Molecular surveillance of gastrointestinal parasites in wild herbivores of the Dooars region, India with implications for future one health monitoring

Wild herbivores are important components of natural ecosystems, but gastrointestinal (GI) parasites can adversely affect host health and population dynamics. Understanding wildlife parasitism is also important in regions with close human–livestock–wildlife interactions, where some parasites may have zoonotic potential. However, information on the diversity and molecular characterization of GI parasites in free-ranging wild herbivores from the biodiversity-rich Dooars region of Northern West Bengal, India, remains limited. This study aimed to assess the occurrence and distribution of GI parasites in wild herbivores across three protected areas: Jaldapara National Park, Chapramari Wildlife Sanctuary, and Gorumara National Park of northern West Bengal, India utilizing an integrative approach of morphological and molecular identification. Faecal samples from bison, spotted deer, sambar deer, and hog deer were collected from the three protected areas and subjected to coprological screening for morphological identification of eggs and larvae followed by molecular validation, targeting the ribosomal ITS2 region through PCR amplification, Sanger sequencing, and subsequent phylogenetic analysis. Minimum free energy (MFE)-based RNA secondary structure prediction was employed to enhance species identification accuracy. The study identified eight distinct nematode species- Haemonchus placei, Trichostrongylus colubriformis, Trichostrongylus axei, Cooperia oncophora, Ostertagia ostertagi, Dictyocaulus cervi, Strongyloides papillosus, and Toxocara vitulorum. High ITS2 sequence homology (96.55–98.85%) confirmed identities. RNA secondary structure predictions provided robust genotypic differentiation. H. placei, T. colubriformis, S. papillosus, and C. oncophora dominated parasite infections across sites, with the highest prevalence seen in bison and sambar and lower rates in spotted deer. The occurrence of livestock-associated nematode taxa indicated a risk of bidirectional, cross-species transmission. This research provides critical baseline data on GI parasite diversity in wild herbivores of the Dooars region, highlighting significant zoonotic and ecological implications. Integrated multi-host longitudinal surveillance is essential to clarify parasite epidemiology and zoonotic risk. Sustained surveillance and a One Health approach are crucial to manage parasite spillover and safeguard regional biodiversity and public health in the region.