Elephant endotheliotropic herpesviruses (EEHVs) may cause acute, often lethal, hemorrhagic disease (EEHV-HD) in young elephants. Prevalence of EEHV in different elephant populations
is still largely unknown. In order to improve diagnostic tools for the detection of EEHV infections
and to obtain insight into its spread among elephants, we developed novel ELISAs based on EEHV1A
gB and gH/gL. Performance of the ELISAs was assessed using sera from 41 European zoo elephants
and 69 semi-captive elephants from Laos, one of the Asian elephant range countries. Sera from
all (sub)adult animals tested (≥5 years of age) showed high reactivity with both gB and gH/gL,
indicating that EEHV prevalence has been highly underestimated so far. Reactivity towards the
antigens was generally lower for sera of juvenile animals (1 > 5 years). Only one (juvenile) animal,
which was sampled directly after succumbing to EEHV-HD, was found to be seronegative for EEHV.
The two other EEHV-HD cases tested showed low antibody levels, suggesting that all three cases died
upon a primary EEHV infection. In conclusion, our study suggests that essentially all (semi-)captive
(sub)adult elephants in European zoos and in Laos carry EEHV, and that young elephants with low
antibody levels are at risk of dying from EEHV-HD.