Canine Roundworms: Causes, Signs, and Treatment

Updated on August 21, 2019
alexadry profile image

Adrienne is a certified dog trainer, former veterinary assistant, and the author of "Brain Training for Dogs."

Learn about the species of roundworms that affect dogs, as well as the symptoms and treatment.
Learn about the species of roundworms that affect dogs, as well as the symptoms and treatment. | Source

Causes of Canine Roundworms

Roundworms are one of the most common parasites affecting puppies and dogs. There are three species of roundworms that mainly affect dogs: Toxocara canis, Toxocara cati, and Toxocara leonina.

  • Toxocara canis and Toxocara cati: In order to get infested with these types of rondworms, the dog must ingest the eggs, prey on an intermediate host, or, in the case of puppies, ingest the larvae passed from the mother's milk or placenta.
  • Toxocara leonina: In order to get infested with this type of roundworm, a dog must ingest roundworm eggs. The ingested eggs will hatch in the dog's small intestine and will multiply, giving birth to about 200,000 eggs that are passed in the feces. An intermediate host such as a rodent will ingest the eggs, and if the rodent is ingested by a dog, the life cycle will continue.

Therefore, puppies tend to get roundworms even before they are born. Adult dogs tend to get roundworms from ingesting eggs found in the soil or from ingesting animals infected with immature roundworms (usually rodents). A dog could even become infected by walking in an area where roundworm eggs are laid and then grooming its feet.

If feces are picked up after walking a dog on lawns and public places, the roundworms will not be given the chance to mature to an infective stage. This is why there are strict pick-up laws in public places or places where dogs tends to gather: The risks of roundworm infestation are pretty high!

In order for roundworm eggs to infect a dog, they must be in the soil for some time, generally from one to three weeks.

Signs Suggesting Roundworms

Roundworms may or may not be seen in a dog's feces. For this reason, it is important to have your veterinarian run annual fecal tests. With a fecal flotation test, the vet will see the presence of eggs in the feces. However, lack of eggs does not necessarily mean the dog is free of roundworms, since roundworms do not continuously shed eggs. Often vets will assume a dog is infected, especially when dealing with young puppies, and therefore will treat regardless.

If the worms are visible in the feces, they will be whitish or yellowish and resemble strands of spaghetti usually up to 6 inches long. The worms may be passed in the feces and move about, or they may be vomited live.

Not all dogs infected with roundworms will develop signs. However, dogs with heavy infestations may develop the following:

  • Diarrhea
  • Vomiting
  • A dull coat
  • Weight loss
  • Coughing. The larvae often migrate to the host’s lungs, causing a cough. The dog may cough them up and swallow them, allowing them in the intestinal tract.
  • Pneumonia

Puppies may develop a pot-bellied appearance and may fail to thrive.

Roundworm Treatment in Dogs

The most effective dewormers against roundworms are pyrantal pamoate (Drontal®, Strongid®) and fenbendazole (Panacur®). These can be found over the counter.

Because of the health risks associate with roundworm infestation, The American Association of Veterinary Parasitologists, recommends deworming puppies at 2, 4, 6, 8, and 12 weeks and providing monthly heartworm preventative that also kills roundworms.

Following treatment, worms are killed rapidly (the dewormer will anesthetize the worm so that it lets go of its grip on the intestinal tract and therefore dies once out of its environment) and the eggs will no longer be shed after two days. Dead or dying worms may be seen in the stool. A second treatment after two weeks is recommended to get rid of all stages of worms, since a new stage of worms may be migrating. Putting a dog on a heartworm preventives such as Heartgard Plus and Interceptor which also control infections with roundworms can be a great addition.

Can Humans Get Roundworms From Dogs?

Humans are not a regular host for roundworms,therefore, if the eggs are accidentally ingested, the larvae will not behave normally. Rather, they will migrate through the human body.

