To understand how Fronline controls fleas it’s important to get to know their habits a bit better. Aside from the uncomfortable situation where pets experience intensive itching and scratching as  a result of flea bites, other problems can also be experienced such as Flea Allergy Dermatitis (FAD), flea-bite anaemia and tape worm infestations.

Flea Allergy Dermititis

FAD occurs when your pet becomes sensitised to flea bites and large “hotspot” develops at the base of the tail. This area will become red and irritated and very painful, often developing a secondary bacterial infection. A vet will have to diagnose this condition and treat it with both antibiotics and cortisone. The lesions will continue to recur if the pet is not kept flea free.

Flea-bite anaemia

Not as well-known and usually occurring in small puppies and kittens. Since the body mass and blood volume is low in these small animals, anaemia or even death may result with just a moderate flea burden.


Fleas are the intermediate host of some species of tapeworms, and it is therefore important to deworm more often in households where there is a flea burden. Since these worms can be transmitted to humans, both pets and owners should be regularly dewormed.

Flea Epidemiology

There are many different fleas species globally but Ctaenocephalides felis (the Common Cat Flea) is by far the most common, resulting in flea infestations in homes all over the world. This flea will readily infest many different hosts, such as vervet monkeys, rats, mice, rabbits and many other animals. Unfortunately this does mean that while we diligently treat our homes and pets, re-infestations may occur as a result of feral animals carrying fleas back into our gardens and homes. In South Africa fleas are a constant problem, especially in the coastal areas due to the heat and higher humidity.

The Flea Life Cycle:


The female flea jumps onto the dog or cat, takes her first blood meal and then mates with a male flea. After about 24 hours she will start to lay eggs at a rate of approximately 40-50 per day, and  with a life span off 100 days, she can lay up to 2000 eggs in her lifetime! The eggs are laid on the skin of the host (pet), dry out and then fall off into the environment. The pets acts as a dispersal mechanism, moving around the home and garden shedding eggs wherever he goes. There will naturally be an accumulation of flea eggs in the areas where the pets spend more time, for example in its bedding.


After about 3-5 days larvae will emerge from the eggs and, since they are photosensitive (light sensitive) they will more away from light, burrowing into vegetation and under carpets and furniture. They are very sentivie to heat, low humidity and air movement and are therefore prone to desiccation (drying out), thus they cannot survive outside unprotected, hostile areas.

Larva will feed on organic debris, including flea faeces, until they spin a cocoon to form pupae. This larval life stage lasts for around 5-11 days depending on the availability of food and the climatic conditions.


Pupae are the most resilient stage of the flea life cycle and effectively ensure the survival of the species. They are unaffected by almost all chemicals, therefore it is extremely difficult to eradicate them. Pupae can emerge in 6-11 days under ideal conditions, but are also able to lie dormant for extended periods of time, waiting for optimal conditions to emerge as adult fleas.

Adult fleas

Adult fleas will only emerge from their pupae once the conditions are ideal: heat (a minimum of 18C), humidity (a min of 50% relative humidity) and the presence of a host.

Fleas will feed on any available mammals but problematic for us once they bother us and our pets. Once the female flea has taken her first blood meal and mated, she will start laying eggs 24-48 hours later and so perpetuates the cycle.

Interestingly, adult fleas only make up 5% of the flea population – the other 95% is made up of eggs, larvae and pupae.

Under ideal conditions the flea cycle can be completed in as little as 2-4 weeks.

Flea Infested Households

Home environments can quickly become flea infested, with different stages of the life cycle being found all over the home. It has been calculated that for every one adult flea seen on the pet, 95 immatures (eggs, larvae and pupae) are present in the environment. Adult fleas seen on the pet generally come from eggs laid 8-12 weeks ago, so by the time you see that there are fleas on your pets, it is usually the second or third generation fleas that you are seeing, This means that the environment has already been contaminated with eggs and the other life stages, resulting in continuous re-infestation. Thus, regardless of the product used, a continual flea burden will be seen on the pet. It is therefore vital to break the life cycle by inhibiting egg production, killing the adults as the emerge and infest the pet, and in doing so, eventually cause population decline.

It must be understood that eradicating a flea infestation is a process rather than a single event, and may take 3-6 months to achieve. It takes an indeterminate amount of time for the pupae to hatch therefore fleas will be emerging from time to time. However, as long as Frontline is being used correctly, the environment is being treated with an appropriate spray and various other measures are put into place, the flea problem will be brought under control.

Common reasons for unsatisfactory results following Frontline application:

Incorrect dosing or application

Applying too little; applying to the hair instead of the skin; pet swimming or being bathed within 3 days after Frontline application; applying to a wet coat; not achieving good coverage with the spray; applying too low down on the shoulders so the pet licks it off; inaccurate dosing such as splitting pipettes to divide the contents amongst pets. All of these result in the pet being under-dosed and the product will not be as effective.

Infrequent applications

Ensure that Frontline treatments are not stretched further than the recommended 4 weekly intervals.

High parasite challenge

The environment may be so burdened (eg as a result of infrequent Frontline applications) that the pets are continuously re-infested.

Wild or feral animals infesting the environment with parasites

It is extremely difficult to control this, and neighbourhood cats that roam the property for instance, are often the culprits. It is vital that pets are treated with Frontline Plus to break the flea life cycle crucial to preventing the population from growing. A good premises spray will also be needed to help eradicate some of the flea eggs and larvae.

Pets with excessively dry skin

Since the active ingredient of Frontline, fipronil, is concentrated in the sebum (natural skin & coat oils), an animal with a dry skin will not have as good a distribution of Frontline. Some areas may have an insufficient concentration of fipronil and thus ticks and fleas will live longer than they should. If this is suspected, contact your vet for advice on treating the dry skin.

Climate changes

Our increasingly more temperate climate is optimal for many parasites, allowing their life cycles to speed up, resulting in an almost year-round emergence.

Unobserved fleas

Some pets, like cats, are masters at self-grooming, removing a lot of the evidence of a flea problem. Since the problem goes unnoticed for a length of time, a large flea population builds up in the home. Pets should also be regularly checked flea dirt as well a fleas.

Unrealistic expectations

Given all we have learnt about fleas and their habits, we now know that flea erradication is not an instantaneous thing and takes constant action over an extended time period to achieve the desired results.

Reference: Merial FrontlinePlus Manual.

Leave a Reply

Your email address will not be published. Required fields are marked *