Whole genome sequence analysis of Strongyloides stercoralis from sympatric human and dog populations in Asia to investigate the zoonotic potential of dog-derived parasite
Gut nematode worms are important parasites of people and other animals. The parasitic nematode Strongyloides stercoralis infects an estimated 500 million people worldwide, and is one of the soil-transmitted helminthiases, a WHO-defined neglected tropical disease. It has long been suggested that human S. stercoralis infection may be a zoonosis from dogs. We investigated this by whole genome sequence analysis of S. stercoralis from sympatric human and dog populations in Asia. We find that human- and dog-derived S. stercoralis have genetically distinct nuclear genomes, but we also find evidence of rare cross infection. Analysis of the S. stercoralis mitochondrial genome reveals evidence of historical introgression between human- and dog-derived parasites. Based on these data we suggest that S. stercoralis was originally a parasite of canids, that began to infect humans when people domesticated dogs, since when human- and dog-derived parasites have differentiated, but have not become separate species.