Human toxocariasis: visceral and ocular larva migrans in children
A family with a 4-year-old child adopts a puppy. The father has read that "dog worms can blind a child" and asks you whether it is true.
Which statement about human toxocariasis is correct?
chevron_right Show answer and explanation
A. It is caught mainly by stroking the dog or letting it lick the face
The risk comes mainly from ingesting embryonated eggs from contaminated soil or sand; direct contact with the animal is a minor and poorly documented route.
B. In humans the worms become adults in the gut and eggs are passed in the faeces
Humans are accidental (paratenic) hosts: the larvae migrate through the tissues but do not mature, so there are no eggs in the faeces and diagnosis is serological.
C. The ocular form is usually unilateral, can cause permanent visual loss and is due to the migration of few larvae
Correct. Ocular larva migrans occurs in somewhat older children, usually affects one eye (retinal granuloma, endophthalmitis) and is associated with low burdens; the visceral form occurs in young children with geophagia and causes eosinophilia and hepatomegaly.
D. It is a zoonosis caused only by Toxocara canis; Toxocara cati does not infect people
Toxocara cati also causes human toxocariasis. Cats defecating in sandpits and gardens are an important source of eggs.
lightbulb Key takeaway
Freshly passed eggs are not infective: they need weeks in the environment to embryonate, and then survive for years in the soil. The message for owners: deworm at the right frequency, pick up faeces promptly and make children wash their hands after playing in parks and sandpits.
Test yourself with 10 random questions
Parasitic diseases · 100 questions, a different test every time
Related questions
Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.