仿刺参耳状幼体“烂边症”的病原及其来源分析

Etiology of rotting edges syndrome in cultured larval Apostichopus japonicus at auricularia stage and analysis of reservoir of pathogens

【目的】查明仿刺参耳状幼体"烂边症"的病原及其来源,并获得该病的治疗药物。【方法】对烂边症状较为典型的育苗场的发病幼体进行病原学分析,对可疑病原进行人工回接感染并进行形态学、生理生化和16S rDNA序列分析鉴定,对养殖场育苗系统,包括水源、饵料、育苗池水、育苗池底污物和亲参池水进行细菌学分析,对病原菌进行药敏测试。【结果】从患病幼体分离得到1种优势菌株,人工回接感染证明它对健康仿刺参有较强的致病性,且感染发病与自然发病仿刺参幼体的症状相同。鉴定出"烂边症"的病原为弧菌Vibrio lentus。养殖系统中的细菌浓度均较高(2.8×102-8.8×107cells/mL);病原来源较复杂:育苗池水、池底污物和亲参池水均发现了病原菌,病原菌浓度以池底污物中最多,育苗池水次之,亲参池水最少。新霉素等15种常用抗生素可有效抑制该病原菌的生长。【结论】"烂边症"的病原为弧菌Vibrio lentus;池底污物、育苗池及亲参均可能是本次"烂边症"的病原来源;新霉素等15种常用抗生素可用于该病的防治。

[Objective]We clarified pathogens and its sources of the disease called rotting edges syndrome at the auricularia stage in the larval culture of Apostichopus japonicus,and further developed effective medicines against this disease.[Methods]Etiological analysis was performed on larvae with typical rotting edges syndrome from larvae culture farm.Suspicious pathogen was used for artificial infection test,and then identified through morphological,physiological and biochemical tests,and 16S rDNA sequence analysis.Bacterial analysis on the culture system of the factory,including water sources,feeds,rearing water,bottom ordure and water from cultivation pond for parent sea cucumber,was carried out.Finally,drug-sensitive tests were performed on the pathogens.[Results]A common dominant bacterium strain was isolated from all ill larvae included in the study.Artificial infection test showed it was the causative pathogen associated with the disease,and the artificially infected sea cucumbers had the same syndromes to the naturally ill ones.The bacterium was identified as V.lentus.Bacterial quantity of rearing water system were at a high range （2.8 × 10^2-8.8 × 10^7 cells/mL）.The sources of the pathogen were complicated,since pathogens were discovered in the rearing water,bottom ordure and water from cultivation pond for parent sea cucumber.However,the density of causative bacteria was the highest in the bottom ordure,middle in the rearing water,and lowest in the water from cultivation pond for parent sea cucumber.Fifteen antibiotics could inhibit growth of the pathogens.[Conclusion]The possible pathogen for rotting edges syndrome was V.lentus.The bottom ordure,rearing water and parent sea cucumber may be the main infective origin of the pathogen.Fifteen antibiotics including neomycin,could be applied for disease prevention and treatment of Apostichopus japonicus.