Fatal parasite-induced enteritis and typhlocolitis in horses in Southern Brazil

Abstract Diseases related to the alimentary system are the main cause of death in horses. This retrospective study aimed to describe the pathological findings of fatal parasite-induced enteritis and typhlocolitis caused by cyathostominae, Eimeria leuckarti, Balantidium coli, and Strongyloides westeri in horses. The records of parasite-induced intestinal lesions in horses necropsied in Southern Brazil between 2005 and 2017 were reviewed. Ten horses had fatal parasitic enteritis and/or typhlocolitis, and the main causes were: cyathostominae typhlocolitis (6/10), E. leuckarti enteritis (1/10), S. westeri enteritis (1/10), B. coli colitis related to cyathostominae (1/10), and infection by multiple agents (1/10). Cyathostominae typhlocolitis showed marked mucosal thickening, with multifocal elevated nodules containing tangled filiform parasites. Microscopic examination revealed that the mucosa and submucosa had encysted parasitic structures surrounded by eosinophilic and granulomatous inflammation. E. leuckarti enteritis was microscopically characterized by macrogamonts, microgamonts, and oocysts inside the host cells. S. westeri enteritis showed microscopic atrophy of the villi with numerous mucosal encysted parasitic structures. B. coli typhlocolitis showed severe diffuse mucosal reddening, with microscopic superficial mucosal necrosis associated with multiple protozoan trophozoites. Fatal parasite-induced enteritis and typhlocolitis are important causes of death in horses in Southern Brazil.摘要 消化系统疾病是马匹死亡的首要致死原因。本回顾性研究旨在描述由圆线虫亚科（Cyathostominae）、勒氏艾美耳球虫（Eimeria leuckarti）、结肠小袋纤毛虫（Balantidium coli）以及韦氏类圆线虫（Strongyloides westeri）引发的致死性寄生虫性肠炎与盲肠结肠炎的病理学特征。本研究回顾了2005年至2017年间巴西南部地区马类尸检档案中寄生虫性肠道病变的相关记录。共计10匹马出现致死性寄生虫性肠炎和/或盲肠结肠炎，主要致病原包括：圆线虫亚科引发的盲肠结肠炎（6/10）、勒氏艾美耳球虫性肠炎（1/10）、韦氏类圆线虫性肠炎（1/10）、合并圆线虫亚科感染的结肠小袋纤毛虫性结肠炎（1/10），以及多病原混合感染（1/10）。圆线虫亚科引发的盲肠结肠炎可见显著的黏膜增厚，伴有多发隆起性结节，结节内可见缠绕的丝状寄生虫。显微镜检查可见黏膜与黏膜下层存在包囊化的寄生虫结构，周围伴有嗜酸性粒细胞性与肉芽肿性炎症反应。勒氏艾美耳球虫性肠炎的显微镜下特征为宿主细胞内存在大配子体、小配子体与卵囊。韦氏类圆线虫性肠炎可见显微镜下的绒毛萎缩，同时黏膜内存在大量包囊化的寄生虫结构。结肠小袋纤毛虫性盲肠结肠炎可见严重的弥漫性黏膜发红，显微镜下可见浅表黏膜坏死，并伴随大量原虫滋养体。致死性寄生虫性肠炎与盲肠结肠炎是巴西南部地区马类死亡的重要致死诱因。