Cats get worms in their poop because intestinal parasites living inside the digestive tract shed eggs, segments, or sometimes whole worms that pass out with feces. The three most common culprits are roundworms, tapeworms, and hookworms, and each one has a different way of getting into your cat in the first place. Understanding how your cat picked up the infection helps you treat it and prevent it from coming back.
How Cats Pick Up Worms
The route depends on the type of worm, but nearly all infections start with your cat swallowing something contaminated.
Roundworms are the most common intestinal parasite in cats. A cat gets roundworms by swallowing microscopic eggs from contaminated soil, grass, or surfaces, or by eating a rodent that carries larvae in its tissues. Kittens are especially vulnerable because larvae can pass through an infected mother’s milk, meaning newborns can be infected within days of birth. This is why roundworms are so widespread in young cats even before they ever go outside.
Tapeworms follow a more indirect path. The most common feline tapeworm relies on fleas as an intermediary. Flea larvae swallow tapeworm eggs from the environment. As the flea matures, the tapeworm develops inside it. When your cat swallows an infected adult flea during grooming, the tapeworm is released into the small intestine, where it attaches and grows into a full adult over about one month. This is why a flea problem and a tapeworm problem almost always go hand in hand.
Hookworms can be swallowed, but they can also burrow directly through a cat’s skin or paw pads from contaminated soil. Once inside, they latch onto the intestinal wall and feed on blood.
What You’ll Actually See in the Litter Box
Not all worms look the same, and knowing what you’re looking at can help your vet act faster.
- Roundworms are 3 to 6 inches long, cream-colored, and look like spaghetti noodles. They’re the worms most people notice because of their size.
- Tapeworms don’t usually appear as whole worms. Instead, you’ll see small white segments that look like grains of rice, either in the stool or stuck to the fur around your cat’s rear end. These segments are packets of eggs that break off from the adult worm inside.
- Hookworms are only about an eighth of an inch long and look like tiny thin strings. Most people never spot them with the naked eye.
Sometimes you won’t see worms at all. Many infections are only detectable through a fecal test at the vet, where a stool sample is examined under a microscope for eggs.
Signs Beyond Visible Worms
A dull, rough coat is one of the earliest and most overlooked signs of a worm infection. Other common symptoms include vomiting, diarrhea, mucousy or bloody stool, loss of appetite, and a potbellied appearance, especially in kittens. Some cats lose weight despite eating normally.
Hookworm infections can cause anemia because the parasites feed on blood. In severe cases, a cat’s stool turns black and tarry from digested blood, and the gums may look pale. This is more dangerous in kittens and older cats, who have fewer reserves to handle blood loss.
Plenty of infected cats, particularly adults with mild infections, show no obvious symptoms at all. A cat can carry worms for weeks or months before you notice anything in the litter box. This is why routine fecal screening matters even when your cat seems perfectly healthy.
Why Kittens Are Hit Hardest
Kittens face a double disadvantage. Their immune systems are still developing, and they’re exposed early through their mother’s milk. A kitten with a heavy roundworm load can develop a visibly swollen belly, chronic diarrhea, and poor growth. In severe cases, a mass of roundworms can actually block the intestine. This is why most veterinary deworming protocols start when kittens are just a few weeks old, well before any symptoms appear.
Why Indoor Cats Aren’t Immune
You might assume an indoor cat can’t get worms, but several infection routes don’t require stepping outside. Fleas can hitch a ride into your home on clothing, shoes, or other pets, and a single infected flea is enough to start a tapeworm infection. Roundworm eggs are microscopic and can be tracked indoors on the soles of shoes. If your cat ever catches a mouse that wanders inside, that’s another potential source. Indoor cats are at lower risk overall, but they’re not at zero risk.
How Worm Infections Are Treated
Treatment is straightforward in most cases. Your vet will prescribe a deworming medication based on the type of worm identified. Some dewormers target roundworms and hookworms, while others are designed specifically for tapeworms. Combination products that cover multiple parasite types are also common.
A single dose often kills the adult worms, but eggs and larvae may survive, so a follow-up dose is typically given two to three weeks later to catch newly hatched parasites. For kittens, deworming is usually repeated several times during the first few months of life. Your vet will likely recommend a follow-up fecal test to confirm the infection has cleared.
If tapeworms are the problem, treating the worms alone won’t solve it. You also need to address the flea infestation, or your cat will just get reinfected the next time it swallows a flea during grooming.
Risks to Humans in Your Household
Some cat intestinal parasites can infect people, and roundworms pose the most significant risk. If a person accidentally swallows roundworm eggs, typically from contaminated soil, unwashed hands, or surfaces, the larvae can migrate through the body. This condition, called visceral toxocariasis, can cause fever, coughing, wheezing, belly pain, and an enlarged liver. If larvae reach the eyes, they can cause inflammation, retinal damage, or vision loss, usually affecting only one eye. Children are at highest risk because they’re more likely to put dirty hands in their mouths.
Basic hygiene makes a big difference. Wash your hands after cleaning the litter box or touching soil where cats may have been. Scoop the litter box daily, since roundworm eggs need one to two weeks in the environment before they become infectious. Pick up outdoor pet waste promptly. And keep children from playing in areas where cats frequently defecate.
Preventing Reinfection
Year-round parasite prevention is the most reliable approach. Many monthly preventive products protect against roundworms and hookworms alongside fleas and heartworm. For tapeworms specifically, consistent flea control is the best prevention, since eliminating fleas breaks the tapeworm’s life cycle entirely.
If your cat hunts, reinfection is an ongoing risk. Rodents carry roundworm larvae in their tissues, so every mouse your cat catches is a potential new dose of parasites. Keeping cats indoors or limiting hunting opportunities reduces exposure significantly. Routine fecal exams, at least once or twice a year, catch infections early before they cause symptoms or spread to other pets and family members.