Helminths in Wild Deer Sharing Pastures with Livestock: Baseline Data for Anthelmintic Resistance Surveillance

The interaction between wild and domestic ruminants plays a pivotal role in the epidemiology of helminth infections and the potential spread of anthelmintic resistance. However, data on the helminth fauna of free-ranging red deer ( Cervus elaphus ) in Türkiye remain limited. This study investigated the occurrence of gastrointestinal and respiratory helminths in a free-ranging red deer population in Ankara. Fecal samples (n = 53) were examined using flotation, sedimentation, and Baermann techniques. Helminths were detected in 32% of samples, revealing a community dominated by generalist parasites shared with domestic ruminants, including Trichostrongylidae, Nematodirus spp., Dicrocoelium spp., Paramphistomum spp., and Trichuris spp. Notably, larvae of Cystocaulus spp. and Neostrongylus spp. were identified. These findings confirm active cross-transmission at the wildlife-livestock interface. The predominance of Trichostrongylidae eggs suggests that red deer may act either as reservoirs for resistant strains acquired from livestock or as natural refugia for susceptible alleles. This study highlights the necessity of an approach in parasitological surveillance to monitor transmission dynamics and resistance risks.