Evolutionally history of Strongyloides species that led to S. stercoralis, parasitic nematodes of humans and dogs

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K08809
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Parasitology (including sanitary zoology)
• Research Institution: University of Miyazaki
• Principal Investigator: Nagayasu Eiji 宮崎大学, 医学部, 助教 (20524193)
• Co-Investigator(Kenkyū-buntansha): 吉田 彩子 宮崎大学, 農学部, 教授 (20343486)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 糞線虫 / Strongyloides / 進化 / 食肉目 / 宿主転換 / イヌ

Outline of Final Research Achievements

In the present study, we obtained Strongyloides spp. from various carnivore hosts, namely cats, raccoons, raccoon dogs, Siberian weasels, and Japanese badgers. We observed a presence of a group, which are composed of Strongyloide spp. from various carnivore hosts (stercoralis/procyonis group). It appeared that Strongyloides spp. belonging to this group essentially evolved as parasites of carnivores. Humans may have acquired S. stercoralis from dogs, after domesticating them by host-switch.
For the first time, a substantial numbers of S. stercoralis samples from humans and dogs were obtained in South America (Peru). Detailed analysis using DNA sequence information from these samples will enable us to elucidate how S. stercoralis spread in human population around the globe.

Free Research Field

寄生虫学

Academic Significance and Societal Importance of the Research Achievements

糞線虫(Strongyloides spp.)は様々な脊椎動物の小腸粘膜を最終寄生部位とする腸管寄生線虫である。ヒトに感染するS. stercoralis (ステルコラリス糞線虫)を含め、約50種が知られ、熱帯・亜熱帯地域を中心に約3千万から1億人の感染者がいるものと推定されている。
ステルコラリス糞線虫がいかなる進化的道筋をへてヒトの寄生虫になったのかに関し、我々はイヌの寄生虫からの宿主転換説を提唱した (Nagayasu et al., 2017)。今回の研究において、様々な食肉目動物に由来する糞線虫がステルコラリス糞線虫に対して近縁性を示したことにより、あ前出の仮説は改めて支持された。