Experimental infection and co-infection with Chinese strains of Ehrlichia canis and Babesia vogeli in intact and splenectomized dogs: Insights on clinical, hematologic and treatment responses

• Published in: Veterinary parasitology Vol. 323; p. 110032
• Main Authors: Zhang, Jilei, Wang, Jiawei, Kelly, Patrick John, Zhang, Yuanyuan, Li, Min, Li, Jing, Zhang, Rong, Wang, Yaoyao, Huang, Ke, You, Jinfeng, Qiu, Haixiang, Zheng, Xiaofeng, Wang, Xiaobo, Li, Jianji, Dong, Junsheng, Yang, Yi, Wang, Chengming
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.11.2023
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Anti-Bacterial Agents - therapeutic use; Babesia - classification; Babesia - isolation & purification; Babesia superinfection; Babesiosis - drug therapy; Babesiosis - parasitology; China; Coinfection - veterinary; Dog; Dog Diseases - drug therapy; Dog Diseases - microbiology; Dog Diseases - parasitology; Dogs; Doxycycline; Doxycycline - therapeutic use; Ehrlichia canis - genetics; Ehrlichiosis - drug therapy; Ehrlichiosis - veterinary; Experimental infection; Female; Male; Rickettsial diseases; Rifampicin; Rifampin - therapeutic use; Splenectomy - veterinary; Vector-borne pathogens; China; Babesia superinfection; Experimental infection; Rickettsial diseases; Rifampicin; Doxycycline; Vector-borne pathogens; Dog
• ISSN: 0304-4017; 1873-2550; 1873-2550
• DOI: 10.1016/j.vetpar.2023.110032

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. •Experimentally infected model to study pathogenicity of first E. canis strain from China.•Doxycycline eliminated E. canis while rifampicin lowered E. canis numbers.•E. canis-free dogs after doxycycline treatment were successfully reinfected.•Splenectomized dogs showed higher E. canis numbers than intact dogs.•B. vogeli super-infection led to higher fever, more severe anemia, lower platelet counts.