Viruses such as West Nile and Zika that target the nervous system in the brain and spinal cord can also disrupt bowel movement and cause intestinal blockages, a study in mice has found.
While studying viruses best known for infecting the brain, researchers at Washington University in the US stumbled upon clues to why some people possibly develop digestive problems seemingly out of the blue.
The researchers found that viruses such as West Nile and Zika can kill neurons in the guts of mice, disrupting bowel movement and causing intestinal blockages.
Other viruses that infect neurons also may cause the same symptoms, the researchers said.
The findings, published in the journal Cell, potentially could explain why some people experience recurrent, unpredictable bouts of abdominal pain and constipation -- and perhaps point to a new strategy for preventing such conditions.
"There are a number of people who are otherwise healthy who suddenly develop bowel motility problems, and we don't understand why," said Thaddeus S Stappenbeck, a professor at Washington University.
"But now we believe that one explanation could be that you can get a viral infection that results in your immune cells killing infected neurons in your gut. That might be why all of a sudden you can't move things along any more," said Stappenbeck.
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.
They found that not only West Nile virus but its cousins Zika, Powassan and Kunjin viruses - all of which target the nervous system like West Nile - caused the intestines to expand and slowed down transit through the gut.
In contrast, chikungunya virus, an unrelated virus that does not target neurons, failed to cause bowel dysfunction.
Further investigation showed that West Nile virus, when injected into a mouse's foot, 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 in the process.
"Any virus that has a propensity to target neurons could cause this kind of damage," said Michael S Diamond, a professor at Washington University.
"West Nile and related viruses are not very common in the US. But there are many other viruses that are more widespread, such as enteroviruses and herpesviruses, that also may be able to target specific neurons in the wall of the intestine and injure them," said Diamond.
Such widespread viruses may provide a new target in the prevention or treatment of painful digestive issues.
Having chronic gut motility problems is a miserable experience, and while the condition can be managed, it can not be cured or prevented.
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