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BLOOD and necropsy tissue from Asian elephant (Elephas maximus) calves that die suddenly from acute haemorrhagic disease contain extremely high levels of DNA from an unusual type of herpesvirus known as elephant endotheliotropic herpesvirus (EEHV) (Richman and others 1999). Eight different types or species of EEHV, all belonging to the Proboscivirus genus, are now known that appear to be unique to, and have co-evolved with, the ancestors of modern Asian and African elephant (Loxodonta species) hosts (Garner and others 2009, Latimer and others 2011). Evidently, for as yet unexplained reasons, primary infections with two chimeric variants of the EEHV-1 species (ie, EEHV-1A and EEHV-1B), and rarely with other species, such as EEHV-2, EEHV-3 and EEHV-4, lead to rapid systemic spread and vascular endothelial cell damage associated with uncontrolled virus replication (Richman and others 2000).
This disease primarily affects calves between one and four years of age and has been lethal in at least 80 per cent of all animals with a positive DNA blood test. Only 10 survivors of symptomatic disease are known, which were all treated aggressively with human antiherpes drugs, although such treatments were not effective in many other cases. Overall, there have been 32 confirmed cases of EEHV disease in North America, with at least 25 suspected cases in Europe, and up to two dozen calf deaths with the same disease pathology have been recorded recently in wild and orphan calves in several Asian countries. Up to 24 per cent of Asian elephant calves born in North America and Europe within the past 20 …