Survey on Presence of the Endotheliotropic Elephant Herpesvirus (EEHV) in Thai Camp Elephants
The outbreak of a fatal hemorrhagic disease in captive Asian elephants (Elephas maximus) in Europe1 and the United States2 has alarming consequences for the survival of not only the elephants of both species kept in zoos and animal parks but also for the survival of the already strongly reduced (locally endangered and diminishing) free-ranging wild populations, in particular of the Asian elephant.
Approximately 10 years ago, more than 10 African elephants (Loxodonta africana) were imported to Thailand and kept together with Asian elephants in different zoos and safari parks all over the country. The African elephant is a potential source of the Herpesvirus lethal for Asian elephants. Today only one of these African elephants is still alive. This remaining individual is socialized with Asian elephants at the Korat Zoo. Currently, there are approximately 2300 captive Asian elephants and about 1800 wild elephants in Thailand. The majority of the captive population is involved in tourism business as riding or performing elephants in traditional elephant festivals. The logging industry excluded elephants from work in 1990. A few of the former logging elephants are utilized as so called “begging elephants” and less than 100 elephants are kept in governmental zoos for educational purposes. In general, elephants play an important economic and cultural role in Thailand.
In March 2000, a joint project was started to investigate the possible presence of the endotheliotropic elephant herpesvirus (EEHV) in the captive elephant population in Thailand. In addition, the analysis of the genetic diversity of the Thai elephants was initiated using the microsatellite-technique.
A team of veterinarians from the Institute for Zoo Biology and Wildlife Research, Berlin, the Wilhelma Zoological and Botanical Garden, Stuttgart, and the Mahidol University, Nakhonpathom collected different tissue samples and parasites of 83 elephants for histology, PCR analysis, and DNA sequencing in nine different locations. Twenty-one of these elephants had to be sedated by intravenous injection with 1–3 ml of 10% xylazine (Rompun™, Bayer, Inc., Germany) to allow for diagnostic procedures, like ultrasound guided lymph node biopsies, or treatments, like foot care or abscess lancing and flushing. Transrectal ultrasound investigations and semen collections were performed without sedation. All samples were immediately snap-frozen in liquid nitrogen and subsequently analyzed by PCR in Germany. To date, none of the elephants investigated was positive for EEHV. The project will be continued in the next years.
We thank the Germany Research (DFG) and the Mahidol University for financial and in-kind support. Special thanks to our former institute director Reinhold R. Hofmann, DVM, PhD for his assistance during this project.
1. Ossent, P., F. Guscetti, A.E. Metzler, E.M. Lang, A. Rubel, and B. Hauser. 1990. Acute and fatal herpesvirus infection in a young Asian elephant (Elephas maximus). Vet. Pathol. 27: 131–133.
2. Richman, L.K., R.J. Montali, R.L. Garber, M.A. Kennedy, J. Lehnhardt, Th. Hildebrandt, D. Schmitt, D. Hardy, D.J. Alcendor, and G.S. Hayward. 1999. Novel endotheliotropic herpesviruses fatal for Asian and African elephants. Science 283: 1171–1176.