Hidden Parasite Threat Links Endangered Himalayan Musk Deer and Livestock in Nepal

High in the Lapchi Valley of Nepal’s Gaurishankar Conservation Area, where Sherpa herders drive their chauri—a yak-cow hybrid—through alpine meadows grazed by one of the world’s most elusive endangered ungulates, a new study has uncovered a largely invisible conservation problem. Nearly 95 percent of fecal samples collected from Himalayan musk deer, chauri, and horses in the valley tested positive for gastrointestinal parasites, and six of the twelve parasite species identified were shared between wild and domestic hosts, raising the possibility of cross-species transmission in a landscape where grazing lands overlap.

The research, published in Veterinary Medicine and Science, focused on the Himalayan musk deer (Moschus leucogaster), a solitary and endangered species listed on Appendix I of CITES and classified as Endangered by the IUCN. Nepal holds an estimated 10,000 square kilometers of potential musk deer habitat across multiple protected areas, but populations face pressure from habitat degradation, poaching for musk pods, livestock overgrazing, and disease. Gastrointestinal diseases are particularly common in musk deer and often lead to high mortality; roughly 35 percent of deaths in captive settings have been attributed to coccidian protozoan parasites that damage the intestinal epithelium and predispose animals to fatal secondary bacterial infections.

To assess parasite dynamics in a wild population, researchers conducted a cross-sectional, comparative study across two distinct habitat types in Lapchi Valley, which sits at elevations between 2,600 and 4,950 meters and is bordered by China on three sides. The valley is home to 39 Sherpa households who practice semi-nomadic transhumance, moving chauri and horses seasonally to high-altitude pastures. The team defined four host groups: musk deer in natural habitats with minimal livestock activity (MDN), musk deer in livestock-influenced areas (MDL), horses, and chauri. The MDN site, at an average elevation of 3,880 meters, is separated from the MDL site by the glacier-fed Lapchekhun River and rugged terrain that limits livestock access, while the MDL site comprises subalpine mixed-conifer forest and alpine pastures heavily used by agro-pastoralists, with active chauri sheds and trails leading to Buddhist pilgrimage caves.

Between the two sites, researchers systematically collected 97 fresh fecal samples—67 from musk deer (32 from livestock-influenced areas and 35 from natural habitats) and 30 from livestock (15 chauri and 15 horses)—using belt transects with sampling points placed at 300 to 400 meter intervals to minimize pseudo-replication. Samples were preserved in 2.5 percent potassium dichromate solution and analyzed at Tribhuvan University in Kathmandu using saline wet mounts with Lugol’s iodine staining, supplemented by Stoll’s flotation and modified sedimentation concentration techniques to improve detection of low-abundance eggs and oocysts. Parasites were identified to genus level based on morphological keys, with digital microscopy used to measure parasitic structures for confirmation.

The results revealed a striking parasite burden. Of the 97 samples examined, 92 (94.8 percent) were positive for one or more gastrointestinal parasites. Twelve parasite taxa were identified across three host types: two protozoans (Eimeria sp. and Entamoeba sp.), eight nematodes (ascarid eggs, Bunostomum sp., Capillaria sp., Dictyocaulus sp., Muellerius capillaris, Oxyuris sp., Strongylida larvae, and Trichostrongylus sp.), one cestode (Moniezia sp.), and one trematode (Paramphistomum sp.). Among musk deer, 92.5 percent of pellet samples were infected, with nematodes the most prevalent group. The lungworm Muellerius capillaris dominated, detected in 85.1 percent of musk deer samples—consistent with previous reports of this parasite in wild and domestic small ruminants, including 100 percent prevalence documented in bighorn sheep in Montana.

The high prevalence of M. capillaris is likely explained by its complex life cycle. The parasite uses terrestrial molluscs as intermediate hosts, and first-stage larvae can survive for months within fecal pellets while infective third-stage larvae persist for the lifetime of the mollusc, ensuring year-round transmission. By contrast, Dictyocaulus sp. showed a prevalence of only 8.9 percent in musk deer, likely because its free-living larvae depend heavily on favorable humidity and temperature conditions for survival and development. Ascarid egg prevalence in livestock was roughly double that in musk deer, and the researchers note that the robust outer shell of ascarid eggs allows them to remain viable in the environment for up to 15 years, potentially causing diarrhoea, malnutrition, and intestinal obstruction in infected hosts.

