Sudden elephant mortality in the Okavango delta: field investigation and effective monitoring of wildlife health under environmental change

在博茨瓦纳的奥卡万戈三角洲发生了一场大规模的大象死亡事件（非洲象），迄今已发现359头大象死亡。此类事件的罕见性、偏远且难以进入的地形、当地缺乏病理学和实验室诊断能力，以及因新冠肺炎而难以获得国际支持，阻碍了调查。尽管实验室检测，原因仍然不明。这一点，以及其他有蹄类动物死亡事件的经验，表明可能涉及多个相互作用的因素，需要综合多学科的调查。迫切需要在该领域仍然可以获得证据的情况下推动这项研究，并确定对这一种群和其他大象种群的影响。这次活动进一步提供了一个更好地了解野生动物死亡事件的机会，这些事件似乎越来越频繁，可能与环境变化有关。博茨瓦纳拥有世界上最大的非洲象种群，并且正在扩大，这些大象在周边国家面临着严重的狩猎压力。虽然特定的传染病以前曾导致非洲大象的集群死亡，但大规模的疾病死亡是非常罕见的，考虑到它们脆弱的保护地位和作为生态关键物种的作用，这是令人担忧的。大象是奥卡万戈三角洲生态系统的一个组成部分，在其生物多样性、稳定性和功能方面发挥着关键作用，因此大象数量的大幅减少可能对博茨瓦纳的经济产生不利影响。此外，其他地方较小的脆弱大象种群的类似死亡率可能对种群生存产生更大的影响，重要的是要找出死亡的原因和环境因素的参与。鉴于人们越来越认识到病原体宿主转换在推动人类疾病威胁方面的作用，这一共同使用区域出现的疾病也引起了依赖畜牧业的社区的极大关注，并可能影响到公共卫生。在该项目中，来自博茨瓦纳和英国的多学科科学家团队将共同努力，在证据仍然存在的情况下进行紧急的实地和实验室调查，来确定死亡的原因为了帮助在这样一个充满挑战的环境中实现这一目标，我们将使用先进的分子生物学方法对无脊椎动物（蚊子和蜱虫）载体进行采样，并进行生物分析以检测环境样本中的毒素痕迹。重要的是，包括死亡地点和时间在内的现有证据将由一个国际专家网络进行汇编和评估，以协助博茨瓦纳政府进行解释。空间模型将评估环境和传染因素及其相互作用的相对可能性。博茨瓦纳的伙伴实验室和实地工作人员在全球重要的奥卡万戈生态系统中调查未来此类事件的能力将通过这种合作和在那里建立新的分析得到加强。政府，保护组织，当地社区和博茨瓦纳和国际上的其他相关方将参与整个研究，并在项目结束时聚集在利益相关者论坛上，讨论结果和计划未来应对野生动物死亡，以及使用一个健康的角度在该地区从事野生动物健康研究。

A large and significant mortality event in elephants (Loxodonta africana) has developed in the Okavango Delta in Botswana, with 359 elephants found reported dead to date. Investigations are hampered by the rarity of such an event, remote and inaccessible terrain, lack of local capacity for pathology and laboratory diagnosis, and difficulties accessing international support due to covid-19. Despite laboratory testing, the cause remains unknown. This, and experience from other mortality events in ungulates, suggests that multiple interacting factors might be involved, requiring integrated multidisciplinary investigation. There is an urgent need to instigate this research while evidence remains accessible in the field, and to determine implications for this and other elephant populations. The event further provides an opportunity to better understand die-off events in wildlife, which seem to be increasing in frequency and could be linked to environmental change.Botswana hosts the world's largest and expanding population of African elephants, which are under severe hunting pressure in surrounding countries. While specific infectious diseases have caused clusters of mortality in African elephants previously, large scale die-offs from disease are highly unusual, and are of concern given their vulnerable conservation status and role as a keystone species ecologically. Elephants are an integral part of the Okavango Delta ecosystem and play a pivotal role in its biodiversity, stability and functioning, such that a significant decrease in elephant numbers may have a detrimental effect on Botswana's economy. Moreover, similar mortality in smaller vulnerable elephant populations elsewhere could have larger consequences for population viability and it is important to work out the cause of the die-offs and the involvement of environmental factors. The emergence of disease in this shared use area is also of great concern for livestock-dependent communities and potentially for public health, given increasing appreciation of the role of pathogen host-switching in driving disease threats in people.In this project a multidisciplinary team of scientists from Botswana and the UK will work together to undertake urgent field and laboratory investigations while evidence is still available, to determine the cause of the die-off. To help achieve this in such a challenging landscape, we will use advanced molecular biology methods to sample invertebrate (mosquito and tick) vectors, and bioanalysis to detect traces of toxins in environmental samples. Importantly, existing evidence including the location and timing of deaths will be compiled and assessed by an international network of experts to assist the Botswana government in their interpretation. A spatial model will evaluate the relative likelihood of environmental and infectious factors and their interaction. The capacity of partner laboratories in Botswana, and field workers, to investigate future events like this in the globally important Okavango ecosystem will be enhanced by this collaboration and by setting up new analyses there. Government, conservation organisations, local communities and other interested parties in Botswana and internationally will be engaged in the research throughout and come together in a stakeholder forum at the end of the project to discuss outcomes and plan for future responses to wildlife die-offs as well as engaged research in wildlife health in the area using a One Health perspective.