Ackermann Mathias, Hatt Jean-Michel, Schetle Nelli, Steinmetz Hanspeter
University of Zurich, Vetsuisse Faculty, Institute of Virology, Zurich, Switzerland.
University of Zurich, Vetsuisse Faculty, Clinic for Zoo Animals, Exotic Pets and Wildlife, Zurich, Switzerland.
PLoS One. 2017 May 3;12(5):e0176891. doi: 10.1371/journal.pone.0176891. eCollection 2017.
Elephants, particularly Asian (Elephas maximus), are threatened by lethal elephant hemorrhagic disease (EHD) due to elephant endotheliotropic herpesviruses (EEHV). At least five of seven known EEHV types have been associated to EHD, with types 1, 4, and 5 predominantly affecting Asian elephants. In Switzerland, at least three Asian elephants have been lost due to EHD but nothing is known about the present EEHV1 circulation. Moreover, the prevalence of other EEHV types has never been assessed. Intermittent shedding of EEHV can be monitored through collecting trunk secretions and analyzing them by PCR methods that discriminate the different EEHV types. To identify EEHV shedders, seven of eight Asian elephants in a Swiss zoo were trained to provide trunk wash samples. These were collected at intervals over a period of four months and tested by PCR for presence of EEHV1 through 6. Moreover, the quality of each sample was assessed by testing for the elephant TNF-alpha gene. Overall, 57% of the samples were valid with five of seven participating elephants identified as EEHV shedders. Two of those shed virus only once, whereas the other three, all closely related among each other, shed virus on multiple occasions. One of the frequent shedders had been in very close contact to all of the three EHD victims. Therefore, we speculate that this particular animal may represent the virus source in all three cases. However, when subtyping was conducted, the presently circulating virus was identified as EEHV1B, while the virus subtype causing EHD had been 1A in all three cases. In addition to four animals excreting EEHV1, a recently introduced animal was observed to shed EEHV3/4. We suggest that the policy of trunk washing to identify and characterize EEHV-shedders is to be endorsed in zoos with ongoing or planned elephant breeding programs.
大象，尤其是亚洲象（印度象），受到大象内皮嗜性疱疹病毒（EEHV）引发的致命性大象出血性疾病（EHD）的威胁。已知的七种EEHV类型中至少有五种与EHD有关，其中1型、4型和5型主要影响亚洲象。在瑞士，至少有三头亚洲象因EHD死亡，但目前EEHV1型的传播情况尚不清楚。此外，其他EEHV类型的流行情况从未得到评估。可以通过收集象鼻分泌物并采用能区分不同EEHV类型的PCR方法进行分析，来监测EEHV的间歇性排毒情况。为了识别EEHV排毒者，瑞士一家动物园的八头亚洲象中有七头接受训练以提供象鼻清洗样本。这些样本在四个月的时间里定期收集，并通过PCR检测EEHV1至6型是否存在。此外，通过检测大象肿瘤坏死因子-α基因来评估每个样本质量。总体而言，57%的样本有效，七头参与的大象中有五头被确定为EEHV排毒者。其中两头只排毒一次，而另外三头彼此密切相关，多次排毒。其中一头频繁排毒者与所有三头EHD受害者都有过非常密切的接触。因此，我们推测这头特定的大象可能是所有三起病例中的病毒源头。然而，在进行亚型分析时，目前传播的病毒被鉴定为EEHV1B型，而导致EHD的病毒亚型在所有三起病例中均为1A型。除了四头排出EEHV1的动物外，还观察到一头最近引入的动物排出EEHV3/4型。我们建议，对于正在进行或计划开展大象繁殖项目的动物园，应认可通过象鼻清洗来识别和表征EEHV排毒者的政策。
