Timmy the Tapeworm

Among this year’s Hugo nominees is Parasite by Mira Grant (Seanan McGuire). The novel depicts a world where everyone takes on an engineered tapeworm to maintain their own health. Some readers have questioned how such a world could be–it’s impressive that such a book even made it to the Hugo. But the author herself did her research–she herself hosted a live tapeworm named “Timmy,” as she told us at Boskone.

In fact, some physicians actually recommend hosting a tapeworm (in moderation) as a modulator of the immune system. (Don’t try on your own–there can be complications, like tapeworm in the brain.) As I posted earlier, therapy using pig parasites is now used to restore cytokine balance in the immune system. The therapeutic parasite can grow only for a limited time in the human, and cannot reproduce.

In fact, all our bodies have evolved in the presence of hosted organisms, just as we evolved in the presence of air and water. Even the bacteria that cause intestinal distress (diarrhea) have attributes that protect us from cancer. A study in PNAS 2003 showed an inverse correlation between the rates of diarrheal illness and of colon cancer.

More recently, the basis of the cancer correlation was shown to be certain toxins emitted by the bacteria, called enterotoxins. These enterotoxins mimic the body’s own regulator molecules that cause cells of the intestinal lining to differentiate for digestion. These same toxins (and regulator molecules) down-regulate cell proliferation leading to cancer. It appears that humans evolved to depend on a certain chronic level of diarrhea-causing bacteria to suppress tumor formation in the colon. But now, pharmaceutical companies are working to design versions of the enterotoxin that maximize the helpful effects without unpleasantness.

In effect, we learn something from our unwelcome visitors.