Acute Hemorrhagic Disease Due to Elephant Endotheliotropic Herpesvirus 3a Infection in Five African Elephants (Loxodonta Africana) at One North American Zoological Institution

Primary Infection May Be an Underlying Factor Contributing to Lethal Hemorrhagic Disease Caused by Elephant Endotheliotropic Herpesvirus 3 in African Elephants ( Loxodonta africana )

“…To validate the LIPS assay for use in African elephants, we assessed antibody responses in two distinct groups, i.e., (i) a family herd of 11 elephants in which at least 5 herdmates have demonstrated EEHV3 shedding or viremia, suggesting that most or all herd members have been exposed and are chronically infected ( Table 1 ), and (ii) elephants that died from EEHV3-associated HD (EEHV-HD group I) ( 6 ) ( Table 2 ). Drawing on studies in Asian elephants ( 5 ), we hypothesized that fatal EEHV3-HD was due to a primary infection and thus these animals should lack immunoreactivity against EEHV3-specific proteins.…”

“…At least 5 of the elephants had evidence of latent EEHV infection from either an EEHV-positive trunk wash or viremia (L. Howard and E. Latimer, unpublished data) ( Table 1 ). Sera were also obtained from three other institutions where there was a clinical or fatal EEHV-HD case associated with EEHV3 ( 6 ); these included 8 elephants housed at the Indianapolis Zoo (IDZ), 5 from the Fresno Chaffe Zoo (FCZ), and 4 from the Maryland Zoo in Baltimore (MZiB) ( Tables 2 and 4 ).…”

“…Due to the low incidence of documented clinical disease caused by EEHV in African elephants, the biology of these viruses, compared to those endemic among Asian elephants, is lesser known. Since 2019, however, at least seven cases of EEHV-HD in African elephants, resulting in three fatalities, have occurred ( 6 ), suggesting possible increasing significance of EEHV in African elephants. These cases have also revealed gaps in knowledge and the need for diagnostic tools to study and to monitor EEHV in this elephant species.…”

“…Regardless of host species, viruses within the GC-rich group or the AT-rich group share significant amino acid identity (i.e., 65% to 80%) with each other in their core proteins but retain only 30% to 50% amino acid identity over one-half or less of their length in the novel Proboscivirus genus-specific proteins. The majority of EEHV-HD cases in captive African elephants have been caused by a single GC-rich species, EEHV3 ( 3 , 6 ). Recent sequencing studies from our laboratories have identified at least two distinct chimeric subspecies of EEHV3, i.e., EEHV3A and EEHV3B, which diverge by at least 9% on average across their genomes ( 15 ) (G. S. Hayward and P. D. Ling, unpublished data).…”

Elephant Endotheliotropic Herpesvirus Impact in the European Asian Elephant (Elephas maximus) Population: Are Hereditability and Zoo-Associated Factors Linked with Mortality?

“…EEVH-HD is considered to be an ancient infection among Asian elephants {Formatting Citation} and is not a disease exclusive of this species as it may also affect African elephants. However, the recorded mortality rate in African elephants is lower, and the animals seem to present symptoms at an older age [11][12][13]. Currently, the most used antiviral treatment is a human anti-herpetic drug, despite its high costs and reported as presenting unproven efficacy, so far [4,14,15].…”