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Researchers at Washington University School of Medicine in St. Louis carried out research on why people develop digestive problems. They discovered viruses like West Nile and Zika that target the nervous system in the brain and spinal cord can kill neurons in the guts of mice, disrupting bowel movement and causing intestinal blockages.
According to Thaddeus S. Stappenbeck, MD, PhD, the Conan Professor of Laboratory and Genomic Medicine and the study’s co-senior author, healthy people can suddenly develop bowel motility problems because viral infection can gets in to the immune cells killing infected neurons in the gut.
While studying mice infected with West Nile virus, a mosquito-borne virus that causes inflammation in the brain, researchers noticed that the intestines of some of the infected mice were packed with waste higher up and empty farther down, as if they had a blockage. This expands the intestines and slowed digestion through the gut. In contrast, chikungunya virus, an unrelated virus that does not target neurons, failed to cause bowel dysfunction.
When West Nile virus was injected into a mouse’s foot, it travels through the bloodstream and infects neurons in the intestinal wall. These neurons coordinate muscle contractions to move waste smoothly through the gut.
Once infected, the neurons attract the attention of immune cells, which attack the viruses and kill the neurons. Viruses that target the gut nervous system cause mild and self-limiting infections. Studies have linked bowel motility to changes in the microbiome – the community of bacteria, viruses and fungi that live in the gut.