Saiga antelope (Saiga tatarica tatarica) mortality in Kazakhstan 2015: emergency investigation of disease outbreak to improve knowledge of drivers

灾难性的疾病事件对受威胁物种的生存可能是毁灭性的，并可能逆转多年来的保护努力。当种群数量已经很少，由于偷猎或栖息地丧失而脆弱时，疾病可能是最后一根稻草。作为保护问题的疾病的例子包括埃塞俄比亚狼，它容易受到家犬的狂犬病和狂犬病的影响，以及牛瘟，它在19世纪杀死了非洲的野生和家养有蹄类动物种群。最近人们认识到，在更广泛的背景下更好地理解和解决疾病，而不仅仅是宿主和病原体的单个物种；有弹性的生态系统能够更好地适应疾病的爆发，人类造成的环境变化会使物种更容易受到伤害。赛加羚羊是一种迁徙的有蹄类动物，聚集在一起大量繁殖。由于偷猎它的角和肉，它的种群数量在10年内下降了95%，因此处于极度濒危状态。然而，有一个种群(Betpak-dala)恢复良好，到2015年4月已达到约25万人。疾病导致的大规模死亡在该物种中经常发生，但其原因和促成因素从未得到适当的调查。2015年5月，Betpak-dala人口在几天内死亡了12万头，约占全球人口的一半，占全球人口的三分之一。第一次，一个快速反应小组能够出席并从受影响的赛加及其环境中收集样本。初步观察表明，这些死亡是特殊环境条件(潮湿的天气，茂盛的草地)和刚刚分娩的雌性动物虚弱之间复杂相互作用的结果，导致存在但潜伏在赛加体内的病原体扎根。然而，这还不是全部，还可能包括植物或水中的毒素、昆虫传播的疾病或直接传播的病毒。在这个项目中，我们将分析已经收集的样本，以诊断这种大规模死亡的原因和促成因素。我们将执行一项紧急任务，前往实地收集补充信息，帮助我们了解这种疾病的触发因素。我们将访问受影响和未受影响的地区，以了解其中的区别。我们将与当地牧民交谈，并获得死亡前几天的天气记录。接下来，我们将汇编我们所知道的关于这次疫情以及之前疫情(最近的和历史上的，在赛加和类似物种中)的一切，以获得导致大量赛加死亡的事件和环境条件的总体情况。将这一认识与对未来环境条件(例如气候变化)和新出现的传染病(例如从非洲进入中亚的小反刍动物害虫)的预测相结合，我们将探索从一系列疾病到赛加和牲畜的风险情景，以及如何减轻风险(例如通过接种疫苗或改变土地使用做法)。收集了这些证据后，我们将帮助哈萨克斯坦政府为未来的疾病爆发做好准备；我们将设计监测方案，以便他们能够对潜在的死亡触发因素进行早期预警，并帮助他们检查是否以及哪些干预措施可能降低或缓解疫情爆发的风险。我们将在即将到来的《联合国迁徙物种公约》关于赛加保护的谅解备忘录会议上举办一次技术研讨会，并支持签署国(政府和非政府组织)制定和批准一项行动计划。这个项目是一个独特的机会，可以调查具有巨大保护重要性的戏剧性和复杂的疾病事件，这也将揭示环境变化和疾病之间的关系。这使生态学家对它产生了广泛的普遍兴趣，并成为一个在还有时间采取行动的情况下抓住的至关重要的机会。

Catastrophic disease events can be devastating for the survival of threatened species, and can reverse years of conservation effort. When populations are already small and vulnerable, due to poaching or habitat loss, disease can be the final straw. Examples of disease as a conservation issue include the Ethiopian wolf, which is susceptible to distemper and rabies from domestic dogs, and rinderpest, which decimated the wild and domestic ungulate populations of Africa in the 19th century. Recently it has been recognised that disease is best understood and tackled in a wider context than just the individual species of host and pathogen; resilient ecosystems are better able to accommodate disease outbreaks, and human-caused environmental change can make species more vulnerable.The saiga antelope is a migratory ungulate which gathers to give birth in large aggregations. It is critically endangered due to a >95% decline in population size over <10 years due to poaching for its horns and meat. However one population (Betpak-dala) has recovered well, to about 250,000 individuals in April 2015. Mass die-offs from disease occur regularly in this species, but the causes and contributing factors have never been properly investigated. In May 2015, 120,000 saigas died within a few days in the Betpak-dala population, about half this population, and >1/3 of the global population. For the first time, a rapid response team was able to attend and collect samples from the affected saigas and their environment. Initial observations suggest that the deaths were a result of a complex interaction between particular environmental conditions (wet weather, lush grass) and the weakness of females which had just given birth, causing pathogens which were present but latent within the saigas to take hold. This is not the whole story, however, which may also include toxins in plants or water, an insect-carried disease, or a directly-transmitted virus.In this project, we will analyse the already-collected samples to diagnose the causes of and contributing factors to this mass die-off. We will run an urgent mission to the field, to collect supplementary information which will help us to home in on the triggers for this disease. We will visit both affected and unaffected areas, to understand what the differences are. We will talk to local herders, and get weather records for the days leading up to the deaths. Next, we will compile everything we know about this outbreak, and about previous outbreaks (recent and historical, in saigas and similar species), to get an overall picture of the pattern of events and environmental conditions which leads to mass saiga deaths. Combining this understanding with projections of future environmental conditions (e.g. climate change) and emerging infectious diseases (e.g. peste des petits ruminants, which is entering Central Asia from Africa), we will explore scenarios of risk from a range of diseases to both saigas and livestock, and how risks could be mitigated (e.g. through vaccination or changes in land use practices).Having assembled this evidence, we will help the Government of Kazakhstan to prepare for future disease outbreaks; we will design surveillance protocols so they can have early warning of potential triggers for mortality, and help them to examine whether, and which, interventions might reduce the risk of outbreaks, or mitigate them. We will run a technical workshop at the upcoming meeting of the UN Convention on Migratory Species' Memorandum of Understanding on saiga conservation, and support signatories (governments and NGOs) to develop and ratify an action plan.This project is a unique chance to investigate a dramatic and complex disease event of huge conservation importance, which will also shed light on the relationship between environmental change and disease. This makes it of wide general interest for ecologists, and an opportunity which it is vital to take while there is still time to act.