Jeff Kahler: The frustration with fleas

Today were are going to discuss the frustration with fleas. Yes, those little blood-sucking parasites ravaging our companions and making their lives miserable.

Perhaps that is a bit dramatic but fleas actually can be very frustrating, both for our companions and for us as caretakers.

Over the last couple of years, I have noticed a problem with flea control, especially in dogs.

Clients who are committed to regular flea prevention for their dogs still are seeing their dogs scratching and biting at themselves in response to flea infestations on their bodies. What gives?

What is occurring is a classic biologic response within the flea population. It is called adaptation and it occurs in all species of animals. When a species of animal is faced with a change in its environment, it must deal with that change.

In the case of fleas, they have been challenged with various chemicals designed to kill them. Most of them have obliged and died. In fact, in the past decade or so, with the advent of a product for flea control called fipronil – most commonly under the brand name Frontline – we have been quite successful dealing with fleas. This period of success, however, is waning.

It seems after years of exposure to Frontline, fleas have become resistant to its mechanism of action to kill them. How does this happen, you might ask?

Biological adaptation is the answer. This is a genetic phenomenon that allows a species, in this case fleas, to genetically alter themselves in response to an environmental change.

The environmental change in this case is the addition of Front-line to the flea’s environment ... the dog.

Put in simple terms, when Frontline was first used, it was extremely effective in killing fleas in our companions. Many generations of fleas were exposed and died, but every once in a while there were some that were genetically resistant to Frontline.

This resistance was of no advantage (no pun intended) to these particular fleas until they were exposed to Frontline. Those fleas without this genetic resistance died when exposed to Front-line, those with it did not.

They then did what every species is supposed to do: They bred and thus passed on this resistance to Frontline to their offspring. This resistance was genetically multiplied within the flea population and over many generations and several years of time, we now have a significant population of fleas that can tolerate Frontline.

This is a very simplified illustration, but nonetheless applicable. Incidentally, this is the same thing that occurs in bacterial populations that become resistant to certain antibiotics.

So then what are we supposed to do with these resistant fleas that are sucking the blood out of our companions?

We have to use a new product to which the fleas have not had a chance to develop resistance. I am currently recommending Activyl with the active ingredient indoxicarb.

So far, it has been extremely effective in preventing flea bites and bringing overall relief.

Now, I know what some of you are thinking: What is to prevent fleas from becoming resistant to Activyl?

The answer is, nothing. We just hope it won’t be for several years while work is being done on the next flea prevention medication for our companions.