any easy task) and demonstrating that subsequent flea counts reveal fleas still present on pets, but not the SAME fleas... in other words, products are working well, but cannot keep up with the constant repopulation problems. In these cases, it helps to have owners treat the environments, too (bombs, environmental sprays, diatomaceous earth, professional exterminators etc.) or the flea problem will be very hard to get control of.

As to your question about applying Frontline now, after applying a pyrethroid recently, is absolutely. No problem. Frontline is an extremely low toxicity to mammals and can even safely be applied daily- though this is rarely if ever indicated... but often we recommend, in severe infestations, to apply frontline or advantage 2-3x a month. And these two products are in a completely different class of chemicals than a pyrethrin so will not 'add to any toxicity' already going on (pyrethrins and pyrethroids are potentially much more toxic products for mammals). Just don't be depressed or surprised if the fleas do not die any faster (and probably they will actually die slower... but ALL will die... they just may get immediately replaced with new ones).


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RE: Pyrethrin-based flea preventative not working

Thanks so much for your info. Now I can decide to apply it if I want. But now I'm hesitant because the pyrethrin might be working as it should, just not quick enough for me. I did treat the immediate yard yesterday, although I can't treat the whole 5 acres, so don't know how effective that will be. I concentrated on the areas where she lies most heavily, especially the plant beds near the house. I am going to sprinkle the house with borax tonight and leave it overnight. Up to the last week, we have been experiencing drought and someone said that is a factor, don't know for sure. But this is the first time we've seen fleas on her. As for the ticks, the woods are full of them all the time. I have to check her every day. Don't know if they are dog ticks or deer ticks, but the pyrethrin doesn't prevent them from attaching.


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RE: Pyrethrin-based flea preventative not working

My dogs are 13 and have been on Frontline Plus most of their lives. I do not treat the yard. The benefits from not having ticks or fleas far surpasses any minute risks from the Frontline.
I would apply the Frontline Plus- and it could take several months to break the flea cycle- and if your dog has no obvious side effects, continue with it.
For me, if I go much over the 30 days, I can tell, the dogs start scratching, and they never do that.

I am careful how I apply- the dogs haven't been bathed for at least 4 days and I don't bath them for at least 3 after applying.

I'm all for natural remedies, if they work!


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RE: Pyrethrin-based flea preventative not working

I treat my own dogs with Frontline when they need it.. which is maybe 2-3x a year... products these days work so well that pre-emptive treatments are not so important (unless you live in flea central or have a dog/cat with severe flea allergies). I find, like Bumblebeez, that just treating my pets takes care of the whole yard problem at the same time, as the pets, with Frontline on them, act like flea magnets and eventually wander the entire yard, attracting all available fleas, and eventually they are all gone. So I may treat my pets during an 'outbreak' for 1-2 months, maybe 3 in a row, and problem is over with... but I do not live in a super hot, humid climate like the southeast, where flea problems can quickly get out of control if you treat them so casually.

Tick control is more of a challenge chemically, but there is a collar called preventic (NOT for cats!) that is probably the single most effective preventative for tick control on the market now. It can be used along with Frontline for even better control, but in an overwhelming tick infestation problem, you will still find ticks on your pets often. Ticks, thanks to their much larger size, are more resistant to toxins.


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RE: Pyrethrin-based flea preventative not working

Where are you located, Rita?


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RE: Pyrethrin-based flea preventative not working

I'm in West Central Florida. Up till a week ago we were in a drought situation, don't know if that was the cause. We live on a wooded 5-acre property, fenced in from other dogs. But there are dogs on the adjoining properties. Plenty of deer, racoons, coyotes, etc. around, though.


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