5 Fascinating Facts About Fleas

Published Apr. 30, 2024
A puppy scratches their ear.

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The cat flea, Ctenocephalides felis, is one of the most common external parasites in dogs and cats. Fleas survive by feeding on their host’s blood, and their bite can lead to severe skin inflammation in our beloved furry companions.

A single adult flea can lay up to 50 eggs a day. Eggs often drop into bedding and soil where infested animals spend time.

Under conditions that are favorable to them, these eggs hatch, become larvae, and then grow into new adult fleas in as little as 28 days.

Because of these characteristics, a single adult flea can lead to a serious problem in a short amount of time.

Let’s look at five fascinating facts you may not know about fleas.

1. Fleas Have Been Around for Millions of Years

Fossils found in China indicate that dinosaurs may have benefited from flea collars! Ancient fleas, Pseudopulex jurassicus, have been dated to at least 165 million years ago.

These fleas obviously needed to be larger in size (17 mm long) with much larger mouthparts to get through the thick skin of dinosaurs.

Fossil records show that as mammals developed, fleas became more specialized to adapt to the variety of hosts available until finally developing into the tiny parasites we know today.

2. Fleas May Carry Serious Diseases and Parasites

Flea infestations are more than just itchy and annoying—they may also transmit diseases.

When dogs and cats groom themselves, they have the potential of ingesting fleas infected with the dog tapeworm (Dipylidium caninum). The immature tapeworm emerges from the flea in the dog’s digestive tract and grows up in the intestines.

Tapeworms can cause intestinal irritation and decreased absorption of nutrients. Severe tapeworm infections can even be linked to intestinal blockages in dogs, which require surgery. In rare cases, worms have even been found in humans—usually in children who have accidentally ingested a flea.

Fleas also transmit bacterial infections through their bites. Mycoplasma haemofelis is a bacterium that causes anemia in cats and is often transmitted by fleas.

Bartonella henselae is also transmitted by fleas from cat to cat. Most cats don’t show symptoms of this disease, but humans who are scratched or bitten by an infected cat develop a potentially serious disease called cat scratch fever.

Probably the most famous and deadly bacterium spread by fleas is Yersinia pestis.

Y. pestis is carried by the house flea and is responsible for the “black death,” or bubonic plague, which has killed millions of people throughout history.

This disease still infects and can kill humans today (notably in the western Unites States, due to prairie dogs carrying infected fleas), but modern antibiotics make recovery much more likely and have kept the disease from reaching historic plague proportions.

3. Fleas Love Blood

Fleas feed exclusively on blood and can ingest up to 15 blood meals in a day. Young kittens and puppies with severe flea infestations can lose enough blood from fleas to need transfusions.

Fleas can get blood meals from many different mammals. Rats, mice, rabbits, and other small mammals are common sources of the cat flea in and around the home.

If you are having difficulty eradicating a flea infestation, make sure your exotic pets are being treated as well!

Fleas will generally bite humans only if there are severe infestations in the household. Hungry, newly grown adult fleas can jump onto the nearest moving target hoping for a good host.

Fleas can jump at least a foot in the air, which is around 150 times their height!

4. Fleas Can Jump Surprisingly High

Fleas can’t fly and instead rely on an astounding ability to jump to get to a new host. Fleas can jump at least a foot in the air, which is around 150 times their height!

This means that even if you comb adult fleas off your pet daily, there’s a strong likelihood that an adult will easily jump back onto your pet from the floor. Due to fleas’ natural acrobatic skills, control of flea infestations requires treating both your pet and the environment.

5. Fleas Can Burrow Anywhere

While adult fleas are happiest in the fur of your pet and need blood meals to survive, flea eggs and larvae often fall into the environment and can develop normally anywhere the temperature and humidity are right.

This means that for every adult flea living on your pet, there are many more larvae living in your pet’s bedding, the furniture, and the carpets of your home—ready to develop jumping legs and re-infest your pet.

Luckily, fleas are very sensitive to normal detergents and can be picked up by the vacuum.

If you treat your pet with monthly flea preventatives or long-acting collars and topicals, diligently clean upholstered and carpeted surfaces, and wash bedding, most infestations can be resolved without environmental pesticides such as flea bombs.

Jamie Lovejoy, DVM


Jamie Lovejoy, DVM


Dr. Jamie Lovejoy graduated from Tufts Cummings School of Veterinary Medicine in 2012 after an undergraduate degree in Marine Biology. ...

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