Improved hygiene practices have paradoxically led to an increased risk of developing inflammatory bowel disease (IBD) or similar afflictions. The key to preventing these types of infections may lie within a rather unpleasant creature: parasitic worms. Scientists have found that helminth worms are able to create microbial gut biomes in certain individuals that prevent infection from inflammatory bacteria.
Developed nations have seen a dramatic rise in the incidence of inflammatory bowel disease (IBD) infections such as Crohn’s disease. Ironically, this may be linked to the improved hygiene practices that such countries use, leading to the loss of beneficial gut bacteria that can prevent such infections.
A study led by Deepshika Ramanan, with involvement from Universiti Malaya’s Prof. Yvonne Lim, has found that intestinal parasites known as helminths can protect those susceptible to IBD from such diseases.
During the study, the researchers tested their hypothesis on mice deficient in the NOD2 gene (the lack of which makes them more susceptible to Crohn’s disease), infecting one group with a species of parasitic helminth worm, Trichuris muris.
The researchers found that the helminth-colonized mice did not develop symptoms of intestinal inflammation and other disorders in contrast to the uncolonized mice.
According to their findings, the presence of helminths will promote the growth of beneficial gut bacteria communities such as those of Clostridales strain. These communities will, in turn, combat proinflammatory bacteria such as the Bacteroidales strain and protect their hosts from IBD.
The researchers supported their findings with studies on people from regions where helminth colonization is endemic. Helminth-colonized individuals from the indigenous Orang Asli people of Malaysia display higher diversity in gut flora compared to uncolonized individuals inhabiting Kuala Lumpur.
As a control, the research team performed fecal studies on Orang Asli individuals before and after deworming, searching for the presence (or absence) of helminth eggs.
The researchers state: “Clostridiales are an example of defensive symbionts that will fight against another common commensal bacteria strain in the form of Bacteroidales, which we’ve consistently observed in all human gut microbiome data sets.”
They note, however, that: “Bacteroidales are pathogenic (will cause inflammations) only in susceptible Nod2-deficient hosts, and this competition reverses disease pathologies. Clinical trials have shown that many Crohn’s disease patients who do not carry NOD2 variants may not respond to the helminths.”
From these findings, the research team concludes that the worms will only provide anti-inflammatory and anti-bacterial benefits to certain individuals possessing the necessary genes.
Ramanan, R., Bowcutt, R., Lee, S.C., Tang, M.S., Kurtz, Z.D., Ding, Y., Honda, K., Gause, W.C., Blaser, M.J., Cadwell, K. (2016) Helminth infection promotes colonization resistance via type 2 immunity. Science, 352 (6285), 608-612.