Data_Sheet_1_Clinical Evaluation of Corridor Disease in Bos indicus (Boran) Cattle Naturally Infected With Buffalo-Derived Theileria parva.docx

Corridor disease (CD) is a fatal condition of cattle caused by buffalo-derived Theileria parva. Unlike the related condition, East Coast fever, which results from infection with cattle-derived T. parva, CD has not been extensively studied. We describe in detail the clinical and laboratory findings in cattle naturally infected with buffalo-derived T. parva. Forty-six cattle were exposed to buffalo-derived T. parva under field conditions at the Ol Pejeta Conservancy, Kenya, between 2013 and 2018. The first signs of disease observed in all animals were nasal discharge (mean day of onset was 9 days post-exposure), enlarged lymph nodes (10 days post-exposure), and pyrexia (13.7 days post-exposure). Coughing and labored breathing were observed in more than 50% of animals (14 days post-exposure). Less commonly observed signs, corneal edema (22%) and diarrhea (11%), were observed later in the disease progression (19 days post-exposure). All infections were considered clinically severe, and 42 animals succumbed to infection. The mean time to death across all studies was 18.4 days. The mean time from onset of clinical signs to death was 9 days and from pyrexia to death was 4.8 days, indicating a relatively short duration of clinical illness. There were significant relationships between days to death and the days to first temperature (chi2 = 4.00, p = 0.046), and days to peak temperature (chi2 = 25.81, p = 0.001), animals with earlier onset pyrexia died sooner. These clinical indicators may be useful for assessing the severity of disease in the future. All infections were confirmed by the presence of macroschizonts in lymph node biopsies (mean time to parasitosis was 11 days). Piroplasms were detected in the blood of two animals (4%) and 20 (43%) animals seroconverted. In this study, we demonstrate the successful approach to an experimental field study for CD in cattle. We also describe the clinical progression of CD in naturally infected cattle, including the onset and severity of clinical signs and pathology. Laboratory diagnoses based on examination of blood samples are unreliable, and alternatives may not be available to cattle keepers. The rapid development of CD requires recognition of the clinical signs, which may be useful for early diagnosis of the disease and effective intervention for affected animals.

走廊病（Corridor disease, CD）是一种由水牛源牛泰勒虫（Theileria parva）引发的致死性牛类疾病。与由牛源牛泰勒虫感染所致的类似疾病——东海岸热（East Coast fever）不同，目前针对CD的研究尚不充分。本研究详细描述了自然感染水牛源牛泰勒虫的牛只的临床与实验室检测结果。2013年至2018年间，在肯尼亚奥尔佩杰塔自然保护区（Ol Pejeta Conservancy）的野外环境下，共有46头牛暴露于水牛源牛泰勒虫感染环境中。所有受试动物最早出现的疾病症状为鼻漏（平均发病天数为暴露后9天）、淋巴结肿大（暴露后10天）以及发热（暴露后13.7天）。超过50%的受试动物在暴露后14天出现咳嗽与呼吸困难症状。较为少见的症状包括角膜水肿（占比22%）与腹泻（占比11%），均在疾病进程后期（暴露后19天）出现。所有感染病例均被判定为临床重症，共有42头牛因感染死亡。本研究中受试动物的平均死亡时间为暴露后18.4天。从临床症状出现至死亡的平均时长为9天，从发热至死亡的平均时长为4.8天，表明临床病程相对较短。死亡天数与首次发热天数（χ²=4.00，P=0.046）、峰值发热天数（χ²=25.81，P=0.001）均存在显著相关性，即发热出现越早的动物死亡越快。上述临床指标或可用于未来的疾病严重程度评估。所有感染均经淋巴结活检样本中检出的大裂殖体（macroschizonts）得以确认（寄生虫血症平均出现时间为暴露后11天）。仅2头牛（占比4%）的血液中检测到梨形虫体（piroplasms），另有20头牛（占比43%）出现血清阳转。本研究证实了针对牛类CD的野外实验研究方法的可行性。同时，本研究详细描述了自然感染CD的牛只的临床病程，包括临床症状的出现时序、严重程度及病理变化。基于血液样本检测的实验室诊断方法可靠性较差，养牛户可能无法获得其他替代诊断手段。CD的病程进展迅速，因此识别其临床症状或可用于该病的早期诊断，并为患病动物提供有效干预措施。