What are roundworms?

Roundworms (Ascarids) are a common intestinal parasitic worm found in many species. There are two species which affect cats, Toxocara cati and Toxascaris leonina. Toxocara cati is more commonly found in cats. They feed upon the intestinal contents, competing with the host for food.

Roundworms are around 3 - 5 inches long and spaghetti like in appearance.

How do cats become infected with roundworms?

There are three modes of transmission, all of which occur when the cat consumes the infective eggs. It is possible for larvae to be encysted in the tissues from an earlier infection.

Life cycle of Toxocara cati:

Eggs are passed in the faeces, at this stage they are not infective. Once in the environment they develop into what's known as "second stage larvae". This takes around three weeks.  It is at this time that they become infective. Eggs can survive in the environment for months.

The cat ingests the egg containing the infective larvae. Once inside the cat they hatch in the cat's intestinal tract. The larvae migrate to the liver and other organs. In the liver they develop into the third stage. They then enter the bloodstream and migrate to the lungs. Once in the lungs where they develop into the fourth stage larvae. They are coughed up and into the throat and then swallowed, re-entering the intestinal tract for a second time. Once in the intestinal tract they mature and begin to mate. The female lays her eggs which are passed in the faeces and so the cycle begins once again.

Some of these become encysted in the tissues where they are inactive (or dormant). When a cat is wormed, the worms in the intestines are killed but the encysted larvae.

In rodents, the animal swallows the roundworm eggs which hatch inside the rodent's intestinal tract and then migrate to the organs where they become encysted. They are not able to complete their life cycle in rodents, but if cats eat infected prey, they can become infected.

Life Cycle of Toxascaris leonina:

As with Toxocara cati, the eggs of Toxascaris leonia are passed in the faeces where they develop into the second stage and become infective. The larvae are consumed by the cat they hatch in the cat's intestinal tract.

There is no transmammary transmission with Toxoscaris leonia.

What are the signs of roundworms in cats?

How is roundworm in cats diagnosed?

Diagnosis is performed by examination of the faeces for eggs.

Are roundworms dangerous to cats?

If the infestation is severe roundworms can lead to pneumonia and intestinal blockage. Also, as the roundworms are competing with the cat for food, it can result in your cat not receiving enough nutrients and becoming malnourished. This is usually seen in kittens.

What's the treatment for roundworms?

There are many effective medications to treat roundworms.

Can I catch roundworms from my cat?

Toxocariasis is a disease in humans caused by infection of the roundworm egg. Most cases have been identified as those of T. canis. Occasionally T. cati has been identified. In humans roundworms can't go past "stage 2" (larval stage). As with infection in rodents, the larvae migrate to various tissues in the body (causing a disease called visceral larva migrans or toxocariasis) including the lungs, brain, eyes and liver.

There are two forms of toxocariasis:

The larvae can remain alive for many months, causing damage by migrating through tissues.

Humans are more commonly affected by pinworms, which are a common type of worm found predominantly in school aged children.

How do I prevent roundworms in my pet?