ticks and fleas

Fleas on Dogs

Flea is the general name for wingless insects of the order Siphonaptera. They have mouthparts adapted for piercing the skin and sucking blood. There are more than 2000 different species of fleas. Fleas are found all over the world and they bite just about all warm blooded terrestrial animal.

Fleas go back a long time. There even exists fossil fleas equipped to feed on dinosaurs!

The Dog flea is: Ctenocephalides canis. Although it prefers dogs, it will also bite many other animals including cats. In North America if a dog has fleas it is most likely to be a Cat Flea NOT a Dog Flea. Like the cat flea, the dog flea carries tapeworms (Dipylidium Caninum)

Although the flea that mostly attacks dogs is the cat flea, Ctenocephalides felis, actual identification does not matter very much because the life cycle and treatment methods are the same. The dog flea is more common in Europe than in N.America.

BOTH cat and dog fleas can pass on tapeworm to their host.

Because cats are very sensitive to poisoning, Dog Flea medicine should NEVER be used on a cat.

Although Cat and dog fleas will bite humans any egg produced will not hatch. A researcher found that a flea had to feed continually on human blood for 12 consecutive hours to produce viable eggs.

Some people have strong reactions to flea bites, and the flea can carry nasty bugs of its own. This is mostly harmless to people with normal health but can be more dangerous to people with compromised immune systems.

Fleas can transmit diseases and worms to dogs.

photograph of a fleaphotograph of a flea

What does a flea look like?

Fleas are flattened insects that have no wings but have large back legs which allows them to jump up to several feet in distance. The same large jumping feet also helps move them quickly in animal fur. The backwards pointing hair over the legs and body also helps them move in fur. Fleas are quite flat and slippery which also helps them to move well in hair.

Colour ranges from reddish brown to black.

For more detail on how what fleas look like, here is my web page on what fleas, eggs, larvae and pupa look like I wrote it while I was researching fleas in cats but found that there is very little differences between dog and cat fleas and most so called dog fleas are actually cat fleas anyway.

Life Cycle of the Flea

After a suitable blood meal the female flea lays her eggs on the coat of the host. The dry eggs are slippery and fall off the animal to hatch. The incubation period is 2 to 21 days, temperature and humidity are the main reason some eggs take longer and others less time to hatch. Flea larvae do not hatch on the dog usually, rather they fall off wherever the dog spends most of its time.

cat flea larva

Flea eggs hatch into larvae. The larva are repelled by sunlight and bright lights so they move to escape to darker spots such as cracks in floorboards/baseboards or in cosy carpets. They will also wriggle into the dog's bed where they find lots of food. The flea larvae eat organic matter and in particular feed on flea dirt, the adult flea fecal matter that drops off the dog. One of the ways of finding out if your dog has fleas is to ruffle and shake the dog,s fur over a white paper and check for black spots that turn rusty brown when wet.

After a few days to weeks depending on conditions, flea larvae then spin a sticky cocoon, that is quickly covered by whatever debris is around. This hides the cocoon very well. It's very difficult to see them because the camouflage makes it almost impossible to spot. The flea pupates quietly in its cocoon. Once ready to come out it waits till conditions are good. This wait can last several months. When the warmth, availability of food, vibrations, carbon dioxide and humidity of a potential host is just right, the adult flea hatches. The cat flea has been extensively studied. The pupal stage can be as short as 4 days.

Because of the sturdy cocoon which protects it, it is very difficult to kill a flea pupa.

Within 48 hours of emerging the young flea must starts feeding. Details on the Life Cycle of the Cat Flea

flea diagram

Fleas are not a fussy, and will feast on dogs and cats, skunks, rabbits, raccoons, squirrels, foxes, weasels, calves, and humans as well as many other animals.

Once it has fed the female flea can produce eggs.

A female flea can produce about 40 eggs a day and lives up to a year.

Higher summer temperatures and humidity are better for flea growth. Preferred conditions are 27C-32C with 75-92% relative humidity.

How does a Dog get infected with Fleas?

Anywhere an animal which has fleas has been, is a potential spot of infection.

In and around the house, fleas will be hatching where the dog spends most time: his bed, the couch, a special spot on the floor, a cool spot under a tree, in the carpets where the dog hangs out.

Hanging out with buddies in the park can also get your dog in contact with fleas.

An actively grooming cat can reduce the adult flea population it carries by 50%. Dogs on the other hand don't groom as much and are far less flexible than cats so are not as good as cats in ridding themselves of fleas.

Effect on the Dog

A few fleas are not particularly harmful. However it's not very comfortable to be itchy and a small flea population can grow quickly. Fleas should be controlled. Fleas can also carry some nasty parasites and diseases.

Fleas can attack humans and can carry some nasty bugs. Children who have eaten fleas have become infected with tapeworms.

Sometimes fleas cause allergic reactions on the host dog. This is called flea allergy dermatitis. Link to an article on flea allergies.

Large infestations, particularly on small animals can cause dehydration or severe anemia.

Over grooming and scratching can result in scabs, hair loss and skin irritation and infections.

Secondary infections can set in. In that case antibiotics or anti-fungals might be necessary to clear up the skin.

Fleas can transmit some diseases and parasites


Dipylidium caninum, is a tapeworm that can infect dogs, cats, and humans.

