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Parasitic Worm Eggs Ease Intestinal Ills by Changing Gut Macrobiota

The views expressed are those of the author and are not necessarily those of Scientific American.


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parasitic worm egg monkey colitis ibs

Image of Trichuris trichiura courtesy of Wikimedia Commons/Delorieux for Johann Gottfried Bremser

Intestinal issues are not just for us humans. Whereas the inflammatory bowel disease (IBS) now afflicts some 1.4 million people in the U.S., a similar condition often besets captive monkeys. But these animals are providing new insights about a cure for this condition in both species—and that cure is worms.

Rhesus macaque monkeys living in captivity often develop chronic diarrhea similar to the human autoimmune condition ulcerative colitis. Vets are often unable to treat these ill monkeys, which can suffer from dangerous weight loss and dehydration. New research takes advantage of this trend and has found that after giving the monkeys parasitic whipworm (Trichuris trichiura) eggs, most of them greatly improved. The findings were published online November 15 in PLoS Pathogens.

“The idea for treating colitis with worms is not new,” P’ng Loke, an assistant professor of microbiology at New York University Langone Medical Center and co-author of the new paper, said in a prepared statement. In fact, small human trials have found that giving people pig whipworm eggs can reduce symptoms of IBS. And in developing countries where IBS is much less common, parasitic worms (helminth) are often endemic, perhaps conferring some benefit. But scientists have still been parsing out just why the presence of these worms might work so well.

parasite whipworm egg colitis ibs

Image of whipworm egg at 400x magnification courtesy of Wikimedia Commons/Joel Mills

For the new study, researchers selected five juvenile rhesus macaques with idiopathic (cause unknown) chronic diarrhea. Each monkey was fed 1,000 T. trichiura eggs. After the treatment, four of the five monkeys had substantially improved stool and had regained weight.

In examining the mucosal membranes of the monkeys’ colons both before and after treatment, the researchers found that the ill monkeys started out with an abnormally high rate of bacteria attached to the linings. But after the treatment bacterial communities in their colons had changed substantially.

“Our findings suggest that exposure to helminthes may improve symptoms by restoring the balance to the microbial communities that are attached to the intestinal wall,” Loke said. For instance, three of the five monkeys with diarrhea had high levels of the Cyanobacteria Streptophyta before the worm treatment. But these levels dropped to numbers found in healthy control monkeys. In their paper the team speculated that the presence of the parasite eggs stimulated extra mucus production and healing, in addition to renewing epithelial cells. These changes helped to reduce the quantity of immunity-stimulating bacteria that could attach to the gut lining and rev up the immune response unnecessarily.

They also found that the expression of genes for inflammation had been reduced.

Mounting research points to important interactions between microbes in the stomach and the immune system. In fact, mice raised in germ-free environments and those raised with human gut microbiota fail to develop functional immune responses. Two weeks after the treatment, the researchers examined samples from the mucosal lining of the monkey’s colons. All five appeared to have a much healthier immune-response profile.

Further research remains to be done, including larger and blinded studies in monkeys. And lest you worry about trading an ailment for a parasite, the worms themselves did not appear to have matured inside the monkeys—nor did the eggs get passed on in their stool. And Loke and colleagues are starting a human clinical trial at New York University to test pig whipworm eggs (which cannot infect other people) as a treatment for ulcerative colitis based on this probiotic principle.

So if parasitic egg treatments prove successful and do eventually make it to market, don’t be too squeamish. Perhaps just think of them as the caviar of probiotics.

Katherine Harmon Courage About the Author: Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. robert schmidt 11:08 pm 11/15/2012

    Perhaps it’s a protein in the egg wall that triggers the response. I’m sure they are working to isolate it. That will be the next thing they put in our yogurt.

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  2. 2. jtdwyer 7:19 am 11/16/2012

    Isn’t the function of diarrhea to expel toxic or infectious agents from the digestive tract – a generally healthy response to disruptive agents? Controlling the diarrhea response to intestinal infection is most likely more beneficial to the worm rather than the host.

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  3. 3. ginnyjollykidd 11:28 am 11/16/2012

    Yes. Diarrhea expels toxins and infections. In the first hour of such infections (like food poisoning), diarrhea and vomiting are your best friends. However, if it persists, diarrhea can dehydrate you and unbalance your electrolytes. People and other animals can die from dehydration. This article has cited animals that cannot throw off the infection and thus are continually assaulted by bacteria and their toxins.

    The whole point of this treatment (as squeamish as I am of it) is to provide a way to balance the microflora again so that the body gains immunity and regains homeostasis.

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  4. 4. jtdwyer 3:57 pm 11/16/2012

    ginnyjollykidd – very good point regarding the significant downside of diarrhea – thanks.

    As suggested above, it seems likely that there is some property of the eggs that stimulates the production of extra mucus, thus preventing their expulsion.

    While these worms may not infect humans, they might affect other animals. Overall, it would seem best to identify exactly what property of the worm egg is stimulating overproduction of mucus and formulate a treatment from that.

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  5. 5. shimagyoh 4:44 am 11/18/2012

    We who live in the third world have been regularly deworming our children and pets and constantly improving the hygienic conditions around our homes to distance us from bacterial infections and worm infestations. Now we are being told that our early and profuse contact with bacteria is the probable cause of the lower incidence of asthma and auto-allergic diseases, and now our worms are probably protective against inflammatory bowel diseases? I am going back to the jungle, bye!
    Shima

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