无乳链球菌感染吉富品系尼罗罗非鱼的病理学研究

[目的]确定无乳链球菌侵染吉富品系尼罗罗非鱼的途径及靶器官,为罗非鱼抗病育种及无乳链球菌病疫苗的研发提供理论依据.[方法]分别采用腹腔注射、经口灌胃及体外浸泡3种方式对吉富品系尼罗罗非鱼进行无乳链球菌感染,然后采集感染罗非鱼的鳃、脾脏、肝脏和小肠组织进行病理形态学观察,并利用家兔抗无乳链球菌血清进行免疫组织化学定位,明确不同感染途径下无乳链球菌在鱼体内各组织中的分布规律及其浸染的靶器官.[结果]3种人工感染方式均能促使吉富品系尼罗罗非鱼感染无乳链球菌,其中,腹腔注射和经口灌胃在感染2h后即出现病理变化,而体外浸泡感染方式出现病理变化的时间约在感染5h后,且病变程度较腹腔注射和经口灌胃的感染方式轻.免疫组织化学定位发现,腹腔注射组吉富品系尼罗罗非鱼的病原菌信号出现顺序为脾脏→肝脏和鳃→小肠,经口灌胃组的病原菌信号出现顺序为小肠→鳃和脾脏→肝脏,体外浸泡组的病原菌信号出现顺序为鳃→脾脏→肝脏和小肠.[结论]采用腹腔注射、经口灌胃及体外浸泡3种方式均能促使吉富品系尼罗罗非鱼感染无乳链球菌,其对应的病原菌信号分别优先在脾脏、肠道和鳃组织出现.因此,自然养殖条件下防止养殖水体和食源被无乳链球菌污染是防控罗非鱼无乳链球菌病暴发的有效措施.

Pathological research of GIFT tilapia infected by Streptococcus agalactiae

[Objective]The infection approach of Streptococcus agalactiae to GIFT tilapia and target organs were stu-died to provide reference for disease resistant breeding and development of S.agalactiaevaccine.[Method]The GIFT tila-pia was inoculated by S.agalactiae through intraperitoneal injection,gavage and soak,and samples of gill,spleen,liver and small gut were collected for pathomorphology observation.Immunohistochemical location was conducted using anti-S.agalactiae serum of rabbit to research the distribution regulations in each tissues under various inoculation approaches and the inoculated target organs.[Result]The three artificial inoculation methods could all lead to S.agalactiae inocula-tion of GIFT tilapia.In intraperitoneal injection and gavage inoculations,pathological changes occured after 2 h of inocu-lation,but in soak inoculation,pathological changes occured after 5 h,and the degree of pathological changes was less serious than the other two.Immunohistochemical localization results showed that,in intraperitoneal injection treatment, the order of pathogenic bacteria occured in GIFT tilapia was spleen→liver and gill→small gut;the order in gavage inocu-lation was small gut→gill and spleen→liver;and the order in soak inoculation was gill→spleen→liver and small gut.[Conclusion]Intraperitoneal injection,gavage and soak can all lead to S.agalactiae inoculation in GIFT tilapia.The sig-nal of pathogenic bacteria would appear first in spleen,gut and gill.Therefore,the effective measures to control the out-break of S.agalactiaedisease in GIFT tilapia under natural aquaculture conditions are preventing the aquaculture water and food from infection of S.agalactiae.