PDF(Pubmed)
Abstract：
Since September 2020, the clinical symptoms of Muscovy duck spleen spots have appeared in Guangdong, Guangxi, Jiangxi, Hunan, Hubei, and other provinces, resulting in a large number of Muscovy duck deaths and great economic losses. The absence of the typical clinical symptoms caused by pathogenic microorganisms makes the cause of the spotted spleen a mystery. High-throughput sequencing results suggested that Riemerella anatipestifer (R. anatipestifer) may be the pathogen. Then, R. anatipestifer was regarded as the research target for isolation, identification, and pathogenicity assessment. After biochemical test, PCR amplification, and serotype determination, it was confirmed that the isolated strain CZG-1 was serotype 15 R. anatipestifer. Typical spotted spleen symptoms were observed after CZG-1 infection. Furthermore, drug sensitivity assays showed the similar drug-resistant spectrum of R. anatipestifer serotype 15 to other serotypes; for example, all test strains were resistant to polymyxin, gentamicin, and neomycin. The CZG-1 strain has high pathogenicity, and its lethal dose of 50% (LD50) is 35.122 CFU/ml. Virulence gene determination showed that the CZG-1 strain had at least five virulence genes, bioF, TSS9-1, TSS9-2, PncA, and 0373Right. Above all, this study identified and proved that the pathogen of spotted spleen in ducks was R. anatipestifer serotype 15, which caused death of ducks without the typical symptoms of bacterial infection. The results of this study enriched the knowledge of symptom after R. anatipestifer infection, provided a reference to the identification of the pathogen of spotted spleen, and provided theoretical basis for prevention and control of spotted spleen.
摘要：
2020年9月以来，广东出现番鸭脾斑的临床症状，广西,江西,湖南,湖北,和其他省份,造成大量番鸭死亡和巨大的经济损失。由于病原微生物引起的典型临床症状的缺失，使得斑纹脾的病因成为一个谜。高通量测序结果提示，犬瘟病Riemerellaanatipestifer(R.anatipestifer）可能是病原体。然后，R.anatipestifer被视为隔离的研究目标，identification,和致病性评估。生化试验后,PCR扩增,和血清型测定，证实了分离的菌株CZG-1是血清型15R.anatipestifer。CZG-1感染后观察到典型的斑点脾症状。此外，药物敏感性试验显示，15型R.anatipestifer的耐药谱与其他血清型相似；例如，所有测试菌株都对多粘菌素具有抗性，庆大霉素,和新霉素。CZG-1菌株具有较高的致病性,其致死剂量为50％（LD50）为35.122CFU/ml。毒力基因测定表明CZG-1株至少有5个毒力基因,bioF,TSS9-1,TSS9-2,PncA,0373Right最重要的是,这项研究鉴定并证明了鸭脾斑点的病原体是R.anatipestifer血清型15，它导致了鸭的死亡，没有典型的细菌感染症状。这项研究的结果丰富了R.anatipestifer感染后的症状知识，为斑点脾病原体的鉴定提供了参考，为防治斑脾提供理论依据。
