Coprological assessment of gastrointestinal parasites in free-ranging Nilgai (Boselaphus tragocamelus)

Introduction

India supports one of the world's richest assemblages of wildlife, with diverse ecosystems that sustain a wide range of herbivorous mammals and their associated parasite communities. Among these, the Nilgai (Boselaphus tragocamelus), the largest extant Asian antelope, is widely distributed across the Indian subcontinent and occupies habitats ranging from dry deciduous forests and scrublands to agricultural landscapes and protected areas (Dookia et al., 2013; Chandra & Gupta., 2022) [5,2] . Owing to its ecological adaptability, the species frequently occurs in landscapes influenced by both natural and anthropogenic factors, where it contributes to vegetation dynamics through selective browsing and grazing (Bisht, 2012) [1] . Nilgai are primarily mixed feeders, consuming grasses, leaves, shrubs, fruits, pods, and young shoots according to seasonal availability. They often cause financial losses to the agrarian communities due to crop raiding. Despite the conflict and financial losses, the species enjoys communal tolerance due to the belief that the species has descended from cows (Chandel et al., 2025; Chauhan, 2011) [3,4] . They exhibit a distinctive behavioural trait of repeatedly defecating at communal dung heaps, commonly referred to as midden sites. These sites function as centres of chemical communication, territorial marking, and social interaction, while also serving as repositories of faecal material that can provide valuable Because Nilgai habitually deposit faeces at communal midden sites, these locations provide an efficient opportunity for systematic sampling and epidemiological surveillance (Zoromski et al., 2022; Kozhayeva et al., 2026) [17, 9] . Despite the broad distribution of Nilgai in India, information on their gastrointestinal parasite fauna remains limited for several regions, including central India. Therefore, the present study was undertaken to investigate the prevalence and diversity of gastrointestinal parasites in free-ranging Nilgai inhabiting the Gorewada landscape, Nagpur, Maharashtra, thereby contributing baseline information for wildlife health monitoring, parasite ecology, and conservation-oriented management.

Materials and Methods

Study Area

The present investigation was conducted in the surrounding landscape of the Gorewada Rescue Centre, Nagpur, Maharashtra, India, where a free-ranging population of Nilgai (Boselaphus tragocamelus) occurs. The study area comprises a mosaic of dry deciduous vegetation, scrubland, grass-covered patches, and open forest interspersed with anthropogenic influences, providing suitable habitat for the species. Nilgai inhabiting this landscape exhibit the characteristic behaviour of repeatedly defecating at communal dung heaps (midden sites), which facilitated noninvasive sampling for the present study.

Sample Collection

Fresh faecal samples were collected directly from identified midden sites during the early morning hours to minimize environmental contamination and ensure sample freshness. A total of 80 faecal samples were collected over a onemonth study period from 12 active midden sites distributed across the study area (Fig. 1). Care was taken to collect only freshly voided faeces based on their physical appearance, moisture content, and absence of desiccation. Each sample was collected using sterile disposable gloves and transferred into individually labelled sterile collection containers. The samples were transported to the laboratory for parasitological examination under appropriate storage conditions and processed as early as possible after collection.

Parasitological Examination

Each faecal sample was examined qualitatively for the presence of gastrointestinal parasites using standard coprological techniques. Initially, direct faecal smear examination was performed to detect motile protozoa, helminth eggs, larvae, and other parasitic stages. Subsequently, the salt flotation technique was employed to concentrate parasite eggs and oocysts, thereby improving the detection of low-intensity infections. The recovered parasitic stages were identified based on their characteristic morphological features, including size, shape, shell morphology, colour, and internal structures, using standard parasitological identification keys. Microscopic examination was carried out using a compound light microscope under 10× and 40× objective magnifications for routine screening and identification. Where required, observations under 100 × magnifications were performed to examine finer morphological details essential for accurate identification of parasitic ova and other developmental stages.

Results

A total of 80 fresh faecal samples were collected from 12 identified communal midden sites of free-ranging Nilgai (Boselaphus tragocamelus) over a one-month sampling period and examined using direct smear and flotation techniques. The samples were identified based on typical nature of the dropping and camera trapping exercise. Of the total samples examined, 26 (32.50%) were positive for one or more gastrointestinal parasites. Strongyle-type eggs were detected in all 26 positive samples; 23 were single infections and 3 occurred with Eimeria spp. Eimeria spp. was detected in 3 samples (3.75%). In addition, a mite was observed during direct smear examination of one faecal sample and was recorded as an incidental finding (Fig. 2). The distribution of parasitic stages detected during the study is presented in Table 1 & 2.

