Canine Roundworms: Causes, Signs, and Treatment

Updated on September 16, 2015

My foster Lab diagnosed with tapeworms and roundworms.


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.
  • Toxicara 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 which 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). All that may be needed is walking in an area where roundworms eggs are laid and then the dog grooms its feet to become infected. If feces are picked up after walking a dog on lawns and public places, the roundworms will not be given a chance the chance to mature to an infective stage. This is why there are strict laws in public places, or places where dogs tends to gather: the risk of roundworm infestations 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 diarrhea, vomiting, a dull coat, and weight loss. Puppies may develop a pot bellied appearance and may fail to thrive. 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. Heavy infestations may cause pneumonia.

Roundworm Treatment

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 provide 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?

Humans are not a regular host for roundworms,therefore, if the eggs are accidentally ingested, they 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.

Effective dewormers

8in1 Safe-Guard Canine Dewormer for Large Dogs, 3 Day Treatment
8in1 Safe-Guard Canine Dewormer for Large Dogs, 3 Day Treatment

Safe and effective for the treatment and control of: tapeworms, roundworms, hookworms, whipworms.


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 pyrantal pamaote.

Viewer dicretion advised: may make you lose your appetite! Picture of normal looking stool...(you do not have to necessarily see worms for a dog to have worms!)


Viewer dicretion advised: may make you lose your appetite! Picture with dead roundworms hours later of administering dewormer


Questions & Answers


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      • alexadry profile image

        Adrienne Janet Farricelli 5 years ago from USA

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

      • profile image

        Josefina 6 years ago

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