There has been much discussion recently over why the incidence of allergies and chronic diseases is rising in Western industrialized countries. Some theories have been proposed, such as the hygiene hypothesis (that early childhood environments are too sterile and so that the developing immune system isn't properly "trained"), or that medicines such as antibiotics kill off beneficial bacteria, whille others say it is due to our Western diet and lifestyle. However, recently some researchers have proposed that the absence of intestinal worms, called helminths, in our bodies is actually negative for our health and could be a reason for the rising incidence of allergies and these diseases.
Over the centuries intestinal worms (such as hookworms) have caused a lot of human suffering, and therefore have been viewed as disease causing parasites. Western industrialized countries made major efforts (such as improved sanitation) to get rid of all intestinal worms in humans, and were generally successful. It is now rare to hear of someone in these countries having intestinal worms.
Dr. William Parker, an associate professor of surgery at Duke University in North Carolina, has written an interesting and thought-provoking article about the role of helminths in human health. He states: "A barrage of scientific evidence points toward helminths as being important regulators of immune function." In other words, we need them in order for our immune system to function properly.
Research actually shows that introducing certain species of intestinal worms, such as roundworms or flatworms, into the human gut successfully treats certain diseases in humans. But medicine has been slow to adopt such a view. Dr. Parker writes that viewing certain helminths as beneficial for proper immune functioning would be a "paradigm shift" in medicine.
By the way, the research looking at intestinal worms found benefits from low levels of helminths, not huge amounts. Having higher levels of helminths (such as roundworms) results in various symptoms (e.g. fever, abdominal pain, diarrhea)
Do go read the full article. Excerpts are from Dr. William Parker's article in Aeon: We Need Worms
... But we and others are coming to a fascinating conclusion: intestinal worms are almost certainly involved. But it’s not the presence of the worms that is hurting us. To the contrary, the almost complete loss of intestinal worms in modern society is, surprisingly, a very significant problem. Intestinal worms, called ‘helminths’, have caused untold human suffering, killing the weak and disabling the strong. Labelled uniformly as disease-causing parasites by biologists, they have inspired fear and hate, leading to major campaigns aimed at their eradication. ...
But what if we erred? What if our bias against a handful of helminths led us to slaughter billions of innocent and even helpful worms? Indeed, my research and the research of many others tell us that helminths are necessary for our health. A barrage of scientific evidence points toward helminths as being important regulators of immune function. Because of this, our genocidal campaign against intestinal worms apparently has a very nasty backlash that nobody saw coming. But science moves very slowly. All helminths are still labelled as parasites in textbooks, despite the fact that we now know this to be incorrect.
One of the first to light the way was Peter J Preston, a medical doctor with the Royal Navy. In 1970, Preston reported that 12 naval officers who ‘had suffered from hayfever for some years’ were free of hayfever after acquiring the human roundworm. Preston reported that other individuals ‘amongst a large series of patients’ continued to suffer from allergy. Then, six years later, a young British scientist, John Turton, found that intentionally inoculating himself with hookworms eliminated his seasonal allergies.
My own research has shown that thousands of humans are now using intestinal worms, from a variety of sources, to effectively treat a wide range of allergic, autoimmune and digestive diseases. Based on previous studies, we were not surprised that people were having success. But we did find one puzzler: people and their doctors were reporting that helminths were helping to treat neuropsychiatric problems such as anxiety disorders and migraine headaches.
Excerpts from an earlier (2016) article about research on benefits of intestinal worms from NPR: When Parasites Could Be The Treatment Instead Of The Illness
Loke and Caldwell suspected the helminths alter the bacterial population in the intestine. The intestine is a lot like a bustling metropolitan city, but populated with bacteria, not people. Just like a city, some of the intestine's residents are helpful, and some harmful. The ratio of helpful to harmful bacteria plays a role in the development of many diseases, including Crohn's.
The researchers wanted to see if feeding parasitic worm eggs to mice would decrease the number of bad bacteria that are associated with Crohn's and increase the numbers of helpful bacteria.
When the researchers fed the mice worm eggs, the population of good bacteria, called Clostridiales, shot up. In contrast the amount of bad bacteria, called Bacteroides, went down. The mice also had reduced inflammation in the gut, an increase in the helpful mucus-producing cells, as well as reduction in harmful intestinal abscesses. Loke and Cadwell published their findings in the journal Science.
Great for mice, but what about people?
The scientists weren't ready to start feeding worm eggs to sick people, so they tried an indirect research approach. They surveyed a small population in Malaysia, called the Orang Asli tribe. The Orang Asli experience virtually no inflammatory bowel diseases, and a high percentage of them have chronic parasitic worm infections. Loke and Cadwell wanted to know: If we remove their worms, will we see an increase in harmful bacteria? The answer turned out to be yes.
Before the worms were removed, the tribe members had higher levels of helpful bacteria and lower levels of harmful bacteria. After taking a deworming drug, that healthy ratio was flipped. Cadwell and colleagues concluded that parasitic worms increase the population of beneficial bacteria in both humans and mice.
Roundworm. Credit: Wikipedia