Extended genotypic evaluation and comparison of twenty-two cases of lethal EEHV1 hemorrhagic disease in wild and captive Asian elephants in India

Abstract

Thirteen new lethal cases of acute hemorrhagic disease (HD) with typical histopathogical features were identified in young Asian elephants (Elephas maximus indicus) in India between 2013 and 2017. Eight occurred amongst free-ranging wild herds, with three more in camp-raised orphans and two in captive-born calves. All were confirmed to have high levels of Elephant Endotheliotropic Herpesvirus type 1A (EEHV1A) DNA detected within gross pathological lesions from necropsy tissue by multi-locus PCR DNA sequencing. The strains involved were all significantly different from one another and from nine previously described cases from Southern India (which included one example of EEHV1B). Overall, eight selected dispersed PCR loci totaling up to 6.1-kb in size were analyzed for most of the 22 cases, with extensive subtype clustering data being obtained at four hypervariable gene loci. In addition to the previously identified U48(gH-TK) and U51(vGPCR1) gene loci, these included two newly identified E5(vGPCR5) and E54(vOX2-1) loci mapping far outside of the classic EEHV1A versus EEHV1B subtype chimeric domains and towards the novel end segments of the genome that had not been evaluated previously. The high levels of genetic divergence and mosaic scrambling observed between adjacent loci match closely to the overall range of divergence found within 45 analyzed North American and European cases, but include some common relatively unique polymorphic features and preferred subtypes that appear to distinguish most but not all Indian strains from both those in Thailand and those outside range countries. Furthermore, more than half of the Indian cases studied here involved calves living within wild herds, whereas nearly all other cases identified in Asia so far represent rescued camp orphans or captive-born calves.

Lethal Hemorrhagic Disease and Clinical Illness Associated with Elephant Endotheliotropic Herpesvirus 1 Are Caused by Primary Infection: Implications for the Detection of Diagnostic Proteins

“…variants of EEHV1-EEHV1A and EEHV1B (1,2); both EEHV4 and EEHV5 are also endemic in Asian elephants but have only rarely been fatal (3,4). EEHV2, -3, -6, and -7 are recognized as endemic in African elephants (1), but to date, hemorrhagic disease caused by these viruses has not been documented to the same extent as for EEHVs in Asian elephants.…”

Elephant Endotheliotropic Herpesvirus Hemorrhagic Disease in Asian Elephant Calves in Logging Camps, Myanmar

“…Conventional PCR amplifications were performed at the University of Veterinary Sciences (Yezin, Myanmar) during an EEHV workshop. These DNA samples were used as templates to amplify and sequence 7 standard preferred EEHV1 PCR DNA loci ( 22 , 27 ) from all 3 cases, as well as an eighth locus (U51, vGPCR1) from 1 of these cases. We performed Sanger DNA sequencing and DNA sequence editing and constructed phylogenetic trees as described ( 6 , 10 , 22 ).…”

“…We performed Sanger DNA sequencing and DNA sequence editing and constructed phylogenetic trees as described ( 6 , 10 , 22 ). We used the updated sets of PCR primers reported by Zachariah et al ( 27 ).…”

“…We have also expanded the studies in India to 22 lethal cases, including 12 in wild free-ranging calves ( 27 ). In this study, we report DNA sequence–confirmed cases of lethal EEHV1A disease in 3 young logging camp elephants in Myanmar, including partial genetic analysis by PCR sequencing of the strains involved and comparison with all the cases from India and other representative cases worldwide.…”

Editorial: Conservation of Elephants

“…Elephants are charismatic and easily attract media attention. Over the last 10 years, great improvements have been made in the care and welfare of elephants in zoos across the world, including advances in occupational safety (Lehnhardt & Galloway, ; AZA, ), operant conditioning and keeper–elephant relationships (Carlstead et al , ), social management (Greco et al , ; Meehan et al , ), disease research (Luz & Howard, ; Bauer et al , ; Howard & Schaftenaar, ; Zachariah et al , ; Edwards et al , ), reproduction (Hildebrandt et al , ; Lueders et al , ), nutrition (Clauss et al , ; Hatt & Clauss, ; Sach, Dierenfeld et al , ) and habitat development (Holdgate et al , ; Meehan et al , ; Miller et al , ).…”