NOV 15, 2016 10:55 AM PST

Infection with a Protozoan Directly Linked to Colitis

Bacteria have all but hogged the limelight in our recent understanding of microbiomes and how these ecosystems influence our risks for disease. But let’s not forget there’s other types of microorganism that’s also responsible for this balance inside us.

Publishing in the Journal of Experimental Medicine, scientists at the University of Toronto discovered that a common gut protozoan, Tritrichomonas muris, is linked to development of inflammatory colitis in mice. The results underscore “the need for a better understanding of cross-kingdom interactions between host and protozoa within the gastrointestinal tract," said Dana Philpott, one of the study’s senior authors.
The team identified the link between T. muris and colitis on a serendipitous whim, while studying T cell–driven colitis. They noticed that mice infected with the T. muris protozoan were more likely to also develop colitis.
In relation to human health and disease, ulcerative colitis is one of the two most common forms of inflammatory bowel disease. Unlike Crohn’s disease, which affects the digestive tract, for colitis the inflammation happens in the colon and rectum. Symptoms of colitis include stomach pain or cramps, and diarrhea. And because the inflammation can lead to ulcers in the colon, bleeding from the rectum is also a common indicator.
Importantly, inflammation from ulcerative colitis is known to increase the risks of colon cancer. In fact, people who have a history of colitis for 8 or more years are at very high risks for developing the cancer.

But how does a protozoan – a eukaryotic organism from the kingdom Protista – influence colitis? Philpott and her team think the inflammation happens because T. muris increases pro-inflammatory T cells and cytokines in the gut of the mice. This environment promotes and even exacerbates the disease. They confirmed the disease-causing properties of the microorganism when its presence in otherwise healthy mice led to an increased T cell response.
It’s not the first time that protozoans are linked to diseases. For example, leishmaniasis and malaria are diseases caused by common protozoans. In all of the cases, researchers underscore the complex relationship that animals’ guts have with their microbe counterparts.

Additional sources: Rockefeller University Press via EurekAlert!
About the Author
Doctorate (PhD)
I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at
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