Evidence of high EEHV antibody seroprevalence and spatial variation among captive Asian elephants (Elephas maximus) in Thailand

Taweepoke Angkawanish,Kannika Na Lampang,Hans Vernooij,Janine L Brown,Peter J S Van Kooten,Victor P M G Rutten,Mirjam Nielen,Willem Schaftenaar,Petra B Van Den Doel

doi:10.1186/s12985-019-1142-8

Abstract

BackgroundElephant endotheliotropic herpesviruses (EEHV) can cause an acute highly fatal hemorrhagic disease in young Asian elephants (Elephas maximus), both ex situ and in situ. Amongst eight EEHV types described so far, type 1 (subtype 1A and 1B) is the predominant disease-associated type. Little is known about routes of infection and pathogenesis of EEHV, and knowledge of disease prevalence, especially in range countries, is limited.MethodsA large cross-sectional serological survey was conducted in captive elephants (n = 994) throughout Thailand using an EEHV-1A glycoprotein B protein antigen specific antibody ELISA.ResultsAntibody seroprevalence was 42.3%, with 420 of 994 elephants testing positive. Associations between seropositivity and potential risk factors for EEHV infection were assessed and included: elephant age, sex, camp cluster size, management type (extensive versus intensive), sampling period (wet vs. dry season) and location of camp (region). Univariable regression analysis identified management system and region as risk factors for the presence of EEHV antibodies in elephants, with region being significant in the final multivariable regression model. Prevalence was highest in the North region of the country (49.4%).ConclusionsThis study produced baseline serological data for captive elephants throughout Thailand, and showed a significant EEHV burden likely to be maintained in the captive population.

Highlights

Elephant endotheliotropic herpesviruses (EEHV) can cause an acute highly fatal hemorrhagic disease in young Asian elephants (Elephas maximus), both ex situ and in situ
The aim of the present study was to assess EEHV seroprevalence in a large cross-sectional survey of elephants in Thailand using the EEHV-1A glycoprotein B (gB) protein antigen Enzyme-Linked Immunosorbent Assay (ELISA) [23], and to obtain preliminary data on factors potentially associated with infection throughout the captive population in Thailand
Our study showed that 43.8% of young elephants were antibody seropositive, similar to the older age groups, which suggests that elephants of all ages are being exposed to this potentially deadly virus

Summary

Introduction

Elephant endotheliotropic herpesviruses (EEHV) can cause an acute highly fatal hemorrhagic disease in young Asian elephants (Elephas maximus), both ex situ and in situ. Amongst eight EEHV types described so far, type 1 (subtype 1A and 1B) is the predominant disease-associated type. Methods: A large cross-sectional serological survey was conducted in captive elephants (n = 994) throughout Thailand using an EEHV-1A glycoprotein B protein antigen specific antibody ELISA. Of great concern over the past two decades is infection with the elephant endotheliotropic herpesvirus (EEHV), which can cause hemorrhagic disease (HD). In Asian elephants, EEHV-1 (subtypes 1A and 1B) is the most common and Angkawanish et al Virology Journal (2019) 16:33 elephant calves born in zoos globally [9]. More than 100 deaths from EEHV have been confirmed globally [3, 13], with many more cases likely going undiagnosed

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