Huchzermeyer K D A
Sterkspruit Veterinary Clinic, P.O. Box 951, Lydenburg 1120. Republic of South Africa.
Onderstepoort J Vet Res. 2003 Jun;70(2):95-105.
Infection with a faecal Streptococcus species belonging to Lancefield group D has been a major cause of mortalities on certain trout farms on the escarpment of the Mpumalanga Province in the Republic of South Africa. Evidence is given of a connection between subclinical gas bubble disease and infection with this organism in rainbow trout, Oncorhynchus mykiss. The condition causes serious losses during the summer months when water temperatures rise above 18 degrees C. The larger table-size fish are affected first and present with exophthalmos before developing signs of a typical bacterial septicaemia. The design of the water supply to the fish ponds on these farms allowed supersaturation of the water with atmospheric gas. Vortex formation at water extraction points appears to have been the main cause of air entrainment into the water supply leading to the ponds. By correcting the faults responsible for the development of hyperbaric gas pressure in the water, it was possible to control this disease on two badly affected farms. The overlapping similarities in the clinical signs and pathology of gas bubble disease and that seen in fish suffering from Streptococcus D infection are discussed, as well as the diagnostically significant changes in the gill tissues that are specific to subclinical exposure to gas supersaturation in the water. An explanation is given for the increased susceptibility to infection with this organism.
感染属于兰斯菲尔德D组的粪链球菌一直是南非共和国姆普马兰加省悬崖上某些鳟鱼养殖场死亡的主要原因。有证据表明虹鳟（Oncorhynchus mykiss）的亚临床气泡病与这种微生物感染之间存在联系。这种情况在夏季水温升至18摄氏度以上时会造成严重损失。体型较大的食用鱼首先受到影响，在出现典型细菌性败血症迹象之前会出现眼球突出。这些养殖场鱼塘的供水设计使水中的大气气体过饱和。取水点的漩涡形成似乎是空气进入通向池塘的供水系统的主要原因。通过纠正导致水中高压气体形成的故障，有可能在两个受严重影响的养殖场控制这种疾病。文中讨论了气泡病与感染D组链球菌的鱼在临床症状和病理学上的重叠相似之处，以及鳃组织中对于水中气体过饱和亚临床暴露具有诊断意义的特定变化。文中还解释了对这种微生物感染易感性增加的原因。
