Genetic characterization of Angiostrongylus cantonensis in Rattus norvegicus in Hokkaido, Japan: A rediscovery record in Hokkaido after 44 years.

Angiostrongylus cantonensis is a zoonotic nematode causing eosinophilic meningitis in humans. This species was confirmed to exist in Hokkaido until 1982, its current status remained unknown. In the present study, we detected A. cantonensis in brown rats (Rattus norvegicus) in Hokkaido for the first time in 44 years. We conducted the first genetic characterization of A. cantonensis in Hokkaido by performing a phylogenetic analysis using two genes. We identified A. cantonensis using morphological and genetic analysis, which confirmed its current presence in Sapporo City. The small subunit of the nuclear ribosomal RNA gene and the mitochondrial cytochrome c oxidase subunit 1 gene analysis showed that specimens from Hokkaido belonged to the G2 clade and the ac7 haplotype, respectively. These clade and haplotype are consistent with those identified along the Pacific coast of Honshu, suggesting that the distribution of this parasite may have expanded through human logistics and economic activities. However, the true prevalence and spatial distribution of A. cantonensis in Sapporo City remain unclear due to the limited sample size in this study. To effectively manage the risk of human infection, it is important to investigate the prevalence and spatial distribution of A. cantonensis in Sapporo City, as well as to identify its intermediate hosts. Furthermore, genetic studies of A. cantonensis at multiple locations across Hokkaido could provide valuable insights into its dispersal and transmission dynamics.