Non-parasite genome-encoded virus-like RNAs reprogramthe pathogenicity of human blood flukes

Written by: Farah Doctor

Reference Paper: https://www.nature.com/articles/s41467-025-67822-1

Image representive of RNA

This paper by Nature investigates the virus-like RNAs (also called ngRNAs) that are found not in

viruses but encoded outside of a parasite’s own genome, in a parasite known as Schistosoma

japonicum. It is a type of blood fluke (parasitic flatworm) that causes a serious disease called

schistosomiasis. These ngRNAs resemble viruses as they can replicate the RNA and encode

viral-like enzymes.

Blood flukes (parasitic worms) infect millions of people around the globe and cause chronic

illness. The symptoms are itchy skin, high fever, headaches, stomach aches and joint pain,

lethargy, coughing and diarrhoea. These symptoms come from the eggs produced by the

parasite, not adult worms. Parasites often interact with viruses but the focus of this study is the

virus-like RNAs. Scientists have been studying the parasite’s biology for many years, but little

was known about the role of the virus-like RNAs in the parasite and how it impacted the

development and disease severity.

Researchers have used RNA sequencing, single-cell analysis and experimentation to detect the

presence of these ngRNAs and study them in Schistosoma japonicum. They examined the

locations of these ngRNAs throughout the parasite and their impact on its biological processes.

The researchers found that the ngRNAs were mainly present in germ cells, the cells responsible

for reproduction (oogenesis and egg production) of the parasite. The ngRNAs also encode an

enzyme called RNA-dependent RNA polymerase (RdRp), which helps copy RNA inside the

parasite itself. The activity of the ngRNAs influences and governs embryo viability (potential to

develop) and egg production, which are crucial for the life cycle of the parasite, helping it cause

disease in humans. These eggs produced trigger the disease symptoms people see, and

therefore, ngRNAs affect the severity of infection of the parasite. Similar virus-like RNAs have

also been found in another planarian (free-living flatworm) species, Duegesia japonica,

suggesting that this mechanism could be common in other organisms that are also parasitic.

This study matters as it suggests that virus-like RNAs (when they are not part of a virus but

behave similarly to one) can shape the severity of disease caused by parasites. Virus-like

molecules are able to cause diseases without being actual viruses. Using this information,

scientists may be able to find new treatments for schistosomiasis that reduce egg production

rather than killing the parasite or be able to control the spread of the disease, opening

possibilities for new drug targets.

In conclusion, the non-parasite genome-encoded virus-like RNAs exist inside blood flukes and regulate reproduction and development. By targeting the ngRNAs, researchers can reduce the impact of the schistosomiasis disease and also control the spread of the disease better.