Health Hygiene

Parasites in Cats: Roundworms aka Spaghetti Imposters

We’re back to diving into the ewy world of parasites, specifically roundworms. Because they are so common and can actually be seen in your cat’s vomit or stool, it’s important to understand where they come from, how to treat them, and how to lower your cat’s exposure to them. Nearly every cat is exposed to them at some point in their life, but most of the time, they are harmless (remember, I said “most of the time”). We’ll cover everything you need to know about these spaghetti noodle imposters.

IMPORTANT: That’s Not Spaghetti

You need to know about this, because I promise you, being aware of it is better than being surprised. If your cat vomits or poops and you see something that looks like round, long, thing, spaghetti noodles moving in it, it’s roundworms. Roundworms die shortly after leaving the body, so no, you won’t have a new pet to care for. I know, it’s horrifying, but with your eyewitness testimony, your vet will know how to properly treat your cat. The other way roundworms are diagnosed is by the presence of eggs in a stool sample.

Where Roundworms Come From

The origin of roundworms is similar to other parasites. There are three main ways cats can get them:

kitten and women
Drake was a very photogenic foster who also had roundworms.
  1. From dinner. The larvae do not mature in accidental hosts called paratenic hosts, but instead use the paratenic hosts’ bodies as a vehicle to get to their intended host. Paratenic hosts include birds and rodents, common prey for cats, and even earthworms.
  2. From Mama. One of the most common ways cats are exposed to roundworms is through nursing from their mother. The larvae hang out in the mammary glands, and then are passed through her milk. Another way is that some larvae encase themselves into a cyst (called encyst) and go into a dormant state. In pregnant females, the larvae can come out of the cyst and pass through the placenta to the kittens, or, again, through the milk.
  3. From the environment. Eggs are shed in the stool, which is another way they can find a host. Now before your mind goes to a gross place (it prob already did), it’s not that the stools are consumed. Cats sharing a litter box will likely come in contact with the other cat’s stool, just from pawing, digging and burying. Outdoor cats can be infected from exposure to soil or plants that have been in contact with egg-ridden feces.

Zombie Cysts

Another reason so many cats have roundworms is that encyst larvae can be dormant for months or even years in a cat’s body. This is why it’s a good idea to follow the protocol for deworming kittens and especially adults that come from shelters (with unknown histories).

Lifecycle of Roundworms

There are two types of roundworms that infect cats: The very common Toxocara cati, and the very rare Toxascara leonina. Unlike many other parasites that attached to the intestinal wall like tapeworms, roundworms live in the intestines but don’t attach. Here’s a quick overview of their lifecycles.

The CDC put together this lovely diagram of the lifecycle of roundworms.

Type 1: Toxocara cati – According to the CDC, the larvae hatch in the GI tract, then migrate to the esophagus, lungs, and bronchial tree. Next, they are coughed up, swallowed (ewww), and return to the intestines where they grow into adult worms, turn into Michael Phelps, and swim freely.

Type 2: Toxascara leonina – These worms are less common and have a more traditional worm life cycle, but still don’t attach to the intestinal wall. The eggs are consumed, then hatch and swim in the intestines.

Both types of roundworm consume nutrients from the host as they endlessly swim, and they don’t even pay a membership fee.

Symptoms of Roundworms

In mild cases there won’t be any symptoms, and the only way to check for and diagnose a cat with roundworms is to find eggs in a stool sample. The stool will be examined for eggs or worms. As I mentioned earlier, vomiting or pooping live worms will give your cat an immediate diagnosis.

Medium haired kittens snuggling.
Sansa (formerly Jocelyn) and Drake loved cuddling.

In extreme cases, a major infection can lead to anemia, stomach, or even an intestinal rupture. Kittens are most at risk for these serious infections, called ascariasis, which also lower the effectiveness of their immune systems, leaving them more susceptible to viral or bacterial infections. Seniors can be at risk as well.

General symptoms cover pretty much the symptoms of every other cat illness or issue (but no excessive thirst for once!):

  • Lethargy
  • Vomiting
  • Diarrhea
  • Constipation
  • Pot-bellied appearance
  • Coughing
  • Inability to gain weight

Operation: Kill the Spaghetti

Dewormers administered by your vet will kill the adult roundworms, but not larvae or migrating larvae. For this reason, you’ll want to treat an infected cat or kitten at least 2-3 times every 2-3 weeks. Work with your vet on a selecting the best dewormer along with a deworming schedule.

Three kittens.
Jocelyn, Drake, & Tupac (back to front)

Preventing Roundworms


You can start deworming kittens around two weeks old. Yes, this is young and they will not receive a vaccine yet, but it’s better to start deworming early to keep them healthy. (Note: You can ask your vet if they can administer an intranasal vaccine that can be given once kittens open their eyes.)


Always deworm the mother before breeding her, and again late in pregnancy. If she’s already had kittens, she should be treated at the same time as her litter.


Cats that catch mice, other rodents, and birds; outdoor cats; and indoor/outdoor cats should all be regularly dewormed because they are at high risk for infection. All adults cats are at risk for reinfection, mostly because of the encyst larvae, so talk with your vet about how frequently to deworm. And of course, if you see anything in your cat’s vomit or stool, tell your vet.


Selamectin, under the brand name Revolution, is a monthly flea and tick preventative as well as a dewormer that kills roundworms and other parasites.

Litter Box Management

If you know or suspect your cat of having a roundworm infection, be very careful when handling feces. Scoop multiple times a day and clean the litter box with a bleach solution to kill the eggs.

Final Note: Roundworms & Humans

The good news is we are paratenic hosts, so the roundworms never become full adults. The bad news is the larvae can still do damage to our bodies. Children are most susceptible. The most important things are to properly prepare and cook meat, practice good hygiene, be careful when cleaning litter boxes, and remind children to be careful around sandboxes (where outdoor cats sometimes do their business).


Gastrointestinal Parasites of Cats, Cornell Feline Health Center.

Parasites – Toxcariasis, CDC.

Roundworm in Cats, by Lianne McLeod, The Spruce Pets.

Roundworms in Cats Are No Joke—Here’s What You Should Know, by Heather Louge, The Dog People by

Roundworm Infection in Cats, by Ernest Ward, updated by Amy Panning, VCA Hospitals.

By LizsKittyBootCamp

Hi, I'm Liz, and I'm a cat behaviorist who provides advice and insights on cat behavior.

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