International Journal for Parasitology: Parasites and Wildlife · Published 2026-07-04 · DOI 10.1016/j.ijppaw.2026.101259
Magdalena Świsłocka-Cutter, Anetta Borkowska, Rafał Kowalczyk, Marta Kołodziej-Sobocińska
The invasive blood-sucking nematode Ashworthius sidemi, originally parasitising Asian cervids, has spread across Europe following human-mediated introductions of sika deer (Cervus nippon). In this study, we characterised the molecular variation of A. sidemi obtained from two neighbouring populations of European bison (Bison bonasus) in northeastern Poland, located in the Białowieża Primeval Forest and Knyszyńska Forest. Individual worms (one per host) were analysed using nuclear molecular markers (18S rRNA, 28S rRNA, ITS-1) and mitochondrial markers (COX1, ND4). All analysed markers revealed no detectable intraspecific genetic variability among the 16 specimens sequenced, with a single haplotype identified for each marker. This finding is consistent with a founder effect and/or recent introduction of the parasite. The genetic homogeneity observed across geographically close bison herds may also reflect host mobility. Phylogenetic analyses based on both nuclear and mitochondrial markers consistently placed A. sidemi within the subfamily Haemonchinae, closely related to Haemonchus spp. and Mecistocirrus digitatus. The ITS-1, COX1, and ND4 markers provided sufficient resolution to differentiate A. sidemi from other Trichostrongylidae species, whereas the 18S and 28S rRNA genes were too conserved to discriminate species- or subfamily-level relationships. Our findings demonstrate the utility of nuclear and mitochondrial markers for the identification and phylogenetic classification of trichostrongyloid nematodes. These results provide important insights into the invasion dynamics of A. sidemi, which may support parasite surveillance and conservation efforts of endangered host species.
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Świsłocka-Cutter, M., Borkowska, A., Kowalczyk, R., et al. (2026). Phylogenetic and molecular insights into the genetic diversity of the invasive nematode Ashworthius sidemi infecting Poland's free-ranging European bison (Bison bonasus). International Journal for Parasitology: Parasites and Wildlife. https://doi.org/10.1016/j.ijppaw.2026.101259