Analysis of the mitochondrial genome to determine the origins and pathways of entry of in continental Europe (Valencia, Spain).

, the rat lungworm, is a zoonotic parasite mainly of rats which act as definitive hosts. If humans become accidentally infected, the nematode is capable of migrating to the brain causing meningoencephalitis. Intermediate hosts are snails and slugs. Although originating from mainland China, has now spread to various countries and continents. The precise timing of its departure from mainland China remains uncertain although it is often associated with significant historical events or migratory movements. The exit of from mainland China is believed to have occurred in a singular event, followed by its divergence into 2 distinct clades: clade I, originating from mainland China, and clade II, representing global spread. was first identified in continental Europe in 2021, specifically in Valencia, Spain. Illumina genome sequencing of 7 individuals isolated from rats captured in 2 different districts in the city of Valencia was carried out. The complete mitochondrial genome was assembled and compared with published mitochondrial genomes through Bayesian phylogenetic analysis, both for complete mitochondrial genomes and for the cytochrome c oxidase I gene, given its widespread use for identification of the species. The findings revealed the presence of 2 different haplotypes in the rats studied in Valencia, both belonging to clade II. In 2 rats both clades were present.