Parasitic worms cause terrible diseases — could the viruses they carry be to blame?

Roundworms, also known as nematodes, are a leading cause of parasitic infection worldwide, causing painful swelling, severe abdominal pain and even blindness. Now, scientists say that viruses carried by these worms may be one reason they cause such severe illness.

In a recent study, published in September in the journal Nature Microbiology, the researchers looked at more than 40 parasitic nematodes, zooming in on a molecule called RNA. A cousin of DNA, RNA helps cells make proteins and also forms the basis of various viruses.

The scientists uncovered 91 RNA viruses in 28 of the worm species studied, representing about 70% of the roundworm species that infect humans.

This study represents "the beginning of a whole other area of research on virology, pathology and more," Elodie Ghedin, a parasitologist and microbiologist at the National Institutes of Health who was not involved in the work, told Live Science.

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Shannon Quek, study lead author and a parasitologist at the Liverpool School of Tropical Medicine (LSTM) in the U.K., had been studying viruses in mosquitoes, and through that work, he came up with a way to find viruses within nematodes.

Quek built an algorithm to search for signs of viruses in mosquito RNA, Mark Taylor, the senior study author and a LSTM parasitologist, told Live Science in an email. "In an inspired 'lightbulb' moment, he decided to use the same algorithm to search parasitic nematode transcriptomes," meaning readouts of all the RNA in the worms.