From the Editor-in-Chief

If you want to lose your mind—and your appetite—dive into parasitology. In the helminthic subcategories of cestodes, nematodes, and trematodes, we find delicious sounds and mellifluous names—Diphyllobothrium latum, Paragonimus westermani, Ancylostoma duodenale, Enterobius vermicularis, Onchocerca volvulus, and Fasciolopsis buski—coupled with some of the most disgusting images and complex pathophysiology in medicine.

And helminthic worms are just a tiny sample of the vast array of parasites that beset us. It seems that every worm, larva, protozoan, arthropod, and insect wants a part of us—most commonly our blood and iron, though many will take any tissue they can get. They certainly don’t hesitate to take it in the most indecorous ways.

The present issue of JVRD contains a remarkable report by Ms. Katie Li and Drs. Brooke Geddie, Liliya Sutherland, Sumit Sharma, Sunil Srivastava, and Joseph Boss describing an 11-year-old boy with chronic uniocular uveitis with reduced visual acuity, intraocular inflammation, and multiple subretinal fluid blebs that persisted for years despite intensive anti-inflammatory therapy. Upon collapse of the subretinal lesions, a suspicious free-floating vitreous cyst was observed; astute questioning led to the discovery that the patient had a pet pig and visited pigpens frequently. Cysticercosis of both the eye and brain was proven, and targeted therapy was effective and visually restorative.

As for many parasites, the life cycle of the pork tapeworm Taenia solium is exceedingly complex. Humans are the sole definitive host for the adult worms and harbor the parasite in the small intestine, where it reaches a length of 2 to 7 meters on maturity. Infestation with an adult pork tapeworm is known as taeniasis and can be asymptomatic or lead to symptoms including abdominal pain, weight loss, diarrhea, nausea, and even the passage of visible ova-containing worm segments called proglottids in the stools. Though millions are infected worldwide, death from adult-worm infestation is uncommon. However, the shedding of the pork tapeworm ova and proglottids in human feces poses the far greater threat, as we will shortly see.

It is helpful to distinguish 2 different cycles, both of which begin with egg and proglottid-containing human feces. The first cycle passes through pigs that ingest food and water contaminated by these feces; these early-stage T. solium forms develop in the pig intestine into the next stage of worm maturation called oncospheres, which migrate throughout the animal and further develop into encysted larvae (cysticerci) in muscle and elsewhere.

This first cycle, in which the pig develops the condition known as cysticercosis, sustains the spread of the intestinal tapeworm infestation (taeniasis) to humans who eat these encysted larvae in undercooked pork. The second cycle is the direct human ingestion of the similarly contaminated water or food (typically uncooked vegetables); the egg and proglottid forms again develop into oncospheres in the stomach, which then circulate throughout the body. Larval cysts develop in the subcutaneous spaces, abdominal organs, brain, and eye, resulting in human cysticercosis.

As if the above complexity were not enough, tapeworm-harboring individuals can also develop cysticercosis through autoinfection by passing eggs and proglottids to themselves (or others) through fecal-oral transmission—or even without eating anything at all when eggs and proglottids shed by the resident worm enter the stomach through retrograde passage. Alert readers will discover a perhaps-unexpected corollary to the cycles presented above, and it is relevant to how the boy with the pet pig might have developed cysticercosis; more details ahead.

Cysticercosis is extremely common in the developing world, affecting tens of millions of people, and neurocysticercosis is the most common cause of adult-onset seizures in many countries. While it’s easy to eliminate the adult tapeworm from the gut, managing neurocysticercosis is extremely complex and difficult.

Taeniasis and cysticercosis are common in certain areas, but these conditions are, perhaps surprisingly, considered eradicable given that the cycles are tightly limited to man and pig, and 1) widespread education, 2) improved hygiene, 3) anti-helminthics, and 4) newly developed and effective recombinant vaccines to prevent cysticercosis in pigs can all be brought to bear.

