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Survival analysis of confirmed elephant endotheliotropic herpes virus cases in Thailand from 2006 - 2018.

ABSTRACT: The elephant endotheliotropic herpesvirus (EEHV) has been a known cause of death of young elephants in Thailand for over a decade. In this study, we report on the demography, disease characteristics and mortality of 58 elephants with confirmed EEHV hemorrhagic disease between January 2006 and August 2018 using retrospective data subjected to survival analysis. Median age of EEHV presentation was 29 months, and the mortality rate was 68.97% with a median survival time of 36 h. Most EEHV cases occurred in the north of Thailand, the region where most of the country's captive elephants reside. The hazard ratio analysis identified application of medical procedures and antiviral medications as being significant factors correlated to the risk of death. Our results indicate a need to focus EEHV monitoring efforts on young elephants and to follow current protocols that advise starting treatments before clinical signs appear.

SUBMITTER: Boonprasert K

PROVIDER: S-EPMC6611605 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Survival analysis of confirmed elephant endotheliotropic herpes virus cases in Thailand from 2006 - 2018.

Boonprasert Khajohnpat K Punyapornwithaya Veerasak V Tankaew Pallop P Angkawanish Taweepoke T Sriphiboon Supaphen S Titharam Chatchote C Brown Janine L JL Somgird Chaleamchat C

PloS one 20190705 7

The elephant endotheliotropic herpesvirus (EEHV) has been a known cause of death of young elephants in Thailand for over a decade. In this study, we report on the demography, disease characteristics and mortality of 58 elephants with confirmed EEHV hemorrhagic disease between January 2006 and August 2018 using retrospective data subjected to survival analysis. Median age of EEHV presentation was 29 months, and the mortality rate was 68.97% with a median survival time of 36 h. Most EEHV cases occ ...[more]

PMID: 31276571

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Project description:IntroductionOxidative stress refers to an imbalance between oxidant and antioxidant activity and accumulation of reactive oxygen species, which can have detrimental effects on animal health. Annual fluctuations in oxidative stress status can occur, increasing disease susceptibility during certain time periods. However, a full understanding of factors related to oxidative stress in Asian elephants and how to mitigate the negative consequences is lacking.MethodsThis study measured six serum oxidative stress markers [reactive oxygen species (ROS), malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), albumin, glutathione peroxidase (GPx), and catalase] and two stress markers [serum cortisol and fecal glucocorticoid metabolites (fGCM)] in 23 captive Asian elephants in Thailand over a 12 months period to examine relationships with age and season.ResultsSeasonal variations were observed, with several markers exhibiting significantly higher concentrations in the summer (ROS, MDA, 8-OHdG, albumin) and lower values during the rainy/winter seasons (MDA, 8-OHdG, albumin, catalase). By contrast, GPx was the only marker to be highest during the rainy season. For the stress markers, higher fGCM concentrations were noted during the rainy season, which contrasts with earlier studies showing more activity in the winter (tourist season). Positive correlations were found between the temperature-humidity index and ROS, GPx, and fGCM, while a negative correlation was observed with serum albumin. Elephant endotheliotropic herpesvirus (EEHV) shedding events were associated with higher concentrations of ROS and MDA. A moderate negative correlation was observed between 8-OHdG and the PCR threshold cycle of EEHV shedding (Ct), indicating DNA damage may be involved in EEHV shedding in elephants.DiscussionResults revealed significant age and seasonal effects on several oxidative stress markers, indicating those factors should be considered in study design and data interpretation. There also may be physiological adaptations in oxidative stress conditions in relation to environmental changes that could impact health outcomes.

Project description:UnlabelledThe genomes of three types of novel endotheliotropic herpesviruses (elephant endotheliotropic herpesvirus 1A [EEHV1A], EEHV1B, and EEHV2) associated with lethal hemorrhagic disease in Asian elephants have been previously well characterized and assigned to a new Proboscivirus genus. Here we have generated 112 kb of DNA sequence data from segments of four more types of EEHV by direct targeted PCR from blood samples or necropsy tissue samples from six viremic elephants. Comparative phylogenetic analysis of nearly 30 protein-encoding genes of EEHV5 and EEHV6 show that they diverge uniformly by nearly 20% from their closest relatives, EEHV2 and EEHV1A, respectively, and are likely to have similar overall gene content and genome organization. In contrast, seven EEHV3 and EEHV4 genes analyzed differ from those of all other EEHVs by 37% and have a G+C content of 63% compared to just 42% for the others. Three strains of EEHV5 analyzed clustered into two partially chimeric subgroups EEHV5A and EEHV5B that diverge by 19% within three small noncontiguous segments totaling 6.2 kb. We conclude that all six EEHV types should be designated as independent species within a proposed new fourth Deltaherpesvirinae subfamily of mammalian herpesviruses. These virus types likely initially diverged close to 100 million years ago when the ancestors of modern elephants split from all other placental mammals and then evolved into two major branches with high- or low-G+C content about 35 million years ago. Later additional branching events subsequently generated three paired sister taxon lineages of which EEHV1 plus EEHV6, EEHV5 plus EEHV2, and EEHV4 plus EEHV3 may represent Asian and African elephant versions, respectively.ImportanceOne of the factors threatening the long-term survival of endangered Asian elephants in both wild range countries and in captive breeding populations in zoos is a highly lethal hemorrhagic herpesvirus disease that has killed at least 70 young Asian elephants worldwide. The genomes of the first three types of EEHVs (or probosciviruses) identified have been partially characterized in the preceding accompanying paper (L. K. Richman, J.-C. Zong, E. M. Latimer, J. Lock, R. C. Fleischer, S. Y. Heaggans, and G. S. Hayward, J. Virol. 88:13523-13546, 2014, http://dx.doi.org/10.1128/JVI.01673-14). Here we have used PCR DNA sequence analysis from multiple segments of DNA amplified directly from blood or necropsy tissue samples of six more selected cases of hemorrhagic disease to partially characterize four other types of EEHVs from either Asian or African elephants. We propose that all six types and two chimeric subtypes of EEHV belong to multiple lineages of both AT-rich and GC-rich branches within a new subfamily to be named the Deltaherpesvirinae, which evolved separately from all other mammalian herpesviruses about100 million years ago.

Dataset Information

Survival analysis of confirmed elephant endotheliotropic herpes virus cases in Thailand from 2006 - 2018.

Publications

Survival analysis of confirmed elephant endotheliotropic herpes virus cases in Thailand from 2006 - 2018.

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