How are horses infected by worms?
Adult worms live in the intestines of the horse where they eat and breed. One little worm can lay tens of thousands of tiny eggs every day, so small they are only visible under a microscope. These eggs are passed out in the horse’s poo, like the redworm in this picture, and onto the fields where the horses graze.
The worm eggs hatch into larvae and wriggle away from the dung.
Did you know that these baby worms can travel up to 3 metres from the pile of poo in which they were laid, an amazing feat for such a tiny creature!
Their aim is to journey to a tasty piece of grass and hang out there in the hope of getting back inside a passing horse. Most larvae shrivel up and die waiting, while others might be eaten by a different kind of animal such as a sheep or a cow. These larvae would also perish because the gut conditions of these animals are very different to a horse.
But for some lucky larvae a horse will come along and eat the blade of grass they’re sitting on. They get taken along for the ride, munched up in the horse’s mouth, swallowed into its belly and down into the gut. Here they can get cosy and grow up to continue the worm lifecycle over again.