Roundworms in Dogs & Cats: Signs & Treatment
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Roundworms are the most common intestinal parasite in dogs and cats — long, spaghetti-like worms that live in the intestines. Puppies and kittens are especially prone, often infected before birth or through their mother's milk. Signs include a pot-bellied appearance, vomiting, diarrhea, poor growth, and visible worms in stool or vomit. They're easily treated with deworming medication, but because they can also infect people, prevention and good hygiene matter.
What roundworms are
Roundworms (Toxocara and Toxascaris species) are among the most common parasites vets see. Adult worms live in the small intestine, where they can grow several inches long and look like white or tan strands of spaghetti. They steal nutrients from your pet and, in heavy infections, can cause real harm — especially in young animals.
They're so common in puppies and kittens that vets generally assume young pets have them and deworm routinely as a precaution.
How dogs and cats get roundworms
There are several routes of infection, which is why they spread so easily:
- From the mother: puppies can be infected in the womb, and both puppies and kittens can pick up larvae through their mother's milk.
- Contaminated environment: pets swallow microscopic eggs from soil, grass or surfaces where infected animals have defecated.
- Eating infected prey: hunting and eating rodents or other small animals can transmit larvae.
Roundworm eggs are hardy and can survive in soil for a long time, so contaminated yards and parks are a persistent source.
Signs of roundworms
Many adult pets with light infections show no obvious signs. When symptoms do appear — most often in puppies and kittens — watch for:
- A pot-bellied, bloated appearance, especially in the young
- Vomiting and diarrhea, sometimes with visible worms
- Worms that look like spaghetti in stool or vomit
- Poor growth, dull coat and weight loss despite eating
- Coughing in some cases, as larvae migrate through the lungs
Practical take: Seeing spaghetti-like worms in your pet's stool or vomit is a classic sign of roundworms — save a sample if you can and call your vet.
Diagnosis and treatment
Vets diagnose roundworms with a fecal test that detects worm eggs under the microscope, and sometimes by seeing the worms themselves. Treatment is straightforward and effective:
- Deworming medication kills the adult worms; because it doesn't kill all larval stages at once, treatment is usually repeated after a couple of weeks.
- Puppies and kittens are dewormed on a schedule starting at a few weeks of age.
- Many monthly heartworm preventives also control roundworms year-round.
Your vet may recheck a stool sample to confirm the worms are gone.
Can people catch roundworms?
Yes — roundworms are zoonotic and can infect people, especially children. If a person swallows eggs (usually from contaminated soil or unwashed hands), migrating larvae can occasionally cause serious problems, including damage to the eyes or organs.
The risk is real but preventable. Pick up dog waste promptly, wash hands after handling pets or gardening, keep children's sandboxes covered, and keep pets on year-round parasite prevention. Regular deworming of your pet protects your family too.
Prevention and tracking
The best defense is routine: year-round parasite prevention, prompt cleanup of feces, and regular fecal checks — often once or twice a year for adult pets, more for those at higher risk. It's easy to lose track of when the last dewormer or stool test was done, especially across multiple pets. Logging preventive doses, deworming dates and fecal-test results keeps you on schedule and gives your vet an accurate history at each visit.
Never lose track of a dewormer dose again
Tavi lets you log parasite preventives, deworming dates and fecal-test results for each pet and reminds you when the next one is due — so protection never lapses. Free for your first pet.
Frequently asked questions
What do roundworms look like in dogs and cats?
Adult roundworms look like white or light tan strands of spaghetti, usually a few inches long. You may see them in your pet's stool or vomit, which is a classic sign of infection. If you spot them, save a sample if possible and contact your vet.
How do puppies and kittens get roundworms?
Young pets are often infected by their mother — puppies can pick up larvae in the womb, and both puppies and kittens can get them through nursing. They can also swallow eggs from contaminated soil or surfaces. Because it's so common, vets routinely deworm young pets as a precaution.
Can humans get roundworms from pets?
Yes, roundworms are zoonotic. People, especially children, can become infected by accidentally swallowing eggs from contaminated soil or unwashed hands, and migrating larvae can occasionally cause serious harm. Good hygiene, prompt waste cleanup and year-round pet parasite prevention greatly reduce the risk.
How are roundworms treated?
Roundworms are treated with deworming medication that kills the adult worms, usually repeated after a couple of weeks to catch newly matured worms. Many monthly heartworm preventives also control roundworms. Your vet may recheck a stool sample to confirm the infection is cleared.
How can I prevent roundworms?
Keep your pet on year-round parasite prevention, pick up feces promptly, have regular fecal exams (often once or twice a year), and deworm puppies and kittens on schedule. Washing hands after handling pets and keeping play areas clean protects the people in your home too.
Tavi's guides are informational and not a substitute for professional veterinary advice, diagnosis or treatment. When in doubt, call your veterinarian. Sources: Companion Animal Parasite Council (CAPC); Centers for Disease Control and Prevention (CDC); American Veterinary Medical Association (AVMA); Merck Veterinary Manual