Roundworms in Cats: Signs, Testing, and Prevention

What roundworms are and how cats encounter them

Cornell identifies Toxocara cati and Toxascaris leonina as roundworms that can infect cats. Adult worms live in the intestine, and infected cats can pass eggs in their feces. Infection can follow ingestion of infective eggs from the environment or larvae in prey. Kittens may also acquire Toxocara infection through an infected mother’s milk.

Tell your veterinarian about your cat’s age, previous parasite care, access to prey, and contact with other cats. For a newly adopted kitten, bring any available shelter or previous veterinary records. Those details help the team build a plan that fits the cat instead of guessing from whether it currently looks healthy. Ask how the recommendations apply to other animals living in the same household.

Signs may be visible, subtle, or absent

The Companion Animal Parasite Council notes that cats of any age can have infections without obvious illness. Its cat guidance describes poor growth and a potbellied appearance in affected kittens, as well as vomiting or diarrhea in some infections. Adult roundworms may sometimes appear in vomit. These findings are reasons for investigation, but they are not unique to roundworms.

If you see something that looks like a worm, contact the clinic and ask whether to bring a sample or photograph. Explain whether the cat is eating, gaining weight, and behaving normally. A sick kitten needs prompt advice rather than an assumption that any stomach upset will resolve after a dewormer. Ask the team how urgently the animal should be seen and what changes should trigger an earlier call.

Testing provides information that appearance cannot

CAPC recommends testing cats using a fecal examination that includes centrifugation to look for eggs. It also describes antigen or DNA testing that can detect some infections when few or no eggs are present. The clinic selects and interprets testing in the context of the animal’s history. Not seeing worms in the litter box does not establish that a cat is parasite-free.

Ask how to collect, store, and deliver the stool sample for the tests your veterinarian recommends. Tell the clinic about recent parasite medication so the result can be considered alongside that history. If the result is negative but concern remains, ask what it rules out and whether follow-up testing is needed. Before leaving the appointment, make sure you know who will communicate the result, when to expect it, and whom to contact if the cat becomes unwell before the result arrives. Keep a record of results and treatment dates for future appointments, especially when different clinics have cared for the cat.

Use an individual treatment and prevention plan

Cornell explains that several medications can treat roundworms, but reinfection after treatment is possible. CAPC recommends ongoing parasite control and fecal testing, with kittens needing more frequent attention than adult cats. Ask your veterinarian to set the schedule and choose a product appropriate to the cat’s age, health, and exposures rather than selecting a medication solely because its package mentions worms.

Confirm whether further treatment or testing is planned and what to do if you cannot give a prescribed product successfully. Do not combine parasite medications, use a dog product on a cat, or substitute a home remedy without veterinary direction. Tell the clinic if vomiting, diarrhea, poor appetite, or low energy continues. An assumed parasite infection should not prevent investigation of another problem when the cat is still unwell.

Scooping the litter box daily with the right litter accessories helps limit reinfection while treatment works.

Reduce contamination and protect the household

Cornell explains that Toxocara can cause illness in people after eggs are swallowed from contaminated soil or hands. Children can be particularly exposed through contact with contaminated ground. Its guidance emphasizes handwashing and reducing contact with cat feces. CAPC notes that eggs can remain infective in the environment for years and that common disinfectants do not reliably kill them.

Ask the veterinary team about prompt litter waste removal and practical cleaning for your home. Keep children away from areas where animals defecate, and supervise handwashing after outdoor play or contact with soil. Tell your own healthcare professional about a concern involving human exposure rather than treating people with pet medication. Combine hygiene with the cat’s prescribed parasite plan, and discuss how to reduce hunting or other opportunities for reinfection.

This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.