The first cell atlas of the critical life stage of Schistosoma mansoni, a parasitic worm that endangers hundreds of millions of people every year, was developed by researchers at The Wellcome Trust Sanger Institute.
The study, published today in Nature Communications, identified 13 different types of cells inside the worm at the start of its transformation into a dangerous parasite, including new cell types in the nervous and muscular systems. The Atlas is a guide to better understanding the biology of Schistosoma mansoni. It will allow research into new vaccines and treatments.
This parasite has a complex life cycle. It starts in rivers and lakes. In the form of larvae, parasites enter the human body through the skin after contact with contaminated water. Once inside the body, schistosomes begin the intra-mammalian stage of their life cycle, accompanied by a series of developmental transitions as they mature.
Adult worms live in human blood vessels and multiply by releasing eggs that pass from the body into the water to continue their life cycle. But some eggs get stuck in the body, which leads to a dangerous disease – schistosomiasis.
Schistosomiasis is a long-term illness that can lead to disability, organ damage, and death. It affects hundreds of millions of people every year, mainly in sub-Saharan Africa, and is listed by the World Health Organization (WHO) as one of the most important tropical diseases. There is only one drug currently available to treat the condition. Still, it is not suitable for very young children, and there are concerns that over-dependence on a single treatment will allow parasites to develop resistance to this drug.
Researchers are looking for ways to find new drug targets, but scientists did not have a high-resolution understanding of the parasite’s biology until now.
The new research aimed to map all cells in the first stage of the parasite inside mammals using unicellular technology that identifies the different types of cells present in the body or tissue.
At an early stage, the parasites were separated into individual cells, which were characterized by sequencing single-celled RNA by scientists at the Senger Institute. The data was then analyzed to determine the types of cells according to the genes expressed by individual cells and the location in those cells’ body.
The team identified 13 different cell types, including previously unknown ones – the nervous and parenchymal systems.
Researchers most often look for differences between a pathogen and its human host to identify new drug targets. However, S. mansoni is much closer to us in evolution than most of the main parasites, such as those causing malaria. It is hoped that these results will reveal areas of the parasite’s genetic code that are quite different from our own.