Scratchings-and-Sniffings

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Are Fleas Getting Resistant to Certain Insecticides? Posted: 07 Oct 2009 06:10 AM PDT I hear rumors from time to time that fleas and ticks are getting resistant to the more common forms of insecticides that veterinarians use to control them. It's often the subtext around some new and improved product. The logic goes something like this. If you use the same flea control product every time a small percentage of fleas will survive and pass on flea resistant genes to subsequent generations. Over time enough fleas will become resistant to be a problem. There are anecdotal reports all over the web on suspected flea resistance. I cannot, however, find any real research that demonstrates that fleas are becoming resistant. In fact, it's the opposite. I can find research, some of it funded by the manufacturers themselves, that indicate otherwise.  One company, Bayer Animal Health, funds an independent international program called the Flea Susceptibility Monitoring program or FSM for short. This program got started in 1999 and involves data from the US, Germany, France and the United Kingdom.   In the US there are over 100 participating veterinary hospitals in 23 states that collect and submit samples for testing to independent laboratories.   The testing involves a three step process where flea eggs are treated with a drug called imidacloprid. If any eggs emerge as adults they are again treated with this insecticide and the final step is test any survivors on treated dogs.   So far, in the ten year history of this program none have survived the second step. Imidacloprid is the active ingredient in Advantage and K9 Advantix made by Bayer.    While there are instances where company sponsored research can be less than pure, I tend to be confident in this situation. With so many independent researchers involved and the reputation of one of the leading animal health companies around at stake, I give them the benefit of the doubt. If you have questions about these veterinary dispensed products you should discuss this with your own veterinarian and they can probably site studies showing their preferred brand or brands of flea control to be effective.   So why all the reports of resistance? I would guess it to be some form of operator error or improper handling of the materials. All the more reason to work closely with you vet and his staff. When they recommend a flea control regimen make sure that they show you how to administer the product. Make sure they tell you how often it needs to be applied and how it should be stored.   The old saw, "according to manufacturers instructions" should apply when flea control is concerned and your vet or someone on her staff is the best person to interpret those instructions for you.

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