Elephant endotheliotropic herpesviruses (EEHVs) are a group of viruses that can cause haemorrhagic disease (EEHV-HD) and death in Asian elephants (Elephas maximus). Juvenile mortality caused by these viruses is impacting ex situ conservation efforts globally. Tissue tropism of the virus and viral transmission dynamics are still poorly understood, and there has only been one prior EEHV-HD fatality in Australia. In August 2023, a fatal case of EEHV1B-HD occurred within the Zoos Victoria herd. This case study investigates the clinical challenges, herd viral dynamics, tissue tropisms of the virus and preferred storage media for tissue samples. Quantitative PCR (qPCR) was performed to determine the amount of virus present in each tissue sample stored in different storage media. Additionally, trunk wash samples prior to and after the case were tested for EEHVs with qPCR to determine shedding events of the virus within the herd.
A review of case details reveals a crucial 48-hour delay in receiving results and therefore initiating treatment due to transit time for interstate laboratory testing. Herd trunk wash samples showed a peak in EEHV1B shedding in one of the adult elephants approximately 7 weeks prior to the onset of clinical signs, with multiple subsequent, lower quantity shedding events. There was prolonged shedding of EEHV1B by several animals in the herd after the fatal case. qPCR analysis of tissue samples revealed the greatest number of EEHV1B genome copies (normalised to host cell number) evident in the heart, followed by the liver and gastrointestinal tract. DNA Shield® was the preferred storage media for detection of viral DNA, however samples stored at -80ºC with no storage media provided adequate recovery of DNA. The occurrence of fatal disease in a 9-year-old elephant reveals that age should not be relied upon to inform risk of disease and surveillance practices.