Subclinical Elephant Endotheliotropic Herpesvirus (EEHV) Shedding Surveillance and Novel Clinical Infection with EEHV4 in Asian Elephants (Elephas maximus) at the Houston Zoo
Elephant endotheliotropic herpesviruses (EEHV) can cause fatal hemorrhagic disease in elephants. EEHV1 is the most common and lethal species globally, while EEHV4 has only been described in two fatalities on postmortem examination.1,3 Surveillance for EEHV was conducted on samples from various anatomic sites. EEHV4 shedding was reliably detected in trunk washes and hard palate swabs, which were used to document the transmission of EEHV4 between herdmates. EEHV1 shedding was optimally detected in trunk washes; however, conjunctival and distal trunk swabs also produced positive detections. These findings suggest that EEHV1 and EEHV4 may be sampled in various anatomic sites, which may be applicable to epidemiologic and clinical studies in situ where trunk washes are less feasible.2,4 During the study, the first non-fatal EEHV4 clinical infections were confirmed in two captive-born Asian elephants (Elephas maximus). These were characterized by viremic episodes, initial leuko- and thrombocytopenia followed by leuko- and thrombocytosis, and clinical signs consistent with other EEHV infections. Early detection and administration of the antiviral famciclovir (15 mg/kg rectally TID, Novopharm Limited, Toronto, M1b2K9, Canada) starting on day 4 of viremia helped to successfully resolve these cases, along with supportive fluid and plasma therapy. As has been documented in previous EEHV viremias, viral shedding was detected with quantitative polymerase chain reaction shortly after clinical infection and continued for several months, peaking after approximately 2 mo. The sequential course of clinical infection, treatment, and resolution was carefully documented in these cases, which may be a useful tool to manage future EEHV4 cases.
The authors thank Daryl Hoffman, Martina Stevens, and the elephant keeper team at the Houston Zoo for their expertise and help in sample collection. The authors would also like to thank the Department of Veterinary Services at the Houston Zoo for their contributions in clinical treatments and blood work. Support for this study was provided by the Houston zoo (P.D.L.), a grant from the Institute of Museum and Library Services [MG-30-13-0086-13] (L.H.), and the Morris Animal Foundation (G.R.B.).
1. Garner MM, Helmick K, Ochsenreiter J, Richman LK, Latimer E, Wise AG, Maes RK, Kiupel M, Nordhausen RW, Zong JC, Hayward GS. Clinico-pathologic features of fatal disease attributed to new variants of endotheliotropic herpesviruses in two Asian elephants (Elephas maximus). Vet Pathol. 2009;46:97–104.
2. Hardman K, Dastjerdi A, Gurrala R, Routh A, Banks M, Steinbach F, Bouts T. Detection of elephant endotheliotropic herpesvirus type 1 in asymptomatic elephants using TaqMan real-time PCR. Vet Rec. 2012;170:205.
3. Sripiboon S, Tankaew P, Lungka G, Thitaram C. The occurrence of elephant endotheliotropic herpesvirus in captive Asian elephants (Elephas maximus): first case of EEHV4 in Asia. J Zoo Wildl Med. 2013;44:100–104.
4. Stanton JJ, Nofs SA, Zachariah A, Kalaivannan N, Ling PD. Detection of elephant endotheliotropic herpesvirus infection among healthy Asian elephants (Elephas maximus) in South India. J Zoo Wildl Med. 2014;50:279–287.