Certified Veterinary Homeopathy by Dr. Glen Dupree

While I try to keep a non-confrontational world view, when it comes to fleas and their control the adage "Know thy enemy" rings especially true. The better one understands the lifecycle of the common flea species on our pets, the easier, the more effective, and the safer (for the pet and for the environment) our flea control programs become.

To that end, the following is a primer on the life cycle of Ctenocephalides felis, the common cat flea (despite the name, this is the major flea species of the 20plus species found on our dog and cat pets in most areas), given with acknowledgement to Dr. Michael Dryden of Kansas State University who was among the first to study and write about the life cycle of this particular parasite.

Ctenocephalides felis, the cat flea (hereafter referred to just as "flea") is an obligate parasite who undergoes a complete metamorphic lifecycle. Once this is understood, flea control becomes more directed at the vulnerable stages of flea development and less of a "shot gun" approach which typically includes the non-discriminate use of environmental insecticides.

The flea's lifecycle includes four stages - egg, larva, pupa, and adult. If we begin our study at the adult stage, we find this scenario. The adult flea is an obligate parasite, living out its days on the host. The only reason the adult flea leaves its host is if it is mechanically removed (scratched off) or if another host is in close enough proximity for the flea to jump from host to host (dogs or cats sleeping together, for example). The adult flea feeds on the blood of the host, defecates partially digested blood on the host (those hard black crumbles you find on your pet when they have fleas are really just flea poop), and lay their eggs on the host. If the adult is removed from the host for only a few days it will starve to death.

The eggs laid on the host are small, sticky, translucent orbs that adhere to the host's skin and hair coat. As the eggs dry, they fall off the host into the environment (carpet, cracks in the flooring, under the cushions of furniture, into the grass, into the compost and leaves in the garden, etc). Where ever the host spends most of its leisure time you will find the greatest number of eggs in the environment. These eggs are very fragile and are easily killed by sunlight, drying, and temperature extremes. This is why environments like carpet, sand, leaf mulch, etc. are important in the flea lifecycle. These will provide the proper microenvironment for the flea's survival by protecting the eggs from hazardous conditions.

As part of the grand scheme of flea survival, the partially digested blood meals of the adults are of vital importance. This partially digested blood is defecated on the host and falls into the environment at the same time and in the same place as the eggs. As the eggs hatch into larva, this flea poop provides nutrition for the larvae. The heme in the blood found in the feces also provides necessary elements for the development of chitin - the hard brown exoskeleton of the adult flea. It is important that the "flea dirt" falls into the same area as the eggs, as the larvae only move a matter of a very few feet from where they were hatched. This readily available food source optimizes their chance of survival.

The correct environment is also important as the larvae are very susceptible to the effects of temperature, drying, and UV light.

Finally as the larvae mature, they form pupae. These are the environmentally protected "cocoons" that protect the immature flea until it is time to hatch into adulthood. These pupae can remain viable for months while waiting the proper time to hatch. For them the proper time to hatch is when a food source (host) is present. Thus they hatch from the pupa in order to immediately attach to a host. The presence of heat (body temperature), vibrations (foot steps), and/or carbon dioxide (respiration) tells them a host is near and triggers their maturation into adult fleas, who continue the life cycle by feeding, pooping, and reproducing on the host.

(This is why you get over run by fleas if you leave your house empty for a few days during summer vacation. Without the presence of a living, breathing body to stimulate the maturation of the pupa to adults, the flea population matures to the pupa stage awaiting a food source. You come home from vacation, walk into your house and become the first and most available food source for the waiting fleas.

This is also why you may find fleas on the pets in the house but do not find them on yourself. The pets are closer to the flea's environment so the proximity of their respiration and body heat selectively attract the fleas to them, rather to you.)

Let's see what all of that means as far as our flea control programs are concerned.

The adult stage comprises only about 5% of the total flea population but is the stage which has historically been targeted by the common flea control programs - collars, sprays, dips, powders, house treatment, and yard sprays. So while we were battling the 5%, the other 95% were developing and maturing to fill the ranks. The programs for the houses and yards were wasteful and ineffective at best because the adult flea was not in the environment where the toxins were applied. They are only exposed to the environmental adulticide poisons if mechanically removed from the host, which is not a common enough occurrence to justify applying poisons to the ground or into our houses. The sprays, dips, powders and collars used on the pets are ineffective because they do nothing to break the lifecycle and prevent the next generation. They kill only the adults but usually not quickly enough to prevent reproduction. These adulticide toxins are not effective against the eggs although in recent years IGRs (Insect Growth Regulators) have been added to the arsenal to help break the lifecycle by inactivating the eggs.

The eggs and larvae comprise about 85% of the total flea population. They are susceptible to environmental conditions but not to insecticides.

The remaining 10% are in the pupa stage, where they are resistant to most control methods and to most environmental conditions.

So where does this leave us with flea control?

The easiest way of addressing flea control is with the new generation systemic flea controls. These are chemicals applied to the pet's skin at monthly intervals or given orally to kill the adult fleas. Some also include IGRs to help with the control of the immature stages. These are the easiest but are they the best considering all factors??

These systemic products are effective but at a cost to the pet and the environment. As we try to maintain a wholistic relationship with our pet population, we try to limit their chemical exposure and to do no harm as we care for them. Using toxins which stay in their system for at least a month does not seem to fit with this philosophy, especially if there are equally as effective but safer options available.

Also as the pet excretes these chemicals or their breakdown products, what becomes of them? The chemicals, in some form, are passed into our water and soil through the urine and/or feces of the pet. We would like to think that all those flea products, heartworm preventatives, antibiotics, etc. are completely used or destroyed by the body but they are not. In some form, all the chemicals we give our animals (or take ourselves) are returned to the environment through excretions. This is one of the contributing factors to the degradation of our aquifers and our soil.

A better alternative is to look at the most vulnerable stages of the life cycle and act there. The eggs and larvae are the largest percentage of the flea population and are also the most vulnerable. Since they are susceptible to the effects of drying and to UV radiation, keeping the grass cut in the yard and keeping the pets out of the flower beds and from under the house will dramatically help flea control. Inside the house removing old carpeting will help.

Using an environmental IGR targeted at the areas where the pets spend their leisure time will help both indoors and outdoors. Most naturally occurring IGRs are eventually broken down by UV radiation and must be reapplied every few months. Some have also been incriminated in mutations of amphibian populations so they must be used with caution.

The most readily available naturally occurring IGR is methoprene, which is marketed under a variety of trade names. Methoprene is usually found in a 1 ounce concentrate which mixes a gallon of spray. The spray should be applied every 3-4 months to target areas.

Safer still is the use of desiccants in the house, especially if the house is floored with carpet. These desiccants are mostly boric acid compounds which dry the microenvironment in the webbing of the carpet. This targets the weakness of the egg and larvae directly and in a way that causes very few "down stream" environmental problems.

FleaBusters RX is the prototypical desiccant type flea control product ( I have no financial interest in this company but have successfully used the product for years).

In the yard, the use of parasitic nematodes is a safe and effective option. These are microscopic worms which eat the eggs, larvae, and even the pupae of insects. As long as the ambient temperature is above the mid-60's, there is adequate moisture, and a food supply, the worms will remain active. Once they have eliminated their food source (the immature insect population), the nematodes will themselves starve out, leaving no environmental contamination. They will also not be washed off by rainfall so there is no accidental exposure outside the treated area.

Finally, as with any other parasite control program, do those things which foster health and vitality in your pet(s). Parasites, fleas included, will target the weaker, less thrifty members of the population. Good health is the best flea control program.

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