Roundworms in Dogs
Roundworms in dogs are extremely common. In fact many puppies are born with the parasite. Roundworms are easy to spread and difficult to control. Learn more about the symptoms and treatment of canine roundworms here.

Roundworms, aka ascarids, have different species. Adult roundworms have a rather thick body and can grow up to 7 inches (18 cm) long. They live in dogs’ stomach and intestines.

The two species that most commonly infect dogs are Toxocara canis and Toxascaris leonina.

Roundworms are the one worm parasite that can frequently be found in dogs and cats.

Over 95% of puppies are born with roundworms. A female worm can lay – get ready for this – 200,000 eggs in one day!

The egg has a hard outer shell so it is very hardy and can live for months or even years in the soil.

Dogs can pick up the worms in various ways. Therefore, they can get infected easily.

Life Cycle of Roundworms

It is important to understand the life cycle of roundworms in dogs if we want to use effective treatment to eradicate them.

The life cycle of T. canis in dogs is as follows:

  • Eggs are passed in a host’s feces.
  • Dogs pick up the eggs from soil (usually in the course of normal grooming) and they hatch in the dog’s stomach and intestinal tract.
  • The larvae burrow their way out of the intestinal tract to encyst in the dog’s other body tissues, usually the liver.
  • When the right time comes, the larvae excyst and, using the dog’s circulatory system, get to the lungs of the dog.
  • Once in the lungs, the larvae burrow into the small airways and crawl up the dog’s windpipe.
  • The larvae are coughed up into the dog’s throat where they are swallowed.
  • Back in the intestinal tract for the second time, the larvae develop into adult worms.
  • The adult worms pass eggs that become infective in soil in 3-4 weeks.

Four Ways to Get Infected with Roundworms

There are four ways that a dog can get infected with roundworms.

  • Prenatal Infection: This can occur when the encysted roundworm larave migrate through the placenta and infect an unborn puppy in utero. The larvae migrate to puppy’s lungs and, when the puppy is born, the larvae will be coughed up from the lung into the puppy’s mouth, which are then swallowed. They then take up residence in the puppy’s digestive system and grow into adults in the puppy’s intestine.
  • Infection While Nursing: Some roundworm larvae may migrate to a bitch’s mammary gland and they will be ingested by the young pups through the mother dog’s milk. The larvae then migrate to the young puppies’ stomach and intestines where they grow into adult worms.
  • Ingestion of Roundworm Eggs : Puppies and adult dogs can get infected by roundworms by ingesting eggs in the soil.
  • Ingestion of an Intermediate Host: Eggs of roundworms can be carried by other animals that act as intermediate or transport hosts. A dog can become infected with roundworms by eating one of such intermediate hosts, e.g. a rodent or a mouse.

Symptoms of Roundworms in Dogs

Essentially, the signs and symptoms of roundworms in dogs depend on various factors, such as how old and how healthy the dog is; where the worms are located inside the dog’s body; and whether the dog is infected with adult worms or other life stages of the worm.

Aduld dogs with roundworms seldom show symptoms.

In puppies older than 2 months of age, they may show symptoms such as intermittent vomiting and diarrhea.

Worms that look like strands of moving spaghetti may be found in the stool or vomitus.

If a very young puppy is infested, it will result in severe illness or even death.

Besides causing vomiting and diarrhea as described above, if a puppy is infested with adult worms, you can also see the following signs and symptoms:

  • The puppy shows signs of pain in the stomach
  • The puppy has a pot belly
  • The puppy will lose weight
  • The hair coat will be dull
  • The puppy will not thrive

If the infestation is serious, the puppy may become anemic. A large number of worms in a small puppy’s small intestine can cause intestinal obstruction which is fatal.

When the roundworm larvae migrate to the puppy’s respiratory system, the larvae will cause coughing and breathing difficulty in the puppy. Sometimes pneumonia will result.

Diagnosis and Treatment of Roundworms in Dogs

If you find worms in your dog’s stool or vomitus, there is a good chance they are roundworms (especially in a puppy).

Newborn puppies should have fecal tests for the presence of roundworm eggs.

Older puppies and adults should also be tested for roundworms regularly.

Conventional treatment of roundworms in dogs is using deworming medications. There are quite a few effective dewormers, some are over the counter and some are prescription.

Dewormers work by anesthetizing the adult worms. As a result, the worms cannot hang on to the dog’s intestines and can be passed with the stool.

It is therefore not uncommon to see worms (alive and moving) in your dog’s stools after a course of deworming treatment.

Dewormers cannot kill worms that are in their larval stage, so a second, and sometimes even a third deworming is needed to get rid of worms that were in the larval stage during the first deworming treatment.

With the above in mind, puppies should be dewormed by 2 weeks of age, and deworming treatment should be repeated at 4, 6, and 8 weeks of age.