Elephant endotheliotropic herpesvirus in Elephas maximus - epidemiology, risk factors and coagulation parameters

The Asian elephant (Elephas maximus) is an endangered species, suffering a continuous decline in their population numbers. Elephant Endotheliotropic Herpesvirus haemorrhagic disease (EEHV-HD) is the primary cause of calf mortality of Asian elephants worldwide. The disease is presented as an acute haemorrhagic syndrome caused by vast endothelial destruction and disseminated intravascular coagulation, leading to sudden death.
In this thesis, we investigated 1) the impact of EEHV-HD in the European captive Asian elephant population, 2) the presence of hereditary or zoo-associated factors as a risk to develop the disease in Europe, 3) the coagulation status of healthy Thai and European Asian elephant populations, 4) the presence of genomic mutations in coagulation factor VII that could lead to a hereditary coagulopathy in Thai and European Asian elephants.
Our findings reveal that more than half of the captive born fatalities were caused by EEHV-HD alone and suggest the involvement of zoo-associated factors with a possible sire and/or dam influence on the onset of the disease. Using a specific fast point-of-care analyser we have stablished reference values for coagulation parameters, such as coagulation times (PT and aPTT) and fibrinogen concentration in healthy elephants, detailed by gender, age, regions at study and EEHV status (survivors of EEHV-HD or animals that never present the disease). Our methods and results regarding coagulation assessment, can be used and compared for future routine health check-ups or in emergency, such as during an EEHV-HD outbreak. Furthermore, we report the finding of several new single point mutations in coagulation F7 gene, found in Elephas maximus from Thailand and Europe.
Overall, our findings highlight the importance of doing continuous retrospective epidemiological studies and stresses the need to further investigate the underlying risks or protective factors that make calves especially susceptible or resistant to the onset and outcome of EEHV-HD.