Discussion

The present study recorded an overall sample-level prevalence of 32.50% gastrointestinal parasites in freeranging Nilgai (Boselaphus tragocamelus). Strongyle eggs were not identified to genus because morphological differentiation is not possible without larval culture or molecular methods. This prevalence was lower than that reported in Nilgai from Hisar, Haryana (Gupta et al., 2018) [12] , Barnawapara Wildlife Sanctuary, Chhattisgarh (Verma et al., 2020) [16] , and considerably lower than the prevalence documented in free-ranging herbivores of central India (Singh et al., 2009) [14] . Variations in parasite prevalence among studies are expected because gastrointestinal parasite transmission is influenced by climatic conditions, habitat characteristics, host density, seasonal variation, forage availability, and sampling strategy (Singh et al., 2009; Sengar et al., 2017) [14,11] . In the present investigation, samples were collected during a single month from communal midden sites using a non-invasive approach, which may also have contributed to the observed differences. The observed prevalence may be explained by the life cycle of gastrointestinal parasites and the environmental conditions favouring their development and persistence. The third-stage larva (L3) of the strongyle nematodes is infective and warm and moist conditions are conducive for the transmission of the parasite (Hoberg et al., 2001) [6] . Similarly, coccidian oocysts also require suitable environmental temperature and humidity for sporulation before becoming infective. Factors such as warm temperatures, seasonal monsoon rainfall, and dense vegetation in the Gorewada landscape prolong the survival of the infective stages and also increase the probability of susceptible host infection. Furthermore, water sources, grazing patches, salt-lick sites and midden sites may themselves act as a source of infection (Utaaker et al., 2023) [15] . Strongyle-type eggs constituted the predominant parasitic finding (28.75%). Similar observations have been reported in free-ranging Nilgai and other wild herbivores from Barnawapara Wildlife Sanctuary (Verma et al., 2020) [16] and Panna Tiger Reserve (Sengar et al., 2017) [11] , where strongyle nematodes were among the most frequently encountered gastrointestinal parasites. The predominance of strongyle infections is consistent with the biology of these parasites, whose direct life cycle facilitates rapid transmission through contaminated pasture. Free-ranging Nilgai regularly graze and browse on vegetation close to the ground, increasing their exposure to infective larvae present on herbage and soil. Previous studies have similarly suggested that grazing behaviour and continuous environmental contamination are major factors favouring strongyle transmission in wild herbivores (Singh et al., 2009; Sengar et al., 2017) [14,11] . Eimeria spp. oocysts were detected in 3.75% of the examined samples, indicating a comparatively lower occurrence than strongyle nematodes. A relatively low prevalence of coccidial infection has also been reported in several coprological investigations of wild herbivores (Khutey et al., 2020; Sengar et al., 2017) [8,11] . Differences in the occurrence of Eimeria among studies may reflect variation in environmental humidity, temperature, stocking density, faecal contamination of grazing areas, and the survival of sporulated oocysts. Although coccidial infections in adult wild herbivores are frequently subclinical, they remain epidemiologically important because they may affect young or immunocompromised animals under favourable conditions (Sofi et al., 2026) [13] . Mixed infection involving strongyle-type eggs and Eimeria spp. was detected in 3.75% of the positive samples. Concurrent parasitic infections are commonly reported in free-ranging herbivores because multiple infective stages coexist within shared grazing habitats (Sengar et al., 2017; Singh et al., 2009) [11,14] . Even when present at relatively low frequency, mixed infections may influence host nutrition, immune responses, and overall health, highlighting the importance of continuous parasitological surveillance in wildlife populations. An important feature of the present study was the collection of fresh faecal samples from communal midden sites. Nilgai repeatedly use these sites for defecation, making them suitable for non-invasive monitoring of gastrointestinal parasites while minimizing disturbance to animals. Similar non-invasive faecal sampling approaches have been successfully employed in epidemiological investigations of free-ranging herbivores because they provide practical information on parasite circulation within wildlife populations without the need for capture or restraint (Sengar et al., 2017; Singh et al., 2009) [11, 14] . Nevertheless, repeated use of midden sites by multiple individuals should be considered when interpreting prevalence estimates, as the results represent sample-level rather than individual-level infection. This study recorded the baseline sample-level prevalence of 32.50%. This study provides baseline information on gastrointestinal parasites of free-ranging Nilgai in central India. Strongyle-type nematodes dominated this study and Eimeria spp. occurred at a low prevalence rate. These findings demonstrate the usefulness of communal midden sites for non-invasive parasite surveillance. Further seasonal studies incorporating quantitative and molecular techniques are recommended to better understand parasite dynamics and their significance for wildlife health and conservation.

