Nemabiome metabarcoding to assess the diversity of trichostrongyle nematodes in plains bison from the mid-western USA

Abstract

Background Parasitic gastrointestinal nematode (GIN) infections in North American plains bison, predominated by trichostrongyles of Clade V, are a major cause of health and production losses, even death. The diversity and distribution of trichostrongyles in bison in the USA remains poorly understood. The aim of this study was to assess the diversity of GIN in plains bison and to identify key species to target for parasite control strategies in bison herds. Methods We used the “nemabiome” deep amplicon sequencing technique to amplify the ITS2 region from DNA derived from trichostrongyle third-stage larvae obtained by coproculture of the feces of 134 individual bison belonging to 16 herds from 8 mid-western states in the USA. ITS2 amplicons were library prepped and sequenced on an Illumina MiSeq. Anthelmintic usage history in the herds was unknown. Sequencing data was analysed using the DADA2 pipeline and diversity metrics were calculated. Results Analysis revealed 269 amplified sequence variants (ASVs), belonging to 5 genera and 9 species. A significant proportion of individual bison and herds had multiple infections with ≥ 2 trichostrongyle infections. Cooperia oncophora, Ostertagia ostertagi and Haemonchus placei were the most abundant species. Individual bison harbored an average of three trichostrongyle species, while herds harbored an average of 4.5 species. In a majority of individuals and herds, Shannon alpha diversity index was < 1, indicating lower species abundance and richness, while inverse Simpson index was between 1–3 indicating moderate species diversity. Conclusion There was variation in parasite diversity within and between individual bison and herds. This is the first study to utilize the “nemabiome” technique in plains bison herds living in the USA and results of this investigation reveal the importance of understanding key species to target for parasite control strategies.