Tiny masters of the universe — the unconquerable flea

Ever wonder what good is a flea? Like most living things, fleas do have an important role in our ecosystem. And a better understanding of their habits can lead to a more environmentally sensitive and sustainable way to control them. 

The life of a flea

Cat and dog fleas (Ctenocephalides felis and C. canis) are closely related and differ only slightly when it comes to morphology: roundness of head and number of notches on legs. The cat flea is a little larger and can be said to infest many more species of mammal than dog fleas—which seem to have a preference for canines (even though they will also infest other warm blooded mammals). Being more common, cat fleas are more likely to be what you find on your dog.

These tiny brown, six-legged, wingless sesame seeds are incredibly well designed.  As much as we hate them, they have mastered their world and appear to be thriving in it. The millions of litres of toxic chemicals that we squirt on our pets may be doing nothing but killing our environment.

Their laterally flattened bodies, covered with hard plates and backward-facing Velcro-like hairs and barbs help them to move through fur and stay anchored during the most vigorous scratching/biting attack or even wetting.

Close-up, their mouth parts look like something out of a horror movie. A complex set of segmented tubes and serrated plates saw into the host mammal’s skin, injecting saliva laced with anti-coagulant and histamines. A mouth and gut pump also create a powerful suction.

The multi-segmented hind legs contain a pad of elastic resilin. The flea prepares to jump by compressing hind legs and body onto the pad. Upon release, the pad returns to normal size and projects the flea about 15cm through the air.

The flea’s life cycle consists of adult, egg, larva and pupa. Understanding the insect’s life cycle and adaptations is vital in controlling them in our environment. For far too long we have been led to believe in one small aspect of their control, i.e. elimination of the adult.  But adult fleas make up only 5% of the population.

It is important to note that fleas don’t generally jump from host to host.  Both male and female fleas will bite and ingest blood. An adult flea can live anywhere from 3 months to a year in favourable conditions. They will jump from the environment onto a host but once there, will only really leave if physically or chemically removed.  This is why they are called parasites.

About 24 to 48 hours after a blood meal the female lays her eggs on the host (an average of 25 eggs laid at night).  They are not sticky and so will either hatch on the host or fall off into the environment and hatch into larvae in 1 - 10 days.

Flea larvae do not like to be dry. They actively avoid direct sunlight, preferring darkness, humidity (50% or more) and peace. They move deep into undisturbed carpet fibers, animal bedding, mats, couches, pillows, under skirting and between floorboard cracks.

They feed on the partially digested blood in flea faeces as well as organic debris. If conditions are favourable, larvae will pupate in 1 to 2 weeks and emerge as adults.

However, pupae will only hatch in response to movement and heat (presence of a host) and can remain viable in the environment for months.  Cocoons become covered with debris which protects the pupae from insecticides and adverse conditions. Therefore this is the hardest stage to eliminate with chemicals.

All life stages of the flea are susceptible to extreme heat and cold.  However, humans have created a safe-haven for them to thrive in. The temperatures that we are most comfortable with in our homes just happens to be the very same range that fleas love. In South Africa, the absence of European-styled central heating and the fact that many dogs live outside means that winter heralds a blessed reduction in the amount of fleas we see on our pets.

Human approach to flea control

Without being biased against the myriad chemicals we regularly subject our pets to, here is a list of commonly employed flea control methods.  All make use of powerful chemicals that have been proven to build up in the environment thereby causing harm to other species.

Flea collars - plasticised collars are infused with chemicals that kill adult fleas on contact. This reduces the fleas chances of biting but the collar is not as effective as other forms of treatment in the long run.

Powder - considered to have lower potency than other options, tick and flea powders contain ingredients that can be toxic to cats. Also, re-application is necessary every 3 - 4 days and pets can ingest the powder if they lick their fur.

Dip - some of the commercially available dips contain ingredients that, despite stating use for dogs and cats, are dangerous for use on cats (pyrethroid derivatives are all toxic to cats). Dips kill fleas on contact and have a short-lived efficacy (few days) before environmental re-infestation of the host.

The above methods generally only target adult fleas, killing on contact. As mentioned above, this is only 5% of the flea population and re-infestation is certain as adult fleas emerge from the environment continually. However, this method reduces flea bites and assists with flea bite allergies.

Spot-on - Some types of spot-on preparations contain chemicals that bind with oils in the sebaceous glands which coat the skin and hair thereby killing fleas on contact. Others enter the blood stream through the skin but they rely on fleas to bite and ingest blood of their hosts in order to be killed. These same treatments are often formulated to kill certain internal parasites simultaneously.

Oral forms – Because these chemicals are systemic, fleas must bite the host in order to ingest the insecticide. Not suitable as a repellent, oral tick and flea medication will not help flea bite allergic pets in the short term. Fleas can also transmit some species of tapeworm to the host which are not susceptible to current tick and flea preparations.

Is it time for a different approach?

If we are focussing our primary chemical approach on a mere  5% of the population, surely we can’t expect long lasting success?  It is true that for every adult killed there are no more eggs but for every adult that is not killed, 25 eggs per day can add up to sheer volumes of pupa just waiting to hatch in the background. Some flea preparations contain IGR’s (Insect growth regulators) which interfere with the development of the egg and larval stage. But these are often more expensive and outside the reach of many pet owners.

If you are using a tick and flea control and consider that, as parasites, fleas don’t generally jump between hosts, is it worth considering that the fleas on your dog have hatched in your very own home?  Instead of poisoning your dog or cat next time, it may be wiser to inspect your home for areas that may provide safe hiding places for eggs, larvae and pupae.

Moreover, if pupa are hard to kill with chemicals and larvae don’t like dehydration, what better way to provide them with an unfavourable condition than to physically get them out in the open? 

Here are some practical solutions:

-          Physical removal of eggs, larvae and pupae as well as their food source (flea dirt,

organic debris, shed skin and hair) through regular vacuuming or sweeping. Focus

on quiet areas that don’t often get disturbed. Remember also to destroy the contents

of the vacuum bag or sweep-ups instead of disposing of them in the bin inside!  

-          Placing soft furnishings like couches, pillows, bedding and mats in the sun to

dehydrate larvae and eggs.

-          Wash dog bedding regularly and hang dog blankets in the sun daily.

-          Shift dog kennels or bedding to new places regularly. This disturbs and exposes

eggs, larvae and pupae.

-           Remove unnecessary soft furnishings from the house and kennels.  Use cardboard

to line a kennel instead of fabric and change it regularly - cheap and easy plus

cardboard is a great heat insulator.

-          Use of natural repellents like strong-smelling herbs and essential oils in undisturbed

areas of the home.

I am a vet nurse who is passionate about reducing the amount of harmful chemicals we use in the environment and on our pets. I have also realised that since the domestication of dogs and cats, humans have unwittingly provided a nirvana for fleas to thrive in. 

All of which is to say that we are approaching flea control the wrong way around and in doing so we are continually pumping our fragile eco-system full of insecticides that wipe out a broad spectrum of beneficial insects as well as aquatic animals, plants and a host of other unintended victims.

While I don’t see humans ever relinquishing the convenience of such a huge variety of toxic chemicals available to them, it is always worth looking at challenges from different perspectives, especially when we are trying to protect and nurture the only place we all have to call home.

Happy hounding!

©Liz Roodt 2025