In 2004, three wild sea otters were diagnosed with putative Sarcocystis neurona-associated meningoencephalitis by histopathology and immunohistochemistry. Schizonts, free merozoites and tissue cysts were observed in the brains of all three infected animals. Tissue cysts walls from sea otter 1 (SO1) stained positively using anti-S. neurona polyclonal antiserum. However, positive staining does not preclude infection by closely related or cross-reactive tissue cyst-forming coccidian parasites. Two immature tissue cysts in the brain of SO1 were examined using transmission electron microscopy. Ultrastructural features included cyst walls with thin villous projections up to 1 microm long with tapered ends and a distinctive, electron-dense outer lining layer composed of linearly-arranged, semi-circular structures with a "hobnailed" surface contour. Small numbers of microtubules extended down through the villi into the underlying granular layer. Metrocytes were short and plump with an anterior apical complex, 22 sub-pellicular microtubules, numerous free ribosomes and no rhoptries. Some metrocytes appeared to be dividing, with two adjacent nuclear profiles. Collectively these ultrastructural features were compatible with developing protozoal cysts and were similar to prior descriptions of S. neurona tissue cysts. Panspecific 18S rDNA primers were utilized to identify protozoa infecting the brains of these otters and DNA amplification and additional sequencing at the ITS1 locus confirmed that all three otters were infected with S. neurona. No other Sarcocystis spp. were detected in the brains or skeletal muscles of these animals by immunohistochemistry or PCR. We believe this is the first ultrastructural and molecular confirmation of the development of S. neurona tissue cysts in the CNS of any animal.

中文翻译：

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南方海獭（Enhydra lutris nereis）中枢神经系统中肉囊藻神经元组织囊肿发育的超微结构和分子确认。

2004 年，通过组织病理学和免疫组织化学，三只野生海獭被诊断出患有肉囊藻神经元相关脑膜脑炎。在所有三种感染动物的大脑中都观察到裂殖体、游离裂殖子和组织包囊。来自海獭 1 (SO1) 的组织包囊壁使用抗 S 染色呈阳性。神经元多克隆抗血清。然而，阳性染色并不能排除密切相关或交叉反应的组织包囊形成球虫寄生虫的感染。使用透射电子显微镜检查 SO1 脑中的两个未成熟组织囊肿。超微结构特征包括具有长达 1 微米长的细绒毛突起的囊肿壁，末端呈锥形，以及由线性排列的半圆形结构组成的独特的电子致密外衬层，带有“钉子” 表面轮廓。少量微管通过绒毛向下延伸到下面的颗粒层。母细胞短而丰满，具有前尖复合体、22 个亚膜微管、大量游离核糖体且无菱形结构。一些母细胞似乎正在分裂，具有两个相邻的核轮廓。总的来说，这些超微结构特征与发育中的原生动物囊肿相容，并且与先前对 S. 神经元组织囊肿的描述相似。泛特异性 18S rDNA 引物用于鉴定感染这些水獭大脑的原生动物，DNA 扩增和 ITS1 基因座的额外测序证实所有三只水獭都感染了神经元链球菌。没有其他肉孢子虫属。通过免疫组织化学或 PCR 在这些动物的大脑或骨骼肌中检测到 。