Parasite sharing between wild and domestic hosts emerged as a central finding. One protozoan (Eimeria sp.) and two nematodes (ascarid eggs and Strongylida larvae) infected all three host species, while Entamoeba sp., Bunostomum sp., Capillaria sp., and Muellerius capillaris occurred exclusively in musk deer. Dictyocaulus sp. infected both musk deer and horses, Moniezia sp. and Paramphistomum sp. infected only musk deer and chauri, and Trichostrongylus sp. infected both chauri and horses. Oxyuris sp. was found only in horses. Strongylida larvae dominated livestock infections overall, with a prevalence of 56.7 percent—higher in horses (66.7 percent) than in chauri (46.7 percent). Notably, Moniezia sp. was detected only in musk deer from livestock-influenced areas, suggesting potential interspecies infection.

When the researchers compared musk deer from the two habitat types, overall parasite prevalence was remarkably similar: 93.7 percent in livestock-influenced areas versus 91.4 percent in natural habitats. However, protozoan infections were higher in the livestock-influenced areas (25.0 percent) than in natural habitats (14.3 percent), with Entamoeba sp. showing a greater prevalence in livestock-influenced sites (18.8 percent) compared to natural sites (8.5 percent). Ascarid eggs, Bunostomum sp., and Strongylida larvae were also more prevalent in livestock-influenced areas, while Muellerius capillaris and Capillaria sp. were higher in natural habitats. Principal coordinates analysis based on Bray–Curtis dissimilarity showed that horse and chauri samples clustered closely together, while musk deer samples from both habitat types overlapped considerably with each other but showed partial overlap with livestock patterns, suggesting potential parasite spillover. Permutational multivariate analysis of variance confirmed that host group explained 38.2 percent of the total variation in parasite community composition (F = 18.13, p = 0.001).

The findings align with previous work in Nepal’s Langtang National Park, where gastrointestinal parasite prevalence in musk deer was reported at 88.9 percent and Eimeria spp. were documented in both musk deer and chauri, hinting at mutual transmission. They also echo broader reviews showing substantial parasite overlap between wild and domestic ungulates. However, the Eimeria prevalence of 7.5 percent in musk deer here is considerably lower than the 65 percent reported in captive forest musk deer from Chinese breeding centres, a difference the researchers attribute to environmental and management factors such as soil moisture, sanitation, and climatic conditions. Molecular studies in China have also detected Enterocytozoon bieneusi in captive alpine musk deer at 6 percent infection, with genotypes common to both humans and animals, highlighting potential zoonotic concerns.

The study provides an important ecological baseline for a remote and understudied region, showing that musk deer face high baseline parasite pressures regardless of livestock influence, while livestock presence clearly alters the composition of specific parasite taxa. Because the identification relied on morphological techniques, the researchers emphasize that future work should integrate molecular tools to achieve species-level resolution, which will be key to tracking cross-species transmission pathways. For an endangered ungulate whose populations already contend with poaching, habitat loss, and competition with livestock, the shared parasite community documented in Lapchi Valley adds a further layer of risk—one that early monitoring and coordinated management of grazing lands may help mitigate before spillover becomes outbreak.

Subject of Research: Gastrointestinal Parasites in Himalayan Musk Deer (Moschus leucogaster Hodgson, 1839) and Sympatric Livestock in Gaurishankar Conservation Area, Nepal

Article Title: Gastrointestinal Parasites in Himalayan Musk Deer (Moschus leucogaster Hodgson, 1839) and Sympatric Livestock in Gaurishankar Conservation Area, Nepal

Article References: Sharma, R., Koju, N. P., Adhikari, A., Maharjan, M., & Deshar, R. (2026). Gastrointestinal Parasites in Himalayan Musk Deer ( Moschus leucogaster Hodgson, 1839) and Sympatric Livestock in Gaurishankar Conservation Area, Nepal. Veterinary Medicine and Science, 12(6), Article e71266. https://doi.org/10.1002/vms3.71266

Image Credits: AI Generated

DOI: 10.1002/vms3.71266

Keywords: Gastrointestinal, Parasites, Himalayan, Musk, Deer, Moschus, leucogaster, Hodgson, Sympatric, Livestock, Gaurishankar, Conservation