How were these absurdly complicated cycles discovered? The adult worm lives only in humans and there is no animal model available. The history of helminthic research includes episodes in which brave researchers self-ingested various worms while other no-less-intrepid colleagues combed through piles of feces and minced animal and human cadavers. Nevertheless, the method for elucidating the connection between the larval form of T. solium (known as Cysticercus cellulosae) and the adult worm was more distasteful in many ways: human experimentation on unwitting convicts sentenced to execution.

Friedrich Küchenmeister was a physician in private practice in obstetrics and gynecology in Zittau, Germany. He was an energetic parasitology researcher and apparently quite strong willed, known to complain that his insights and discoveries were often ridiculed or ignored. Dr. Küchenmeister became convinced that C. cellulosae and T. solium were different stages of the same organism and attempted to establish the connection by feeding larval worms to a “murderess under sentence of death” ¹ in 1853; this effort was a failure.

A couple of years later, on learning that a convict was due to be executed by guillotine several miles from his home, Dr. Küchenmeister secured the collaboration of unnamed colleagues for his plan and quickly searched for C. cellulosae but, unable to find these worms, had the unsuspecting convict fed other Cysticercus organisms in the days before his execution.

While this grisly experiment was incubating in the final days before the convict’s demise, Dr. Küchenmeister was about to dine at home with his wife and was thrilled (!) to discover that their local restaurant had delivered a meal of roast pork infested with worms. Realizing that these were C. cellulosae and a definitive demonstration of their relation to T. solium might be at hand, he raced to the restaurant and pleaded for information about the source of the contaminated meat.

“Finally, I discovered that the pork came from a pig that had been slaughtered in this restaurant about 60 hours previously, and I received one pound of raw meat, which had been kept in the cellar, containing the greatest number of bladder worms. . . . Exactly 72 hours before the death of the convict, I had arrived at the convict’s place of detention and, at once, the first-mentioned doctor prepared a breakfast for the convict with the bladder worms I supplied.

“Since soup at this time might have been suspicious, I suggested a few slices of bread and butter with Cervelat sausage from which the peppercorns were removed and peeled out and the holes filled with bladder worms. . . .The doctor in question did not have Cervelat sausage at hand, so he took blood sausage and removed some of the fat pieces from it; it their place he inserted some of the bladder worms, and everything else was smoothed over from the side.” ¹

Over the next 3 days, the convict received 4 additional C. cellulosae-laden meals including rice soup, noodle soup, and more sausage. Dr. Küchenmeister (marvelously translated as Kitchen Master) eerily—and no doubt self servingly—reported that the convict expressed warm appreciation for the tasty soups and sausage. Dissection of the cadaver would later disclose young T. solium in the gut and establish its connection to C. cellulosae.

Dr. Küchenmeister would repeat his experiments with other convicts prior to execution, even arguing that this “surely harmless experiment” might be extended to convicts under probable death sentence and, if they were pardoned, “the tapeworms can be easily expelled; this would calm anxious souls and will serve science at the same time.” ¹ Indeed, it is difficult, almost 5 centuries later, to find an appropriate context to comment on this abhorrent yet seminal line of investigation, apart from affirming that it is certainly a classic study in the annals of T. solium research.

The issue of JVRD also contains insightful articles on a variety of subjects including further characterization of pentosan polysulfate sodium-associated maculopathy, an examination of coagulation status in central retinal vein occlusion, a stepwise approach to managing hemorrhagic choroidal detachments, the use of hypochlorous acid 0.01% vs povidone-iodine 5% for ocular antisepsis, and other informative studies for your education and enjoyment.

How did the 11-year-old boy acquire cysticercosis? We can never know for sure, but we can speculate that he developed it from contact with a T. solium-harboring family member or friend at the pig farm. Perhaps this person prepared his lunch without washing hands after using the toilet or took gastrointestinal relief in the vegetable garden, or maybe the boy ingested some contaminated water near the outhouse at the pig farm. We will never know. But one thing is certain—he didn’t get it from his pet, because as the cycles have proven, you can’t get cysticercosis from pigs!

Donald J. D’Amico
Editor-in-Chief
Journal of VitreoRetinal Diseases