Yangzhou University College of Veterinary Medicine, Yangzhou, Jiangsu, China; College of Medicine, University of Illinois Chicago, Chicago, IL, USA.
Yangzhou University College of Veterinary Medicine, Yangzhou, Jiangsu, China.
Vet Parasitol. 2023 Nov;323:110032. doi: 10.1016/j.vetpar.2023.110032. Epub 2023 Sep 24.
Animal infection models are crucial for studying various aspects of Ehrlichia canis infections. To understand the pathogenesis of the first Chinese isolate of E. canis and simulate the natural progression of canine ehrlichiosis, we developed a model with 18 Beagle dogs that consisted of E. canis initial infection (days 0-17), treatment with doxycycline or rifampicin (days 18-32), recovery (days 33-66), E. canis reinfection (days 67-91), and Babesia vogeli superinfection (days 92-116). We measured body weight and rectal temperature every other day, drew blood every 4 days for routine hematology and biochemistry tests, and for quantification of E. canis and B. vogeli by quantitative PCRs. In this study, the first isolate of E. canis from China was used to experimentally infect dogs, and the infected dogs exhibited clinical signs of acute severe ehrlichiosis, including high fever, loss of appetite, dehydration, and body weight loss, confirming the similar pathogenicity of E. canis in China as compared to isolates from other regions. Infection with E. canis and B. vogeli led to reduced body weight and fever in dogs. Doxycycline treatment led to absence of E. canis DNA in infected dogs, while rifampicin treatment lowered the blood E. canis copy number up to 1.5 folds. E. canis-free infected dogs after doxycycline treatment were successfully re-infected with E. canis, indicating dogs with antibodies are still at risk of re-infection. Super-infection with B. vogeli resulted in higher fever, more severe anemia, and a reduced number of platelets. Splenectomized dogs showed significantly higher E. canis numbers during recovery and re-infection than intact dogs. The histological changes were observed in brain, lung, kidney, liver and spleen of the infected dogs. The findings in this study provide insights into clinical and hematologic responses, as well as effective treatment options, for dogs infected with the first Chinese isolate of E. canis, and may contribute to our understanding of the diagnosis and prevention of tick-borne diseases in dogs, including canine monocytic ehrlichiosis.
动物感染模型对于研究犬埃立克体感染的各个方面至关重要。为了了解中国首例犬埃立克体的发病机制并模拟犬埃立克体病的自然进展，我们使用 18 只比格犬建立了一个模型，该模型包括犬埃立克体的初始感染（第 0-17 天）、多西环素或利福平治疗（第 18-32 天）、恢复（第 33-66 天）、犬埃立克体再感染（第 67-91 天）和伯氏考克斯体超感染（第 92-116 天）。我们每隔一天测量一次体重和直肠温度，每 4 天采集一次血液进行常规血液学和生化学检查，并通过定量 PCR 定量检测犬埃立克体和伯氏考克斯体。在这项研究中，我们使用中国首例犬埃立克体分离株对犬进行了实验性感染，感染犬表现出急性严重埃立克体病的临床症状，包括高热、食欲不振、脱水和体重减轻，这证实了中国的犬埃立克体与其他地区的分离株具有相似的致病性。感染犬埃立克体和伯氏考克斯体导致犬体重下降和发热。多西环素治疗导致感染犬体内无犬埃立克体 DNA，而利福平治疗可使血液中犬埃立克体拷贝数降低 1.5 倍。多西环素治疗后犬埃立克体感染犬成功再感染犬埃立克体，表明具有抗体的犬仍有再感染的风险。伯氏考克斯体超感染导致更高的发热、更严重的贫血和血小板减少。脾切除术犬在恢复和再感染期间的犬埃立克体数量明显高于完整犬。感染犬的大脑、肺、肾、肝和脾均观察到组织学变化。本研究结果为中国首例犬埃立克体感染犬的临床和血液学反应以及有效治疗方法提供了见解，并可能有助于我们了解犬 tick-borne 疾病的诊断和预防，包括犬单核细胞埃立克体病。
