Failure of Flea Prevention? Nope!

Posted on by Christopher Bern, DVM

Fleas are very sturdy creatures that can go 100 days without feeding and can live year-round inside a home. We talk to our clients daily about proper flea prevention, but it’s not uncommon for someone to say “I’ve tried everything and nothing is working!” These people hear talk about potential resistance of some fleas to current preventatives and are genuinely frustrated. It can drive you crazy when you’re using products and still seeing these little blood-sucking parasites. But there’s hope!

I can promise that in about 99% of those cases, I can find some problem with the client’s expectations, application, or other situations that are unrelated to the actual efficacy of the product. Not long ago, a parasitologist from the College of Veterinary Medicine at Kansas State University, Dr. Mike Dryden (sometimes called “Dr. Flea” because of his extensive research on these insects), did a study on apparent failure of flea products. He visited 1,000 homes in the Tampa, Florida area, all of whom said that they were using preventative appropriately. In all of those homes he found no real evidence of flea resistance, and in all but one or two found that the client had the wrong understanding of fleas and how the products work or weren’t using them properly. Anecdotally, I have seen the same situation time and time again. There is little to no evidence of any sort that fleas have developed any resistance to products released in the last few years, and these products are actually very effective.

“But I’m using it!” you might say. ”I still see fleas!  It’s just not working!” Here is a list of common reasons why a product might appear to “fail”, when in actually it’s working just fine.

  • Over-bathing: Bathing a pet more often than 1-2 times per month with most shampoos can significantly reduce the natural oil layer in this skin. This oil layer is what carries the topical flea products, so removing it will significantly decrease the effectiveness of anything placed on the skin. Talk to your vet about soap-free shampoos that won’t strip this oil.
  • Inconsistent use: Since fleas can live for 100 days without feeding, and a flea egg can take up to six months before becoming an adult, you need to use flea preventions every single month. If you skip months you can allow adults to feed and reproduce, continuing the problem.
  • Not treating every pet: Fleas aren’t picky about their choice of meal and will potentially choose any warm-blooded animal. In order to get fleas under control, you need to treat every pet in your household, even if you’re not seeing fleas on them. Otherwise, the fleas will continue to feed and reproduce from the untreated pets. Sometimes this can mean giving prevention to ferrets, guinea pigs, and rabbits. There are products safe to use on these “exotic” pets, so check with your vet for the proper recommendations.
  • Not treating the environment: Adult fleas are only 5% of the flea population. If you’re not treating your house and yard, you’re missing the eggs, larvae, and cocoons, which account for the other 95%!
  • Many wild animals: If you have a high population of wild animals (raccoons, opossums, deer, etc.), or stray dogs and cats, you may never completely control your yard. In one of the cases that Dr. Dryden examined, he found that the client actually was doing everything they should have, but was still having fleas. Upon further investigation, they found a family of raccoons in the woods just behind the client’s house. These animals were infested with fleas, and were continually bringing flea eggs into areas that the client’s dogs also walked. Without eliminating the raccoons and other wild animals, it may be impossible to completely eradicate some populations of fleas. 
  • Not treating for long enough: A single treatment on your pet or in your house will not resolve a problem! Because of the flea life cycle and the delay from egg to adult, you will have a staggered population in the environment. You will need to treat for several months (2-3 minimum) before you can expect to start seeing a significant effect. If you used one dose and are still seeing fleas, I will tell you to keep treating for longer
  • Stopping treatment too soon: Remember that fleas can be delayed in their development. Eggs laid in July may not become adults until Thanksgiving! If you think you have the fleas under control after a few months and stop using prevention, there may be some undeveloped stages that will then have an opportunity to grow and start the cycle all over again.
  • No “force field”: Most flea products have minimal to no repellency. In fact, they are all dependent on the fleas actually coming in contact with the skin or even biting the pet. With no contact the fleas won’t be killed. Simply seeing fleas doesn’t mean that the product isn’t working, though it does mean that you need to work in all areas for complete control
  • Flushing effect: Some flea preventions (such as FirstShield and Vectra) have a “flushing effect”. When the fleas contact the skin and therefore the product, they begin to feel nerve stimulation, which they don’t like. They quickly try to get away from the skin, which “flushes” them to the surface of the coat where they may be more noticeable. If you see a lot of fleas on the top of the coat, but few on the surface of the skin, the product is actually working well!

As you hopefully can see, complete flea control requires much more than simply giving a prevention once per month. You need to understand the flea life cycle and how the products work in order to have maximum effectiveness and get your problem under control. As always, using prevention before you see fleas is going to be much more effective than waiting until you have them. Talk to your vet today about the best products for your pet!

About Christopher Bern, DVM

Dr. Bern has been with the practice since 1999 and currently works as the Chief of Staff for the Woodstock, GA hospital. View all posts by Christopher Bern, DVM →


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