The Truth about Lice Revealed. A new discovery about the human holobiont

 "Lice Capades," an episode of the TV series "South Park." Lice are being understood as an important part of the human holobionts and, who knows? One day they may be considered as an essential component of human health, just as gut bacteria. 

 

Today I had a little revelation on lice. I had been writing about some recent discoveries on the beneficial effects of lice on human health and I had reported a story that I heard from my wife about people swallowing live lice as a remedy for jaundice (hepatitis b). And of people in Florence selling lice just for that purpose. But I wasn't sure if it was a real story or a legend. 

But, today, I heard a talk by Maurizio Naldini, a Florentine journalist, who told several stories about the Florence of his youth. And, yes, he had met in person the woman who sold lice! It was true: people would buy lice in Florence as late as some 50 or 60 years ago. 

The curious thing about this story is that Mr. Naldini had no idea of why people bought lice and what they did with them. So, he listened with great interest to my wife telling him the story of lice being swallowed inside a wheat wafer to cure jaundice. 

In my case, hearing Mr. Naldini had a different effect. Now that I knew that the story was most likely true, then I could examine it more in depth. Of course, the idea that lice would suck out the bile of jaundice makes no sense. Swallowed lice (dead or alive) can hardly suck anything. But then, why would people do such a thing? 

Of course, there is a tradition for people paying good money to do the strangest things when they are sick and they think something can help. CBS has a list of the 15 most bizarre (and disgusting) cures ever invented, and it is surely interesting to learn about such ideas as placing a dead mouse in the mouth to cure toothaches or using crocodile dung as a contraceptive. But they don't mention lice!

Yet, even the most bizarre ideas have an origin and I think that the lice market of Florence had a justification, probably better than that of crocodile dung. It has to do with the concept of holobiont, the fact that the human body (just as that of most animals) is an incredibly complex assemblage of creatures. Most of them very small (bacteria and viruses), some a little larger (lice and others), and with the actual human organism as just one of the many, although surely the biggest. 

Now, holobionts exist, and if something exists it means there are good reasons for it to exist. Most of the creatures that populate the human holobiont are there for a reason. Maybe they are just harmless commensals but in many cases, they are useful symbionts. And that may well be the case of lice, too. 

I already mentioned a study that found "Unexpected Benefits from Lice." The little critters seem to boost the human immune system. But there may also be another benefit. You see, there are three kinds of lice inhabiting the human holobiont: the body louse, the head louse, and the pubic louse. 

Of these three, the only one that may be harmful to human health is the body louse. It may be because it is a relatively recent human parasite having developed in parallel with the use of clothing. But another study argues that the "good" head lice can be beneficial in stimulating the development of an immune response against the "bad" body lice. So, if you have (or have had) head lice, you are healthier.

Perhaps this is the key to the story of the market of lice in Florence. Ancient Florentines knew little about immunity, but they may well have noted that people who had head lice were less prone to have body lice. Perhaps even that head lice could help people get rid of body lice.  Lice don't jump around or fly, so moving from one body to another is not so easy. And so they would ask their friends and relatives if they could give a hand in passing lice to someone who was lice-deprived. Then, why not? Some enterprising people thought they might make a little cash by providing others with a commodity that was needed: lice. 

Maybe this was the origin of the legend that my wife told me. Once that lice were understood as beneficial, it was natural that they could be tested on other kinds of illnesses. Then, the placebo effect would convince people that lice were effective in curing jaundice. With the more enlightened (so to say) 20th century, lice of all kinds became anathema and a social stigma, But the idea that you could eat lice in a wafer to cure a rather stubborn illness such as jaundice remained for some time. 

It is an interesting story that goes in parallel with that of the discovery of the bacterial flora in the guts. Some people understood right away their importance and their beneficial effects, but others thought that it was not hygienic having bacteria in your guts and thought it was a good idea to get rid of them. Now, of course, you buy probiotic supplements just to get more good bacteria inside your guts. Who knows? Maybe one day it will be fashionable to buy head lice in a pharmacy in order to prime people's immune systems!

And this is the story. The more things you know, the more you discover. And so, onward, fellow holobionts!

 

Note: After publishing this post, I received a link from Jan Barendrecht to a paper that describes how swallowing lice was considered a therapy for several kinds of illness in Spain. But not just in Spain. The authors say that: 

Numerous authors show that using animal resources as therapy is a widely distributed atavistic practice [52,53], a fact that is demonstrated by the use of head louse against jaundice in distant geographical areas [54,55]. Its use is particularly common in the Hebrew culture. Izaak Walton in his famous book “The Compleat Angler” (published in 1653) records that the Jews were the first to say that swallowing live lice is a good remedy for jaundice [56]. For their part, the German rabbi Yair Bacharach (1639–1702), author of the collection of responsa known as “Havvot Yair” (“Villages of Yair”), indicates that the patient should take 8 lice taken from his/her own head–see Rosner and Bleich 2000 [57]. Ben-Ezra in 1949 recorded in Horodetz (one of the oldest Jewish communities in Russia-Poland) the introduction of lice in an omelette as treatment [58]. In Latin America there are also references to this medical practice. In this case, the remedy would have been brought by the Spanish conquistadors and assimilated by the Spanish American folk medicine in an eclectic form [9]. The recommended number of specimen to take in Chile, Peru, Guatemala and Argentina is 4 or 5 with examples found using measures such as a thimbleful [59-62].