Clavarial Hyperostosis in Lions

Link to Zoo Survey

A World Survey of Neurological Diseases among Captive Lions (Panthera leo) in Zoological Gardens



Merav Shamir, DVM Dipl. ECVN
Professor of Veterinary Neurology & Neurosurgery



Rona Nadler Valency, DVM
Wildlife Veterinarian and PhD student

School Contact Information

Koret School of Veterinary Medicine,
The Robert H. Smith Faculty of Agricultural, Food & Environment,
The Hebrew University of Jerusalem.

Address: Herzl 229, P.O. Box 12,
Rehovot 76100, Israel

Phone: +972-(0)8-9489021/31;
Fax: +972-(0)8-9467940


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Clavarial Hyperostosis in Lions (Panthera leo) Research Group

The Lion (Panthera leo), was once abundant over most of the African continent, vast areas of Asia and even Europe. Having two subspecies; the African and Asiatic lions, are facing grave danger of extinction due to habitat loss, illegal poaching and persecution. The current geographical range and lion population have frightfully decreased and is now considered at a vulnerable - VU (African subsp.) and endangered - EN (Asiatic subsp.) conservation status by the International Union for Conservation of Nature (IUCN). Several hundreds of lions are reported to be domiciled in captivity, with their role in the future conservation of their species yet to be determined.

Lions have been kept in zoological gardens worldwide for decades and are considered the highlight in many parks. They seem to adjust to captivity well and usually are easy to reproduce. Therefore lions are not at the center of attention when zoological gardens are asked to take part in conservation programs. Nevertheless, it is well documented that stillbirth, cub’s and young adult’s death due to neurological dysfunction are frequently seen in many zoological gardens around the world. Most of the reports are related to Clavarial Hyperostosis which results in reduced volume of the caudal fossa that causes compression of the cerebellum and spinal cord leading to sever ataxia, discomfort and finally death.

Our group has been studying neurological diseases in lions for several years now, specifically looking at ways to achieve diagnosis, treatment and prevent the occurrence of Clavarial hyperostosis. Through the years we were approached by zoo and private veterinarians from different parts of the world, looking for advice regarding the diagnosis and treatment of neurologically affected lions. Although vitamin A deficiency is believed to be the underlying cause, our findings could not rule out genetic and other environmental factors that may predispose certain lions to develop the abnormal bone growth while others in the group remain healthy. Although the disease has been so far documented in captive lions only, further understanding of its precise pathophysiology is needed before it is guaranteed to not be a possible risk for the health of the entire lion population.