Roundworms in Dogs

Facebook Icon Twitter Img Email Img Print Img

Roundworms are common canine parasites that can significantly impact puppy health as well as posing potential risks for humans. The most common type of roundworm in dogs is Toxocara canis, although dogs do occasionally pick up other species of roundworms.

Roundworms commonly affect puppies. Being aware of the signs of a roundworm infection in dogs will help you detect a possible infection before the intestinal parasites cause lasting damage or fatalities.

Signs & Symptoms of Roundworms in Dogs

The symptoms of roundworms in dogs are similar to the signs of other intestinal parasites.

  • Dull haircoat
  • Pot-bellied appearance
  • Secondary cough in young puppies due to pneumonia
  • Poor growth rate
  • Decreased body condition
  • Vomiting (may see worms in vomit)
  • Diarrhea with mucus (may see worms)

The first thing most owners notice about a puppy or dog with roundworms is a slow growth rate and an overall loss of condition. Although some dogs with roundworms are asymptomatic, they often present with dull coats and a pot-bellied appearance, which may come on gradually. As the infection worsens, you might notice vomiting and diarrhea, and may even see worms, which look like pieces of white spaghetti. Puppies with severe cases can develop pneumonia, which is caused by migrating larvae. Roundworm infections in puppies can be fatal.

How Did My Dog Get Roundworms?

Dogs contract roundworms from infected environments or during pregnancy. The most common method of infection for puppies is during gestation, where roundworm larvae pass through the placenta and into the puppy. Puppies are then born already infected with roundworms, which go on to mature in their intestines.

Common causes:

Dogs older than three months become infected with roundworms through their environment, which can occur when dogs come into contact with contaminated soil, like a sandbox used by outdoor cats or soil contaminated by other dog feces. Once ingested, roundworm eggs hatch, penetrate the intestinal mucosa, and make their way to the lungs, where they are coughed up, swallowed, and mature to adulthood in the small intestine. They then lay the eggs that are passed into the environment, completing the life cycle. However, in older dogs, the larvae often migrate to organs, connective tissues, and other types of tissues. These larvae remain dormant, causing few if any symptoms, until something like pregnancy triggers them.

Transplacentally and through environmental contamination are the two leading causes of roundworm infection in dogs. Transplacental infection is most common in puppies, whereas environmental contamination is the most common cause of roundworm infections in adult dogs.

Diagnosing Roundworms in Dogs

Veterinarians diagnose roundworms in dogs based upon clinical signs and a fecal analysis. Your veterinarian will look for evidence of roundworm eggs in the fecal sample, and they will also determine which species of roundworm your dog is infected with to determine if there is a risk that it has been passed to yourself or other humans in the household.

Roundworm eggs are spherical and pitted, and adult worms may show up in samples from dogs with heavy parasite loads. However, eggs do not always appear in fecal samples. This is because sample sizes are small, and eggs may shed intermittently. If your veterinarian suspects that roundworms are the cause of your dog’s condition, or if you have seen evidence of roundworms in your dog’s vomit or feces at home, they may recommend treating for roundworms even without a definitive diagnosis. Repeat fecal testing can lead to a definitive diagnosis in a later visit, and determining the parasite is essential for preventing the spread of the disease to humans.


Veterinarians use fecal testing to diagnose roundworms in dogs. Clinical signs, like a dull coat and a pot-bellied appearance, may also point toward a roundworm infection.

Treating Your Dog for Roundworms

Treating roundworms in dogs is relatively straightforward. After making a diagnosis, your veterinarian will most likely prescribe a dewormer, like fenbendazole and pyrantel, or milbemycin. These medicines eliminate worms from your dog’s intestinal tract. Once the initial parasite load is eliminated, it’s important to prevent reinfection by continuing treatment with a monthly preventative that targets roundworms.

Puppies with severe infections may require additional treatment to resolve their symptoms. Roundworms in puppies can lead to pneumonia and abdominal fluid, which may require supportive care to resolve, along with antibiotics to prevent secondary infections. Because some puppies with roundworms are asymptomatic, routine deworming of puppies is often recommended.

