Background: Elephant endotheliotropic herpesvirus haemorrhagic disease (EEHV HD) is the leading cause of death in captive Asian elephant calves in Asia, North America, and Europe with a mortality rate of ~ 65% in calves that are under human care. Although EEHV HD was first found in elephant camps, more recently it was identified in wild populations which poses a greater threat to the elephant population. Deaths due to EEHV HD have been seen in wild elephants, but the in-situ prevalence and mortality rate is unknown. We report the first EEHV HD cases in Malaysia from 3 wild born endangered Bornean elephant calves from Sabah with known typical clinical signs. Case presentation: The first calf died within 24 h of the onset of clinical signs; the second calf died within 12 h of the onset of clinical signs. The third calf succumbed within 72 h. Necropsies revealed that all 3 calves had similar presentations of EEHV HD but in the third calf with less severity. We conducted conventional polymerase chain reaction (cPCR) assays and found EEHV DNA at all 7 loci in the 3 calves; it was identified as EEHV1A, the virus type that has been found in most other reported cases. Conclusion: Typical EEHV HD clinical signs and the molecular confirmation of EEHV by cPCR and sequencing point to EEHV as the cause of death. Further genetic investigation of the strain is in progress.

Elephant Endotheliotropic Herpesvirus (EEHV) is a leading cause of fatal hemorrhagic disease in juvenile Asian elephants and represents a significant concern for elephant conservation. However, information on the epidemiology of EEHV in Bornean elephants (Elephas maximus borneensis) remains limited. This study investigated the prevalence and subtype distribution of EEHV in wild and captive Bornean elephants in Sabah, Malaysia, using samples collected during conservation management activities including rescue operations, translocation, GPS collaring, necropsies and routine veterinary examinations between 2009 and 2026. A total of 240 samples, comprising 100 whole-blood and 140 tissue samples from 110 elephants, were analyzed by conventional polymerase chain reaction (cPCR) targeting EEHV1 and EEHV4. EEHV DNA was detected in 6.4% (7/110) of elephants. Most positive cases were identified post-mortem, indicating a possible association of EEHV infection with mortality. EEHV1 was the only subtype detected, and sequence analysis showed close similarity to previously reported EEHV1A cases from Sabah. No EEHV4 was detected. Although no significant associations were observed between EEHV detection and population type, age group, sex, or sampling location, the detection of EEHV in both wild and captive elephants indicates that the virus is circulating in this endangered population. These findings provide baseline epidemiological data and support the need for continued surveillance and strengthened diagnostic capacity to inform EEHV management and conservation strategies in Sabah.