Know Your Enemy – Fleas

It is said that the best offensive is a good defense and the best defense comes from knowing your opponent. In this installment of Know Your Enemy, we take a look at one of the most annoying pests: The Flea.

The Enemy

Fleas are flightless parasitic insects that feed on blood from mammals and birds. Their bodies are flat and reddish brown. Fleas do not have wings; however they can jump approximately 8 inches in height and 16 inches in distance.

There are four stages of the flea life cycle: egg, larva, pupa, and adult.

drawing of dog and cat scratching and flea in hair laying eggs

To view the flea life cycle please click on the picture (courtesy of Bayer – Animal Health)

After an adult female flea has eaten (blood from your dog, cat, or other small pets like guinea pigs and ferrets) she will lay a bunch of approximately 20 eggs at a time in the coat of your dog or cat. These eggs are small, white, and round. These eggs are designed to fall from your pet into the environment (like your house). Depending on temperature and conditions, the eggs can take from two days to two weeks to hatch (the warmer the environment, the quicker they will hatch).

Once the egg has hatched, the larva emerges. These are approximately 1/4 inch long, almost transparent, and legless. They do not like light and will hide surviving from predigested blood (the flea “dirt” you can see on your cat or dog). Within 5-20 days the larva will spin a cocoon and enter the third stage.

The pupae is the final stage before the adult flea is created. The cocoon protects the young flea and they will stay in the cocoon until there are signs of a host nearby (these signals include changes in temperature, vibrations, and body heat).The adult flea can emerge in as little as several days/a week, but they can remain protected for months, and in rare cases years before breaking free.

The final stage is the adult flea. This is the stage you are most likely to see on your pets or in your house. Once free from the cocoon, they immediately find a host for their first meal. A female will not start laying eggs until she has eaten. Once fed, they begin a cycle of breeding, laying eggs, and eating.  Most of their life (which can range from a few weeks to months) is spent on your dog or cat.

Signs and Symptoms

Fleas are not just an annoyance. Unlike other insects that can be found around your house, fleas can cause discomfort and pain for your dog, cat, and even yourself! There are many people and animals that are allergic to the flea’s saliva causing itching, redness, and rashes. Even those who are not allergic will still find the bites painful and irritating. It can takes weeks for the bite to completely heal.

Fleas can lead to hair loss due to continual clawing, biting, and scratching. In rare cases of extreme infestation, amenia (due to loss of blood) can be fatal. Secondary infections are common in infected animals from bacteria entering the wounds caused by the animal seeking to stop the itch.

Fleas can also transmit diseases. Remember the Bubonic Plague? It was caused the the fleas transmitting the bacteria between the rats and humans. Luckily the Bubonic Plague isn’t a threat to us and our animals, but fleas do transmit tapeworm (if your cat or dog ingests the flea while grooming) which requires medical treatment. Fleas can also pass on zoonotic diseases (diseases that can be passed from animals to humans).

Symptoms of fleas:

  • Your pet is scratching or biting at themselves more often.
  • You can see red bumps, hair loss, scabs, and papules (FAD = flea allergic dermatitis) at the base of the tail, belly, and armpits.
  • You can see flea “dirt” which is the already digested blood from fleas’ previous meals.
  • You can see actual fleas or flea eggs on your cat or dog.

Preventative flea treatment makes for a happy pet

Prevention and Treatment

Now that you know the life cycle of the flea, the big question is how to prevent or treat for fleas. There are many options; however, it is important to realize that prevention is worth a pound of cure. For every flea you see, there would be many more either on your pet or in the house. Regular preventative treatment is the key to a flea-free home.

The  veterinary suggested methods of flea prevention are topically applied (spot on treatments), oral (pills), and injectable. Spot on treatments are applied between the shoulder blades of the cat or dog monthly (for larger dogs, additional spots along the back may be used) and pills are given every 30 days. Both products can work by interrupting the flea life cycle and/or killing the adult fleas. The injectable treatment is for cats only, and lasts one month.

Another pill is available from veterinarians which only lasts two days; however, it kills fleas fast and can be useful if you find yourself battling a flea infestation.

For topical treatment your pet should not get wet (baths, swimming, etc) until the product has had a chance to dry. Specific topical flea treatments may also cover other pests such as ticks, ear mites, heartworm, and certain species of worms.


Pet owners must remember that care must be taken when treating your pet for fleas. While pill and spot on treatments are safe, we would suggest speaking with your veterinarian when choosing a method. Different products work for different animals. Age, breed, and health can all influence whether a specific product would be safe for your pet.

Using medication labelled for dogs for your cat can cause severe illness and possible death as they are much more sensitive to chemical use. Another concern is that not all flea treatments are created equal and we would always suggest visiting your veterinarian for the best product for your pet.

Happy dog

No fleas on me!


Not sure what flea treatment plan would work best for you cat or dog? Speak with your veterinarian for advice. Together, you can create the best offensive plan to protect your pet from fleas.

A final note: Remember when combating fleas year-round treatment is best. This stops the fleas from restarting a cycle of infestation on your pet or in your home.