Roundworms in Cats - Symptoms and Treatment - Cat-World
Cat Health

Roundworms in Cats – Symptoms and Treatment

roundworms in cats

Also known as ascarids, roundworms are a common intestinal parasitic worm. There are two species which affect cats, Toxocara cati and Toxascaris leonina. Infection with T. cati is most common.

Roundworms feed upon the intestinal contents, competing with the host for food. They are around 3 – 5 inches long with a spaghetti-like in appearance.  Both T. cati and T. leonina are found throughout the world.

What are the signs of roundworms in cats?

  • Poor coat condition, appearing rough and dull
  • Vomiting, if the infestation is heavy there may be worms present in the vomit
  • Pot-bellied appearance, especially in kittens
  • Coughing, when the roundworm larvae have migrated to the cat’s lungs
  • Severe cases can lead to pneumonia and intestinal and bowel blockage
  • Diarrhea
  • Anorexia (loss of appetite)
  • Stunted growth (in kittens)


roundworms in cats

Life cycle of roundworms and how they are transmitted

Life cycle T. Cati

Roundworm eggs are passed out via the cat’s feces, at this stage, they are not infective. Once in the environment, the eggs develop into second stage (L2) at which point they become infective. This takes between 3 to 4 weeks. Roundworm eggs are known for their hardiness and can survive in the environment for months. I have heard the only way to kill roundworm eggs is with a flamethrower (I don’t suggest you try this).

Once inside the cat, the eggs hatch in the intestinal tract, from there the larvae migrate to the liver and other organs where they develop into the third stage larvae (L3). They then enter the bloodstream and migrate to the lungs. Once in the lungs where they develop into the fourth stage larvae (L4). 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 roundworm lays up to 200,000 eggs per day.

Some larvae remain in the tissues (such as the liver) where they become encysted, remaining dormant. When a cat is wormed, the worms in the small intestine are killed but the encysted larvae are not. These become re-activated during pregnancy and migrate to mammary glands, where they infect the kittens during nursing.

Cats become infected in one of three ways:

  • Direct ingestion of infective roundworm eggs via contaminated food, water, feces or the environment.
  • Transport hosts such as mice or rats which have ingested roundworm eggs. Once inside the rodent’s intestinal tract the eggs hatch 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.
  • Transmammary infection. Kittens can become infected via their mother’s milk.

Life cycle T. Leonina

This roundworm has a much simpler life cycle compared to T. Cati as there is no migration once inside the cat.

Eggs are passed out of the infected cat via the feces but are not infective.  They remain in the environment and develop into the second stage, at this point they are now infective. The cat ingests infective second stage (L2) eggs via the environment or a transport host containing the encysted third stage (L3). Once inside the small intestine, the larvae matures into adult heartworms and begin to mate, shedding eggs in the feces.

Toxascaris leonina

Cats become infected in one of two ways:

  • Direct ingestion. As with Toxocara cati, the eggs of Toxascaris leonia are passed in the feces. Infective eggs are consumed by the cat they hatch in the cat’s intestinal tract.
  • Transport hosts such as mice, rats, beetles and earthworms which contain the encysted L3 stage larvae that are then eaten by the cat.

How are roundworms diagnosed?

cat roundworm
Image Denni Schnapp, Flickr

Diagnosis is performed by examination of the feces for the presence of roundworm eggs. Adult roundworms can sometimes be seen in the vomit of an infected cat.

Are roundworms dangerous to cats?

If the infestation is severe roundworms can lead to pneumonia as the roundworms migrate to the lungs as well as intestinal blockage.

As the roundworms are competing with the host for food, a heavy infestation can lead to malnutrition as well as stunted growth in kittens.

A heavy infestation, especially in kittens, can cause death.

Do I need to worm my indoor only cat?

Yes, even indoor cats can still potentially catch worms and should be regularly wormed unless advised otherwise by your veterinarian.

Are roundworms contagious to other cats?

Infected cats shedding roundworm eggs in their feces can contaminate the environment, which can then infect other cats who come into contact with the infective eggs.

Nursing cats can pass roundworms onto her kittens via her milk.


Can I catch roundworms from my cat?

Toxocariasis is a disease in humans caused by roundworm infection. 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. 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:

  • Ocular larva migrans (OLM) results from the larvae entering the eye, causing an inflammatory response, which leads to damage to the eye, in severe cases, it can result in blindness.
  • Visceral larva migrans (VLM): The larvae migrate to the various organs and cause an (inflammatory immune response) which leads to damage to the organs.

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?

  • Preventing hunting behaviour as well as maintaining rodent control.
  • If you are planning to mate your queen, she should be de-wormed prior to mating and receive another dose late in pregnancy.
  • Keep litter trays clean, solids should be scooped at least once or twice a day and thoroughly disinfected once a week.
  • Dispose of cat feces in the garbage, don’t put it in the garden.
  • If your cat does defecate in the garden, remove feces daily.
  • If you have a sandpit in your garden, make sure it is covered up when not in use to prevent cats defecating in it.
  • Kittens should be dewormed from two weeks of age, and every two weeks until they are 12 weeks old.
  • Adults should be de-wormed every 3-6 months, or as stated on your worming medication.

How are roundworms treated?

Brand name/active ingredient Parasites treated Age/pregnant etc
Advocate/Advantage Multi (Imidacloprid and Moxidectin)Spot on (monthly) Fleas (adult), roundworms, hookworms,  lungworm and ear mites. Heartworm preventative. Does not treat tapeworm. 9 weeks old. Safe use on pregnant and lactating females has not been established.
Aristopet (Praziquantel and Pyrantel embolate)Tablets Roundworm, hookworm and tapeworm. 6 weeks old. Can be used on pregnant and lactating females.
Excelpet (Praziquantel and Pyrantel Embolate)Tablets Roundworm, hookworm and tapeworm. 6 weeks old. Can be used on pregnant and lactating females.
Heartgard (Ivermectin and Pyrantel)Chews Roundworm, hookworm, heartworm preventative. 6 weeks old. Can be used on pregnant and lactating females.
Milbemax (Milbemycin Oxime and Praziquantel)Tablets Roundworm, hookworm, tapeworm. Heartworm preventative. 6 weeks and over 500g. Can be used on pregnant and lactating females.
Panacur (Fenbendazole)Tablets and paste Tapeworm (Taenia taeniaeformis species), roundworm, hookworm, whipworm, lungworm and giardia. Does not treat Dipylidium caninum tapeworm. Can be used on pregnant and lactating cats and kittens over 2 weeks.
Popantel (Praziquantel)Tablets Roundworm, hookworm and tapeworm. Can be used on pregnant and lactating cats and kittens over 6 weeks.
Profender (Praziquantel and Emodepside)Spot on (monthly) Roundworm, hookworm, tapeworm and lungworm. 8 weeks and over 500g. Can be used on pregnant and lactating cats.
Purina Total Care (Pyrantel embolate and Niclosamide)Paste and tablets Roundworm, hookworm and tapeworm. 6 weeks old. Can be used on pregnant and lactating cats.
Revolution (Selamectin)Spot on (monthly) Fleas (adult, larvae and eggs), intestinal worms (except tapeworm), lungworm and ear mites. Heartworm preventative. Does not treat tapeworm. 6 weeks old. Can be used on pregnant and lactating females.