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Cat Vomited Roundworms and Tapeworm

Updated: Nov 16, 2021

Here is another PSA! All indoor/outdoor cats need regular deworming.


Those long spaghetti-like worms are a type of roundworm. Most likely Toxocara cati, since it was found in the vomit of a cat. But we didn't look for the species as it does not change the treatment outcome.

The even more fun part about roundworms is that they are zoonotic! What is zoonotic you say? It means that these fun little critters can cause illness in people. Children and immunocompromised people are at higher risk. There was a report of a child becoming blind due to larval migration. Educate yourself and your family.

As one of our parasitologists in school used to say, itchy bum, sucky thumb! That just means it can be passed on from the feces of an infected animal to the oral cavity of a person. Or pinworms in people, but we can discuss that another day.

Treatment and prevention of Toxocara cati depends on a few factors. The age of the cat - is it a kitten and still nursing or is it weaned; the lifestyle of the cat - is it an indoor only kitty, or barn cat that is hunting; the cleanliest of its environment - is it apt to reinfecting itself with grooming or grooming another cat?

Since I have moved to a more rural area, I am seeing a lot more internal parasites and a lot more intact female cats. Educating pet owners is key to prevention.

Life Cycle:

The life cycle of the parasites is always the tough part. I am so glad I do not have to study this, I can just look it up!

How does your cat get Toxocara roundworms?

Your cat can consume the L3 larvae in the tissue of a paratenic host (in this diagram the duck or the rabbit, but mice and rats are also paratenic hosts). The L3 larvae migrates through the liver and lungs, and manages to be coughed up by the cat and swallowed into the stomach - very strange, but it needs to do this in order to become an adult worm. The adult worms lay eggs, and the eggs get pooped out. Eggs are then consumed by the paratenic host (or reinfection when the cat grooms itself or eats some infected grass in the environment).

If your cat is pregnant, then there is vertical transmission to the kittens. At birth, the kittens are not infected, but when they drink their mother's milk, it goes through a transmammary route. That is a whole new level of breast is best - but I digress! Larvae are found in kittens from days 15 to 22 after birth, when they are nursing from an infected mother.

What to do for prevention?

Well, you need to break up the life cycle somewhere in there. Preventing your cat from consuming paratenic hosts, preventing your cat from chewing infected materials that are contaminated by feces, cleaning up the feces to prevent contamination of the environment, and regular deworming.

The period of time in which the pet is infected and the time where the parasite is susceptible to medications will be important in the treatment regimen. Every 2 to 3 weeks for kittens and once a month for adults seems to be sufficient when using selamectin, moxidectin or milbemycin.

Deworming medication

There are a few products out there, some I use for treatment and some I use for prevention. Definitely discuss the cat's prevention with your veterinarian! Below are just some of the options we use in Canada, by drug name, not brand name, but you can look up what you are using easily.

Fenbendazole: It's a fairly safe medication as it preferentially binds to nematode tubulin (the proteins that are required for mobility). However, it's not the most efficacious medication, so it needs to be given in multiple doses once daily for 3 to 14 days, depending on if the worms have some resistance to the medication. It does come in a liquid oral suspension though, which can be mixed with wet food, making it easier than pilling your cat. It also comes in granules, but those I find more difficult to dose.

Milbemycin: One of the many macrocyclic lactones available. It is more efficacious than Fenbendazole, only needing a single dose, but for outdoor cats, repeating the dose monthly is recommended. It can also come in a product combined with Praziquantel. The down side... very few cats will willingly chew a tablet, so its down the hatch!

Pyrantel: It is a nicotinic building medication - causing the worms to contract and then be paralyzed. Again, this can come in a liquid oral suspension. It is also labeled to be given to kittens as young as 2 weeks. As mentioned above, kittens can get Toxocara from their mother through the transmammary route. There is a tablet form that comes in combination with Praziquantel as well, but most people with kittens will stick with the liquid.

Selamectin: Instead of pilling your cat, you can apply a topical product once monthly. This is a macrocyclic lactone, working by paralyzing the worms. But your kitten has to be 6 weeks for labeled use of the topical medication. This medication gets the added protection from fleas and ear mites.

Moxidectin: Another macrocyclic lactone also coming in a topical formulation for cats, similar to selamectin. However, it is not labeled for kittens under 9 weeks of age, or smaller than 2 lbs.

Emodepside: Comes in a topical with Praziquantel and is labeled for use in your queen (mother cat) to prevent the kittens from becoming infected through the transmammary route. The transmission from queen to kitten is decreased by greater than 98%.

I know I said Praziquantel a few times up there.

So let's take a look at tapeworms.


Echinococcus multilocularis

Why am I starting with this one? Because it is zoonotic. So for the protection of your family, your dogs and cats need prevention. I already wrote about this tapeworm species, but here's how it works with your cat.

Cats are rarely infected or show clinical disease from this Echinococcus species, but they can get it from eating one of the intermediate hosts, mice or voles.

Cats can act as the definitive host by shedding the eggs of the tapeworm. Humans are a incidental host - but can get infected by consuming a tapeworm egg, getting the hydatid cystic form of the disease. See my previous article for more info.

Disease or infection in your pets can be prevented with monthly Praziquantel products (topical or oral as discussed above).

Taenia taeniaeformis

This is likely the species of tapeworm in our lovely video. They are the flat and wide worms that look like a piece of tape. Fortunately not pathogenic to humans, but gross none-the-less.

Taenia taeniaeformis are passed from a mouse host, surprise, surprise, on to your cat. In cats with really high infestations, you might see intestinal impaction from too many worms.

Prevention is keeping your cat indoors or on monthly deworming medication.

Dipylidium caninum

This is the third genus of tapeworms we will discuss. This one is not passed on through a mouse host! This one is passed on through fleas or lice. The flea larvae consume the eggs of the worms. Then when the cat or dog has a flea on it, and it eats the flea when they are grooming themselves, then they become infected with the tapeworm.

Flea prevention will prevent infection, however, you can also use monthly praziquantel for this tapeworm as well.

On the rare occasion, your child may ingest an infected flea and become mildly ill.

There are other species of tapeworms, so depending on the area of the world you live in, be sure to discuss with your veterinarian if you or your pet could be at risk.

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