Table_2_Risk Factors for New Zealand Sea Lion (Phocarctos hookeri) Pup Mortality: Ivermectin Improves Survival for Conservation Management.DOCX

Septicaemia due to hypervirulent (HV) Klebsiella pneumoniae is the leading cause of neonatal pup mortality in endangered New Zealand sea lions (Phocarctos hookeri) at Enderby Island, in the New Zealand sub-Antarctic. Accounting for approximately 60% of annual pup mortality at this site following an epizootic event in 2001–02, HV K. pneumoniae is also emerging worldwide as a significant community-acquired human pathogen. To facilitate efficient direct mitigation to reduce pup mortality, a case-control study and prospective cohort study were conducted to identify risk factors amenable to active management. Additionally, to investigate impacts of hookworm (Uncinaria spp.), a nested treatment trial with the anthelmintic ivermectin was undertaken concurrently. During two austral summer field seasons (2016–2018), 698 pups were captured for treatment trial recruitment and the collection of morphometric measurements, biological samples and risk factor data. Gastrointestinal carriage of the virulent phenotype of K. pneumoniae was a consistent risk factor, while ivermectin treatment and higher body condition index consistently reduced risk of HV K. pneumoniae mortality. Significantly fewer ivermectin-treated pups were found dead (24.1% control, 11.1% treatment), with a trend towards a higher proportion of HV K. pneumoniae deaths amongst the control group. This study provides evidence to support ivermectin treatment as a pup mortality mitigation strategy in New Zealand sea lions at Enderby Island. If applied to larger colonies where HV K. pneumoniae and hookworm impact pup survival, this intervention could have population-scale benefits for this endangered species. Further work is required to understand how ivermectin prevents HV K. pneumoniae septicaemia, but removal of hookworms before intestinal mucosal damage occurs could limit systemic spread of virulent bacteria from the gastrointestinal tract.

在新西兰亚南极地区的恩德比岛，由高毒力肺炎克雷伯菌（Klebsiella pneumoniae, HV）引发的败血症，是濒危物种新西兰海狮（Phocarctos hookeri）幼崽死亡的首要诱因。2001至2002年发生兽疫后，该区域约60%的幼崽死亡案例均由该型HV肺炎克雷伯菌导致；同时该菌也在全球范围内逐渐成为一类重要的社区获得性人类致病菌。为高效开展直接防控以降低幼崽死亡率，本研究通过病例对照研究（case-control study）与前瞻性队列研究（prospective cohort study），识别出可通过主动管理进行干预的风险因素。此外，为探究钩虫（Uncinaria spp.）的影响，本研究同步开展了一项以驱虫药伊维菌素（ivermectin）为干预手段的嵌套治疗试验（nested treatment trial）。在2016至2018年的两个南半球夏季野外季中，研究人员共捕获698只海狮幼崽，用于治疗试验的招募，并采集其形态学测量数据、生物样本与风险因素相关信息。肺炎克雷伯菌毒力表型的胃肠道定植是一项稳定的风险因素；而伊维菌素干预与更高的体况指数，则持续降低了HV肺炎克雷伯菌引发的死亡风险。经伊维菌素处理的幼崽死亡率显著更低（对照组死亡率为24.1%，处理组为11.1%），且对照组中由HV肺炎克雷伯菌导致的死亡占比呈现升高趋势。本研究提供了证据，支持将伊维菌素干预作为恩德比岛新西兰海狮幼崽死亡的防控策略。若将该干预手段应用于同时受HV肺炎克雷伯菌与钩虫影响幼崽存活的更大规模海狮聚居地，将可为这一濒危物种带来种群尺度上的益处。目前仍需进一步研究以阐明伊维菌素如何阻断HV肺炎克雷伯菌败血症的发生，但在肠黏膜损伤发生前清除钩虫，或可限制毒力细菌从胃肠道向全身的扩散。