Last edited 12/2022 and last reviewed 12/2022

Toxocariasis is infection with worms of the genus Toxocara, a genus of nematode parasites found in dog - T.canis - and cats - T.cati. Both species can sometimes be found in man.

  • Toxocara canis (from dogs) is recognised as a potential cause of human toxocarosis, but Toxocara cati (from cats) and other species (eg, Toxascaris leonina found in foxes) are also possible causes

It occurs in two types:

  • visceral larva migrans
  • ocular larva migrans also referred to as retinal granuloma

The phrase larva migrans refers to the fact that the worm fails to mature in humans.

Most colonisation with Toxocara species does not lead to symptomatic infection in well-cared for adult animals; young and debilitated animals are at greater risk

  • humans can acquire infection from infected animals, for example, via soil contaminated with faeces; however, most human infections are asymptomatic, with symptomatic infection being very rare in the UK (1)

Toxocarosis is not spread by person-to-person contact (1)


  • Patterson J. Toxocarosis in humans: how much of a problem is it in the UK? Drug and Therapeutics Bulletin 2023;61:7-11