Toxocara cati (toxo=arrow + cara=head; synonym Toxocara mystax, common name feline roundworm) is worldwide distributed parasite of cats and other felids and it is one of the most common nematodes of cats. This parasite is dangerous as it can infect both wild felids as well as domestic felids. Adult worms are localised in the gut of the host. In adult cats, the infection – which is called toxocariasis – is usually asymptomatic. However, massive infection in juvenile cats can be fatal.