Elephant Endotheliotropic Herpesvirus (EEHV) Routine Monitoring for “At Risk” Juvenile Asian and African Elephants, Updated July 2025

Careful preparation for an EEHV case is an essential part of excellent elephant care. The website eehvinfo.org is a valuable resource, and should be consulted for protocols, training recommendations, recommended treatments, and clinical findings, among other information prior to an elephant becoming ill with EEHV. The calf training needed for proper care in monitoring for and treating EEHV is lengthy and should be accomplished long before an EEHV viremia occurs. Routine monitoring of elephant calves for EEHV by quantitative PCR (qPCR) is proven to detect low levels of EEHV in the blood (viremia) before clinical signs occur (Stanton et al., 2013). The increased sensitivity and ability to quantify whole blood viral levels with qPCR allows for earlier detection of viremia and monitoring for rapid increase in viral levels which will guide intervention and management of calves. A rapid, logarithmic increase in viremia levels and high levels of virus are typically found in cases that develop EEHV Hemorrhagic disease (EEHV HD). If qPCR is not available, multiple rounds of cPCR can be a sufficient, but not ideal, replacement. Viral DNA has been detected in blood at low levels (100-1,000 vge/ml) in clinically healthy elephants for as much as one month before clinical signs occurred and EEHV HD developed, highlighting the critical importance of routine surveillance (Stanton etal., 2013). Elephants may have a persistent low level EEHV viremia for months to years post infection (Bauer et al, 2018).

Trunk wash screening can detect shedding of virus (as DNA, detected by qPCR) for several months to a year during convalescence after primary viremic infection or occasionally from reactivation of a latent infection. While there may be some overlap between high levels of viremia (virus in the blood) and trunk wash shedding, viremia is the only parameter that correlates most consistently with disease. Screening trunk wash samples may allow for the determination of the types of EEHV present in the herd, with the caveat that only EEHVs that are being shed in the trunk secretions during the collection period would be detected. Non-invasive methods of detecting EEHV shedding (feces and saliva) have shown some
promise but trunk wash sampling remains the gold standard for detection of active viral shedding (Common et al., 2022; Jeffrey et al., 2020).

The following protocol has been developed as a guide for the monitoring and testing of any managed elephant:

A. Routine EDTA whole blood (WB) screening

• Recommended for calves aged (1-10 years (Asian) and 1-15 years (African)) and seronegative individuals.
• Weekly to twice weekly EDTA WB testing by qPCR (or two rounds of cPCR).
  • Asian elephants: EEHV1, EEHV4 (or EEHV3/4/7), and EEHV5
  • African elephants: EEHV 2, EEHV3/4/7, and EEHV6
• Bank EDTA WB and serum samples from the rest of the herd weekly for epidemiological investigation in case of a positive EEHV PCR result or clinical signs in a member of the herd.

Suggestions:

1. Look at your elephants every day for any behavior changes that deviate from normal as that could be an early indication of the onset of EEHV.
2. Perform a weekly CBC to have normal values for calves and to quickly detect changes in values.
3. Consider collecting weekly TEG long enough (four to five months is recommended as a minimum) to get baseline normal values for calves to be able to detect variations in hemostasis during a viremia or EEHV HD event.
4. Perform serum biochemistries monthly.

B. Serology screening

• Recommended for all individuals in the herd.
• At birth and then every 6 months for at-risk calves. Once for adults to get baseline values for individual and herd status.
  • Asian elephants: Pan EEHV, EEHV 1A, EEHV 1B, EEHV 4
  • African Elephants: Pan EEHV, EEHV 2, EEHV 3, EEHV 6

Suggestions:

1. Consider reducing frequency of testing for a specific EEHV type if/when calf seroconverts due to primary infection.
2. Utilize serology data to inform EEHV routine surveillance and case management decisions.

