Roundworms In Dogs: Symptoms, Treatment & Prevention

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Roundworms under microscope (caption:Roundworms In Dogs)

Roundworms are the most common worms in dogs, and many young puppies get infected. Although routine de-worming can prevent serious problems, it’s important to know how to spot the signs of a roundworm infestation in your pup. Left untreated, puppies and even some adult dogs can become very ill.

What Are Roundworms?

Roundworms are tubular-shaped, pale-colored intestinal parasites that affect almost all dogs at some point, particularly in puppyhood. There are 2 main species of roundworms in dogs: Toxocara canis and Toxascaris leonine. Toxocara canis can cause more significant health problems, can be transmitted to humans and can grow up to several inches long.

Puppies are most susceptible to health threats from roundworms because their immune systems aren’t mature enough to fight them off. The worms feed off of partially digested food in the intestinal tract, and if there are a large number of roundworms, they can rob a puppy of vital nutrients and cause stunted growth. 

How Do Dogs Get Roundworms?

There are several ways dogs get roundworms.

From The Mother

First, puppies can be born with them. Roundworm larvae can migrate from the intestine and become enclosed cysts in the body’s tissue. If this happens in pregnant dogs, the encysted larvae can cross through the placenta into an unborn puppy. The larvae can also migrate to the mother’s mammary glands and be passed to puppies through milk.

From The Environment

While in the intestine, adult roundworms shed eggs that then get passed into the environment through an infected dog’s feces. Other dogs can become infected by sniffing or licking infected feces or soil, plants or other objects that have been contaminated by infected feces.

From Eating Contaminated Animals

Several small animals, such as rodents, birds, earthworms and some insects, can act as carriers for roundworm eggs. These animals aren’t the roundworm’s normal host, so the eggs never mature in them. But if your dog eats these “transport hosts,” the eggs can then grow into roundworms inside your dog.


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Some dogs won’t ever show symptoms of roundworms, but here are the most common signs.

  • Bloated stomach
  • Diarrhea
  • Vomiting
  • Malnourishment (including weakness and poor growth)
  • Coughing (larvae can migrate to the lungs and cause respiratory symptoms and even pneumonia in some cases)
  • Worms in vomit or feces (3-5 inches long, pale-colored, round-shaped)

Diagnosis & Treatment

Your vet can diagnose roundworms by examining a stool sample for the presence of eggs. Since roundworms are extremely common in young puppies, most vets assume their presence (especially because eggs aren’t always present in feces). So regular de-worming is a routine practice for young puppies.

Veterinarians also treat adult dogs with a de-wormer. Keep in mind, however, that this treatment is only effective for fully-grown worms living in a dog’s intestinal tract, not for larvae or eggs. So it’s important to administer a full course of de-wormer prescribed for roundworms to ensure that you completely eradicate the infestation. Your vet will tell you how long to continue treatment.

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The most commonly prescribed medications for roundworms include:


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Many monthly heartworm preventative medications also help prevent roundworms as well as hookworms. So be sure to ask your vet which one they recommend. Some of the most commonly used heartworm preventative medications that also prevent roundworms include:

You’ll also want to decontaminate your environment to prevent future roundworm infestations. Eggs that are shed into the environment through feces turn into infective larvae within several weeks. These larvae can live in soil, on plants and other objects for years. So your best course of action is to clean up your dog’s poop immediately. Find the best pooper scooper and poop bags here.

Can Humans Get Roundworms From Dogs?

If people swallow the eggs of Toxocara canis, the eggs can become larvae and invade human tissues and become encysted in various organs. Although the larvae don’t fully mature into adult roundworms in humans, this can still cause eye, lung, heart and neurologic problems in rare cases.

This is most likely to happen when children are playing outside and get contaminated dirt in their mouths. So be sure to keep your yard clean from dog feces and don’t let your kids play in parks or playgrounds that are soiled with pet feces. In most cases, roundworm infections aren’t serious and many people who are infected may not notice any symptoms.

What Do Roundworms Look Like In Dogs?

The video below shows how roundworms look when they are matured. As you can see, they are tubular-shaped and pale-colored and can be several inches long. They’re similar in appearance to a white or tan spaghetti noodle.

Roundworms in dog poop can appear as eggs or the spaghetti-like noodle in the video above. Dog poop needs to be examined under a microscope to determine if roundworm eggs are present.

Frequently Asked Questions

Here are the top questions our readers ask about roundworms.

How Long Does It Take To Get Rid Of Roundworms?

The majority of roundworm cases are resolved by administering a medicine that kills the worms in roughly 3 days. However, infection can reoccur, which is why it’s important to eradicate it entirely from the yard and pick up your dog’s poop immediately.

Other Common Dog Parasites

Not sure your dog has roundworms or another type of worm or parasite? Be sure to read our comprehensive article on worms in dogs, where we explain common symptoms and treatments for heartwormshookworms, roundworms, tapeworms, whipworms as well as other intestinal parasites.

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