roundworm in cats: signs, transmission, treatment, and prevention
You are cleaning the litter box and notice something that looks like a small piece of spaghetti moving in the waste. Or maybe your kitten has a potbelly that seems out of proportion to how much they eat. Roundworm in cats is one of the most common parasitic infections in domestic cats, particularly in kittens and cats with outdoor access, and most owners encounter it at some point.
Round worm in cats refers to Toxocara cati, the most common species, though Toxascaris leonina also infects cats. Cat roundworm can reach several inches in length and lives in the small intestine, absorbing nutrients before the cat can. Roundworm cats carry may produce thousands of eggs daily that pass in feces. Roundworm cat infections are highly treatable, but understanding the transmission routes helps you protect both your cat and your household.
How Cats Get Roundworms
Transmission Routes
Kittens most commonly get roundworms through nursing. An infected mother cat can pass larvae through her milk even if her own infection is not currently active. This is why roundworm treatment in kittens is routine starting at two weeks of age in many veterinary protocols.
Older cats typically acquire roundworms by ingesting infected prey. Mice, birds, and other small animals serve as intermediate hosts, carrying dormant larvae in their tissues. A cat that hunts regularly is at sustained risk of reinfection even after successful treatment. Ingesting contaminated soil or feces is another transmission route, which affects cats with outdoor access or those in multi-cat environments with poor sanitation.
Zoonotic Risk
Roundworm eggs from cat feces can infect humans, particularly children who play in areas where cats defecate. The larvae in humans can migrate through tissues in a condition called visceral larva migrans, which in rare cases affects the eyes or other organs. This zoonotic risk makes deworming and litter hygiene a household health matter, not just a pet health issue.
Recognizing an Infection
Common Signs
A potbellied appearance in kittens is one of the most recognizable signs of a heavy roundworm burden. Dull coat, poor growth, vomiting, and diarrhea also appear in significantly infected animals. Some cats vomit actual roundworms, which are visible as off-white or tan spaghetti-like parasites. In mild infections, especially in adult cats with some immune exposure, signs may be subtle or absent entirely.
Weight loss despite a good appetite, intermittent soft stools, and general failure to thrive in a kitten who should be growing well are all reasons to request a fecal examination at your next vet visit.
Treatment and Prevention
Deworming Options
Pyrantel pamoate is the most commonly used dewormer for roundworms in cats and is available both by prescription and over the counter in many countries. It works by paralyzing the worms, which are then passed in feces. A second dose two to three weeks later kills larvae that were not yet adults at the time of the first treatment.
Broad-spectrum monthly parasite preventatives that include roundworm coverage are available through your vet and offer ongoing protection for cats at continued risk of reinfection through hunting or outdoor exposure.
Environmental Control
Roundworm eggs become infectious in soil after a few weeks and can survive in the environment for years. Remove feces from the litter box daily to reduce the time eggs have to develop. Wear gloves when gardening in areas where cats defecate. Keep sandboxes covered when not in use.
Indoors, regular vacuuming and prompt feces removal limit egg accumulation. Roundworm eggs are resistant to most household disinfectants but are killed by steam cleaning and direct sunlight exposure over time.
Bottom line: roundworm in cats is very treatable and manageable with consistent deworming and hygiene practices. Annual fecal testing catches infections before they become heavy, and routine preventative deworming for high-risk cats keeps both your cat and your household safer year-round.
