Parasite that lived in woman's eye for 2 years likely came from crocodile meat

A mass that had been growing in a woman's eye for two years turned out to be a parasite that sometimes passes from reptiles to humans, doctors say.

The doctors flagged contaminated crocodile meat as a potential source of the rare infection, which may make it the first case of its kind in medical literature, they reported Thursday (April 11) in  JAMA Ophthalmology.

The report's authors diagnosed the woman with an infection called "ocular pentastomiasis," a rare eye infection caused by parasites called pentastomids. In this case, a parasite had embedded itself under the conjunctiva, or clear outer membrane, of the patient's left eye. There, it had grown to about 0.4 inch (10 millimeters) long.

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The 28-year-old, from Basankusu in Congo, showed no symptoms other than the notable mass in the corner of her eye, her doctors reported. Upon examination, they found the mass could move and surgically removed it, which revealed a pale, C-shaped larva. They shipped the grub off for further analysis, and scientists found that it belonged to a species called Armillifer grandis.

This species, along with another in the genus Armillifer, is known to sometimes cause human infections in Africa. Other types of pentastomid have been reported to infect people in other regions of the world.

Armillifer parasites use snakes as their hosts in the final stage of their life cycle, laying their eggs in the respiratory tracts of various vipers and pythons. These eggs eventually exit the lungs and enter the environment via the snake's mouth or digestive tract. There, they're picked up by a rodent or other small maMMAl that a snake is likely to eat; they typically develop into larvae in these hosts before getting gobbled up by a snake, thus completing the parasite's life cycle.