A squeamish case of parasitic infestation detailed in an April edition of JAMA Ophthalmology certainly isn’t easy on the eyes.

By the time the team of Indian doctors saw their teenage patient, the girl had already been suffering from double vision, centered around her left eye, for three days. Upon preliminary examination, they noticed a cyst buried just underneath the eye’s conjunctiva, a thin, clear, and mucus-rich membrane that covers the white portion of our eyes as well as the inside of our eyelids.

They prepared to examine the girl with a slit-lamp, a tool that combines a low-power microscope with a high-intensity, thin beam of light. But just as she sat down for the exam, doctors noticed a milky discharge emanating from the cyst. A moment later, the cyst had popped out of the eye on its own, landing on the table below.

After presumably breathing a sigh of relief that it didn’t start sprouting tentacles, the doctors confirmed the grossly horrible truth — the cyst was in fact the larval form of the pork tapeworm (Taenia solium).

Tapeworm Travel

The origin of the girl’s eye invader is almost as strange as how it was discovered.

Ordinarily, people become sick with tapeworm because they ate raw or undercooked meat containing tapeworm cysts, which are the middle stage of the parasite’s life cycle. These cysts find their way into our guts and become full-fledged tapeworms over a span of two months. From there, they can cause symptoms ranging from stomach pain to weight loss in their unwitting hosts, although many are unaware of their presence entirely. Importantly, they also lay eggs that hitch rides on our bowel movements and get released into the wild when hosts forget to properly wash their hands after using the restroom.

The girl’s condition, more formally called cysticercosis, was different. Rather than swallowing a cyst, she swallowed an egg. Once haplessly ingested, these tapeworm eggs can develop into cysts that then have the ability to lodge themselves into various areas of the human body. The cysts, for some unknown reason, are unable to become adults this time around and essentially become the worm equivalent of deadbeat slackers who never pay the rent.

People living with someone else who has the typical tapeworm infection, called taeniasis, are obviously much more likely to catch cysticercosis — often from eating food contaminated by their inconsiderate roommate’s feces. And yes, someone with a tapeworm can give themselves cysticercosis too, in a perverse twist of fate that would make Shakespeare cringe with sympathy.

While both conditions are much more common in developing areas of the world, such as India, cysticercosis has earned a badge of infamy stateside as well, as it’s considered one of five neglected parasitic infections by the Centers for Disease Control and Prevention (CDC). The worst-case scenario for cysticercosis is when the cysts end up in the brain, and this leads to approximately 1,000 hospitalizations in the United States annually, according to the CDC. Though many brain cysts can be asymptomatic, they can also cause headaches, seizures, and even death, especially once the cysts eventually die off.

As seen with the current case study, the cysts can also cause discomfort when they end up elsewhere. Most either resolve on their own or can be surgically removed with ease. Rarely do they get shot out of the corner of someone’s eye like a cannon, though it has apparently happened at least three other times in India, according to a 1992 study.

Tapeworm cyst
A before-and-after snapshot of the titular cyst, which measured no more than 15 millimeters. Bhatia et al, JAMA Ophthalmology

Thankfully, the girl’s bizarre case does have a perfectly happy ending: Brain imaging revealed that no cysts had made their way to her brain. She received treatment to eliminate any left-behind worms, and a week later, she returned with eyes as healthy as they had ever been.

Now if only there was a treatment that could help someone instantaneously forget they ever had worms temporarily calling their eyes home.

Source: Bhatia K, Sengupta S, Sharma S. Spontaneous Extrusion of Subconjunctival Cysticercosis Cyst. JAMA Ophthalmology. 2016.