Predicting Parasite Dynamics in Mixed-Use Trans-Himalayan Pastures to Underpin Management of Cross-Transmission Between Livestock and Bharal

Zoonotic risks and conservation challenges: Gastrointestinal parasites in wild mammals of Chitwan National Park, Nepal

Gastrointestinal parasites (GIPs) pose a significant threat to wildlife health and biodiversity, impacting reproductive activities, behavior, survival, and population dynamics. Identifying parasitic infections in wild animals can help to mitigate extinction risk and support conservation efforts. This study investigates the prevalence, diversity, and zoonotic risks of GIPs in six large wild mammals in Chitwan National Park, Nepal. Fresh fecal samples were collected between December 2022 and April 2023 and examined using direct wet mount and concentration methods. By analyzing 63 fecal samples: Royal Bengal Tiger (Panthera tigris) (n = 7), Asian elephant (Elephus maximus) (n = 9), One-horned rhinoceros (Rhinoceros unicornis) (n = 10), Sloth bear (Melursus ursinus) (n = 9), Spotted deer (Axis axis) (n = 25), and Rhesus Monkey (Macaca mullata) (n = 3), we identified 19 GIP types: 3 protozoan species (Balantioides coli, Isospora spp., and coccidia) and 16 helminth species, revealing an 85.7% infection rate. Helminths had a higher prevalence (85.7%) than protozoans (22%). Among helminths, nematodes were the most prevalent (69.8%) followed by trematodes (38.0%) and cestodes (17.4%). Eleven types of nematodes, three types of cestodes, and two types of trematodes were recorded. Multiple infections were more common than single infections. The high prevalence of GIPs indicates a major health issue that could affect species survival and conservation efforts in Chitwan National Park, highlighting the need for proactive conservation and health monitoring strategies for conservation.

Gastrointestinal parasites of the wild ungulates (Mammalia: Cetartiodactyla) in the Hemis National Park, Ladakh, India

We evaluated the gastrointestinal parasitic prevalence and intensity of wild ungulates in the Hemis National Park of Ladakh by examining their fresh faecal samples. A total of 327 fresh faecal samples from three wild ungulates, blue sheep Pseudois nayaur (n = 127), Ladakh urial Ovis vignei vignei (n = 110), and Himalayan ibex Ibex siberica (n = 90) were collected between June 2021 and May 2022. The techniques of flotation and sedimentation were used to find parasite eggs and oocysts from the faecal samples. Out of 327 samples examined, 165 samples were infected with gastrointestinal parasites making an overall prevalence of 50.45%. Seven parasitic taxa, including one protozoan (Eimeria spp.), five nematodes (Nematodirus spp., Strongyloides spp., Haemonchus sp., Trichuris sp., and Trichostrongylus spp.), and one cestode (Monezia spp.), were found during the current investigation. Mixed infection was reported in 36 (11%) of the total examined samples. The prevalence of gastrointestinal parasites was found to be highest in blue sheep (55.11%), followed by Ladakh urial (49.09%) and Himalayan ibex (45.55%). The highest prevalence was recorded in the summer (64.42%), and the lowest in the winter (33.82%). A significant difference in parasitic prevalence was observed across seasons in each of the three wild ungulate hosts. However, there was no significant difference in the prevalence of parasites between these hosts.

Host movement dominates the predicted effects of climate change on parasite transmission between wild and domestic mountain ungulates

Climate change is shifting the transmission of parasites, which is determined by host density, ambient temperature and moisture. These shifts can lead to increased pressure from parasites, in wild and domestic animals, and can impact the effectiveness of parasite control strategies. Understanding the interactive effects of climate on host movement and parasite life histories will enable targeted parasite management, to ensure livestock productivity and avoid additional stress on wildlife populations. To assess complex outcomes under climate change, we applied a gastrointestinal nematode transmission model to a montane wildlife-livestock system, based on host movement and changes in abiotic factors due to elevation, comparing projected climate change scenarios with the historic climate. The wildlife host, Alpine ibex (Capra ibex ibex), undergoes seasonal elevational migration, and livestock are grazed during the summer for eight weeks. Total parasite infection pressure was more sensitive to host movement than to the direct effect of climatic conditions on parasite availability. Extended livestock grazing is predicted to increase parasite exposure for wildlife. These results demonstrate that movement of different host species should be considered when predicting the effects of climate change on parasite transmission, and can inform decisions to support wildlife and livestock health.

Mathematical modeling at the livestock-wildlife interface: scoping review of drivers of disease transmission between species

