The microscopic world of intestinal parasites (IP) may seem imperceptible, but this world really exists. One must know that a pet’s IP have the potential to spread to humans (zoonosis1). Some individuals are more vulnerable to zoonosis: seniors and immunocompromised, young children and pregnant women.

Here are the most common propagation methods:

With our animals

  • By ingestion of eggs, cysts2 or larvae found in feces, in wild animals or contaminated water
  • By the placenta
  • By breast milk
  • By larvae penetrating the skin

With humans

  • By ingestion of eggs from contaminated food, animal hair or hands dirtied by contaminated soil
  • By larvae penetrating the skin.

In North America, IP encountered are well adapted to our climate. They belong to the protozoa reign, or those helminths (worms). In the protozoa reign, we find giardia and coccidia. In the helminths reign, there is the ronds roundworm (ascaris), the hookworm (ancylostoma), the whipworm (trichuris) and the tapeworm (tenias).


The giardia affects different mammals, including humans, and is the most common protozoa. It causes fever, diarrhea sometimes with blood. It can produce a zoonosis.

The coccidia destroys the intestinal cells and limits food absorption. It’s widespread among young animals, the symptoms are chronic diarrhea, that may be bloody, and stunted growth. Many animal species can be affected and this infection can be transmitted to humans.


The ascaris larvae develop into adults in the animal’s gut. These worms lay microscopic eggs that are extremely resistant and can survive many years in the environment once excreted by the host. They are especially worrisome for puppies and kittens, because they cause a lowered immune system, stunted growth, digestive, respiratory and skin disorders. If in large quantity in the digestive tract of a young animal, the ascaris can obstruct the intestines. In humans, the ingested larvae can migrate to organs such as the eye or brain.

As the name suggests, Hookworm clings to the intestinal wall and feeds on the blood of its host. This blood loss causes decreased vitality in young animals. The adults have symptoms of diarrhea and weight loss. In humans, the larvae, migrate under the skin and cause skin irritationcutanée known as creeping grooves. These lesions cause rashes, but it is easily treatable once diagnosed.

Whipworms also feed on blood in the digestive tract of dogs and cats. They cause bloody diarrhea that can be fatal. Repeated treatments are necessary to eliminate this parasite. It is also a zoonosis in humans where it causes a skin infection with creeping eruptions. As for the hookworm, if the infestation is severe, it can cause anaemia.


The common tapeworms are not considered zoonotic in humans. Cats are more susceptible then dogs to have tapeworm. They get it by ingesting fleas and rodents which are the intermediate host. Eliminating fleas is definitely the first step to protecting your cat against tapeworm. It is the segments of the worm (rice grains) that are released into the environment.

Prevention Here are some preventive measures to eliminate and prevent infection due to PI :

  • Check for fleas on your pets
  • cover childrens sandsbox
  • wash your hands, bedding and children toys regularly
  • never drink water from a river or a lake
  • wear gloves when working in your garden
  • preventing cat hunting behavior
  • pick up and dispose of fecal matter
  • deworm adults two or three times a year
  • deworm puppies and kittens at regular intervals several times the first year of their life

In conclusion, regular deworming of your pet is important and remains the best way to protect you and your family from intestinal parasites that can cause a zoonosis!

Martine Lavallée, BAA and animal health technician 

1 A zoonosis is a transmissible disease from animal to human and vice versa.
2 A cyst has a highly resistant outer layer and is capable of surviving in extreme environmental conditions for years.