New Delhi: Scientists have detected multiple cases of a lethal haemorrhagic viral infection for the first time in wild elephant calves in India and raised concerns that it could threaten the long-term survival of some Asian elephant populations.
Wildlife officials in India have identified 13 lethal cases of elephant endotheliotropic herpes virus (EEHV) between 2013 and 2017, eight among them in elephant calves living among free-ranging wild herds, three in camp-raised orphans and two in captive-born calves.
Since the early-1990s, scientists have documented the deaths of more than 100 captive elephant calves from EEHV, a mammalian herpes virus that can cause acute haemorrhagic disease and that had been identified in 1990 in an elephant calf in a circus in Switzerland.
The International Elephant Foundation estimates EEHV has been responsible for the deaths of 20 per cent of all Asian elephant calves born in zoos and elephant housing facilities over the past 25 years.
The virus has since then also turned up in captive elephant calves in Borneo, Cambodia, Indonesia, Laos, Singapore and Thailand, prompting some scientists to suggest that EEHV affects only captive elephants and that it had crossed into Asian elephants from African elephants.
"What is unusual is that we're seeing this infection among elephant calves in the wild," said Arun Zachariah, a wildlife veterinarian with Kerala's forest and wildlife department at Sultan Bathery in Wayanad. Almost all previous cases in Asia were in captive-born calves or rescued camp orphans.
Zachariah had first documented EEHV infections in nine elephant calves between 2005 and 2011, including four wild free-ranging calves, three rescued orphans and two captive-born calves.
All the infections were reported from Kerala and one from Maharashtra. Zachariah said he had also confirmed one case of EEHV in a sample sent from Assam but did not hear from the forest officials again.
In their new study, Zachariah and his collaborators with SciGenom Research Foundation in Kerala and the Johns Hopkins School of Medicine in the US have analysed segments of the EEHV genomes from the earlier set of nine calves and the 13 new infections up to 2017.
The study's findings, published on Thursday in the journal PLOS One, appear to corroborate earlier suggestions that despite the severity of the infection Asian elephants appear to be an ancient host for the EEHV virus.
"It is possible that Asian elephants and EEHV co-evolved over millions of years," Zachariah told The Telegraph. "We still need to understand why more cases appear to be emerging and why adult elephants appear protected."
The scientists say the widespread presence of the disease "raise serious concerns" about its impact on the long-term survival of the highly endangered Asian elephant populations and its challenge on efforts to breed elephants in captivity.
"Fragmented elephant populations may be at risk," Zachariah said. With growing pressures on wildlife habitats, conservation scientists have long been worried about habitat fragmentation leadingo the isolation of small elephant herds.
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