Out of Sight

This might make you want to wash your hands. One in ten of us has at some point swallowed eggs from Toxocara – a roundworm carried by dogs and cats that causes the commonest parasitic infection in industrialised countries. Children are most at risk because the parasite’s eggs find their way into humans on unwashed hands and foods after lying dormant in soil fouled by dog poo. Around one in four sandpits – irresistible to pets too – is contaminated. Mostly, the parasite dies before it can inflict harm. But it can also seriously damage our sight if it reaches the eyes, where it wreaks havoc on the retina by causing it to peel-off or fold (top left and right), or by spinning opaque veils across the clear gel that maintains the shape of the eye-ball (bottom). Although laser surgery and vitrectomy offer effective treatments, prevention through good hygiene is better than cure.

Written by Tristan Farrow

Tristan Farrow

Writer

British Science Association Media Fellow. He holds a degree in quantum physics from the University of Cambridge and a Research Fellowship in quantum effects in biology.

• Adapted from image by Seong Joon Ahn and colleagues
• Seoul National University College of Medicine, Korea
• Originally published under a Creative Commons Licence (BY 4.0)
• Research published in PLOS Neglected Tropical Diseases, June 2014