A free-ranging juvenile male black bear (Ursus americanus), found dead in Alberta, Canada, had severe nonsuppurative encephalitis. Lesions in the brain were most severe in the gray matter of the cerebral cortex, and included perivascular cuffs of lymphocytes and plasma cells, areas of gliosis that disrupted the neuropil, and intralesional protozoan schizonts. The left hindlimb had suppurative myositis associated with Streptococcus halichoeri. Immunohistochemistry and molecular analyses (PCR and sequencing of 4 discriminatory loci: 18S rDNA, ITS-1 rDNA, cox1, rpoB) identified Sarcocystis canis or a very closely related Sarcocystis sp. in the affected muscle and brain tissues. The main lesion described in previously reported cases of fatal sarcocystosis in bears was necrotizing hepatitis. Fatal encephalitis associated with this parasite represents a novel presentation of sarcocystosis in bears. Sarcocystosis should be considered a differential diagnosis for nonsuppurative encephalitis in bears.

一只在加拿大艾伯塔省被发现死亡的自由放养的幼年雄性黑熊 ( Ursus americanus ) 患有严重的非化脓性脑炎。大脑中的病变在大脑皮层的灰质中最为严重，包括淋巴细胞和浆细胞的血管周围袖带、破坏神经细胞的神经胶质增生区域和病灶内的原生动物裂殖体。左后肢有化脓性肌炎，与链球菌有关。免疫组织化学和分子分析（PCR 和 4 个区分位点的测序：18S rDNA、ITS-1 rDNA、cox 1、rpoB）鉴定出犬肉孢子虫或非常密切相关的肉孢子虫sp。在受影响的肌肉和脑组织中。先前报道的熊致命肉囊病病例中描述的主要病变是坏死性肝炎。与这种寄生虫相关的致命性脑炎代表了熊肉囊病的一种新表现。肉囊病应被视为熊非化脓性脑炎的鉴别诊断。