Overview 

Roundworms are internal parasites that are commonly found in dogs. They are long, tube-shaped worms that infect a dog's intestines. Routine deworming and prompt disposal of feces is essential for preventing roundworm infections. 

Humans may also become infected with roundworms if they accidentally consume a roundworm egg in the soil or from an object left in an environment contaminated by roundworm-infected feces. This presents a higher risk for young children, who may put items in their mouth while playing outside. 

Causes 

Puppies can become infected with roundworms from their mother — both before they are born and while nursing. Dogs can also get infected with roundworms by either ingesting the parasite’s eggs (from feces-contaminated soil and other contaminated objects), or by eating a rodent that is already infected with roundworms.  

Infected dogs shed roundworm eggs through their stool. Larvae develop inside the eggs 2-4 weeks later, making them infectious to another dog.  

After ingestion, roundworm larvae migrate through the walls of the intestines, liver and lungs. Larvae are then coughed up from the lungs, swallowed and finally grow into adult roundworms that live in the dog’s intestines. 

Clinical signs 

Dogs of any age can get roundworms, and some may have no symptoms. Puppies are more likely to experience clinical signs.   

Signs of a roundworm infection may include: 

• Diarrhea 

• Vomiting 

• Pot-bellied appearance 

• Poor coat quality 

• Weight loss 

• Stunted growth 

In rare cases, a severe infestation can cause a blockage in the intestine, which could be deadly. 

Diagnosis 

Roundworms can be diagnosed by using a microscope to identify eggs in a dog’s stool sample. Pet owners may also see adult worms in their dog’s stools or vomit.  

A fecal test called an antigen test can also be helpful for detecting the presence of roundworms, especially if the dog has a low number of eggs in their stool. 

Treatment 

Treatment typically consists of deworming medications, such as pyrantel or fenbendazole.  Monthly heartworm preventatives containing medications such as milbemycin, can also treat roundworms. Repeating treatment after two weeks is often necessary to ensure the complete resolution of roundworm infections. 

Puppies should receive dewormer routinely — starting at two weeks of age, repeating every two weeks until approximately eight weeks of age, and then continued monthly.  

Pregnant dogs should be treated late in pregnancy, around 40 days, and they should receive treatment at the same interval as their puppies while nursing.  

Outcome 

Most dogs recover from roundworm infections after proper treatment.  

Young puppies with severe infestations are at the highest risk from nutritional depletion that then stunts their growth. A rare, but dangerous complication can occur in puppies if an intestinal blockage forms due to heavy worm infestations.  

Zoonosis 

It is possible for roundworms to infect humans if a larvated egg is ingested. This is more likely to occur in children, who may put objects in their mouth or accidentally consume dirt in a contaminated environment such as parks, sandboxes, playgrounds, gardens and other similar environments. 

Unlike in dogs, adult roundworms do not develop in the intestines of humans, and roundworm larvae can migrate through organs, often without any symptoms. However, in some cases, the migrating larvae could cause serious damage to the nerves or eyes.  

Prevention 

Proper prevention tactics will decrease the number of roundworm eggs in the environment and reduce the risk of infection in dogs and humans. 

Strategies include: 

• Prompt removal and disposal of feces 

• Keeping dogs on monthly dewormer  

• Routine deworming of puppies 

• Preventing dogs from eating rodents  

• Good hand hygiene  

• Preventing children from playing in areas where pets or other animals defecate