The worms mate in the human eyes and are removed just before the larvae burst

The worms’ life cycle depends on flies that feed on the animals’ eyes, sucking up tears and secretions. When feeding on an infested eye, flies can catch the first instar larvae of the worms, which use the insect as both an incubator and an air taxi. Inside the fly, the larvae molt twice, becoming third instar larvae, which then migrate to the fly’s mouthparts and await the next stop in a suitable watery eyeball. The larvae disembark from their flying nannies and settle into a permanent residence, where they transform into adults after further molting. Adult worms live and mate directly on the victim’s eyes.

Unlike other worms, the female T. callipaeda are ovoviviparous, meaning the embryos develop in eggs inside the body of the female worm. Females release large clutches of densely coiled first instar larvae, which wait to be washed by a thirsty fly.

Some of the female flies removed from the man’s eyes were filled with embryonated eggs. Doctors noted that coiled larvae had begun to emerge from some of them after being plucked from the man’s eyes. Male worms, meanwhile, were identified by their copulatory spicules, needle-like structures used to facilitate mating.

Fortunately for the man, having all the adult worms removed from his orbs meant the infection was over: no antiparasitic medication was needed, although some of the larvae had been left behind. At a follow-up appointment two months later, doctors found that all of her eye symptoms had disappeared and there were no more worms.