Doctors Pluck 11 Mating Worms From a Farmer's Eyes Before Larvae Emerge

A 71-year-old crop farmer in South Korea spent two months with eyes that felt as if something were stuck in them, and that were red and blurry. When doctors finally looked closely, they found the cause: 11 living worms, wriggling on his eyeballs. Several of the female worms were pregnant, and once the worms had been pulled out, tightly coiled baby worms began bursting out of them.

Eleven worms, plucked out one by one

The man went to an eye clinic after the discomfort had lasted two months. Doctors saw several moving, whitish roundworms. The blood vessels in the clear membrane that covers the eye were enlarged, which made his eyes look red, and cells on the surface of the clear dome at the front of the eye had worn away.

After numbing his eyes with a treatment applied to the surface, the doctors used fine forceps to lift the worms out one at a time. They collected 11 adult worms, each between 11 and 22 millimeters long. The case was written up in the New England Journal of Medicine.

Because every adult worm was removed, the infection was over. The man did not need antiparasitic medicine, even if some baby worms had been left behind. Two months later, his eye symptoms had cleared up and there were no more worms.

Why the baby worms were about to arrive

Adult worms do not simply visit an eye; they live and mate there. The males can be told apart by needle-like structures used in mating.

The females have an unusual way of reproducing. Biologists call it ovoviviparous: the young develop inside eggs inside the mother's body, and she releases them as live, tightly coiled baby worms rather than laying eggs that hatch outside. Some of the females taken from the man's eyes were plump with eggs that already held developing young. After the worms were removed, coiled young worms began bursting out of some of them.

The fly that delivers the worms

The worms belong to a species called Thelazia callipaeda, which is widespread across Asia and has also established itself in parts of Europe. It mainly infests the eyes of cats and dogs, but people can pick it up too.

The worms depend on flies. Flies that feed at an animal's eyes take in tears and secretions, and from an infested eye they can also pick up the worms' first-stage young. Inside the fly, those young worms molt twice, then move to the fly's mouthparts and wait. When the fly next feeds at a suitable eye, they drop off, take up residence, and molt once more into adults. Then the cycle starts again, with adult worms living and mating on the surface of an eye.