A possible origin population of pathogenic intestinal nematodes, Strongyloides stercoralis, unveiled by molecular phylogeny

• Main Authors: Eiji Nagayasu, Myo Pa Pa Thet Hnin Htwe Aung, Thanaporn Hortiwakul, Akina Hino, Teruhisa Tanaka, Miwa Higashiarakawa, Alex Olia, Tomoyo Taniguchi, Soe Moe Thu Win, Isao Ohashi, Emmanuel Igwaro Odongo-Aginya, Khin Myo Aye, Mon Mon, Kyu Kyu Win, Kei Ota, Yukari Torisu, Siripen Panthuwong, Eisaku Kimura, Nirianne M. Q. Palacpac, Taisei Kikuchi, Tetsuo Hirata, Shidow Torisu, Hajime Hisaeda, Toshihiro Horii, Jiro Fujita, Wah Win Htike, Haruhiko Maruyama
• Format: Article
• Language: English
• Published: Nature Publishing Group 2017-07-01
• Series: Scientific Reports
• Online Access: https://doi.org/10.1038/s41598-017-05049-x

Abstract Humans and dogs are the two major hosts of Strongyloides stercoralis, an intestinal parasitic nematode. To better understand the phylogenetic relationships among S. stercoralis isolates infecting humans and dogs and to assess the zoonotic potential of this parasite, we analyzed mitochondrial Cox1, nuclear 18S rDNA, 28S rDNA, and a major sperm protein domain-containing protein genes. Overall, our analyses indicated the presence of two distinct lineages of S. stercoralis (referred to as type A and type B). While type A parasites were isolated both from humans and dogs in different countries, type B parasites were found exclusively in dogs, indicating that the type B has not adapted to infect humans. These epidemiological data, together with the close phylogenetic relationship of S. stercoralis with S. procyonis, a Strongyloides parasite of raccoons, possibly indicates that S. stercoralis originally evolved as a canid parasite, and later spread into humans. The inability to infect humans might be an ancestral character of this species and the type B might be surmised to be an origin population from which human-infecting strains are derived.