Widely distributed aquatic species such as terns are highly dependent on, and can serve as indicators of, the global health of marine and other aquatic environments. Documented mass mortality events in terns have been associated with anthropogenic, weather-related and, less commonly, infectious causes. This study describes a multispecies mortality event associated with brevetoxicosis and Bisgaard taxon 40-induced sepsis involving common (Sterna hirundo) and sandwich (Thalasseus sandvicensis) terns off the southwest coast of Florida, USA, in November and December 2018. During an approximately 6–8-week period, a large number of birds were found dead or displayed weakness, ataxia or other neurological signs. Many were admitted to a wildlife hospital for evaluation, but most died or were euthanized due to poor prognosis. Necropsy of 12 birds revealed minimal or non-specific gross lesions. Initial toxicology screening of tissues for brevetoxins revealed levels that could be consistent with brevetoxicosis. However, histology revealed multiorgan inflammation and necrosis associated with a gram-negative bacillus. A bacterium isolated on aerobic culture of liver and heart tissues was unidentifiable in the MALDI-TOF database. Subsequently, 16 S rRNA gene sequencing revealed that the isolate shared 99.33% homology with Bisgaard taxon 40 from the Pasteurellaceae family. While the source of the bacterium and potential association with brevetoxin exposure are unclear, histopathology suggests that the bacterium was the proximate cause of clinical signs and mortality in all birds examined as well as the scale of the mortality event. This report highlights the need to conduct detailed investigations into wildlife mortality events and expands on the current, limited knowledge of the effects of novel Pasteurellaceae bacteria on avian health.

燕鸥等广泛分布的水生物种高度依赖海洋和其他水生环境的全球健康状况，并可作为其指标。记录在案的燕鸥大规模死亡事件与人为、天气相关以及不太常见的传染性原因有关。这项研究描述了与短毒中毒和 Bisgaard 分类群 40 引起的败血症相关的多物种死亡事件，涉及普通 ( Sterna hirundo ) 和三明治 ( Thalasseus sandvicensis)。) 2018 年 11 月和 12 月在美国佛罗里达州西南海岸附近的燕鸥。在大约 6-8 周的时间里，发现大量鸟类死亡或表现出虚弱、共济失调或其他神经系统症状。许多人被送往野生动物医院接受评估，但大多数人因预后不佳而死亡或被安乐死。12 只鸡的尸体剖检显示有轻微或非特异性的肉眼损伤。对组织进行的短管毒素初步毒理学筛查揭示了可能与短管毒素中毒一致的水平。然而，组织学显示与革兰氏阴性杆菌相关的多器官炎症和坏死。在 MALDI-TOF 数据库中无法识别在肝脏和心脏组织的需氧培养物中分离的细菌。随后，16 S rRNA 基因测序显示该分离株共有 99 个。与巴斯德氏菌科 Bisgaard 分类群 40 的同源性为 33%。虽然细菌的来源和与短管毒素暴露的潜在关联尚不清楚，但组织病理学表明，细菌是所有检查的鸟类的临床症状和死亡以及死亡事件规模的近因。本报告强调了对野生动物死亡事件进行详细调查的必要性，并扩展了目前关于新型巴斯德氏菌对鸟类健康影响的有限知识。