Surviving and fatal Elephant Endotheliotropic Herpesvirus-1A infections in juvenile Asian elephants – lessons learned and recommendations on anti-herpesviral therapy

Abstract

BackgroundElephant Endotheliotropic Herpesviruses (EEHVs) can cause acute haemorrhagic disease in young Asian elephants (Elephas maximus) and clinical EEHV infections account for the majority of their fatalities. The anti-herpesviral drug famciclovir (FCV) has been used routinely to treat viraemic at-risk elephants, but thus far without proven efficacy. This paper presents clinical and virological investigations of two EEHV-1A infected elephants treated with FCV, and discusses anti-herpesvirus therapies of viraemic elephants.Cases presentationsTwo 1.5 year old male Asian elephants at a zoological collection in the UK developed clinical EEHV-1A infections. Case 1 showed signs of myalgia for the duration of 24 hours before returning back to normal. EEHV-1A DNAemia was confirmed on the day of clinical signs and continued to be present for 18 days in total. Trunk shedding of the virus commenced 10 days after detection of initial DNAemia. Case 2 tested positive for EEHV-1A DNAemia in a routine blood screening sample in the absence of clinical signs. The blood viral load increased exponentially leading up to fatal clinical disease seven days after initial detection of DNAemia. Both calves were treated with 15 mg/kg FCV per rectum on detection of DNAemia and penciclovir, the FCV metabolite, could be detected in the blood at assumed therapeutic levels. The early indicators for clinical disease were a marked absolute and relative drop in white blood cells, particularly monocytes prior to the detection of viraemia. The most prognostic haematological parameter at later stages of the disease was the platelet count showing a continuous sharp decline throughout, followed by a dramatic drop at the time of death.ConclusionsThe EEHV-1A viraemic animals investigated here further highlight the ongoing threat posed by these viruses to juvenile Asian elephants. The findings call into question the efficacy of rectal FCV in clinical cases and direct towards the use of alternative anti-herpesvirus drugs and complementary treatments such as plasma infusions if no improvement in either viral load or the above-mentioned blood parameters are observed in the initial days of viraemia despite anti-herpesvirus therapy.

Tayland’da Evcil Asya Filinin (Elephas maximus) Kan ve Biyokimyasal Referans Aralıkları

“…However, we found that monocytes were in higher proportion than eosinophils, which were the same as Dastjerdi [15] reported that monocytes were the main WBC in juvenile elephants. This was contrasted with de Mel [9] and Salakij [3] who reported finding more eosinophils than monocytes.…”

Possible roles of monocytes/macrophages in response to elephant endotheliotropic herpesvirus (EEHV) infections in Asian elephants (Elephas maximus)

“…Eight species of EEHV, including EEHV1A, EEHV1B, and EEHV2-7, have been identified; they are collectively classified as members of the subfamily Betaherpesvirinae, genus Proboscivirus [4]. Although adult elephants also appear susceptible to EEHV, mortality from EEHV-HD has mostly been observed in young animals, especially those 1-8 years old [1,5]. Most elephants that succumbed to EEHV-HD presented clinically with decreased thrombocytes and monocytes in their blood [5][6][7][8][9].…”

“…Although adult elephants also appear susceptible to EEHV, mortality from EEHV-HD has mostly been observed in young animals, especially those 1-8 years old [1,5]. Most elephants that succumbed to EEHV-HD presented clinically with decreased thrombocytes and monocytes in their blood [5][6][7][8][9]. The marked reduction of peripheral blood thrombocytes (thrombocytopenia) and monocytes (monocytopenia) can, therefore, provide a prognostic hematological parameter for EEHV-HD cases [1,5].…”

“…Most elephants that succumbed to EEHV-HD presented clinically with decreased thrombocytes and monocytes in their blood [5][6][7][8][9]. The marked reduction of peripheral blood thrombocytes (thrombocytopenia) and monocytes (monocytopenia) can, therefore, provide a prognostic hematological parameter for EEHV-HD cases [1,5]. While thrombocytopenia in EEHV-HD cases is hypothesized to be a mechanism associated with consumption coagulopathies [5], the pathomechanisms underlying monocytopenia in EEHV-HD cases remain poorly understood.…”

Review of the management of the Asian elephant Elephas maximus EEP: current challenges and future solutions

“…This disease has a sudden onset and multiple symptoms, such as massive internal haemorrhages, which can lead to death within 12–72 hours (van den Doel et al , ). A lot of scientific research has been carried out into EEHV in cooperation with the Animal and Plant Health Agency in Weybridge (UK), Erasmus MC/Artemis‐One Health (Rotterdam, The Netherlands), Institute für Zoo‐ und Wildtierforschung (Berlin, Germany), Nottingham University (UK) and the Vetsuisse Faculty of the University of Zurich (Switzerland) (Bennett et al , ; van den Doel et al , ; Dastjerdi et al , ; Kendall et al , ; van Ackermann et al , ). Much of this research is co‐funded by Asian elephant EEP participants, some of whom contribute financially [e.g.…”