Review of a newly recognized disease of elephants caused by endotheliotropic herpesviruses

Abstract

There are two newly recognized herpesviruses that cause a fatal disease syndrome in elephants. They are known as the elephant endotheliotropic herpesviruses, of which one is fatal for Asian elephants (Elephas maximus) and the other for African elephants (Loxodonta africana) [Richman et al., Science 283:1171–1176, 1999a]. The disease syndrome affects predominantly young elephants and has been described in North America [Richman et al., J Wildl Dis 36:1–12, 2000], Europe [Richman et al., Verhandlangsbericht des 39 International Symposium uben Erkrankungen der Zoo und Wildtiere, Wien, 39:17–21, 1999b; Ossent et al., Vet Pathol 27:131–133, 1990], and Israel [Richman et al., Verhandlangsbericht des 39 International Symposium uben Erkrankungen der Zoo und Wildtiere, Wien, 39:17–21, 1999b]. The predominant clinical signs for both species include lethargy, edematous swellings of the head, neck, and thoracic limbs, oral ulceration, cyanosis of the tongue, and death of most elephants in 1–7 days [Richman et al., J Wildl Dis 36:1–12, 2000]. Three affected young Asian elephants recovered after a 3–4‐week course of therapy with the anti‐herpesvirus drug famciclovir [Richman et al., J Wildl Dis 36:1–12, 2000; Schmitt and Hardy, J Elephant Managers Assoc 9:103–4, 1998]. Additional reported herpesvirus‐associated lesions in otherwise healthy elephants include localized skin papillomas in African elephants [Richman et al., Science 283:1171–1176, 1999a; Jacobson et al., J Am Vet Med Assoc 189:1075–8, 1986], proliferative vulval lymphoid patches in African elephants [Richman et al., Science 283:1171–1176, 1999a; Munson et al., J Zoo Wildl Med 26:353–8, 1995], and pulmonary nodules in African elephants [Richman et al., J Wildl Dis 36:1–12, 2000; McCulley et al., Onderstepoort J Vet Res 38:225–236, 1971]. Recent findings suggest that these localized herpesvirus‐associated lesions in healthy African elephants may be one source of the herpesvirus that causes disseminated disease and death in the Asian species [Richman et al., Science 283:1171–1176, 1999a] and the African species [Richman et al., J Wildl Dis 36:1–12, 2000]. These findings have implications for management practices in facilities keeping both African and Asian elephants and in protecting natural elephant habitats from virulent forms of the virus. Zoo Biol 19:383–392, 2000. © 2000 Wiley‐Liss, Inc.

Detection of Quiescent Infections with Multiple Elephant Endotheliotropic Herpesviruses (EEHVs), Including EEHV2, EEHV3, EEHV6, and EEHV7, within Lymphoid Lung Nodules or Lung and Spleen Tissue Samples from Five Asymptomatic Adult African Elephants

“…One of these two nodules had previously proven positive for a small U38(POL) DNA segment of EEHV2 but was negative for EEHV1 by using redundant panherpesvirus PCR primers in the original studies by Richman et al (28), whereas the second nodule was negative for both EEHV1 and EEHV2. Here, we used a new set of more sensitive diagnostic PCR primers designed specifically for the EEHV2 DNA POL gene, which yielded a strong 500-bp firstround band from AfLng54 DNA (Fig.…”

“…Richman et al (1,28) originally suggested that cross-species transmission of EEHV1 infection from African elephant herd mates to Asian elephant calves in captivity may be the reason for the devastating nature of the acute hemorrhagic disease observed. This interpretation was based on preliminary PCR evidence for EEHV1 being present in archival paraffin block sections from several skin nodules found among African elephant calves imported to Florida in the mid1980s (27).…”

“…Similar inclusion bodies were also observed in epithelial cells from an outbreak of skin nodules on the trunk and head of a subset of orphan African elephant calves imported from Zimbabwe to Florida and Texas in the 1980s (27). From preliminary evidence by PCR amplification of EEHV1 DNA from several of these African elephant skin nodules from archival paraffin blocks, an initial plausible model that EEHV1 may have crossed from African to Asian elephants in zoos was proposed (28). On the other hand, one of two tested lung nodules from culled adult South African elephants in the same study proved to contain EEHV2 DNA instead.…”

Comparative Genome Analysis of Four Elephant Endotheliotropic Herpesviruses, EEHV3, EEHV4, EEHV5, and EEHV6, from Cases of Hemorrhagic Disease or Viremia

“…Acute hemorrhagic disease is an unexpected feature for herpesvirus infection of a natural endogenous host to which it should have become well adapted. Therefore, mixing of elephant host species from different continents in captive situations was originally suggested to have led to occasional cross-species primary infections to explain the disease severity (1,31). Because EEHV1A and EEHV1B have been by far the most predominant causative agents of fatal disease in Asian elephants, the focus for this scenario has obviously fallen onto those two virus types in particular.…”

Major histocompatibility complex variation and evolution at a single, expressed DQA locus in two genera of elephants

“…Characterizing MHC diversity is important for predicting how captive and wild elephant populations will respond to disease threats. In the last decade, herpes viruses killed at least 25 captive elephants (Richman et al 1999;Richman et al 2000;Ryan and Thompson 2001), and encephalomyocarditis, salmonellosis, and anthrax have all threatened wild African elephants (Grobler et al 1995;Lindique and Turnbull 1994;Mbise et al 1998). In addition, some diseases affect Asian and African elephants differently, and these specieslevel differences might be explained by differences in the MHC.…”