This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Note for Pet Owners:
Toxocara cati is a common worm infection in cats.  Humans are occasionally reported to be infected by picking up the disease from the environment or from handling cats. ALL cats should be routinely treated against this worm to reduce the number in the cat population and in the environment, and so reduce the risk of contact and  transmission to humans. (See Zoonoses).

Kittens are not born with the disease but they are infected after birth

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Infection with the worm Toxocara cati is called Toxocariasis. Many cats have the worm present in their body but they may show no external signs of disease. However, these cats periodically pass the egg stage of the worm in their faeces and so contaminate the environment and act as a source of infection for spread  to other animals.

Feline toxocariasis is caused by a nematode - Toxocara cati - which is a roundworm. These worms live in the small intestine of cats



Electron Microscope Image


Breed Occurrence
There are no specific breed predispositions. All cats can be infected by Toxocara cati. Wild cats can also be infected by this parasite.

The vast majority of cats infected with T.cati show no signs of disease.

Young kittenss are most likely to show clinical signs, and these will be worse if the kitten has a large number of worms.

Signs include vomiting, diarrhoea, stunted growth rate, distended abdomen (pot-bellied appearance), pale mucus membranes (eg gums). Sometimes infected kittenss have abdominal discomfort, groan when touched or lifted and are reluctant to move.

Death is rare , but has been reported and has been due to obstruction  of the intestine or ulceration and perforation of the intestine wall.

It is important to understand the life-cycle of the worm so that it can be properly controlled:

  1. Worm eggs are passed in the faeces of cats infected with the worm. These eggs are very small but can be seen by examining samples of the faeces under a microscope. 
  2. After a period of maturation in the environment these eggs become infective to other animals. This period of maturation depends upon weather conditions and environmental temperature in particular. In the UK it takes 2-3 weeks during the summer and several months during the winter. The eggs can survive for 2 years or more in the environment.
  3. The infective eggs are ingested and can develop in intermediate hosts including earth-worms, cockroaches, birds, rodents and dogs. The infective eggs or larvae are then ingested by a cat.
  4. The larvae that hatch from the eggs develop into mature worms in the small intestine and start shedding eggs after a few weeks. 

Kittens can be infected after birth  through milk - but they are not infeted in the uterus.

All kittens should be assumed to be infected.

Diagnosis can be confirmed by identifying Toxocara cati eggs in faeces samples. However it should be remembered that eggs are not being shed into the faeces all the time, so false negative results are possible.

The aim of treatment is to protect young kittens and they should be treated routinely at 3 weekly intervals from 4 weeks to 16 weeks of age.

In addition regular treatment of adults is advisable to reduce the re-infection rate. In the UK the following products are licensed for use in cats:

The prognosis is good.

Long term problems
Re-infection is a problem in dogs living in areas in which there is high environmental contamination.