从江县鲤爆发性死亡病例实验室诊断

LABORATORY DIAGNOSIS OF OUTBREAK DEATH CASES OF CYPRINUS CARPIO IN CONGJIANG COUNTY

2018年10月贵州省从江县某水产养殖专业合作社鲤爆发死亡,本研究对死亡病例进行了流行病学调查、病理学观察、寄生虫学检查、细菌分离鉴定和病毒PCR检测等诊断。结果显示:病鲤病变以鳃丝溃烂、体表出血、肛门红肿和眼球凹陷为主要特征,组织的主要病变是肾小球萎缩出血、肾小囊空腔、鳃丝肿胀粘连及上皮细胞脱落等;细菌分离培养可得到圆形凸起、表面光滑的灰白色菌落,经染色镜检、生理生化鉴定和16S rRNA基因测序分析,鉴定该分离菌为嗜水气单胞菌;PCR检测显示鲤浮肿病毒(Carp edema virus,CEV)为阳性,未检出鲤春病毒血症病毒(Spring viremia of carp virus,SVCV)和鲤疱疹病毒(Koi herpesvirus,KHV);显微镜观察亦未见到寄生虫虫体;分别取分离菌和鲤浮肿病毒阳性病例组织悬液进行人工感染试验,均可引起健康鲤发生死亡。上述结果表明,从江县鲤的死亡是嗜水气单胞菌和鲤浮肿病毒混合感染所致。

In October 2018,an outbreak of death of carp occurred in an aquaculture base in Congjiang county,Guizhou Province.Laboratory diagnoses of diseased carp were conducted through epidemiological investigation,pathological observation,identification of parasitology,bacteriology and virology.The pathological changes were characterized by gill filament ulceration,body surface bleeding,anal redness and swelling,and enophthalmus.Histopathological observation showed significant changes such as glomerular hemorrhage and atrophy,renal capsule cavity,gill filament swelling,adhesion and epithelial cells shedding.No parasite was observed in the pressed specimens of diseased carp under microscope.Round,smooth and grayish white bacterial colonies appeared after the bacteria were isolated and cultured in medium.The isolated bacterial was identified as Aeromonas hydrophila by Gram's method and microscopy,physiological and biochemical identification and 16S rRNA gene sequencing analysis.PCR test showed weak positive for Carp edema virus.Spring viremia of carp virus and Koi herpesvirus showed negative.The artificial infection test showed that the isolated bacterial and Carp edema virus had different degree of pathogenicity to carp.All results showed that the explosive death was caused by mixed infection of Aeromonas hydrophila and Carp edema virus.