Effects of between and within Herd Moves on Elephant Endotheliotropic Herpesvirus (EEHV) Recrudescence and Shedding in Captive Asian Elephants (Elephas maximus).

Sanna Eriksson Titus,Joanna Prince-Wright,Fieke Marije Molenaar,Akbar Dastjerdi,Stuart Patterson

doi:10.3390/v14020229

Abstract

Haemorrhagic disease associated with elephant endotheliotropic herpesvirus (Elephantid herpesvirus, EEHV) infections is the leading cause of death for Asian elephant (Elephas maximus) calves. This study assessed the effect of captive herd management on EEHV shedding, as evidence of latent infection reactivation, focusing on: (1) the influence of social change on the odds of recrudescence; (2) the respective effects of between and within herd moves; and (3) characteristics of recrudescent viral shedding. Trunk and conjunctival swabs (n = 165) were obtained from six elephants at an EAZA-accredited zoo, collected during a period of social stability, and at times of social change. Longitudinal sampling took place at times of moving two bulls out of the collection and one new bull into an adjacent enclosure to the cow herd (between herd moves), and during a period of mixing this new bull with the cow herd to facilitate mating (within herd moves). Quantitative PCR was employed to detect EEHV 1a/b, 4a/b, and EF–1–α (housekeeping gene). Generalised estimating equations determined EEHV recrudescence odds ratios (OR) and relative viral DNA load. Sixteen EEHV 1a/b shedding events occurred, but no EEHV 4a/b was detected. All management-derived social changes promoted recrudescence (social change OR = 3.27, 95% CI = 0.412–26, p = 0.262; and between herd moves OR = 1.6, 95% CI = 0.178−14.4, p = 0.675), though within herd movements posed the most significant increase of EEHV reactivation odds (OR = 6.86, 95% CI = 0.823−57.1, p = 0.075) and demonstrated the strongest relative influence (post hoc Tukey test p = 0.0425). Shedding onset and magnitude ranged from six to 54 days and from 3.59 to 11.09 ΔCts. Differing challenges are associated with between and within herd movements, which can promote recrudescence and should be considered an exposure risk to naïve elephants.

Highlights

Haemorrhagic disease associated with elephant endotheliotropic herpesvirus (Elephantid herpesvirus, Endotheliotropic Herpesvirus (EEHV)) infections is the leading cause of death for Asian elephant (Elephas maximus) calves
The haemorrhagic disease (HD) process associated with clinical elephant endotheliotropic herpesvirus infections is the leading cause of death in captive Asian elephant (Elephas maximus) calves in Europe and North America [1,2]
DNA extractions were successful for all samples (n = 165) and all extractions yielded sufficient DNA for Quantitative PCR (qPCR), as determined by the spectrophotometer

Summary

Introduction

The haemorrhagic disease (HD) process associated with clinical elephant endotheliotropic herpesvirus (elephantid herpesvirus, EEHV) infections is the leading cause of death in captive Asian elephant (Elephas maximus) calves in Europe and North America [1,2]. Captive collections are especially vulnerable to HD mortalities [1,5], which are essential for species conservation by serving as a reserve for genetic diversity, research, and future reintroduction initiatives Both in- and ex-situ breeding programmes are presently unsustainable due to the effects of EEHV-HD, and if current trends continue, captive Asian elephants in North America will be demographically extinct before 2050 [6,7,8]. EEHV prevalence and exposure routes have been defined, but researchers have called for greater understanding of recrudescent cases and actions promoting viral shedding [5,6,9]

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Results

Conclusion