References

1. Bisht K. Population status and habitat use of nilgai (Boselaphus tragocamelus) in Suklaphanta Wildlife Reserve [doctoral dissertation]. Kirtipur, Kathmandu, Nepal: Department of Environmental Science, Tribhuvan University; 2012.
2. Chandra K, Gupta D. Faunal diversity at ecosystem level in India: dynamics and status. In: Biodiversity in India: Status, Issues and Challenges. Singapore: Springer Nature Singapore; 2022. p. 463-492.
3. Chandel CS, Madan S, Jain D, Kumar U, Kolipakam V, Kawlni L, et al. Holy yet hindered: habitat use patterns of a large herbivore reveal challenges to farmers in India. Environ Challenges. 2025;20:101198.
4. Chauhan NPS. Agricultural crop depredation by nilgai antelope (Boselaphus tragocamelus) and mitigation strategies: challenges in India. In: 8th European Vertebrate Pest Management Conference; 2011. doi:10.5073/jka.2011.432.104.
5. Dookia S, Rawat M, Jakher GR. Wild ungulates in Rajasthan. In: Faunal Heritage of Rajasthan, India: General Background and Ecology of Vertebrates. New York, NY: Springer New York; 2013. p. 573-583.
6. Hoberg EP, Kocan AA, Rickard LG. Gastrointestinal strongyles in wild ruminants. In: Parasitic Diseases of Wild Mammals. 2001. p. 193-227.
7. Jaiswal AK, Srivastava A, Sudan V, Singh R, Shanker D, Parashar R. Prevalence of endoparasitic infections in wild cervids of Army Golf Course, Mathura. J Parasit Dis. 2014;38(4):358-360.
8. Khutey JK, Chandrakar S, Roy S, Singh J, Mishra B, Jambagi K, et al. Studies on prevalence of gastrointestinal parasites in captive wild herbivores in Nandanvan Zoo, Raipur. J Entomol Zool Stud. 2020;8(2):645-648.
9. Kozhayeva A, Kushaliyev K, Satybaev B, Zainettinova D, Turganbaeva G, Mendybayeva E, et al. Gastrointestinal nematodes of the saiga antelope: a review of diversity, epidemiology, pathophysiology and conservation significance. Pak Vet J. 2026;46(2):272281. doi:10.29261/pakvetj/2026.021.
10. Meena M, Choudhary K. A perceptive study on feeding pattern of nilgaii, Boselaphus tragocamelus in Jodhpur region, Rajasthan, India. J Exp Zool India. 2019;23(2):1951.
11. Sengar A, Shrivastav AB, Singh KP, Rokde A. Noninvasive assessment of gastrointestinal parasites infection in free-ranging wild herbivores and adjoining livestock of Panna Tiger Reserve, Madhya Pradesh, India. Vet World. 2017;10(7):748.
12. Gupta SG, Vohra SV, Sangwan AK, Singh SS, Gupta SK. A preliminary study of gastrointestinal parasites in wild animals at Hisar (Haryana). Haryana Vet. 2018;57(1):70-72.
13. Sofi OMUD, Godara R, Katoch R, Yadav A, Nabi Z, Sofi TA. First altitudinal epidemiology and morphomolecular assessments of different Eimeria spp. (Apicomplexa: Eimeriidae) in small ruminants from the Northwestern Himalayas in India. Small Rumin Res. 2026:107852.
14. Singh S, Shrivastav AB, Sharma RK. The epidemiology of gastrointestinal parasitism and body condition in free-ranging herbivores. J Threat Taxa. 2009;1(10):535537.
15. Utaaker KS, Ytrehus B, Davey ML, Fossøy F, Davidson RK, Miller AL, et al. Parasite spillover from domestic sheep to wild reindeer-the role of salt licks. Pathogens. 2023;12(2):186.
16. Verma MD, Singh RK, Verma LK, Sonwani A, Kumar H. Study on gastro-intestinal parasites in wild herbivores animals of Barnawapara Wildlife Sanctuary of Chhattisgarh. J Entomol Zool Stud. 2020;8(5):828831.
17. Zoromski LD, DeYoung RW, Goolsby JA, Foley AM, Ortega-S JA, Hewitt DG, et al. Latrine ecology of nilgai antelope. J Mammal. 2022;103(5):1194-1207.