Genetic Characterization of the Co-Invasive Rodent Parasite Heterakis spumosa (Nematoda, Heterakidae).

Simple Summary: Heterakis spumosa Schneider, 1886 is a parasite commonly found in rodents, primarily associated with the black rat Rattus rattus and the brown rat R. norvegicus, two global invasive rodent species, and the house mouse Mus musculus. This parasite originated probably from Asia, and has been reported in various rodent species, but molecular information from its putative native region is still lacking. Our sampling efforts across Southeast Asia allowed us to collect and analyze this species from two localities in Lao PDR and five localities in Thailand. Additionally, specimens from Europe were included in the analysis. All specimens were analyzed using mtCOI gene and nuclear ribosomal ITS1. Our findings revealed the presence of two distinct clades of H. spumosa, with no discernible association with hosts and geographical localities. Heterakis spumosa, a parasitic worm infecting rodents, is globally prevalent in black rats, brown rats, and house mice. It is hypothesized to originate from Asia due to its widespread presence in Southeast Asia in various Murinae. Previous molecular studies focused on European, African, and Japanese specimens, but none included samples from the putative native range. Rodents were collected between 2008 and 2015 across various localities in Southeast Asia and Europe, identified by morphology or genetic barcoding. Viscera were examined or preserved for later inspection. DNA was extracted from H. spumosa. PCR amplification targeting the mtCOI gene and ITS1 region was conducted in this study using newly designed primers (based on Heterakis reference sequences). PCR amplicons were subsequently sequenced and analyzed. In this study, the phylogenetic analysis using ITS1 sequences revealed that Heterakis samples from Thai and Laotian rodents belong to the species H. spumosa, exhibiting low genetic variation compared to samples from other regions. Genetic distance calculations using mtCOI sequences confirmed the marked distinction of H. spumosa from other Heterakis species. Our phylogenetic analyses using partial mtCOI and ITS1 sequences have significantly enhanced our comprehension of the genetic diversity and evolutionary history of the nematode H. spumosa. [ABSTRACT FROM AUTHOR]