Trouble starts when the larvae migrate to the eye and then die, causing a condition that may lead to blindness known as ''ocular larva migrans'' which is more common in children aged 6 to 14. Children younger than five instead may be prone to visceral larva migrans, where the larvae travel to organs, but generally do not cause any symptoms.

Generally, direct exposure to the dog will be unlikely to cause problems, since it takes about two weeks for the eggs to become infective after being in the feces. There may be some small risks at times due to feces being caked in the fur near the rectum in small puppies, but generally they should be very few.

Backyards therefore remain the biggest risk area for roundworm eggs to infect. It is estimated that eggs can live in a yard for several years Because direct sunlight may kill the eggs, sunny areas of the yard, are generally safer before shaded areas.

Unfortunately, there are no products capable of killing roundworm eggs, they are quite hardy and capable of withstanding extreme temperatures and they appear to also be resistant to almost all disinfectants.

My foster Lab was diagnosed with tapeworms and roundworms.
My foster Lab was diagnosed with tapeworms and roundworms. | Source

My Personal Experience

I fostered a Lab Mix from my local shelter and since I saw some parasites in her stool, I collected a stool sample for the vet to analyze. It was evident she had tapeworms, since there were rice-shaped segments laying and moving around her stool. But the vet wanted to test the sample for other worms.

This because, dogs are prone to parasites that are not always visible to the naked eye. While often roundworms can be seen in the stool as they resemble long strands of spaghetti, they are not always visible depending on their stage of growth. So, despite stools appearing free of parasites, there can still be an abundance of them depriving your dog from essential nutrients.

The picture below shows before and after pictures of her stool. The first picture shows a normal stool that may appear free of worms, the second picture (quite graphic, do not look if you are prone to getting sick) shows dead roundworms being expelled just hours after giving her one tablet and as half of pyrantel pamoate.


The content below may disturb some viewers. Scroll at your own risk.

Picture of normal looking stool...(you do not have to necessarily see worms for a dog to have worms!)
Picture of normal looking stool...(you do not have to necessarily see worms for a dog to have worms!) | Source
Picture with dead roundworms hours later of administering dewormer.
Picture with dead roundworms hours later of administering dewormer. | Source

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

  • After giving my puppy worm medicine will I see dead worms in the stool?

    It depends on the type of worms your dog has and the type of dewormer product used. With my foster lab, I saw both dead roundworms and dead tapeworms in her stool. Often the worms just dissolve, but if there are large numbers of them, then it is possible you will see them in the stool and possibly again when she gets her next dose of dewormer.

© 2011 Adrienne Farricelli


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    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      7 weeks ago

      Hi Jess,

      With heavy parasite loads, it sometimes takes several deowormings to kill all the stages of these parasites.

      In order to get roundworms, your children would have to do what dogs end up doing when they get them. In other words, by eating feces which happen to have roundworm eggs in it. They cannot be transferred by the dog licking. The biggest concern would be making sure your children wash their hands after being in the yard where your dog's feces may be. Removing feces would therefore be important. Consult with your vet on whether a follow up de-worming may be needed.

    • profile image


      8 weeks ago

      Hi, we got a puppy today and the they said it had been dewormed. Of course when we got home it had worms in her stool. I told the puppy to the vet and unfortunately they couldn’t get a stool sample but treated the puppy anyways. We think it is probably round worm. We have small children and the puppy did lick one of them around the neck. Not the face. We will call the vet tomorrow to ask about this. What are your thoughts or advice?

    • profile image

      I gave my puppy trifexis two weeks ago. 

      17 months ago

      I seen dead worms in her poop after 2 weeks of a dose of of trifexis. Should I be concerned or wait the two weeks to go to my next scheduled vet visit? These looked like thick spaghetti.

    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      7 years ago

      Well, this hub is a bit disgusting since dog worms are just that way; but happy you find them inspirational after all!

    • profile image


      9 years ago

      Your posts are a real inspiration for people like me! Have a nice day!


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