Modeling of infectious diseases at the livestock-wildlife interface is a unique subset of mathematical modeling with many innate challenges. To ascertain the characteristics of the models used in these scenarios, a scoping review of the scientific literature was conducted. Fifty-six studies qualified for inclusion. Only 14 diseases at this interface have benefited from the utility of mathematical modeling, despite a far greater number of shared diseases. The most represented species combinations were cattle and badgers (for bovine tuberculosis, 14), and pigs and wild boar [for African (8) and classical (3) swine fever, and foot-and-mouth and disease (1)]. Assessing control strategies was the overwhelming primary research objective (27), with most studies examining control strategies applied to wildlife hosts and the effect on domestic hosts (10) or both wild and domestic hosts (5). In spatially-explicit models, while livestock species can often be represented through explicit and identifiable location data (such as farm, herd, or pasture locations), wildlife locations are often inferred using habitat suitability as a proxy. Though there are innate assumptions that may not be fully accurate when using habitat suitability to represent wildlife presence, especially for wildlife the parsimony principle plays a large role in modeling diseases at this interface, where parameters are difficult to document or require a high level of data for inference. Explaining observed transmission dynamics was another common model objective, though the relative contribution of involved species to epizootic propagation was only ascertained in a few models. More direct evidence of disease spill-over, as can be obtained through genomic approaches based on pathogen sequences, could be a useful complement to further inform such modeling. As computational and programmatic capabilities advance, the resolution of the models and data used in these models will likely be able to increase as well, with a potential goal being the linking of modern complex ecological models with the depth of dynamics responsible for pathogen transmission. Controlling diseases at this interface is a critical step toward improving both livestock and wildlife health, and mechanistic models are becoming increasingly used to explore the strategies needed to confront these diseases.

Pastoralism in the high Himalayas: Understanding changing practices and their implications for parasite transmission between livestock and wildlife

Rangelands are increasingly being affected by climatic variations, fragmentation and changes in livestock management practices. Along with resource competition between livestock and wildlife, disease transmission has implications for people and wildlife in these shared landscapes. We worked with two pastoral communities in the Western Indian Himalayas: the migratory Kinnauras that travel to the Trans-Himalayan Pin valley in summer and the resident herders of Pin Valley. Asiatic ibex (Capra sibirica) is the predominant wild herbivore in Pin. The pastures in Pin are grazed by both livestock (migratory and resident) and ibex, with the potential for disease transmission. We investigate the effects of herding practices on livestock health and disease transmission, while focusing on gastro-intestinal nematodes (GINs) as they can spread by sharing pasture between wild and domestic ungulates. Surveys were carried out between June and August 2019, the period when migratory Kinnauras, local herders and Asiatic Ibex are found in Pin Valley. We found that the Kinnaura flocks share pasture with ibex during their time in Pin, exhibiting significantly higher endo-parasite burdens than sedentary livestock, and the Kinnaura flocks are increasing in number. This suggests GIN cross-transmission is possible, as GINs have low host specificity and a free-living, environmental stage that is trophically acquired. As local (sedentary) sheep and goats rarely share pasture with ibex, have low endo-parasite burdens and are few in number, they are unlikely to transmit parasites to ibex. However, increasingly large local stock numbers may be contributing to pasture degradation which could cause nutritional stress and resource competition, exacerbating GIN impacts. We also find evidence for transhumance persisting, in spite of signs of pasture degradation that are seemingly affecting livestock productivity and potentially disease transmission. It is critical that proactive measures are taken, like participatory disease management with the Kinnauras, to align livelihoods with wildlife and rangeland conservation.

Possible Consequences of Climate Change on Survival, Productivity and Reproductive Performance, and Welfare of Himalayan Yak (Bos grunniens)

Simple Summary

Climate change is a global issue, with a wide range of ecosystems being affected by changing climatic conditions including the Himalaya. Yak are exquisitely adapted to the high-altitude conditions of the Himalaya and are thus highly likely to be affected by climate change. This paper reviews the evidence of how the reported impacts of climate change on the environment and ecosystem of the Himalaya are affecting the survival, productivity and welfare of Himalayan Yak. This review identified that we do not know how big the impact of climate change is on yak as very few papers have measured that impact and, in many cases, potentially climate-change-related effects (such as changes in feed supply) are principally driven by human factors.

Abstract

Yak are adapted to the extreme cold, low oxygen, and high solar radiation of the Himalaya. Traditionally, they are kept at high altitude pastures during summer, moving lower in the winter. This system is highly susceptible to climate change, which has increased ambient temperatures, altered rainfall patterns and increased the occurrence of natural disasters. Changes in temperature and precipitation reduced the yield and productivity of alpine pastures, principally because the native plant species are being replaced by less useful shrubs and weeds. The impact of climate change on yak is likely to be mediated through heat stress, increased contact with other species, especially domestic cattle, and alterations in feed availability. Yak have a very low temperature humidity index (52 vs. 72 for cattle) and a narrow thermoneutral range (5–13 °C), so climate change has potentially exposed yak to heat stress in summer and winter. Heat stress is likely to affect both reproductive performance and milk production, but we lack the data to quantify such effects. Increased contact with other species, especially domestic cattle, is likely to increase disease risk. This is likely to be exacerbated by other climate-change-associated factors, such as increases in vector-borne disease, because of increases in vector ranges, and overcrowding associated with reduced pasture availability. However, lack of baseline yak disease data means it is difficult to quantify these changes in disease risk and the few papers claiming to have identified such increases do not provide robust evidence of increased diseases. The reduction in feed availability in traditional pastures may be thought to be the most obvious impact of climate change on yak; however, it is clear that such a reduction is not solely due to climate change, with socio-economic factors likely being more important. This review has highlighted the large potential negative impact of climate change on yak, and the lack of data quantifying that impact. More research on the impact of climate change in yak is needed. Attention also needs to be paid to developing mitigating strategies, which may include changes in the traditional system such as providing shelter and supplementary feed and, in marginal areas, increased use of yak–cattle hybrids.