Understanding the Flea Life Cycle

Jack Russell Terrier puppy and ginger Domestic Long Haired kitten

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Fleas are one of the most common ectoparasites in dogs and cats. Not only are they a nuisance, they can transmit diseases. A study of the prevalence of fleas in pets across the country showed that depending on the region, the incidence of flea infestations in dogs ranged from 0.4% - 10.2%. The same study showed that the incidence of flea infestations in cats ranged from 0.5% - 19.2%. In order to treat an infestation and prevent fleas from returning, it's critical to understand the flea life cycle.

The most commonly known disease spread by fleas is the plague. Bacteria that cause plague are transmitted by the oriental rat flea. Cat fleas and oriental rat fleas can also transmit flea-borne typhus (murine). The cat flea can also transmit the bacteria Bartonella henselae, which causes Cat Scratch Disease. Fleas can also transmit tapeworms if they are accidentally ingested by a host cat or dog when grooming themselves. 

The Flea Life Cycle 

The entire life cycle of a flea consists of four stages: egg, larvae, pupae, and adult. Oftentimes, a flea infestation will be depicted as a pyramid, with eggs making up the largest portion, or base of the pyramid, and the adults making up the smallest portion, or the peak of the pyramid.


Adult fleas that have found a host animal will begin mating after taking a blood meal. The subsequent eggs will be laid either in the fur of the host animal or in the environmental surroundings of the host. This can be bedding, furniture, and flooring. Environmental factors effect how quickly these eggs will hatch, but generally they hatch after 1 to 10 days. Flea eggs account for half of a flea infestation in the home.


Once the eggs hatch, they enter the larval stage of the lifecycle. The flea larvae feed on blood as well as flea excrement (also called flea dirt). They will stay in this larval stage for 5 to 20 days before entering the pupa stage. Flea larvae account for about 35% of a flea infestation in the home.


The pupae are safely encased in a cocoon. This lifestage is the hardiest, withstanding most cleaning agents and environmental harshness. The flea will remain in this stage until conditions are right to hatch into adults. They will stay in their cocoon until the ambient temperature is warm enough and there is a warmblooded host animal nearby. They can stay in this stage for days, weeks, or even months. Pupae account for just 10% of a flea infestation in the home. 


The adult fleas, or evidence of adult fleas in the form of flea dirt (flea excrement) are often what a pet owner will see in an infestation. This is despite the fact that adult fleas comprise the smallest portion of an infestation at less than 5%. Adult female fleas will begin feeding from the host animal within hours of hatching and, on average, live anywhere from 2 to 3 months. 

How to Treat a Flea Infestation

If your pet has fleas and you have an infestation in your home, the first thing is to treat all the pets in the home with a veterinarian-approved flea treatment. Most available products are topically applied once a month, although there are products that are formulated as chews to be given either monthly or once every 3 months. Cats are especially sensitive to certain flea treatments that contain pyrethrin and permethrin. These products are are otherwise safe for use in dogs and many products labeled for use in dogs will contain them, so be sure to check product labels, drug inserts, and consult with your veterinarian before selecting a flea preventative for your cat. 

Since adult fleas can live 1 - 2 months, and factoring in the time spent in the egg, larvae, and pupae form, it is said that the life cycle of a flea is 3 months. So pets will need to be treated with a flea prevention for at least 3 months. There are also cleaning products that can be used to clean carpeting, baseboards, and hardwood floors where eggs and pupae are usually found. These products should be used with care in regards to the pets in the home. Oftentimes it is recommended to keep cats in one room while treating the rest of the house. Once the product is dried and the rooms are aired out, the cats can be let out and the room they were in can be treated. Be sure to not let cats back into that room until the product is dried and the room is aired out. Alternatively, you can treat your house and then take your dogs out to the park or simply a drive around town while the product dries and the house airs out. If you have birds, speak to your veterinarian before using any household cleaning products for fleas, as birds can be especially sensitive to aerosolized cleaning products. 

In most cases, fleas can be treated with diligent preventions that are given at their recommended dosing intervals. Since the pupae can withstand most cleaning products and preventions, it is imperative to continue the prevention for at least 3 months so that they can be treated as they hatch into adults but before they have the chance to mate and lay eggs. If you have concerns about a flea infestation in your home, speak to your veterinarian for further tips.

Article Sources
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