Roundworms in Dogs and Cats: What Every Pet Owner Should Know
Roundworms are among the most common intestinal parasites found in dogs and cats. Known scientifically as Toxocara canis (in dogs) and Toxocara cati (in cats), these spaghetti-like worms live in your pet’s intestines, stealing nutrients and potentially causing serious health problems — especially in puppies and kittens.
As part of our ongoing parasite awareness series at Dunedin Animal Medical Center, we want to help you understand how roundworms spread, what symptoms to watch for, and how to keep your furry family members safe.
What Are Roundworms?
Roundworms are large, white or cream-colored parasites that can grow up to several inches long. They live in the small intestine, where they feed on partially digested food. A single female roundworm can produce up to 200,000 eggs per day, which pass into the environment through your pet’s feces and can survive in soil for years.
How Do Dogs and Cats Get Roundworms?
There are several ways pets can become infected with roundworms:
Ingesting Eggs from Contaminated Soil
Roundworm eggs shed in feces can persist in soil, grass, and sandboxes for months or even years. Dogs and cats that sniff, dig, or eat grass in contaminated areas can easily ingest these microscopic eggs. In Florida’s warm, humid climate, roundworm eggs thrive particularly well in outdoor environments.
Mother-to-Puppy and Mother-to-Kitten Transmission
This is one of the most common routes of infection. In dogs, dormant roundworm larvae living in the mother’s tissues can reactivate during pregnancy and cross the placenta to infect puppies before they are even born. Both dogs and cats can also pass larvae to their young through nursing. This means puppies and kittens can be born with roundworms or become infected within their first few days of life.
Eating Infected Prey
Cats and dogs that hunt and eat rodents, birds, or other small animals can ingest roundworm larvae that have encysted in the prey’s tissues. Outdoor and indoor-outdoor cats are especially at risk through this route of transmission.
Signs and Symptoms of Roundworm Infection
Many adult pets with roundworms show no obvious symptoms, which is why routine screening is so important. However, puppies, kittens, and pets with heavy infections may display:
- A pot-bellied appearance, especially in young animals
- Vomiting (sometimes you may see worms in the vomit)
- Diarrhea or loose stools
- Dull, rough coat
- Weight loss or failure to thrive despite a good appetite
- Visible worms in the stool that resemble strands of spaghetti
- Coughing (as larvae migrate through the lungs)
- Lethargy and general weakness
In severe cases, particularly in very young puppies and kittens, a heavy roundworm burden can cause intestinal blockage, which is a life-threatening emergency.
Diagnosing Roundworms
Roundworm infection is typically diagnosed through a fecal examination, also known as a fecal float test. During this test, a small stool sample is mixed with a special solution that causes roundworm eggs to float to the surface, where they can be identified under a microscope.
At Dunedin Animal Medical Center, we recommend fecal testing as part of your pet’s annual wellness exam, and more frequently for puppies and kittens during their initial vaccination series. Because roundworm eggs are not shed continuously, a single negative test does not always rule out infection, which is why your veterinarian may recommend preventive deworming even without a positive result.
Treatment for Roundworms
The good news is that roundworms are highly treatable. Your veterinarian will prescribe a deworming medication (anthelmintic) that kills the adult worms in the intestines. Common medications include pyrantel pamoate and fenbendazole, both of which are safe and effective.
Because these medications only kill adult worms and not migrating larvae, treatment is usually repeated two to three weeks later to catch any larvae that have since matured into adults. Puppies and kittens typically begin deworming as early as two weeks of age and receive multiple treatments during their first few months of life.
Preventing Roundworms
Prevention is always better than treatment. Here are the most effective ways to protect your pets from roundworms:
- Year-round parasite prevention: Many monthly heartworm preventives also protect against roundworms. Ask our team which product is right for your pet.
- Regular fecal testing: Annual stool checks help catch infections early, even when your pet looks healthy.
- Prompt waste cleanup: Pick up your pet’s feces from the yard, parks, and public areas promptly to reduce environmental contamination.
- Deworming puppies and kittens early: Follow your veterinarian’s recommended deworming schedule starting at two weeks of age.
- Limit hunting behavior: Keep cats indoors when possible and discourage dogs from eating wildlife or rodents.
- Practice good hygiene: Wash your hands after handling pets, cleaning litter boxes, or gardening in areas where pets have access.
A Note About Zoonotic Risk
Roundworms are a zoonotic parasite, meaning they can be transmitted to humans. Children are at highest risk because they are more likely to play in contaminated soil and put their hands in their mouths. In humans, migrating roundworm larvae can cause a condition called visceral larva migrans or, if they reach the eyes, ocular larva migrans. Keeping your pets on a regular deworming schedule protects your entire family.
Schedule a Parasite Screening Today
Whether your pet is a brand-new puppy, a senior cat, or anything in between, routine parasite screening and prevention are essential to keeping them healthy. At Dunedin Animal Medical Center, our veterinary team is here to help you develop a comprehensive parasite prevention plan tailored to your pet’s lifestyle and risk factors.
Call us at (727) 738-1441 or contact us online to schedule your pet’s wellness exam and fecal screening today. As part of our parasite awareness promotion, ask about special offers on wellness packages that include deworming and fecal testing.