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The Two Types of Roundworms in Cats

There are two species of roundworms that affect cats: Toxocara cati and Toxascaris leonina. Both are found to be very common in felines and most cats often become infected with one or the other at some point in their lives. Comparing the two, Toxocara cati is considered more of a threat since it can potentially infect humans, while Toxascaris leonina can only affect cats and dogs.


Life Cycles

The Two Types of Roundworms in CatsToxocara cati begins its life cycle when non-infective eggs are shed by an infected cat through feces. Then, after over a period of three to four weeks, the eggs become infective. Once the infective eggs are ingested by another cat, they hatch into larvae and penetrate the gut wall. Eventually, they migrate through the lungs and esophagus, where they get coughed up and swallowed, allowing them to enter the gastrointestinal tract and mature into adult worms in the small intestine.

If a pregnant cat becomes infected with Toxocara cati, she can pass the worms to her kittens while nursing.

Toxascaris leonina, on the other hand, has a less complicated life cycle. Eggs are shed in an infected cat’s feces and become infective over a period of two to four weeks. These eggs can remain infective and survive in the environment for months if the weather is cool and humid. Then, when unsuspecting cats (or other mammals) ingest the eggs, they hatch into larvae, and penetrate the gut wall, where they molt twice. After that, they grow into mature worms and the cycle repeats.



Cats that are infected with Toxocara cati shed infective eggs through their feces, so the most common way for the infection to spread is through accidental ingestion of the eggs. Other animals, as well as humans, can become infected by coming into contact with contaminated surfaces, toys, water, equipment, and sometimes even undercooked food. Kittens born to an infected mother can also contract the parasitic infection while nursing.

Similar to Toxocara cati, Toxascaris leonina is spread through the shedding of infective eggs. However, it can only affect dogs and cats. Also, it can’t be transmitted via the transmammary route, meaning infected mother cats won’t be able to pass the worms to her kittens through breastmilk.



Signs And Symtoms

The Two Types of Roundworms in CatsSince Toxocara cati and Toxascaris leonina are both roundworms, animals infected with either can display very similar signs. However, humans infected with Toxocara cati show a different set of symptoms.

Signs of infection in animals include diarrhea, vomiting, weight loss or an inability to gain weight, a pot-bellied appearance, dull coat, and for kittens, adult worms in their feces or vomit.

Infected humans mostly don’t show any outward signs of infection since it usually resolves on its own in a few months. But, some people may experience mild symptoms, such as headaches, stomach pain, fever, or a cough. In rare cases, the roundworms can also migrate into other organs, such as the liver, lungs, eyes and brain, causing severe symptoms, such as wheezing or breathing difficulties, loss of appetite, rapid weight loss, rashes, weakness, seizures, blurry vision (usually only in one eye), or a red, painful eye.



Treatment for both roundworms is the same. Your veterinarian will prescribe an anthelmintic medication (anti-parasitic drugs that kill parasitic worms) for your cat, depending on their size, medical history, and the severity of the infection. After prescribing the medication that best suits your cat, they will give you instructions on how and when to administer the medications.

Since anthelmintic drugs only work on adult worms, your veterinarian will mostly advise you to repeat the process of giving your cat their medication at two to three-week intervals until all the worms are eradicated.



The best way to prevent your cat from getting roundworms is to keep their surroundings clean. It also helps to prevent them from roaming outdoors unsupervised. Cats that go outside are more likely to contract roundworms because they can easily come into contact with contaminated food, water, objects, and surfaces, as well as infected animals.

Other ways to prevent roundworm infection include:

  • Making sure all pets are dewormed.
  • Always wash your hands after touching pets or other animals.
  • Maintaining a regular cleaning schedule.
  • Keeping children away litterboxes.
  • Keeping the litterbox clean.
  • Wearing gloves when scooping out feces from the litterbox.
  • Training your cat not to climb on surfaces where food is often prepared.


Has your cat ever been infected with roundworms? How did you get rid of it? We’d love to read about your stories down below!