Toxocariasis is a rare infection in humans caused by the larvae of the dog roundworm Toxocara canis or the cat roundworm Toxocara cati transmitted from eggs in the animals' faeces. Fox poo is another source of infection.
Infection can come from parks, playgrounds and people's own gardens and pet litter trays.
Infection is not usually passed from person-to-person.
Toxocariasis can affect the liver, heart, lungs, muscles, eyes and brain.
People of all ages can be affected, but young children are most at risk through playing outdoors, picking things up, and putting their dirty hands and fingers in their mouths.
It is possible to be infected and not know it, with the eggs or larvae of roundworms dying off before passing on any infection.
Common symptoms of toxocariasis include coughs, fever, headaches and stomach pain.
If the roundworm larvae have spread the infection and the liver, lungs, eyes or brain are infected, more severe symptoms include:
Prompt medical attention should be sought if toxocariasis is suspected to avoid complications.
Diagnosis of toxocariasis is not straightforward, but will be made based on the person's symptoms and a physical examination.
A stool (poo) sample may be taken to look for worms or eggs and a blood test may detect infection.
If treatment is needed for toxocariasis, this will depend on symptoms and the parts of the body affected.
Anthelmintic (anti-worm) medication may be recommended to kill roundworm larvae in the body.
Steroids may be recommended to reduce inflammation for eye infections. Eye surgery may be needed for eye infections.
The key to preventing toxocariasis infection is good handwashing and hygiene, and avoiding unnecessary contact with animal poo or contaminated soil or water.
Teach children about leaving animal poo alone, and cover sandpits when they are not in use to stop cats using them as a litter tray. Make sure children wash their hands after playing outside.
Food grown in gardens with cats and dogs need to be washed carefully to remove any parasites.
If you are a pet owner, talk to your vet about regular worming.