Abstract

Elephant endotheliotropic herpesvirus (EEHV) infection is the leading cause of death among captive Asian elephants (Elephas maximus). The aim of this study was to use retrospective data and archived histology samples, to identify factors common to EEHV fatalities. Stud book data were collated from all Asian elephants born in Europe during 1985–2017. The risk period for EEHV was defined as 9 mo of age (the youngest known case) to 8 yr. Calves were classified as survivors if they exceeded 8 yr of age by the end of the study period. Fatalities were classified as any calf succumbing to EEHV during the study period. Forty institutions recorded a total of 263 birth events, including still births. Fifty-five calves were either born dead or died in the first 24 h leaving 208 live calves. Thirty-one of these died in the risk period, only six from non-EEHV confirmed disease, whereas there were 26 EEHV related fatalities identified from 14 institutions, at an average age of 2.7 yr old and with no sex predilection. Nineteen dams (one to three calves each) and 13 sires (one to five calves each) produced calves that succumbed to EEHV. Tissue location and extent of EEHV lesions (hemorrhage, edema, inflammation, inclusion bodies) were assessed on the basis of a histologic review of 22 cases. Findings were compared to EEHV strain, age and duration of clinical signs. The most consistent lesion was myocardial hemorrhage. Results from this study will help generate hypotheses for risk factors leading to EEHV-associated death.