Roundworms in Cats and Kittens

There are two types of roundworm that affect cats and kittens: Toxascaris leonina and Toxacara cati. Because treatment protocols involve the same medication regime, once eggs are identified on a fecal examination we refer to the infection as roundworm and treat it identically.There are 3 ways cats and kittens can become infected with Toxacara cati:

  1. Consuming a prey animal such as a mouse or rodent that is carrying developing worms
  2. Nursing from a mother cat who had been infected in late pregnancy, most kittens acquire roundworm in this manner.
  3. Consuming infective eggs from the soil and environment, generally through normal grooming practices.
    Roundworm infection can have numerous negative effects on your cat or kitten. In young cats/kittens, it is one of the most common causes of diarrhea and vomiting. The roundworms happily consume the host’s food and can lead to unthriftiness and general ill health, kittens usually have a pot-bellied appearance.

How do we know your cat or kitten is infected?

  • By a routine fecal examination, which is very important for kittens and is highly recommended for adult cats (even if their status is indoors)
  • A fecal sample is tested to confirm the presence of roundworm and although this is a reliable method of detection it is dependent upon the fecal sample containing eggs.
  • Often a cat or kitten may vomit up a worm, and there is a good chance this is a roundworm (especially in a kitten). Roundworms are often described as looking like cooked spaghetti, as they are long and white in appearance. If your cat or kitten vomits up a worm always bring the worm into the clinic for identification, this will help us treat your cat appropriately.

A few interesting facts about roundworm:

  • The roundworm eggs are not only highly infective but also extremely hardy and can withstand even the harshest of environments. This means they remain infective in the soil for many years.
  • Fresh feces are not infective
  • 19% of all indoor potting soil has been identified as carrying roundworm eggs
  • Deworming needs to be carried out over a period of weeks to help clear the roundworms from the intestine.
  • Roundworms can be transmitted to humans by contact with contaminated soil and surfaces, so proper parasitic control is recommended in all households but especially those with small children and immunocompromised individuals.

For more information on roundworms and parasites please visit the Companion Animal Parasitic Council website at

Written by Fairmont Animal Hospital