Dog worms

During an annual health visit, your veterinarian has probably already told you about dewormer… and therefore worms. But what are these little beings that inhabit the intestines or other organ of your dog? Are they dangerous for his health? You will know about dog worms here.

What is a worm?

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Also called Helminths, worms are internal parasites. Helminths are classified into three categories:

  1. the nematodes (round worms);
  2. the tapeworms (tapeworms);
  3. and trematodes (rare in dogs).

There are different species of worms, which are found in various organs or tissues of their host. Indeed, even if most internal parasites occupy the gastrointestinal tract, others settle in the bladder, kidneys, lungs or even the heart and blood vessels.

How does your dog get infected?

Your little companion can ingest larvae or eggs present in its environment. In contaminated food or water, but also when ingesting prey, or simply via contaminated soil. Some worms are also transmitted during gestation or through breast milk, so puppies are real reserves of worms.

Symptoms of internal parasitism in dogs

Unless you see adult worms in your dog’s feces, it can sometimes be difficult to spot an infestation. The symptoms of it depend on the state of health, age and degree of infestation of your pet.

In general, the following symptoms can be a sign of the presence of worms in dogs:

  • Gastrointestinal disorders (diarrhea, vomiting, etc.),
  • Weightloss,
  • Growth retardation, bloating in the puppy (pear belly),
  • Dull coat,
  • Fatigue, depression,
  • Anemia,
  • Agitation…

During massive worm infestation, the lesions caused can be serious and lead to the death of the animal.

The main lines of the dog

Les ascaris (Toxocara canis, Toxascaris leonina)

Without doubt the most famous of puppy owners… the famous spaghetti! Round worm, it measures up to 20 cm once an adult and colonizes the dog’s small intestine. Roundworms feed on food intended for dogs. It is estimated that around 70% of puppies are infested with roundworms, as there is contamination via the placenta and breast milk.

In adult dogs, the larvae become encysted in various organs and then go to sleep. They will only complete their cycle to become adults during stress, illness or gestation of their host, laying eggs which will be excreted with the faeces and thus contaminate the environment.

Les Trichura ( Trichuris fox )

Round worm, nearly 4cm long. It is a common parasite of dogs and foxes. It is mostly found in breeding farms and kennels.

The dog becomes infected by ingesting the eggs present in the environment, which can survive for years in the environment. The parasite is present in the large intestine of the dog and is hematophagous (feeds on blood). It causes damage to the intestine and bleeding from the colon.

Dog worms

Les ankylostomes (Ankylostoma caninum)

Roundworm smaller than the previous ones, it barely reaches 1 cm. It lives in the small intestine, attached to the mucous membrane with its hooks. Contamination occurs through the ingestion of larvae or more frequently by the penetration of these larvae through the skin (in this case resulting in itching and skin lesions).

Les ténias (Dipylidium caninum, Echinococus…)

Dipylidium caninum is the most frequently encountered cestode (flatworm). This tapeworm has the particularity of coming out of the dog’s anus on its own. The adult worm is made up of thousands of small segments. Segments that we find, such as grains of rice, on the anal margins of the dog or on his sleeping place. The dog infests itself by ingesting fleas which are themselves contaminated.

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Cardiopulmonary worms

Dirofilaria immitis, responsible for heartworm disease, or heartworm disease, is transmitted by the bite of a contaminated mosquito. The larvae can develop in the heart and become adult worms up to 20 cm long.

Increasingly present, Angiostrongylus vasorum, is transmitted by ingestion of contaminated slugs, snails or frogs. This small worm about 2 cm long lives in the pulmonary artery and the right heart. It is at the origin of cardio-respiratory symptoms (cough, intolerance to exertion, breathing difficulties, sudden death, etc.).

Risks for humans?

If the worms are pathogenic for dogs, some also represent a danger for humans. Indeed, some are responsible for zoonosis, a disease transmissible to humans.


This is particularly the case with Toxocara. Ascaris larvae migrate through the body and may lodge in muscles, eyes or brain. This phenomenon is called Larva migrans. The dog contaminates the environment by excreting eggs in its feces. It is therefore through contaminated soil that humans infest by ingesting these eggs. In town, green spaces and play areas (sandboxes) constitute an area of ​​high contamination, children are therefore more exposed.

This is also the case with echinococcus-type tapeworms which parasitize the small intestine of dogs and especially foxes. They can cause serious liver damage and often death in humans who become infected by ingesting plants soiled by droppings, especially in forests or mountains.

Some tips to reduce environmental contamination

To reduce the risks for your little companion and those around you, some preventive measures should be observed:

  • Wash your hands regularly , especially after contact with a young (potentially infested) animal,
  • Regularly treat your little companion against internal and external parasites,
  • Adopt good hygiene practices such as picking up excrement,
  • Take care in high-risk areas (sandboxes).

Knowing that a worm can, on its own, lay 100,000 eggs per day, that they can withstand months or even years in the environment, prevention remains essential!