What is that?

Toxocara are intestinal parasites that lodge themselves in the small intestines of their host. The scientific name of the worm that affects dogs is Toxocara canis.  

The adult has a shape resembling sphagetti or a bean sprout and measures between 10 and 18 centimeters in length. 

It is the most frequently seen intestinal worm in Quebec. 

The symptoms

Cats often do not manifest any physical signs indicating that they have a parasitic infestation. 

Otherwise, the symptoms that are most often seen are diarrhea that may or may not be accompanied by vomiting. Worms are sometimes expulsed at the same time, but this is not always the case. 

Moreover, animals can lose weight despite a normal or increased appetite.

When there are many, worms can even cause an intestinal obstruction that can lead to a perforation.

The parasite life cycle

The adult worms lodged in the cat's intestines lay eggs that are secreted in the feces. 

In favorable outdoor conditions, the larvae housed in the egg continues to develop to maturity in approximately four weeks. The eggs become infectious, meaning that they can infect another animal, at the end of this period. 

They are then ingested by a cat and hatch in the stomach or small intestine. The now free larvae will initiate their migration and will reach the lungs where they will mature. 

Thereafter, they will go up to the larynx of the animal, will be expectorated, and then swallowed. Once they've returned to the small intestine, the larvae will become adults.

The life cycle lasts approximately one month. It begins the moment a dog infects itself by ingesting eggs present in the environment and ends when the adult worms housed in the intestines lay their eggs.

The eggs can survive up to 5 years in the environment.

The transmission

Transmission can be achieved in different ways: 

  • By ingesting eggs;
  • Transplacental; 
  • By ingestion maternal milk; 
  • By ingestion of a paratenic host such as a mouse, rat, chicken, etc. A paratenic host is one in which the parasite remains dormant and is not pertinent to it's development.

Is the parasite contagious to humans?

The answer is yes! Humans can contract this parasite by ingesting eggs present in the environment. 

However, the parasite's migration will be erratic in the human body because we are not normal hosts for Toxocara canis. For example, the parasite can often be found in the retina of the person's eye. Their occupying this site can cause problems with vision and can even lead to blindness!  

The diagnosis

The parasite's typical appearance confirms an infection. 

If there are no worms present to identify, we can examine a stool sample under the microscope in order to look for their eggs. These are slightly ovoid in shape with a thick doubled wall: the inner part is dark, while the outer part is clear.

Since the parasite's egg-laying is irregular, it is possible that no eggs are found in the stool sample, so more than one fecal analysis might be required. 

The treatment

There are several medications sold under prescription which are safe and effective to use to treat this parasite. 


It is important to collect the dog's stools as quickly as possible after their excretion to prevent the eggs present in the stools from becoming infectious. 

As a precaution, it is best to wear gloves when handling stools, and, above all, adequately wash your hands afterwards. Furthermore, vegetables grown in the garden should be thoroughly cleaned before being consumed. 

Antiparasitic medication should be administered preventatively to cats who have access to outdoors and for those having contact with outdoor cats. It should administered each month from spring until autumn. 

Do not hesitate to contact one our staff members to know which product is best suited for your pet!