It was a typical day of browsing when, on the image-sharing site Imgur, I encountered a sex myth that needed debunking. Don’t click that link unless you want a fairly graphic account of what happened — to spare you, I now provide a more clinical description: the image shared was a screengrab of an anonymous comment detailing an incident that occurred during anal sex. According to the poster, he was engaging in the activity when he felt something in the anal canal and pulled out to discover a large cestode coiled around his sexual organ.
“Cestode” describes any number of a class of parasitic flatworms, the best known of which is the tapeworm, which also happens to be the star of this horrific anecdote. Now, if you’re familiar with this type of parasite, you can probably guess why this anecdote strikes me as being patently false. But if you aren’t, and you have managed to continue reading despite how uncomfortable it is for many of us to think of parasitic infections, I’ll explain: The tapeworm does not have the sort of musculature that a snake, for instance, has.
“The tapeworm is pretty flaccid and not good for wrapping around anything,” explained parasitologist Dr. Tommy Leung from the University of New England, Australia, when I pinged him to discuss. “The body structure of the tapeworm is essentially a chain. Most of the muscles are for it to wave itself in the intestine to maximize nutritional flow over its body. The most muscular — in terms of strength — bit would be the ‘head,’ called the scolex.”
The tapeworm attaches to the intestinal wall by the scolex, which is why that part of the parasite is stronger than the rest. But it is highly unlikely that a tapeworm would attach itself near the anal canal as the small intestine, where pre-digested food is located, is a much richer environment. By the time food arrives at the colon, the nutritional value is almost nil, and of no interest to a parasite.
There are only two things that could ever lead to a tapeworm presence in that area — one of them is via tapeworm egg packets, called proglottids.
“The proglottids break off from the end of the tapeworm, and make their way to the colon where they can eventually pass out with the host’s faeces,” Dr. Leung told me. However, in the egg state, the tapeworm is within a protective package, not in worm form. The eggs won’t even hatch before reaching the outside world, so, no, there is no chance that tapeworm junior would hatch in the anal canal and live there.
“In some cases, an egg packet won’t start hatching until it is eaten by the correct host,” Dr. Leung added. There a few types of proglottid that are sufficiently muscular to exit the anal canal on their own — dog tapeworm (Dipylidium) is one of them — but their degree of mobility is extremely limited, and again, it is not possible for any coiling to occur.
Other than as an egg packet, the only other way a tapeworm might make an appearance in the anal canal is by dying. If you take anti-worm medication and, a few days later, engage in anal sex, it is not impossible that your sexual partner, while in the general area, might encounter a dead parasite that is on its way to being expelled by your body. But if this happened, the parasite would be quite limp, and completely incapable of constricting the penis, as the poster wrote had occurred.
It is far more probable that the tapeworm would be broken into pieces. In death, the parasite would become incapable of suppressing or tricking its host’s immune system, and as a result, its body would fall victim to the relentless attack of the human body’s arsenal of immune defenses.
So we can safely say that the posting is false. However, this one remains within the realm of possibility. Don’t click unless you are absolutely sure you want to read that!
It’s quite fascinating that on the Imgur share of the original comment, some nine people either expressed interest in witnessing this, or admitted to masturbating while reading about it. Rule 34 applies. Whatever you do, do not search for parasite porn.
(Oh, why can’t I ever take my own advice? You curious? Are you sure? Okay, here you go.)
Header image by brainwise.