Fatal elephant endotheliotropic herpesvirus type 5 infection in a captive Asian elephant

Comparative Genome Analysis of Four Elephant Endotheliotropic Herpesviruses, EEHV3, EEHV4, EEHV5, and EEHV6, from Cases of Hemorrhagic Disease or Viremia

“…Therefore, all three of the latter viruses, EEHV1A, EEHV1B, and EEHV4, now seem likely to be endogenous infections of Asian elephants. In addition, EEHV5 is evidently also a natural infection of Asian elephants that only rarely causes serious disease (8,17). Questions about whether or not prior subclinical latent infections with the other subtype of EEHV1 or by EEHV5 especially might provide immunological protection against EEHV1 disease remain to be addressed in the future.…”

“…The vast majority (over 90%) of the 47 PCR sequenceconfirmed cases of lethal hemorrhagic disease in captive zoo elephants in Europe and North America, as well as nine Asian calf deaths in India (6), have been caused by a large variety of distinctive strains of two partially chimeric subgroups referred to as EEHV1A and EEHV1B. However, six other elephant calf deaths and several cases of mild hemorrhagic disease have instead been associated with either EEHV2 (1), EEHV3 (3), EEHV4 (3, 7), EEHV5 (4,8), or EEHV6 (4). In addition, a large family of five distinctive and highly diverged gammaherpesviruses (elephant gammaherpesvirus 1 [EGHV1] to EGHV5) has also been detected mostly in eye and genital swabs from adult Asian and African elephants (4,9), but the latter have not yet been associated with any disease conditions.…”

“…Two distinct subtypes of EEHV5 referred to here as EEHV5A and EEHV5B each infecting multiple adults and calves proved to be involved in that episode. Finally, a young Asian elephant that died of hemorrhagic disease at a European zoo in 2012 represents the first known fatality associated with EEHV5 (8), and a second lethal case of EEHV4 disease was reported recently in Thailand (7). Initial sequence analysis of just the small POL (480-bp) and TER (340-bp) loci from each of these four new types (3,4) indicated that EEHV3 and EEHV4 might form a distinctive GC-rich branch of the Proboscivirus genus, whereas EEHV1, EEHV2, EEHV5, and EEHV6 fall into an AT-rich branch.…”

Detection of Quiescent Infections with Multiple Elephant Endotheliotropic Herpesviruses (EEHVs), Including EEHV2, EEHV3, EEHV6, and EEHV7, within Lymphoid Lung Nodules or Lung and Spleen Tissue Samples from Five Asymptomatic Adult African Elephants

“…Based on the finding of multiple different EEHV types in four of the five adult African elephants studied here, it seems clear that prior infection by one EEHV species does not necessarily provide protection against the establishment of persistent infection by one or more of the other EEHV types, possibly even including infection by a second strain of the same EEHV type, but it could mitigate the pathological symptoms and disease severity of subsequent primary infections by other EEHV strains or types. On the other hand, the majority of lethal disease cases in young Asian elephants, whether under human care in North America and Europe (19) or within Asian countries such as India (11), Thailand (20), Cambodia (35), and Laos (36), have been caused by a variety of different strains of EEHV1A or EEHV1B (3,7), together with two examples of EEHV4 (18) and one example of EEHV5 (10,23). This suggests that the two subgroups of EEHV1 and probably also EEHV4 and EEHV5 originated in Asian elephants (9,18,19).…”

“…PCRbased DNA sequencing of multiple genetic loci from samples from 58 cases, including 9 in India, revealed that lethal disease is associated predominantly with EEHV1, including Ͼ37 distinct strains of EEHV1A and 6 strains of EEHV1B (11,19). Just one or two known lethal cases each have been associated with EEHV3, EEHV4, and EEHV5 in Asian elephants (8,10,20), there have been just two known deaths caused by EEHV2 in African elephants (1), and one surviving African calf had mild EEHV6 viremic disease (3).…”