Toxocariasis is a rare infection caused by roundworm parasites. It is spread from animals to humans via their infected faeces.

Roundworm parasites are most commonly found in cats, dogs and foxes and usually affect young children. This is because children are more likely to come into contact with contaminated soil when they play and put their hands in their mouths.

However, cases have been reported in people of all ages.

Signs and symptoms

For most people, an infection with these roundworm larvae causes no symptoms and the parasites die within a few months.

However, some people experience mild symptoms such as:

In rare cases, the roundworm larvae infect organs such as the liver, lungs, eyes or brain and cause severe symptoms such as:

  • fatigue
  • loss of appetite
  • breathing difficulties 
  • blurred or cloudy vision in one eye

Read more about the symptoms of toxocariasis.

See your GP as soon as possible if you think you or your child have symptoms that may be caused by toxocariasis.

blood test can usually detect toxocariasis, although you may need an eye examination to look for parasites if your eyes are affected.

Why it happens

The roundworm parasites responsible for toxocariasis (called Toxocara) live in the digestive system of dogs, foxes and cats. The worms produce eggs, which are released in the faeces of infected animals and contaminate soil.

If small particles of contaminated soil get into someone's mouth, they may develop toxocariasis.

It's not possible for someone with toxocariasis to pass it directly to another person.

Read more about the causes of toxocariasis.

Reducing your risk

The best way to reduce the chances of developing toxocariasis is to practise good hygiene.

For example, washing hands with soap and warm water after handling pets or coming into contact with soil or sand.

If you have a pet cat or dog, they should be regularly de-wormed and their faeces should be disposed of immediately.

Read more about preventing toxocariasis.

How it's treated

If you have no or mild symptoms, treatment is not usually necessary.

However, you will need medication if you have a severe infection affecting your organs. Specifically, a type of medication called an anthelminthic is used to kill the parasites.

If your eye is affected by toxocariasis, anthelminthics are not used, but steroid medication (corticosteroids) may be required to suppress inflammation.  Surgery may also be needed, for example if you develop retinal detachment.

Most cases make a full recovery and don't experience any long-term complications. However, there is a risk of permanent vision loss if one of the eyes is affected.

Read more about treating toxocariasis.

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