The occurrence of elephant endotheliotropic herpesvirus infection in wild and captive Asian elephants in Thailand: Investigation based on viral DNA and host antibody

Vet World Vol.14 February-2021 Article-28

Research Article

Veterinary World, 14(2): 545-550

https://doi.org/10.14202/vetworld.2021.545-550

Phirom Prompiram^1,2, Witthawat Wiriyarat^1,3, Benjaporn Bhusri¹, Weena Paungpin¹, Waleemas Jairak⁴, Supaphen Sripiboon⁵, and Tuempong Wongtawan^2,3,6,7

1. The Monitoring and Surveillance Centre for Zoonotic Diseases in Wildlife and Exotic Animals, Faculty of Veterinary Science, Mahidol University, Salaya, Phutthamonthon, Nakhon Pathom, 73170, Thailand.
2. Laboratory of Veterinary Biomedicine, Faculty of Veterinary Science, Mahidol University, Salaya, Phutthamonthon, Nakhon Pathom, 73170, Thailand.
3. Department of Preclinical Science, Mahidol University, Salaya, Phutthamonthon, Nakhon Pathom, 73170, Thailand.
4. Zoological Park Organization, 267 Pracharat 1 Road, Bangsue Bangkok 10800, Thailand.
5. Department of Large Animal and Wildlife Clinical Sciences, Faculty of Veterinary Medicine, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140, Thailand.
6. Centre of Excellence for One Health, Akkhraratchakumari Veterinary College, Walailak University, Thai Buri, Tha Sala, Nakhon Si Thammarat 80160 Thailand.
7. Centre of Excellence Research for Melioidosis and other Microorganism, Walailak University, Thai Buri, Tha Sala, Nakhon Si Thammarat 80160 Thailand.

Background and Aim: Elephant endotheliotropic herpesvirus (EEHV) is a serious disease, threatening the life of young elephants. Many elephants have been infected with no clinical signs and may serve as carriers spreading this disease. It is important to monitor the disease through clinical signs and molecular diagnosis. In this study we investigated the occurrence of EEHV and the efficiency of different techniques used to monitor EEHV infection in various samples and populations of Asian elephants.

Materials and Methods: Blood and trunk swabs were collected from live elephants, while visceral organs (lung, digestive tract, spleen, lymph nodes, and kidney) were collected from dead elephants. EEHV was detected by polymerase chain reaction (PCR) in whole blood, trunk swabs, and visceral organs as samples, while elephant anti-EEHV immunoglobulin G (IgG) in serum was detected by enzyme-linked immunosorbent assay (ELISA). A total of 162 samples were analyzed in this study: 129 from healthy, 26 from dead, and 7 from sick elephants.

Results: The present study showed that the overall incidence of EEHV was 40.1% (n=65/162). Approximately 46.2% (n=12/26) and 85.7% (n=6/7) of dead and sick elephants were positive for EEHV by PCR, respectively. All sick elephants that were young and affected by EEHV clinical disease tested negative for the IgG antibody ELISA, suggesting primary EEHV infection in this group. In addition, 2.3% (n=3/129) of subclinical infections were detected using PCR, and trunk swab samples showed slightly higher sensitivity (5.3%, n=2/38) to detect EEHV than whole blood (1.2%, n=1/84). As many as, 48.4% (n=44/91) of healthy elephants were EEHV seropositive (ELISA-positive), suggesting that many elephants in Thailand had previously been infected. Overall, 30% of dead wild elephants had been infected with EEHV (n=3/10). Moreover, statistical analysis revealed no significant differences in the EEHV detection rate between different age groups or sexes (p>0.05).

Conclusion: PCR is better than ELISA to detect EEHV active infection in dead/sick elephants and to monitor EEHV in young elephants. ELISA is suitable for detecting previous EEHV infection and carriers, particularly adults. Theoretically, we could use both PCR and ELISA to increase the sensitivity of testing, along with observing abnormal behavior to efficiently monitor this disease. Identification of EEHV carriers within elephant populations is important to prevent transmission to healthy individuals, especially young elephants with high mortality from EEHV. This is the first report from Thailand regarding EEHV infection in wild elephants, showing the importance of preventing disease transmission between captive and wild elephants. Keywords: Carrier, elephant endotheliotropic herpesvirus, elephant, enzyme-linked immunosorbent assay, polymerase chain reaction.

Keywords: Carrier, elephant endotheliotropic herpesvirus, elephant, enzyme-linked immunosorbent assay, polymerase chain reaction.

How to cite this article: Prompiram P, Wiriyarat W, Bhusri B, Paungpin W, Jairak W, Sripiboon S, Wongtawan T (2021) The occurrence of elephant endotheliotropic herpesvirus infection in wild and captive Asian elephants in Thailand: Investigation based on viral DNA and host antibody, Veterinary World, 14(2): 545-550.

Received: 15-09-2020 Accepted: 21-01-2021 Published online: 27-02-2021

Corresponding author: Tuempong Wongtawan E-mail: tuempong.wo@mail.wu.ac.th

DOI: 10.14202/vetworld.2021.545-550

Copyright: Prompiram, et al. This article is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.