Roundworms in Dogs: Signs, Treatment and Prevention

By Tailwisp Editorial TeamUpdated October 17, 20263 min read

Nearly every puppy is exposed to roundworms, which is why vets deworm so early and so often.

What they are

The most common roundworms in dogs are Toxocara canis and Toxascaris leonina, which live in the intestines. Adult worms are several inches long and feed on digested food.

How dogs get them

• Before birth, when larvae in the mother cross the placenta
• Through milk while nursing
• By eating eggs from contaminated soil, stool or other animals
• By eating infected rodents or other animals

Eggs in soil can survive for months or even years.

Signs

• Pot belly and thin body in puppies
• Dull coat and poor growth
• Vomiting and diarrhea
• Visible worms in stool or vomit
• Coughing when larvae migrate through the lungs
• Heavy infections, which can cause intestinal blockage

Adult dogs often show no signs.

Diagnosis

Your vet will check a stool sample for eggs under a microscope. Regular fecal testing is recommended, even when worms are not visible.

Treatment

Effective dewormers include pyrantel, fenbendazole and milbemycin, chosen by your vet by age, weight and other conditions. Puppies need repeated treatments, since larvae can emerge later. See puppy deworming schedule.

Preventing reinfection

1. Pick up stool promptly, ideally daily.
2. Keep parasite prevention current, since many heartworm products also control roundworms.
3. Test stool once or twice a year.
4. Control rodents and prevent scavenging.
5. Wash hands after contact with soil or stool.
6. Cover sandpits from animals.

See dog flea, tick and heartworm medications.

Risk to people

Roundworm larvae can cause illness in people, such as visceral and ocular larva migrans, mainly in children who ingest soil or stool contaminated with eggs. Practice hygiene, deworm pets regularly and keep play areas clean.

Pregnant and nursing dogs

Veterinarians may recommend specific deworming protocols for pregnant and nursing dogs to reduce transmission to puppies. Ask your vet about timing and safety. See feeding pregnant and nursing dogs.

Common mistakes

• Using the wrong product or dose
• Not repeating puppy doses
• Leaving stool in the yard
• Skipping fecal tests

Troubleshooting

• My puppy still has worms after one dose: repeat as scheduled.
• My puppy vomited the dewormer: call your vet.
• My child touched worm-contaminated soil: wash hands and mention it to your doctor if concerned.

A simple plan

1. Deworm puppies on schedule.
2. Use monthly prevention.
3. Clean up stool.
4. Test regularly.

Real-life examples

A litter of puppies clears worms after scheduled treatment. A rescue puppy with a pot belly and vomiting improves rapidly after deworming. A family reduces risk by cleaning the yard daily. Simple steps work.

Routine care

Routine deworming and hygiene protect dogs and families.

Fecal tests and what they mean

A fecal flotation test looks for worm eggs under the microscope. Because worms shed eggs intermittently, a single negative test does not guarantee a dog is clear, which is why vets repeat tests in puppies and test adult dogs once or twice a year. Bring a fresh sample, ideally collected the same day, and keep it cool.

Hygiene at home

Wash hands after gardening, handling soil or picking up stool. Cover children's sandpits, clean up fast and keep children from putting dirty fingers in their mouths. Wash raw vegetables grown in soil that animals visit, and discourage dogs from scavenging.

Questions to ask your vet

Ask which dewormer your dog needs, when to start puppies, how often adults should be tested and whether your monthly heartworm preventive covers roundworms. Ask how to handle a pregnant dog and how to reduce risk for children at home, and whether your dog's lifestyle calls for more frequent testing.

Environment and wildlife

Eggs can persist in soil for a long time and wildlife such as foxes and raccoons can contribute to contamination. Fence off dog areas where practical, rake up stool, and avoid letting your dog eat dead animals, rodents or stool on walks.

The takeaway

Roundworms are common and easy to treat. Deworm on schedule, clean up and wash hands.

This article is general educational information, not veterinary advice. Every dog is different. If your dog is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.