PDF(Pubmed)
Abstract：
In Chile, since January 2023, a sudden and pronounced increase in strandings and mortality has been observed among South American (SA) sea lions (Otaria flavescens), prompting significant concern. Simultaneously, an outbreak of highly pathogenic avian influenza H5N1 (HPAIV H5N1) in avian species has emerged since December 2022. To investigate the cause of this unexpected mortality, we conducted a comprehensive epidemiological and pathologic study. One hundred sixty-nine SA sea lions were sampled to ascertain their HPAIV H5N1 status, and long-term stranding trends from 2009 to 2023 were analyzed. In addition, two animals were necropsied. Remarkably, a significant surge in SA sea lion strandings was observed initiating in January 2023 and peaking in June 2023, with a count of 4,545 stranded and deceased animals. Notably, this surge in mortality correlates geographically with HPAIV outbreaks affecting wild birds. Among 168 sampled SA sea lions, 34 (20%) tested positive for Influenza A virus, and 21 confirmed for HPAIV H5N1 2.3.4.4b clade in tracheal/rectal swab pools. Clinical and pathological evaluations of the two necropsied stranded sea lions revealed prevalent neurological and respiratory signs, including disorientation, tremors, ataxia, and paralysis, as well as acute dyspnea, tachypnea, profuse nasal secretion, and abdominal breathing. The lesions identified in necropsied animals aligned with observed clinical signs. Detection of the virus via immunohistochemistry (IHC) and real-time PCR in the brain and lungs affirmed the findings. The findings provide evidence between the mass mortality occurrences in SA sea lions and HPAIV, strongly indicating a causal relationship. Further studies are needed to better understand the pathogenesis and transmission.
摘要：
在智利,自2023年1月以来，南美（SA）海狮（Otariasavescens）的搁浅和死亡率突然明显增加，引发重大关注。同时,自2022年12月以来，在禽类中爆发了高致病性禽流感H5N1（HPAIVH5N1）。为了调查这种意外死亡的原因，我们进行了全面的流行病学和病理学研究。对一百六十九只SA海狮进行了采样，以确定它们的HPAIVH5N1状态，分析了2009年至2023年的长期搁浅趋势。此外,对两只动物进行尸检。值得注意的是,在2023年1月开始观察到SA海狮搁浅的显着激增，在2023年6月达到顶峰，有4,545只搁浅和死亡的动物。值得注意的是,死亡率的激增在地理上与影响野生鸟类的HPAIV暴发相关.在168只采样的SA海狮中，34（20％）的甲型流感病毒检测呈阳性，在气管/直肠拭子池中确认了21例HPAIVH5N12.3.4.4b进化枝。对两只尸体剖检的搁浅海狮的临床和病理评估显示出普遍存在的神经和呼吸体征，包括迷失方向，震颤,共济失调,瘫痪，以及急性呼吸困难，呼吸急促,大量的鼻腔分泌物，和腹式呼吸。在尸检动物中鉴定的病变与观察到的临床体征一致。通过免疫组织化学（IHC）和实时PCR在脑和肺中检测病毒证实了这一发现。这些发现提供了SA海狮和HPAIV大规模死亡事件之间的证据，强烈表明因果关系。需要进一步的研究来更好地了解发病机制和传播。
