Karen C. Drayer Wildlife Health Center and EpiCenter for Disease Dynamics, One Health Institute, University of California Davis School of Veterinary Medicine, 1089 Veterinary Medicine Dr. VM3B, Davis, CA, United States.
U.S. Geological Survey, Western Ecological Research Center, Santa Cruz Field Station, 2885 Mission St., Santa Cruz, CA, United States; Department of Ecology and Evolutionary Biology, University of California, Long Marine Lab, 100 Shaffer Rd., Santa Cruz, CA, United States.
Harmful Algae. 2021 Jan;101:101973. doi: 10.1016/j.hal.2020.101973. Epub 2021 Jan 12.
Harmful algal blooms produce toxins that bioaccumulate in the food web and adversely affect humans, animals, and entire marine ecosystems. Blooms of the diatom Pseudo-nitzschia can produce domoic acid (DA), a toxin that most commonly causes neurological disease in endothermic animals, with cardiovascular effects that were first recognized in southern sea otters. Over the last 20 years, DA toxicosis has caused significant morbidity and mortality in marine mammals and seabirds along the west coast of the USA. Identifying DA exposure has been limited to toxin detection in biological fluids using biochemical assays, yet measurement of systemic toxin levels is an unreliable indicator of exposure dose or timing. Furthermore, there is little information regarding repeated DA exposure in marine wildlife. Here, the association between long-term environmental DA exposure and fatal cardiac disease was investigated in a longitudinal study of 186 free-ranging sea otters in California from 2001 - 2017, highlighting the chronic health effects of a marine toxin. A novel Bayesian spatiotemporal approach was used to characterize environmental DA exposure by combining several DA surveillance datasets and integrating this with life history data from radio-tagged otters in a time-dependent survival model. In this study, a sea otter with high DA exposure had a 1.7-fold increased hazard of fatal cardiomyopathy compared to an otter with low exposure. Otters that consumed a high proportion of crab and clam had a 2.5- and 1.2-times greater hazard of death due to cardiomyopathy than otters that consumed low proportions. Increasing age is a well-established predictor of cardiac disease, but this study is the first to identify that DA exposure affects the risk of cardiomyopathy more substantially in prime-age adults than aged adults. A 4-year-old otter with high DA exposure had 2.3 times greater risk of fatal cardiomyopathy than an otter with low exposure, while a 10-year old otter with high DA exposure had just 1.2 times greater risk. High Toxoplasma gondii titers also increased the hazard of death due to heart disease 2.4-fold. Domoic acid exposure was most detrimental for prime-age adults, whose survival and reproduction are vital for population growth, suggesting that persistent DA exposure will likely impact long-term viability of this threatened species. These results offer insight into the pervasiveness of DA in the food web and raise awareness of under-recognized chronic health effects of DA for wildlife at a time when toxic blooms are on the rise.
有害藻类大量繁殖会产生毒素，这些毒素在食物链中积累，对人类、动物和整个海洋生态系统造成不良影响。硅藻拟菱形藻的大量繁殖会产生软骨藻酸 (DA)，这种毒素最常见于温血动物，会引起神经疾病，对心血管系统也有影响，这种影响最早在南加州海獭身上发现。在过去的 20 年里，软骨藻酸中毒导致美国西海岸的海洋哺乳动物和海鸟的发病率和死亡率显著上升。目前，确定软骨藻酸暴露的方法仅限于使用生化分析在生物体液中检测毒素，但系统毒素水平的测量并不能可靠地指示暴露剂量或时间。此外，关于海洋野生动物重复暴露于软骨藻酸的信息很少。在这里，通过对 2001 年至 2017 年在加利福尼亚州自由放养的 186 只海獭进行的一项纵向研究，研究了长期环境软骨藻酸暴露与致命性心脏病之间的关系，强调了海洋毒素对慢性健康的影响。这项研究使用了一种新颖的贝叶斯时空方法，通过结合几个软骨藻酸监测数据集，并将其与佩戴无线电项圈的海獭的生活史数据结合起来，在一个时依生存模型中进行整合，以描述环境软骨藻酸暴露情况。在这项研究中，与低暴露水平的海獭相比，高暴露水平的海獭患致命性心肌病的风险增加了 1.7 倍。与低暴露水平的海獭相比，摄入大量蟹和蛤的海獭死于心肌病的风险要高 2.5 倍和 1.2 倍。年龄的增长是心脏病的一个既定预测因素，但这项研究首次表明，软骨藻酸暴露对青壮年成年人患心肌病的风险影响比老年成年人更大。一只高暴露于软骨藻酸的 4 岁海獭患致命性心肌病的风险比低暴露于软骨藻酸的海獭高 2.3 倍，而一只高暴露于软骨藻酸的 10 岁海獭患致命性心肌病的风险仅高 1.2 倍。高弓形体抗体滴度也使心脏病死亡的风险增加了 2.4 倍。软骨藻酸暴露对青壮年成年人的危害最大，他们的生存和繁殖对种群增长至关重要，这表明持续的软骨藻酸暴露可能会影响这一受威胁物种的长期生存能力。这些结果深入了解了软骨藻酸在食物链中的普遍性，并提高了人们对软骨藻酸对野生动物的慢性健康影响的认识，因为此时有毒藻类大量繁殖的情况正在增加。
