Roundworms in Dogs.. Puppies Beware!

Roundworms in Dogs.. Puppies Beware!

Roundworms are an intestinal parasite found commonly in dogs, especially young dogs. These worms live in the dog’s stomach and intestines and can grow to be 7 inches long. Roundworms are the most common internal parasite found in dogs. In adult dogs, roundworms rarely cause symptoms, but in puppies, intermittent vomiting and diarrhea may be seen. In very young dogs, roundworms may cause severe illness and even death.


Dogs usually contract roundworms by direct contact with infected soil. They may also get the worm from eating a rodent or insect host, which introduces the roundworm to their digestive tract. Puppies can become infected before birth by larvae migrating through the placenta. Larvae also can reside in their mother’s milk, infecting your dogs while they nurse.

There are two species of roundworms that infect: 

  • Toxocara canis in dogs
  • Toxascaris leonina in cats and dogs

The life cycle of roundworms begins in the intestine after ingestion, where the eggs will hatch. The newly hatched larvae travel through your dog’s liver and bloodstream to the lungs, where they are then coughed up and swallowed. Once back in the digestive tract, the larvae will develop into adult worms which may be 1-7 inches long. The adult female roundworms may lay up to 200,000 eggs a day. These eggs are shed in the feces and are protected by a hard shell which allows them to survive for months, or even years, in the soil.


  • Stunted growth in young puppies
  • Coughing
  • Dull coat
  • Bloated belly 
  • Abdominal pain
  • Adult worms resembling spaghetti may vomited or seen in feces
  • Diarrhea with mucous


Diagnosis begins with a complete history and a physical exam. Your veterinarian will be most likely to do the following:

  • Fecal Floatation - This test is used to determine the presence of parasite eggs in your dog’s stool. It involves taking a small fecal sample from your dog using a lubricated fecal loop. The feces are then put in a small container with a solution that will allow most of the fecal matter to sink and the parasite eggs to float. A slide is then made of the floating material and examined under a microscope. The slide is then scanned for roundworm eggs.


Your veterinarian will likely use a dewormer if your dog is positive for roundworms. Most commonly, a pyrantel pamoate (Nemex or Strongid) drug is used because it is very safe to use in young, nursing dogs. They will have to be retreated multiple times within the first three months of life so that every life stage is killed. The nursing mother may also be dewormed to help control infections in puppies.


Roundworms can be prevented by:

  • Having your dog dewormed multiple times within the first three months of life as a precaution
  • Having regular fecal exams for your dog every 6-12 months
  • Regular use of heartworm preventives that protect against roundworms as well
  • Good sanitation in kennel areas
  • Control of rodents and insects (Use caution with rat poison, it is toxic to your dog!)

Dogs over the age of 6 months are usually resistant to roundworm infection, and though the worm may be present, they rarely complete their life cycle. The larvae will often rest on tissue and become encysted, where they are protected from your dog’s antibodies and most dewormers. Deworming a female before breeding or during pregnancy does seem to reduce these migrating dead-end larvae, but does not seem to prevent infection in puppies.

Roundworms can be transmitted to humans and cause a disease called visceral larval migrans. Roundworm larvae do not develop any further once inside a human host, and travel around the body and tissues aimlessly. It can affect the liver and cause fever, pneumonia, or eye problems. It can be prevented by practicing good sanitation and maintaining infections in your dog.