Fleas are a common topic of conversation amongst pet owners. The blood sucking bugs have an amazing ability to make you itch just by thinking about them. Keeping them out of our homes and off of our pets is on most people’s priority list, but how does that work if you have both cats and dogs? Can cat fleas live on dogs?

To understand this better we should first go back and discuss what a flea actually is.

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What is a flea?

‘Flea’ is the common name for the flightless insect of the order Siphonaptera. This group contains around 2500 flightless insects. That’s a lot of fleas! Referring to our pets, they are often described as being in the category of external parasites (ectoparasites). This means a parasitic organism that lives outside the body, usually on the skin or fur. In comparison, an internal parasite is an organism which lives inside the body, and includes things like parasitic worms that live inside our pets organs. 

Fleas have 3 pairs of legs, 6 in total, and no wings meaning they are unable to fly. No flying means fleas have to find another way to move around, so instead they move by jumping. Incredibly, some species of flea can jump up to 200x their own body length! This is equivalent to a 6ft human jumping 1200ft! 

They jump by using their back legs to propel them up and forwards. They are thought to be one of the best jumpers in the animal kingdom. You can read more about the amazing ability of fleas to jump here.

Fleas get their nutrition from feeding on the blood of their host animals which they access by biting their hosts. Their mouths are able to pierce the skin of the animal, and they can then suck the blood from their host through the hole they have made.

How do fleas survive?

The life cycle of a flea is quite simple.

1) The adult flea finds a host. In this case the domestic dog or cat, by jumping onto them.

2) The adult flea pierces the skin of the host with its mouthpieces and sucks blood to take its first meal.

3) The adult flea mates with other adult fleas on the fur of the host and then lays eggs within the fur of the host. 

4) Flea larvae hatch from the eggs in the fur of the host and feed on blood and faeces of the adult fleas, known as flea dirt, to enable them to grow.

5) The growth process of a flea larvae takes around 5-20 days, at which point the larvae cocoon and are now in the pupa stage. In this stage the larvae are protected until they emerge from their cocoons as adult fleas. 

6) Adult fleas then emerge from the cocoons. This only occurs when there is a signal to the cocoon that food is readily available from a host; so the presence of warmth from the body or movement is needed.

7) Adult fleas begin feeding quickly after emerging from the cocoons and then the cycle begins again. 

As you can see from the above life cycle, fleas reproduce quickly. You can rapidly end up with a large flea population on your pet and in the environment in a short amount of time. Critically, when fleas are inside the cocoon, before they emerge as adults, they are quite well protected from the environment. So insecticides are less likely to be effective on them at this stage. This can be why animals and the environment need repeat treatments of flea products in order to get rid of all fleas at different life stages. 

Are all fleas the same?

No, as discussed before, the order Siphonaptera contains around 2500 insects that are commonly referred to as fleas. These fleas are all different species, in the same way a gorilla and an orangutan are both great apes, they are different species and entirely different animals. Despite being different species they are not host specific. This means that although they may have a preference of who their primary host animal is, they can still happily live on a wide range of other animals. 

For example the dog flea, scientifically known as Ctenocephalides canis, has a primary host of the domestic dog, but it also happily lives on a number of different mammals including the domestic cat, despite being called the dog flea. The dog flea mostly feeds on the blood of dogs and cats but can also bite humans. 

So what about the cat flea? Do I need to worry about my dog?

The cat flea, Ctenocephalides felis, has the domestic cat as its main host. However despite this, cat fleas are still really commonly found on dogs and other mammals. In fact the cat flea makes up 90% of the species of fleas found on both domestic dogs and cats. Despite its name, the dog flea is less common and most dogs actually have the cat flea on them. So yes, the cat flea has a deceptive name, and is commonly found on both domestic dogs and cats, as well as a wide range of other mammalian species. 

Can cat fleas live on humans?

No, cat fleas, like the majority of other species of fleas, can’t live on people. That said, they can (and will!) bite people. But they won’t live on their skin or in their hair the same way they will with dogs and cats. 

Can cat fleas live in my house?

Yes they can. Cat fleas, like many other species of flea including the dog flea, can survive well in the environment thanks to the cocoons that the pupa live in. This means fleas can infest your house without you knowing and then re-emerge as adults and jump back onto your pets. Common places flea cocoons can be found include the carpets, upholstered furniture such as the sofa and other plush furnishings. They can also commonly be found in pet bedding and baskets. 

Are fleas dangerous to humans or pets?

Fleas can carry a number of diseases that can affect humans and pets including cat scratch disease (Bartonella henselae); and in high risk areas, they can even spread the plague (Yersina pestis). Fleas infect individuals by biting them and passing the diseases in their saliva.

In addition to being able to transmit diseases, fleas cause irritation to their hosts by biting them and making them itch. In some cases animals can have allergic reactions to the presence of fleas and flea dirt on their fur. 

What should you do if you think your pet may have fleas?

Certain flea products are available for over the counter purchase from local pet stores. However it is advisable if you notice your pet scratching and are worried they have fleas that you get them examined by your veterinary surgeon. 

Your vet will be able to assess them and look for evidence of fleas and flea dirt. And also assess if they have any other issues which may be causing them to itch or if they are reacting to the presence of fleas. 

If your vet finds your pet has fleas they will be able to offer you a wider range of treatment options than what is available in your pet store. And they will also discuss with you how best to treat your house and environment to prevent re-infection. 

It is important to remember that a pet itching and scratching does not mean they necessarily have fleas. There can be a number of other conditions that can cause a pet to show these signs that will require further treatment and assessment by a veterinary surgeon. 

Summary:

  • Fleas are an insects that can live on many species including cats and dogs; but usually not on people
  • Fleas complete most of their life cycle whilst on their host and feed on the blood of their host for nutrition 
  • Fleas can transmit a number of diseases when they bite their host that can be of concern for both humans and pets
  • Despite the name cat fleas are some of the most commonly found fleas and live on both dogs and cats and can also bite people
  • Fleas can survive in the household environment and are often found in carpets, upholstered furniture and pet bedding
  • If your pet is scratching and you think your pet may have fleas it is important to get them assessed by a veterinary surgeon

Further reading