Is there a cure for roundworms?

Yes. Medications like fenbendazole will cure the initial roundworm infections, and monthly preventatives that contain dewormers can decrease or completely eliminate future infections.

Are Roundworms Contagious For Humans or Other Pets?

Toxocara canis is a zoonotic disease, which means it can be transmitted to humans and other dogs in the household. Humans must swallow infective eggs in order to be infected with roundworms, which can happen after handling feces or infected soil. Most cases of roundworms in humans are asymptomatic, but fever, elevated white blood cell levels, and enlarged liver can occur. As the larvae migrate, then can cause a condition called visceral larva migrans. If the larvae migrate to the eye, they can settle in the retina, impairing vision and even causing blindness.

Recently, veterinarians have detected a rise in another type of roundworm found in dogs called the raccoon roundworm (baylisascaris). The raccoon roundworm also has a zoonotic potential, which can lead to visceral and neural larva migrans.

What is the cost for treating roundworms?

When treating roundworms, you can expect to pay for the cost of the initial office visit and diagnostics, as well as follow-up visits and fecal testing to determine if the medication is working. Deworming medications are relatively inexpensive, and veterinarians recommend continuing treatment with a monthly preventative that targets roundworms. These preventatives should be given for the rest of the dog’s life.


Roundworms in dogs are a treatable intestinal parasite. After a diagnosis, veterinarians will prescribe a dewormer that eliminates roundworms from the dog’s system.

Recovery and Management of Roundworms

In most cases, you can expect your dog to recover from a roundworm infection and return to full health. Severe cases, especially in puppies, may require hospitalization and supportive care, and can be fatal if left untreated.

Once the initial infection has been treated, you will need to continue monitoring your dog for signs of infection. Keeping them on a monthly preventative that targets roundworms will help reduce the risk of reinfection, as will picking up poop immediately to avoid environmental contamination.

It is a good idea to take precautions if your dog has been diagnosed with roundworms. Wash your hands after handling feces and potentially contaminated soil, and educate younger members of your household about proper hygiene.


Managing a roundworm infection requires additional monitoring. Expect several follow-up visits to your veterinarian, along with monthly preventatives and good sanitation practices in the household to reduce the risk of it spreading to other pets or humans.

Preventing Roundworms

Roundworms in dogs are preventable. Talk to your veterinarian about the parasite risks in your area. If roundworms are common, start your dog on a monthly preventative that treats roundworms as a precaution, and deworm breeding and pregnant females to reduce the risk of transplacental infection. Keeping your dog’s living conditions sanitary will also reduce the risk of infection.

Is there a vaccine for roundworms?

Roundworms are not a viral disease. There is no vaccine for roundworms in dogs, but there are monthly preventatives that can treat and prevent infections.


Roundworms in dogs are preventable. With good sanitation practices, appropriate preventatives, and regular veterinarian visits, you can prevent your dog from contracting roundworms.

Facebook Icon Twitter Img Email Img Print Img

Related articles

FIV (Feline AIDS)

Feline immunodeficiency virus (FIV), also commonly referred to as feline AIDS, can…

Cushing’s Disease (Hyperadrenocorticism) in Dogs

Hyperadrenocorticism, commonly known as Cushing’s disease, is an endocrine (hormonal) disorder that is most…

Cat Pregnancy Facts

No matter how isolated your female cat is, if she has not…

Heart Murmur in Dogs

A dog’s heart functions in the same way as their human owner’s heart —…

Dehydration in Cats & Dogs

Dehydration is a serious concern for both us and our pets, particularly…

Conjunctivitis (Pink Eye) in Dogs

Conjunctivitis, sometimes informally referred to as “pink eye,” is an irritation or inflammation of…

Parvo in Dogs

Parvo in dogs is a highly contagious and potentially deadly virus that can be…

Ear Infections in Dogs

Ear infections in dogs are common, especially among certain breeds. Although an ear infection…

Icon of a white arrow in a black circle Back to Learning center