Meningoencephalitis secondary to rhinitis caused by Pythium insidiosum in sheep

ABSTRACT: A case of meningoencephalitis caused by Pythium insidiosum secondary to rhinitis is reported in a three-year-old crossbred sheep from a herd of 15 animals, raised extensively and with free access to a weir. The animal presented mild dyspnea, blindness, mydriasis, opisthotonos, nystagmus, incoordination, decreased mandibular tone, and spasticity of the pelvic limbs. Macroscopic examination of the nasal cavity showed a blackish-red, irregular, friable mass that bilaterally compromised the nasal septum and the rostral portion of the nasal turbinates. In the brain, there was diffuse thickening of the leptomeninges of the cerebellum and ventral portion of the brainstem characterized by yellowish, granular material associated with vessel hyperemia. On the floor of the fourth ventricle, there was deposition of yellowish, irregular, slightly granular material that protruded towards the obex and displaced the cerebellum dorsolaterally. Microscopically, there were pyogranulomatous, eosinophilic, necrotizing rhinitis and fibrinosuppurative, eosinophilic, necrotizing meningoencephalitis, both associated with thrombosis, vasculitis, and intralesional hyphae. The hyphae were impregnated with silver and presented thin, parallel walls, rarely septate and branched. At immunohistochemistry, the hyphae were immunostained with polyclonal anti-P. insidiosum antibody in fragments of the cerebellum and nasal cavity. The findings showed that P. insidiosum rhinitis can secondarily affect the nervous system of sheep, causing nonspecific neurological clinical signs.

摘要：本文报道1例继发于鼻炎的潜伏腐霉（Pythium insidiosum）性脑膜脑炎，病例来源于15头散养、可自由接触饮水堰的杂交绵羊种群中的3岁个体。该患羊表现为轻度呼吸困难、失明、瞳孔散大、角弓反张、眼球震颤、运动失调、下颌肌张力降低及后肢痉挛。
鼻腔大体病理学检查可见黑红色、不规则、质脆的肿块，双侧累及鼻中隔及鼻甲骨吻侧段。脑部可见小脑及脑干腹侧软脑膜弥漫性增厚，表现为淡黄色颗粒状物质伴血管充血；第四脑室底可见淡黄色、不规则、轻度颗粒状物质沉积，向脑闩部突出并将小脑向背外侧推移。
镜下观察可见化脓性肉芽肿性、嗜酸性坏死性鼻炎，以及纤维蛋白性化脓性、嗜酸性坏死性脑膜脑炎，两种病变均伴随血栓形成、血管炎及病灶内菌丝。菌丝经银染显示具有薄而平行的细胞壁，极少有分隔及分支。免疫组织化学检测显示，小脑及鼻腔组织切片中的菌丝可被抗潜伏腐霉多克隆抗体染色。
本研究结果表明，潜伏腐霉性鼻炎可继发累及绵羊神经系统，引发非特异性神经临床症状。