Zhang Qianqian, Lin Yaoyao, Zhang Tanglin, Wu Yafeng, Fang Ping, Wang Shuyi, Wu Zhenbin, Hao Jingwen, Li Aihua
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China; Key Laboratory of Aquaculture Disease Control, Ministry of Agriculture, China; National Aquatic Biological Resource Center, NABRC, Wuhan, China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China; University of Chinese Academy of Sciences, Beijing, China.
J Invertebr Pathol. 2021 Sep;184:107643. doi: 10.1016/j.jip.2021.107643. Epub 2021 Jul 2.
In November 2019, an acute disease outbreak in Australian redclaw crayfish (Cherax quadricarinatus) occurred in a farm in Hubei, China, with a cumulative mortality rate of over 80%. One of the characteristic symptoms of the disease was blisters on the tail. This symptom is also common in diseased Procambarus clarkii every year in this country, but the causative agent has not been determined. This study analyzed the etiological characteristics of this disease. Bacterial isolation and identification combined with high-throughput sequencing analysis were conducted to obtain the microbiota characteristics in the hemolymph, hepatopancreas, and intestines. Results showed that this outbreak was caused by infection from Aeromonas hydrophila and Aeromonas veronii. The underlying cause was stress imposed on crayfish during transferring from outdoor pond to indoor pond because of temperature drops. Aeromonas infection caused remarkable changes in the structure of the microbial composition in the hemolymph, hepatopancreas, and intestines of the crayfish. The abundance of Aeromonas in the hemolymph of the sick crayfish was as high as 99.33%. In particular, KEGG metabolic pathway analysis showed that some antibiotic synthesis, enterobactin biosynthesis, and myo-inositol degradation pathways were abundant in healthy crayfish hemolymphs, which may be the mechanism of maintaining crayfish health. Conversely, inhibition of these pathways led to the disorder of microbiota structure, finally leading to the occurrence of diseases. To the knowledge of the authors, this study was the first to use high-throughput amplicon sequencing targeting the 16S rRNA gene to find the causative bacteria in aquatic animals. This protocol can provide more comprehensive and reliable evidence for pathogen identification, even if the pathogenic bacteria are anaerobes or other hard-to-culture bacteria.
2019年11月，中国湖北一家养殖场的澳洲红螯螯虾（Cherax quadricarinatus）暴发急性疾病，累计死亡率超过80%。该病的一个特征性症状是尾部出现水泡。该国每年患病的克氏原螯虾也常有此症状，但病原体尚未确定。本研究分析了该病的病原学特征。通过细菌分离鉴定并结合高通量测序分析，获取血淋巴、肝胰腺和肠道中的微生物群特征。结果表明，此次暴发是由嗜水气单胞菌和维氏气单胞菌感染引起的。根本原因是由于气温下降，小龙虾从室外池塘转移到室内池塘过程中受到应激。气单胞菌感染导致小龙虾血淋巴、肝胰腺和肠道中的微生物组成结构发生显著变化。患病小龙虾血淋巴中气单胞菌的丰度高达99.33%。特别是，KEGG代谢途径分析表明，健康小龙虾血淋巴中一些抗生素合成、肠杆菌素生物合成和肌醇降解途径丰富，这可能是维持小龙虾健康的机制。相反，这些途径受到抑制会导致微生物群结构紊乱，最终引发疾病。据作者所知，本研究首次使用针对16S rRNA基因的高通量扩增子测序来发现水生动物中的致病细菌。即使致病细菌是厌氧菌或其他难以培养的细菌，该方案也可为病原体鉴定提供更全面、可靠的证据。
