Abstract

The Asian elephant (Elephas maximus) is IUCN listed as an endangered species. With well over 10% of the global Asian elephant population in <2% of the global range for Asian elephants, Sri Lanka is home to the highest density of Asian elephants in the world.² According to the census conducted in 2011 by the Department of Wildlife Conservation of Sri Lanka, there are 5,879 wild elephants living in the country. Human-elephant conflict is the major threat for elephant conservation in Sri Lanka. There are over 200 elephant deaths recorded annually, and most deaths are due to anthropogenic activities. Currently there are several preventive measures implemented by the government in Sri Lanka to reduce the human-elephant conflict. Among these, attempting to confine the movements of elephants to national parks using electric fences is practiced in a number of areas in the country.

The Udawalawe National Park is a protected area and occupies 308 km² in the southern dry zone of Sri Lanka. The park has been electric fenced in successive stages, leaving open two exits for wildlife via the Dahaiyagala and Lunugamwehera corridors.¹

Udawalawe National Park and adjacent elephant ranging areas are home to 600–800 wild elephants. An average of 12 elephant deaths per year are recorded in this ecosystem. The Department of Wildlife Conservation records all elephant deaths and conducts thorough postmortem examinations to establish the cause of death. This study reports the results of postmortem examinations of 14 wild elephants conducted in 2014; deaths of five elephants were due to the parasite Parabromina smithi, and one death was due to tuberculosis (TB). The remaining five deaths were due to a variety of causes (e.g., gunshots, accident, orphaning), while three deaths were not conclusive due to decomposed carcasses.

The five elephant deaths associated with the parasite Parabromina smithi are alarming. This parasite belongs to the Spiruride family and causes caseous ulcers in the stomach wall. On gross necropsy, the margins of the ulcers were elevated, and the Parabromina parasites could be observed in the ulcers as well as in adjacent mucosa of the stomach wall. The parasite was identified by morphology and PCR. The age range of affected animals was 2–35 years. This is the first identification of the parasite, Parabromina smithi, and its associated mortalities in wild elephants in Sri Lanka.

The death due to TB is also a major concern. The elephant was a female of approximately 35 years of age.⁴ There were typical tuberculosis granulomas affecting >60% of lung tissue.⁴ Histopathology, culture and isolation of an acid-fast organism, and PCR confirmed the causative organism as Mycobacterium tuberculosis.⁴

Although tuberculosis is a major re-emerging infectious disease among captive elephants worldwide and a potential concern for wild populations,³ this is the first confirmed case of tuberculosis among wild Sri Lankan elephants in Sri Lanka, and possibly the first confirmed case in a wild elephant in Asia.⁴ Mycobacterium tuberculosis is of course also the primary causative agent for human TB. The source of infection for this elephant was unclear, as no data is available regarding its human contacts, and there are no known wildlife reservoirs of M. tuberculosis in Sri Lanka.⁴ Despite movement restrictions and protection from human-elephant conflict, the elephants in the Udawalawe National Park are exposed to large numbers of visitors who enter the park on safari. The zoonotic potential of TB from wild elephants, therefore, is a matter of concern.

The emergence of parasitic and infectious diseases in wild Asian elephants could be due to chronic stress associated with human disturbances and the increasing density of elephants. Further studies are underway to study the prevalence of these two diseases among wild elephants. In the long term, the effects of anthropogenic activities of habitat destruction and restriction of movements to prevent human-elephant conflict in wild elephants in Sri Lanka requires more thorough investigation to protect the species from stress-related diseases that can lead to more deaths and a reduced population.

Acknowledgments

Authors thank Mr. T.P.M.S.D. Bandara and K.B.A.T. Bandara from the Faculty of Veterinary Medicine and Animal Science, University of Peradeniya, for technical assistance. This work was partially supported by Royal Veterinary College, UK; National Research Council, Sri Lanka; and University of Peradeniya, Sri Lanka.

Literature Cited

1.  de Silva S, Ranjeewa ADG, Weerakoon D. Demography of Asian elephants (Elephas maximus) at UdaWalawe National Park, Sri Lanka based on identified individuals. Biol Conserv. 2011;144:1742–1752.

2.  Leimgruber P, Gagnon JB, Wemmer C, Kelly DS, Songer MA, Selig ER. Fragmentation of Asia’s remaining wild lands: implications for Asian elephant conservation. Anim Conserv. 2003;6:347–359.

3.  Mikota SK, Peddie L, Peddie J, et al. Epidemiology and diagnosis of Mycobacterium tuberculosis in captive Asian elephants (Elephas maximus). J Zoo Wildl Med. 2001;32:1–16.

4.  Perera BVP, Salgadu MA, Gunawardena GSP de S, Smith NH, Jinadasa HRN. First confirmed case of fatal tuberculosis in a wild Sri Lankan elephant caused by Mycobacterium tuberculosis. Gajah. 2015;41:28–31.