Tapeworm Eggs are passed in the dog or cat's feces and ingested by fleas. In order to get infected with tapeworm, the flea then needs to be ingested by another mammal, dog or cat grooming is a common way of eating fleas. Ctenocephalides felis, the cat and dog flea, can spread this tapeworm. In order to be infected a human has to ingest an infected flea.


This is a skin inflammation caused by flea bites. including Ctenocephalides felis, the cat flea. Symptoms might include skin burning feeling, itching, rash, mouth ulcers, irritation, swelling. In some people the reaction can cause soreness and restlessness. More rarely condition can spread to the lymph system and nervous system and become quite serious. Unless it gets infected it is mostly not too serious. Cortisone cream is often prescribed to reduce irritation.


Tularemia (rabbit fever) is caused by a bacteria, Francisella tularensis and is found in rabbits and rodents. Dogs and cats can also become infected and transmit the disease in their fleas.It can be quite serious in Dogs causing fever, enlarged lymph nodes and lethargy. It can be transmitted to humans. Although not common, it is a serious disease.

Many other diseases can be transmitted by fleas. Although not common it happens. Bubonic plague and Murine typhus are other flea transmitted diseases.

Here is a link to a paper on Diseases carried by fleas.

How do I know if my dog has fleas?

For a more detailed article on how to check for fleas on a cat, here is my flea checking page. The same method can be used on dogs.

Flea Control

Because it is almost impossible to completely eliminate all fleas, eggs, larva and pupa, most vets talk about control.

A successful flea control campaign will include several fronts. In particular, adult fleas, both on and off the animal need to be eliminated then eggs, larvae and pupa are targeted.

All Flea Treatment will include killing adult fleas on the dog. A number of treatments exists for dogs. Either applied directly to the animal or taken as medicine by mouth or injected. It is best practice to use both an adulticide, to kill the adult fleas, as well as an insect growth regulator. IGRs target a specific process of the flea development and are very safe for other animals that do not have this process. For example many Growth Regulator interfere with the production of Chitin, which is what the insect shell is made from. Since humans and Dogs don't produce Chitin, the growth regulator has no effect on them. It only affects the flea.

Treatment of the dog's surrounding: involves treating the house, outside areas where the dog goes, and the dog's bed and furniture where he sleeps.

Again an insecticide that targets the adult fleas and an insect growth regulator are recommended.

One way of identifying where fleas are is to use a flea trap. Here is an example: Victor M230 Ultimate Flea Trap (Pack of 2, Multy) The heat of the lamp attracts the flea and when it hops in, it gets stuck in the sticky base. This will not eliminate many fleas but might be a way of figuring out if and where the fleas are. There are many DIY alternatives, such as putting a lanp on the floor and placing a bowl of soapy water under it.

Treating the dog will get rid of the fleas and treating the bedding and area where the dog has been will get rid of the eggs, larvae and some pupae, plus any adult that happens to be there.

There is more need for flea control in the warmer months. Because of the ability of the flea to slow down its development in poor conditions, a flea infestation can persist for several months with no animal present.

University of Kentucky has a good article on Ridding Your Home of Fleas. Flea and Tick Control

Insecticides and Growth regulators are effective but a good easy way of controlling fleas is with frequent vacuuming of the areas where your dog sleeps and hangs out. Vacuuming is also non toxic. Some dogs even let you vacuum them. Make sure you empty the vacuum after because fleas are tough characters and will crawl out of the vacuum bag.

Washing the dogs bed cover in hot water and drying in hot dryer is very effective in controlling larvae and eggs and some pupa.

Specific Recommendations?

It is almost impossible to make a general recommendation. Regional differences are so great that chosing the right combination of products is not possible.

Besides Fleas, is there a danger of ticks? heartworm? worms? mosquitoes? Do you live in an area where there is regular insecticide use such as apartments which regularly spray for roaches? Another question is cost. Many of the newer monthly combination treatments are very effective and quite safe, but are expensive. They might target: TICKS, HEARTWORM, EAR MITES, TAPEWORM AND ROUNDWORMS, MOSQUITOES, LICE and more.

Different insecticides are licensed in different geographic areas.

Where does your dog live, in an apartment, a farm, does he go to a dog park, is he exposed to many other animals?

Once you determine the conditions check with an expert. Check with your vet, or with the the ministry of Agriculture or with Public Health departments or agricultural extension office, for what is recommended and approved in your area.

Do you have other pets? or children? Medicines and insecticides that are safe for dogs can be deadly for other pets. Fish for example are very sensitive to pyrethrins while permethrins are deadly to cats. Check with your vet.

Products that target multiple infections are not necessarily the best one for EACH. So it is often better to give 2 or 3 different treatments to cover all the bases.

There are a great number of products available to control fleas. Some are very effective and quite safe. There are also products that are quite toxic and can do a lot of harm. If there is a cat in the household, any product used on the dog can be toxic to the cats. PERMETHRIN should never be used on or near a cat. It is deadly to cats. Because cat's livers don't produce some of the toxin destroying enzymes, they are much more sensitive to poisoning than dogs.

Read my page on how to control and kill fleas on cats. It has detailed information on flea control that apply to dogs and cats.

I also have a page on less toxic flea control products and methods

Some Images for this article are from Wikipedia the rest are mine.

emails: Christine

This article is provided for information only. It is not to be used instead of consulting a VET. If your kitty is sick get some help.