BACKGROUND : 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. Little is known about routes of infection
and pathogenesis of EEHV, and knowledge of disease prevalence, especially in range countries, is limited.
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.
RESULTS : Antibody 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%).
CONCLUSIONS : This study produced baseline serological data for captive elephants throughout Thailand, and showed
a significant EEHV burden likely to be maintained in the captive population.
Additional file 1: Figure S1. Stacked bar plots with numbers of
negative and positive animals per herd (ranked on herd size). Using as
definitions for a positive sample: both OD ratio ≥ 3 (graph a) and OD
ratio ≥ 4 (graph b).
Additional file 2: Table S1. Seroprevalence based on an EEHV1A
glycoprotein B protein antigen specific ELISA of elephants sampled
throughout Thailand (n = 994) between 2010 and 2015, and the
percentage of samples testing positive1, inconclusive2 or negative3
relative to potential EEHV risk factors based on different interpretation
modalities: 1:100 dilution; 1:200 dilution.
Additional file 3: Table S2. Univariable regression analysis of potential
risk factors for the presence of EEHV antibodies in elephants sampled
throughout Thailand between 2010 and 2015 (n = 994) based on an
EEHV1A glycoprotein B protein antigen specific ELISA. Seroprevalence is
based on strict cutoff: positive if both OD ratio’s > 4.