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Toxocara canis and Toxocara cati are roundworms of dogs and cats respectively.


The adult worm is found in the intestine of dogs and cats. Worm eggs are passed in the faeces to contaminate the environment and act as a source of infection for spread to other animals including people.

Where the disease occurs

This disease can occur anywhere.

The disease in animals

These worms occur commonly in dogs and cats. Many adult dogs are infected with the worm without showing any signs. However, loss of appetite and weight loss can occur. Puppies and kittens are often born with the disease because they can be infected whilst still in the uterus. The growth of the young animal can be restricted due to a high worm burden.

Control of the disease in animals

All dogs and cats should be routinely treated for this worm. Regular treatment of young animals with an anti-parasitic is recommended.

How people can get the disease

Toxocariasis is a disease of people that is caused by the larvae of these worms. Symptoms are associated with the migration of larval forms of the roundworm through organs and tissues. Most human infections are mild enough to go unnoticed and apparently produce no permanent damage. Children are most at risk of developing this condition; with most cases affecting children under 6 years of age. Common symptoms include abdominal pain, headache, weakness, lethargy, loss of appetite, skin rashes, joint or muscle pain  and wheezing. However, sometimes infection results in severe and even fatal disease.

A serious form of this disease, referred to as ocular larva migrans (OLM), affects the eye, producing a paediatric uveitis. This can result in blindness.

All cases of toxocariasis are caused by worms in pets and the majority are associated with dog contact. Most human infections occur in children, usually as a result of eating dirt contaminated with animal faeces.

Treatments for people

Treatments required may vary depending on symptoms. Specific drugs can be used to kill the larvae and reduce inflammation associated with larval migration. In addition, rigorous treatments are available for the disease affecting the eye.  

Preventing disease in people
  • Maintain good hygiene practices.
  • Prevent children from eating dirt.
  • Cover sandpits and prevent dogs and cats from entering areas where children play.
  • Worm dogs and cats regularly with effective treatments, especially when puppies and kittens. Treat bitches prior to whelping.
  • Keep children away from bitches and pups during the suckling period.
  • Discourage children from kissing pets and teach them to wash hands thoroughly after handling dogs and cats.

Further information