Introducing diagnostic solutions for Asia’s real-life unicorns

Unexplained mortality among greater one-horned rhinos in Nepal’s Chitwan National Park has emerged as a serious conservation concern. In collaboration with Nepali partners, we are conducting detailed epidemiological investigations, developing in-country diagnostic capacity, and introducing innovative digital pathology tools that connect local veterinarians with international experts. This integrated approach aims to strengthen Nepal’s capacity for protecting rhinos and other threatened and endangered species—now and for the future.

The greater one-horned rhino (Rhinoceros unicornis) is the largest rhinoceros outside of Africa. As the name suggests, this species has only one horn, unlike the two familiar two-horned African species. These rhinos are solitary herbivores that graze, browse, and even swim underwater to harvest aquatic plants. Greater one-horned rhinos, like their other Asian rhino counterparts, inhabit mixed environments and frequently enjoy mud baths in the ephemeral pools left by the annual monsoons. These rhinos are variably docile, with some being comfortable enough to stroll down the streets of the towns outside of national parks, or even take naps in hotel gardens.

Protected Yet Periled

Twenty percent of the world’s greater one-horned rhino population lives in Nepal. Most of these rhinos are found in Chitwan National Park, the country’s oldest national park and a UNESCO World Heritage Site. This park protects one of the last vestiges of the rhino’s preferred Terai grassland floodplains that once extended across the shadow of the Himalayas from Pakistan to Northeast India.

When Chitwan National Park was established in 1973, fewer than 100 greater one-horned rhinos remained in the area. Under the park’s protection, the population steadily increased. However, this progress was interrupted during the Maoist insurgency of the 1990s and 2000s, when a surge in poaching significantly reduced rhino numbers. In the years since, intensive anti-poaching enforcement measures have helped stabilize and grow the rhino population once again, with more than 600 rhinos currently in the park.

Throughout these changes, other known causes of rhino deaths, such as predation, fighting, and certain human-related incidents, seem to have remained relatively stable. The greater one-horned rhino is still listed as vulnerable on the IUCN Red List, despite anti-poaching successes.

And now, it seems a new threat to the species has emerged. Over the past decade, the number of greater one-horned rhinos dying in Chitwan has increased each year, and the reasons remain unclear.

Improving Rhino Health in Nepal

In partnership with the National Trust for Nature Conservation (NTNC), a leading Nepali conservation organization, we are investigating the causes of greater one-horned rhino deaths in Chitwan. In parallel, we aim to strengthen local diagnostic capacity, working alongside NTNC and other stakeholders to build sustainable solutions for rhino conservation in Nepal.

The primary objective of this initiative is to understand the factors contributing to the elevated rhino mortality in Chitwan and develop actionable strategies to improve the health of greater one-horned rhinos. To do so sustainably, we are working to equip wildlife veterinary teams in Nepal with the necessary skills and facilities to diagnose rhino mortalities. By establishing expertise and laboratory resources within Nepal, we aim to build a self-sustaining system to monitor and address rhino health in country.

Challenges of Rhino Mortality Diagnosis

Previously, the process for diagnosing the causes of greater one-horned rhino deaths involved collecting samples during rhino postmortem examinations and shipping them internationally for analysis. This process faces several significant challenges that delay and complicate timely diagnosis.

We are taking a comprehensive approach to address obstacles previously experienced throughout the process, with a focus on collecting high-quality samples, establishing facilities within Nepal for sample preparation and analysis, and building local expertise in wildlife pathology.

One of the main hurdles is limited access to wildlife pathologists with expertise in histological tissue analysis. The limited number of local veterinary pathologists makes real-time diagnoses challenging, and had previously led wildlife managers to send rhino tissue samples abroad for examination. The tissue export process is cumbersome, particularly for threatened species listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) regulations that require permits for each sample, which is expensive, time-consuming, and sometimes impossible.

Enhancing Diagnosis in the Field

This project aims to enhance field investigations and build in-country laboratory capacity for rhino health diagnostics. Mortality investigations require a multidisciplinary approach, including epidemiology, pathology, molecular biology, and toxicology. A thorough necropsy (veterinary postmortem exam) is essential for identifying causes of death, but often requires additional sample testing for conclusive results. For example, tissue samples collected at the time of necropsy often need to be evaluated microscopically and with other specialized testing (e.g., bacterial cultures or molecular diagnostics) to obtain a final diagnosis.

Our team is working with partners from NTNC to investigate each rhino mortality event comprehensively, maximizing epidemiological information gathered for each case. Our work builds upon the current endeavors of Nepali wildlife veterinarians who collect information on the circumstances around each rhino mortality, perform field necropsy examinations, and collect tissue samples. Together, we are documenting necropsy examination findings and ensuring that optimal tissues of the highest diagnostic value are collected.

Building Long-Term Expertise

A unique component of this project is the focus on building long-term diagnostic capacity within Nepal.

In collaboration with NTNC and the Agriculture and Forestry University, we are helping to establish a wildlife histopathology laboratory in Nepal to process postmortem tissues locally. We are training veterinarians to prepare high-quality tissue sections for microscopic analysis, while also mentoring Nepali postgraduate students in wildlife pathology to build long-term expertise in diagnosing wildlife disease in Nepal. We see this as the most cost-effective and sustainable approach for delivering timely diagnostic results in the place where they are needed.

Overcoming Roadblocks with Technology

In parallel with our efforts to strengthen in-country diagnostic capabilities, we are leveraging innovative technology to address the immediate need to determine the causes of rhino mortalities. Since developing expertise in complex disciplines like veterinary pathology takes years, we are implementing a system that enables remote consultation with board-certified wildlife pathologists worldwide.

The company Grundium generously provided an Ocus 20 digital microscope slide scanner to our team’s efforts, and we are establishing a web-based platform to digitally transfer histological images from locally prepared slides to an international network of wildlife pathology specialists. This approach significantly improves diagnostic efficiency by eliminating the need to export actual tissue samples out of the country. Nepali wildlife veterinarians can quickly consult with expert wildlife pathologists remotely, making the process faster, more cost-effective, and more sustainable than current export practices.

Importantly, this technology maximizes the number of steps performed in Nepal, helping to train local veterinarians in advanced diagnostic techniques and further strengthening local diagnostic capacity. Furthermore, the digital case material and diagnostic reports generated with the Ocus 20 will serve as a valuable resource for future wildlife pathology students in Nepal, enabling them to learn from real-world cases in their training.

Tracking Trends and Emerging Threats

We are collecting epidemiological data on each mortality event, such as timing, geographical location, and environmental conditions. Over time, this information can help identify emerging trends, contributing to better management strategies and more proactive conservation efforts for the greater one-horned rhino.

Beyond Rhino Conservation

We aim to build a foundation for wildlife pathology and diagnostic capacity in Nepal that will benefit all wildlife species. As local expertise grows, a new generation of veterinary pathologists will be equipped to diagnose and respond to mortality events across Nepal’s diverse ecosystems.

With well-equipped laboratories and trained professionals, wildlife health experts in Nepal will be able to process diagnostic samples from a wide range of species, not just rhinos. This expanded capacity will be crucial for protecting the country’s many threatened and endangered species and monitoring broader ecological health.

In a world where zoonotic diseases are an increasing threat, strengthening Nepal’s wildlife disease surveillance capacity will safeguard its iconic species as well as serve as a critical defense to help protect the health and well-being of local communities. By enhancing wildlife pathology capabilities, we are helping to create a system that benefits both conservation and public health, contributing to a healthier future for Nepal’s people and wildlife.