Discovery of microbe in roundworm provides animal model for 'emerging pathogen'

Microsporidia are single-celled parasites that are capable of causing infections in humans - primarily people with compromised immune systems, such as those infected with HIV or who have undergone organ transplants. An article in this week's issue of PLoS Biology documents a newly discovered species of microsporidia, which infects C. elegans, the round worm used as a model system by developmental biologists. The work, undertaken by a team of French and American scientists led by Professor Frederick Ausubel and Dr. Emily Troemel of Harvard Medical School, is a breakthrough for public health researchers who had been looking for a suitable laboratory model in which to study microsporidia. "Microsporidia are classified as 'priority pathogens' by the National Institutes of Health, since they have been found in water supplies and because no drugs are available for treating the most common infections they cause in humans," said Emily Troemel, now an assistant professor of biology at UC San Diego. "The new species we discovered, which infects C. elegans, a small roundworm that is very easy to study in the lab, provides a powerful system in which to study these mysterious microbes, learn how animals respond to infection and develop new drugs to fight infections of microsporidia."

"The discovery is particularly exciting because it potentially offers a unique opportunity to identify new drugs for treating human microsporidian infections," said Professor Ausubel.

The researchers named the new species of microsporidia Nematocida parisii, or "nematode killer from Paris," because it was discovered in the intestines of roundworms found in Parisian compost pits. Authors Marie-Anne Félix and Antoine Barrière initially isolated the infected worms and sent them to Emily Troemel, then a postdoctoral fellow working in the Ausubel laboratory, to determine the nature of the pathogen. Since then, the scientists have found closely related naturally-occurring pathogens in Portugal and India, leading them to conclude that they are widespread natural parasites of C. elegans.

"C. elegans has been a 'lab rat' for scientists for decades. It has intestinal cells that look almost exactly like human intestinal cells, so we're able to tell what these parasites are doing to intestinal cells as they're invading and exiting the cells," said Troemel. "And because these worms are completely transparent, we can take intact worms, put them on a slide and see what's happening. We've already seen some interesting changes in the structure of intestinal cells during different time periods of infection."

Source: Public Library of Science