Endotheliotropic elephant herpesvirus: diagnosis, pathogenesis, and treatment

Endotheliotropic elephant herpesviruses (EEHV) are the causative agents of Elephant Hemorrhagic Disease (EHD), which is a major cause for death among elephants. At least 6 young elephants in Switzerland have succumbed to EHD. These viruses circulate in the respiratory tracts of adult animals without causing disease. However, immunologically naïve animals, particularly in the age between 2 and 5 years, may develop viremia, which is associated with hemorrhagic lesions of the blood vessels, followed by rapid death.

At present, the virus cannot be serially passaged in cell cultures, but genomic analyses have revealed that at least 7 different types of EEHV exist (Ling et al., 2013; Wilkie et al., 2013; Pellet, 2014), five of which are associated with EHD.

Our goals are to understand the pathogenesis of the disease, to improve the diagnostic tools, and to develop strategies for prevention and treatment of EHD.

To know the circulating viruses, we screen the adult animals for virus-shedding from their trunk and the young animals for signs of viremia. Serological tests have been established to monitor the current immunological status of each individual over time.

Elephant cell cultures have been established with the aim to propagate one or several EEHV strains in vitro, which may help to identify virus-neutralizing antibodies and to test novel antiviral compounds for potential toxicity. Moreover, we study several viral glycoproteins (ORFQ-family) for their potential to interact with and damage endothelial cells, which seems to be the key to the observed pathogenetic events.

Finally, we are expanding our collection of mutant herpes simplex viruses, which express particular EEHV1-genes, i.e ETk, ECPK, and U38 DNA polymerase, in order to identify and characterize novel nucleoside-based antiviral drugs for antiviral activity against EEHV.

Publications

1. Ackermann M, Hatt JM, Schetle N, Steinmetz H. Identification of shedders of elephant endotheliotropic herpesviruses among Asian elephants (Elephas maximus) in Switzerland.
PloS one. 2017;12(5):e0176891.

2. Ackermann M, Hatt J-M (2019). To treat or not to treat?
Vet Rec Case Rep 2019;7:e000847.