Soto Esteban, Richey Christine, Stevens Brittany, Yun Susan, Kenelty Kirsten, Reichley Stephen, Griffin Matt, Kurobe Tomofumi, Camus Al
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616, USA.
Dis Aquat Organ. 2017 Mar 30;124(1):11-20. doi: 10.3354/dao03108.
A mortality event in cultured white sturgeon Acipenser transmontanus (Richardson, 1836) sub-adults was investigated. After transfer between farms, high mortality was observed in fish, associated with back arching, abnormal swimming, and ulcerative skin lesions. Necropsy of moribund individuals revealed hemorrhagic ascites and petechial hemorrhages in the coelomic peritoneum and serosa of internal organs. Acipenserid herpesvirus 2 (AciHV-2) was isolated from external tissue samples, then identified and genotyped by sequencing of the terminase and polymerase genes. In addition, Streptococcus iniae was recovered from internal organs of affected fish. Histologic changes were limited to interstitial hematopoietic areas of the kidney and consisted of small foci of necrosis accompanied by fibrin deposition, minimal inflammatory response, and small numbers of bacterial cocci compatible with streptococci. Identity was confirmed by partial sequencing of the 16S rRNA, rpoB, and gyrB genes. Genetic fingerprinting demonstrated a genetic profile distinct from S. iniae isolates recovered from previous outbreaks in wild and cultured fish in North America, South America, and the Caribbean. Although the isolates were resistant to white sturgeon complement in serum killing assays, in vivo challenges failed to fulfill Koch's postulates. However, the clinical presentation, coupled with consistent recovery of S. iniae and AciHV-2 from moribund fish, suggests viral and bacterial co-infection were the proximate cause of death. To our knowledge, this represents the first report of AciHV-2 and S. iniae co-infection in cultured white sturgeon.
对养殖的白鲟（Acipenser transmontanus，理查森，1836年）亚成体的一次死亡事件进行了调查。在养殖场之间转移后，观察到鱼类出现高死亡率，伴有弓背、异常游泳和溃疡性皮肤损伤。对濒死个体进行尸检发现有出血性腹水，以及体腔腹膜和内脏浆膜上的瘀点出血。从外部组织样本中分离出鲟疱疹病毒2型（AciHV-2），然后通过对末端酶和聚合酶基因进行测序来鉴定和基因分型。此外，从患病鱼的内脏中分离出海豚链球菌。组织学变化仅限于肾脏的间质造血区域，表现为伴有纤维蛋白沉积的小坏死灶、最小限度的炎症反应以及少量与链球菌相符的细菌球菌。通过对16S rRNA、rpoB和gyrB基因进行部分测序来确认其身份。基因指纹分析显示，其基因图谱与从北美、南美和加勒比地区野生和养殖鱼类先前疫情中分离出的海豚链球菌菌株不同。尽管这些分离株在血清杀菌试验中对白鲟补体具有抗性，但体内攻毒试验未能满足科赫法则。然而，临床表现以及从濒死鱼中持续分离出海豚链球菌和AciHV-2，表明病毒和细菌共同感染是导致死亡的直接原因。据我们所知，这是养殖白鲟中AciHV-2和海豚链球菌共同感染的首次报告。
