Groff J M, LaPatra S E, Munn R J, Anderson M L, Osburn B I
Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis 95616, USA.
J Vet Diagn Invest. 1996 Apr;8(2):172-80. doi: 10.1177/104063879600800206.
A mild to moderate branchial epitheliocystis infection was diagnosed in subyearling (11 months old, 250-300 g) white sturgeon (Acipenser transmontanus) from a private culture facility with a 4-8% mortality in the population. Infected branchial epithelial cells contained the coccoid to coccobacillary epitheliocystis organisms, which appeared as cytoplasmic inclusions composed of a fine, homogeneous, dense, basophilic, granular material. The infected cells were variably enlarged with spherical to oval profiles and were randomly distributed throughout the branchial epithelium. The cytoplasmic inclusions stained positive with Macchiavello stain but negative with Brown and Brenn, periodic acid-Schiff, and Gimenez stains. Expression of chlamydial antigen was demonstrated within the cytoplasmic inclusions using a standard peroxidase-antiperoxidase immunohistochemical technique. Three stages of coordinated intracellular development were recognized by electron microscopy. The reticulate bodies were oval to spherical and 0.4-0.8 x 0.5-1.4 microns but often exhibited a pleomorphic and convoluted appearance because of variable membrane invaginations and evaginations suggestive of uneven fission and budding. Separate host cells contained intermediate bodies that were spherical to oval and 0.2-0.4 x 0.3-0.6 microns although often observed in the process of apparent uneven division. The presence of a cap or plaque composed of hexagonally arrayed fibrillar surface projections was initially recognized in this stage. A homogeneous population of 0.3-0.4 microns oval elementary bodies were observed separately in individual host cells. This developmental stage had a single, dense, compact, eccentrically located cytoplasmic condensation that occurred opposite to the location of the cap of hexagonally arrayed fibrillar surface projections. Morphologic characteristics of the epitheliocystis organism in these white sturgeon were similar to those previously described in other teleosts and expands the species catalogue of epitheliocystis infection. Furthermore, the ultrastructural similarities to the chalmydiae and the immunohistochemical detection of chlamydial antigen provides further evidence that the epitheliocystis agent is related to members of the Chlamydiales. Although the infection was considered mild to moderate and could not be definitively attributed to the mortality in this population, the potential adverse impact of epitheliocystis infection on sturgeon culture should be considered especially in intensive fish culture operations.
在一家私人养殖设施中，对11个月大、体重250 - 300克的亚成年白鲟（Acipenser transmontanus）诊断出轻度至中度鳃上皮囊肿感染，该种群死亡率为4 - 8%。受感染的鳃上皮细胞含有球状至球杆菌状的上皮囊肿病原体，这些病原体表现为细胞质内含物，由精细、均匀、致密、嗜碱性的颗粒物质组成。受感染的细胞大小不一，呈球形至椭圆形，随机分布于整个鳃上皮。细胞质内含物经马基维洛染色呈阳性，但经布朗和布伦染色、过碘酸 - 希夫染色及吉姆萨染色呈阴性。使用标准的过氧化物酶 - 抗过氧化物酶免疫组织化学技术，在细胞质内含物中证实了衣原体抗原的表达。通过电子显微镜识别出三个阶段的协调细胞内发育过程。网状体呈椭圆形至球形，大小为0.4 - 0.8×0.5 - 1.4微米，但由于可变的膜内陷和外突，常呈现多形性和卷曲外观，提示不均匀的裂变和出芽。不同的宿主细胞含有中间体，呈球形至椭圆形，大小为0.2 - 0.4×0.3 - 0.6微米，尽管常观察到其处于明显的不均匀分裂过程中。在此阶段最初识别出由六边形排列的纤维状表面突起组成的帽或斑块的存在。在单个宿主细胞中分别观察到一群大小为0.3 - 0.4微米的椭圆形原体。这个发育阶段有一个单一、致密、紧凑、偏心定位的细胞质浓缩物，位于六边形排列的纤维状表面突起帽的相对位置。这些白鲟中上皮囊肿病原体的形态特征与先前在其他硬骨鱼中描述的相似，扩大了上皮囊肿感染的物种目录。此外，与衣原体的超微结构相似性以及衣原体抗原的免疫组织化学检测提供了进一步证据，表明上皮囊肿病原体与衣原体目成员有关。尽管该感染被认为是轻度至中度，且不能明确归因于该种群的死亡，但上皮囊肿感染对鲟鱼养殖的潜在不利影响应予以考虑，尤其是在集约化鱼类养殖操作中。
