- Date: October 13, 2020
One of India’s flagship species, the greater one-horned rhinoceros, also known as the Indian rhinoceros, was once found across the entire northern part of the Indian subcontinent. Gradually over the last 400 years, mostly due to habitat destruction and poaching, this rhino is now only found within a few pockets in India and Nepal with a total population of around 3,700 individuals.
Poaching is considered the greatest threat to greater one-horned rhino populations, but we don’t know much about other causes of rhino death. Any death that is not related to poaching is commonly classified as ‘natural’ and could be because of old age, disease, injury, or other causes.
When habitat quality decreases or changes, there is a higher risk of pathogen and disease emerging in the environment and being transmitted among rhinos and other wildlife and livestock they come in contact with. In India, the outbreak of foot and mouth disease, pox, and Anthrax is common and all these diseases have affected wildlife. Many viral, bacterial, and parasitic diseases are shared by both wild and domestic species, including rhinos, so understanding these diseases and how they are linked or transmitted from one species to another—and potentially to humans—is crucial.
Understanding rhino health and disease
Limited knowledge of the prevalence of disease in greater one-horned rhinos prevents conservationists and veterinarians from offering expert health care to the species and making informed conservation management decisions. Therefore, it is important to understand rhino health issues to conserve rhino populations that face increasing pressure from poaching, habitat loss and degradation, and the impacts of climate change.
Over the past four years, the Rhino Task Force of Assam, of which WWF India is a member, set out to help close that knowledge gap. In 2018, WWF India, in collaboration with the forest departments of Assam, Uttar Pradesh, and West Bengal and the College of Veterinary Sciences, Guwahati, initiated a study examining the parasites and bacteria found in fresh rhino dung samples to help detect diseases that may lead to rhino deaths. Viruses, bacteria, protozoa, parasites, congenital anomalies, difficult births, deficiencies, and many more unexplored factors could be related to rhino mortality.
“We have come across many natural [rhino] deaths in the park, and it is good to know that dung can be used to understand the cause of rhino deaths in some cases,” said Babul Deka, head mahout, Pobitora Wildlife Sanctuary, Assam, India. “From this training and experience of dung sampling, we have realized the importance of dung for scientific studies and detection of diseases in rhino.”
Findings from the study
We sampled dung across six locations in Assam and West Bengal, India, and found that parasites from five genuses are found in an estimated 68% of India’s greater one-horned rhino population.
Why does this matter? We now have a baseline for how often and what types of parasites are found in the wild rhino population—a key step in determining the harmful effects the parasites have on their rhino hosts. Parasites alone cannot kill a host most of the time until it becomes a severe infection. The parasite is adapted enough to know that if its host dies, it also dies along with it. Hence, it often stays hidden, while slowly draining its host and making it weak and vulnerable to other diseases.
We also extended our research to the bacterial and viral pathogens that rhinos may harbor, finding bacteria that have never been previously recorded in the greater one-horned rhino population. These include some antibiotic-resistant bacterial species.
The study and findings are preliminary, but can be used as a stepping stone toward filling critical knowledge gaps on rhino health and disease. Moving forward, we plan to investigate the parasites found in this study to better understand their growth or propagation; understand which parasites are most common in various wild and domesticated species; and learn more about the risk of transmission among species and to humans. We will use this information to explore ways to prevent disease in rhinos. We also aim to find out whether viral and other pathogens (likely with a zoonotic nature—meaning they can jump to humans) are found in rhino bearing areas, particularly in Assam.