What is it?

It is a flat worm, measuring between fifteen and seventy centimeters long, that mainly lives in the dog's intestines. 

Although the dog is it's principle host, meaning the host in which the parasites reaches maturity, it can also be found in the domestic cat. 

The parasite attaches itself to the intestinal cells by means of a scolex containing a retractable rostellum armed with thirty to one hundred and fifty small hooks and four suckers. 

It's scientific name is Dipylidium caninum.

The transmission

The cat becomes infected when it accidentally ingests fleas or louse who are carrying the parasite by biting itself in an effort to relieve the itching caused by these critters. 

The parasite cycle

As previously mentioned, the infection is acquired the moment where the dog bites itself to relieve the itching caused by external parasites. 

The digestion leads to the release of the parasite in the pet's intestine. Two to three weeks later, the adult worms lay eggs inside their segments. These will detach and are expulsed with the fecal matter and are then found in the environment. 

The eggs contained in the segments are released and ingested by a flea's larvae or, however rare, by louses' nits, which are also present in the environment or present in the animal's fur respectively. 

A few days after the fleas or louse have reached adulthood and have infected the animal, the Dipylidium eggs become infectious. 

When the fleas or louse are ingested by the animal, the life cycle begins. However, the life cycle cannot continue in the absence of this intermediary host. 

The symptoms

Usually, the cat does not show any visible signs of infection. 

However, itching around the anus can be observed when the segments are coming out of the pet. 

The diagnosis

The presence of segments in the cat's fur near the perineum or in their stools is a confirmation of the infection. 

We can also flatten one of these segments between as blade and slide, then examine the sample under a microscope to look for the eggs. We can usually count twenty-five to thirty per segment. 

Trying to confirm the infection by examining a stool sample through fecal flotation under a microscope is often deceiving because the segments are not uniformly distributed in the feces and the eggs do not always float. 

Is the parasite contagious to humans?

Unfortunately yes! 

However, a cat's lice is not contagious to humans as this parasite is species-specific.

The treatment

Although the infection is rarely associated with any symptoms, it is recommended to treat it for aesthetic and hygienic reasons.

There are various medications, sold under prescription, that are safe and effective to kill the parasite.

It goes without saying that we must also kill fleas or lice on the dog to avoid a new contamination!


It is best to use anti-flea medication administered preventively every month, from spring to fall.