Elephant endotheliotropic herpesvirus haemorrhagic disease of Asian elephants: An updated mini review

Abstract

Asian elephants (Elephas maximus), the National Heritage Animal of India and classified as endangered by the IUCN. Their existence is threatened by habitat loss, poaching, deforestation and emerging diseases such as elephant endotheliotropic herpesvirus (EEHV), which has become a major cause of mortality among elephant calves over the past three decades. First reported in North America in 1995, EEHV has since caused severe losses in both captive and wild populations throughout the world. In India, the first case was recorded in Kerala in 2013. The virus is mainly transmitted through direct mucosal contact, trunk secretions or fomites and may also spread via saliva or intestinal contents. Latent nature of EEHV permits to establish a carrier status in adult Asian elephants and intermittent shedding of the virus without associated clinical disease. EEHV infection classically targets endothelial cells, resulting in widespread haemorrhage, DIC and cardiovascular failure. Clinical signs range from lethargy and facial oedema to acute death. Diagnosis is primarily based on nucleic acid detection methods like both conventional PCR and qPCR methods. The serological method like ELISA is developed to assess antibody status. Despite numerous attempts, EEHV could not be isolated in the cell culture system to date. Therapeutic management includes anti-herpes viral drugs like famciclovir, ganciclovir or acyclovir combined with intensive supportive care. Recent research on EEHV vaccines (viral vector and mRNA vaccines) shows promising results. High fatality rate and widespread occurrence, enhanced surveillance, rapid diagnostic capabilities and development of effective vaccines are crucial for mitigating the impact of EEHV on the conservation of Asian elephants.