Nemabiome metabarcoding reveals strongyle parasite diversity in wild deer in Victoria, Australia.

Interactions between wild deer and domestic livestock are increasingly common in southeastern Australia, but contemporary information on gastrointestinal nematodes infecting wild deer remains limited. In this study, nemabiome metabarcoding of the internal transcribed spacer 2 (ITS-2) region of ribosomal DNA was used to characterise strongyle communities in wild deer from Victoria, Australia. A total of 194 faecal samples from three deer species - sambar (Rusa unicolor), fallow (Dama dama) and hog deer (Axis porcinus) - were analysed using Illumina amplicon sequencing. Strongyle DNA was detected in 104 samples, revealing eleven taxa. Eight species (Cooperia oncophora, Haemonchus spp., Ostertagia ostertagi, O. leptospicularis, O. radiatum, Trichostrongylus axei, T. colubriformis and T. vitrinus) are commonly associated with domestic ruminants, whereas the cervid-associated strongyle Spiculopteragia asymmetrica was the most frequently detected taxon. Deer sampled near farmland harboured significantly greater strongyle diversity than those from more remote locations. Overlapping parasite taxa were also detected in co-grazing deer and cattle. These findings indicate that wild deer in southeastern Australia harbour diverse strongyle communities and highlight the potential for overlapping parasite assemblages at the wildlife-livestock interface.