Fleas make pets' lives miserable, and humans begin to itch just at the thought of them. Vets are often asked what pill, drop, dip, collar, or shampoo works the best to get rid of these persistent parasites. The answer is that there is no single method or insecticide that will completely eradicate (or at least control) a flea problem.


Although only about 1/10 inch long, fleas can bedevil cats, dogs, and humans in a big way - biting their hosts to gorge on blood meals. Fleas thrive in warm, moist environments and climates. The main flea food is blood from the host animal. Host animals are many species: cats, dogs, humans, etc. Fleas primarily utilize mammalian hosts (about 95%). Fleas can also infest avian species (about 5%). Flea saliva, like other biting skin parasites, contains an ingredient that softens, or "digests" the host's skin for easier penetration and feeding. The saliva of fleas is irritating and allergenic. It is the cause of all the itching, scratching, and other signs seen with Flea Allergy Dermatitis, or FAD.


In general, fleas do not transmit diseases from pets to humans, but the potential for this exists; and, they can and do bite humans as well as dogs and cats. Fleas are intermediate hosts for tapeworms. Fleas and flea larvae live in warm climates and will live until the ground freezes in cooler climates. They can live on in your home well past this time. The flea life cycle is fairly complex, and understanding the various stages will help you understand why infestations are so difficult to control.


Life Cycle


Collectively, all species of fleas are categorized under the order name of Siphonaptera. The cat flea, Ctenocephalides felix, is the most commonly found flea in the US and infests cats, dogs, humans, and other mammalian and avian hosts. Fleas have four main stages in their life cycle: egg, larva, pupa, and adult. The entire flea life cycle can range from a couple weeks to several months, depending on environmental conditions .


adult fleaADULT: The adult flea is very flat side to side. There are hair-like bristles on the flea body and legs to aid in their navigation through pet hair. Fleas have 3 pairs of legs, the hindmost pair designed for jumping. Fleas are well known for their jumping abilities. Adult fleas prefer to live on the animal and their diet consists of blood meals courtesy of the host animal. Once on a host the flea will initiate feeding within seconds. Female fleas can consume 15 times their weight in blood daily. Mating will occur on the host in the first 8 to 24 hours. Female fleas begin egg production within 24 to 48 hours of taking their first blood meal, reaching maximum production between 4 and 9 days. They can produce 1 to 2 times their body weight in eggs daily for over 100 days.


flea eggsEGG: The female flea lays white, oval-shaped eggs. The adult female flea can lay as many as 50 eggs per day. The eggs are not sticky (like some parasites), and they fall off of the animal into the carpet, bedding, floorboards, and soil. Flea eggs will be dropped wherever the flea-infested pet has access both inside and outside the home. Eggs usually hatch in 2 to 16 days, depending on environmental conditions. The larva emerges from the egg using a chitin tooth, a hard spine on the top of the head that disappears as the flea matures.


flea larvaLARVA (plural = larvae): The larval stage actually has three developmental stages within it. Larvae are about 1/4" long, and semi-transparent white. They have small hairs along their body and actively move. They eat the feces of adult fleas (which is mostly dried blood) and other organic debris found in the carpet, bedding, and soil. Depending on the amount of food present and the environmental conditions, the larval stage lasts about 5 to 18 days (longer in some cases) then the larva spins a silken cocoon and pupates.


flea pupaePUPA (plural = pupae): The pupa is the last stage before adult. The adult flea can emerge from the cocoon as early as 3 to 5 days, or it can stay in the cocoon for a year or more, waiting for the right time to emerge. When is the right time? (Never, say pet lovers everywhere!) Stimuli such as warm ambient temperatures, high humidity; even the vibrations and carbon dioxide emitted from a passing animal will cause the flea to emerge from the cocoon faster. Once a flea emerges from the cocoon it almost immediately begins seeking a host. This brings us back to the adult flea. The adult flea can be fully developed in 2 to 3 weeks.


The entire life cycle is quite variable, as evidenced by the variability in each life stage progression. As mentioned above, the cycle can be as short as two weeks or as long as one to two years! That is why it is so important to remain vigilant, even when a flea problem is thought to be under control!




Pest control of fleas in the yard, home, and on pets starts with frequent vacuuming of the home, especially areas that pets frequent, clearing the yard of litter and debris, and by establishing a regular bathing and grooming schedule for pets. Note: flea eggs can lie dormant for several years so a flea-free home can be contaminated by introducing used upholstery, carpets and rugs.


flea dirtIf you suspect that your pet has fleas, you should take him/her to your veterinarian. Clinic staff can use a flea comb on your dog or cat looking for “flea dirt” or dried blood flea excrement as well as actual fleas. If fleas are found, your veterinarian will recommend treatment. Most veterinarians recommend preventive treatment for fleas, as it is much easier to prevent them than to treat them. This photo shows flea fecal material, also called 'flea dirt' or 'flea clippings', combed from a cat.


There are several over-the-counter flea treatments available at your local pet store. However, many of these contain toxic substances. If you choose to use an over-the-counter product, you should be aware of the potential side effects. There is a potential threat of toxicity, not just to your dog/cat, but to other animals in the house and humans as well. Make sure you follow the label usage directions and if you have any questions about using these products, consult your veterinarian.


Today, there are many flea treatment products available, and new ones are introduced to the market frequently. Consult your veterinarian for the best course of treatment for your pet.


Remember that it is much easier to prevent fleas than to treat them once your pet has them. If you need more information about fleas and flea prevention, contact our clinic.

Lakeside Veterinary clinic assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.