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Key takeaways

Roundworms are a common type of intestinal parasite in dogs, acquired from consumption or contact with contaminated soil or prey species.

  • Pets are often asymptomatic but when present symptoms include coughing, vomiting, diarrhea, or a swollen belly, and sometimes worms are visible in the feces
  • Roundworms can pass from a pet to a person, or from a pet to a pet
  • Any pet showing symptoms or with parasites in their feces requires prompt treatment to prevent spread of the infection to other animals or people
  • Diagnosis is by stool sample
  • Treatment is dewormer medication, which voids the worms with fecal matter over a course of weeks
  • The prognosis is excellent in most cases, but may be guarded in severe infections, or infections affecting young puppies
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A closer look: Roundworms in Dogs

Roundworms are very common in dogs. Due to their widespread prevalence, routine deworming of dogs is a common practice, even if an infection has not been confirmed.

Roundworms can also pass from dogs to humans, and immunocompromised people are especially vulnerable. Any dog with roundworms requires immediate veterinary intervention to prevent transmission.

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Risk factors

Puppies, elderly dogs, or otherwise sick dogs are more at risk. Most roundworm infections are not an emergency, but require prompt veterinary care to treat the infection. In particularly severe cases, the worms can migrate through the lungs, causing pneumonia, which is a medical emergency.

In cases where larval migration leads to pneumonia, symptoms of respiratory compromise may occur.

In rare cases, the adult roundworms can cause an obstruction of the intestinal tract.

Possible causes

Roundworm eggs develop in feces in the environment. As the feces decompose, it contaminates the dirt beneath it. A dog coming into contact with contaminated soil through rolling in the dirt or licking itself after walking outside may become infected. Roundworm eggs are unable to develop into adults within the intestine, so increasing adult worm populations arise from repeated exposure to eggs in the environment.

Dogs can also become infected with roundworms through eating, licking, or biting an infected prey animal, such as birds or small rodents.

If a dog is pregnant, their puppies can be infected in the womb before whelping. In some cases, puppies may also acquire the infection through milk when they nurse from an infected mother.

Main symptoms

Roundworm infections usually produce no symptoms. Usually the worms stay inside the animal’s gastrointestinal (GI) tract, laying microscopic eggs.

In severe infections, or if a dog has been recently dewormed, the parasites may pass with the animal’s fecal matter. Roundworms look similar to spaghetti noodles.

Testing and diagnosis

An initial suspicion of roundworm infection is based on physical examination. Roundworm infections are confirmed via a fecal exam to identify the parasite eggs. False negatives are possible on fecal examinations, and sometimes multiple tests are necessary for diagnosis.

Steps to Recovery

Infections are usually treated with deworming medication, which targets adult worms so they pass in the pet’s stool. This medication only affects worms already in the intestines, so repeated treatments are needed to ensure all worms in the animal’s system have been removed.

With regular deworming, a roundworm infection typically resolves within six weeks. In most cases the prognosis is excellent. In cases of severe infections resulting in pneumonia, or infections in particularly young or old dogs, the prognosis is more guarded.

Deworming medication gets rid of worms in the dog’s body, but does not prevent the animal from becoming infected again in the future. Proper hygienic care, including removing feces from the environment, and checking for worms during a pet’s health checkup is beneficial.


Roundworm infections are contracted through fecal matter. Ensuring that feces is cleaned up promptly, and that a dog’s accessible area is kept clean, reduces the likelihood of infection. Bathing a dog can wash roundworm eggs or feces from their fur, preventing ingestion and the development of infection.

Following veterinary recommendations for deworming and checking fecal samples is important, especially for pregnant and breeding dogs. Missing or delaying doses decreases the effectiveness of the treatment.

Are roundworms in dogs common?

Roundworm infections are very common in dogs.

Typical Treatment

  • Anti-parasitic medication


No Author - Writing for Companion Animal Parasite Council
Wendy Brooks, DVM, DABVP - Writing for Veterinary Partner
Kristen Sarratt RVT - Writing for PetPlace
Dr. Aly Cohen - Writing for Cornell University College of Veterinary Medicine

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