C. Basic TW screening to determine herd EEHV prevalence

• Recommended for all individuals in the herd
• Weekly trunk wash testing by qPCR to determine shedding incidence and shedding events in the presence of at-risk individuals*
  • Asian elephants: EEHV1, EEHV4 (or EEHV3/4/7), and EEHV5
  • African elephants: EEHV2, EEHV3/4/7, and EEHV6

Suggestions/Options:

1. Annually, collect trunk washes once per week on all herd mates, for a duration of 2 months (minimum) or 3 months (optimal) to determine which species of virus are present/being shed in the herd*
   • Asian elephants: EEHV1, EEHV4 (or EEHV3/4/7), and EEHV5
   • African elephants: EEHV2, EEHV3/4/7, and EEHV6
2. Consider collecting saliva swabs on same days as TWs for comparison of efficacy of EEHV detection in the two samples.

*Note: Only EEHV species that are being shed in the trunk secretions during the collection period will be
detected. If the trunk wash sample is EEHV (+) at high enough levels, consider sequencing appropriate genes to determine the subtype for epidemiology purposes.

D. Develop a fast plan for EEHV response based on routine surveillance results

*Do not wait for the observation of clinical signs before treating; immediate treatment is recommended if CBC is abnormal, or if viral load is >5,000 vge/ml or rapidly rising.

Consult members of the EEHV Advisory Group and the eehvinfo.org professional content subsection for current treatment recommendations and Clinical Findings Associated with EEHV Hemorrhagic Disease in Elephants.

Continue collecting samples up to daily after the first week and use the information on viral load, viral trends, and clinical observations to determine if testing frequency can be reduced. Continue monitoring the viral load until EEHV is undetectable in EDTA WB. Viral DNA may be detectable for a month or more. Resume recommended weekly monitoring after viremia is undetectable.

D. Ancillary testing and research participation

• Consider development of baseline coagulation profiles for at-risk animals. During an EEHV HD event, testing to look for variations may be helpful for determining clinical prognosis (Gentry, etal. 1996, Jesus et al. 2022, Perrin et al. 2018, Ziegner et al. 2022).
• Test serum by qPCR in addition to EDTA WB, for possible clues to prognosis. It has been noted that when EEHV is found at high levels in the serum, the prognosis is poor (Hayward, pers comm).
• Continue banking EDTA WB samples from the rest of herd weekly or according to the Commented [1]: Link to AG member list institution’s normal husbandry procedures.
• Consider submitting samples to ongoing research studies. Current EEHV studies can be found on eehvinfo.org.
• If clinical signs in the EEHV-positive calf are observed, collect EDTA WB samples from the rest of herd (at least twice weekly for calves, up to once weekly for adults) for EEHV PCR testing for at least 3-4 weeks. If no animals are found to be positive for EEHV during this period, return to weekly testing for the at-risk juveniles as above.

References
Bauer KL, et al. 2018. Long-term, intermittent, low-level elephant endotheliotropic herpesvirus 1A viremia in a captive Asian elephant calf. Journal of Veterinary Diagnostic Investigation. 30: 917-919.

Common SM, et al. 2021. Developing a non-invasive method of detecting elephant endotheliotropic herpesvirus infections using faecal samples. Veterinary Record. e833. https://doi.org/10.1002/vetr.833 Gentry PA, et al. 1996. Blood coagulation profile of the Asian elephant (Elephas maximus). Zoo Biology 15: 413-423.

Jeffrey A, et al. 2020. Noninvasive sampling for detection of elephant endotheliotropic herpesvirus and genomic DNA in Asian (Elephas maximus) and African (Loxodonta africana) elephants. Journal of zoo and wildlife medicine. 51:433-437.

Jesus SA, et al. 2022. Assessing Coagulation Parameters in Healthy Asian Elephants (Elephas maximus) from European and Thai Populations. Animals 12: 361. https://doi.org/10.3390/ani12030361

Perrin KL, et al. 2018. Thromboelastography in the healthy Asian elephant (Elephas maximus): Reference intervals and effects of storage. Journal of Zoo and Wildlife Medicine 49: 54-63.

Stanton JJ, et al. 2013. Acute phase protein expression during elephant endotheliotropic herpesvirus-1 viremia in Asian elephants (Elephas maximus). Journal of zoo and wildlife medicine. 44:605-612.

Ziegner KE, et al. 2022. Point-of-care and standard laboratory reference intervals for coagulation values in Asian elephants (Elephas maximus): variation by age class, sex, and time to centrifugation. Journal of Zoo and Wildlife Medicine 53: 291-301.