Inokuma Hisashi, Matsuda Hironori, Sakamoto Leo, Tagawa Michihito, Matsumoto Kotaro
Department of Clinical Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, 080-8555 Obihiro, Japan.
Clin Vaccine Immunol. 2011 Jan;18(1):161-6. doi: 10.1128/CVI.00369-10. Epub 2010 Oct 27.
Rickettsia japonica pathogenesis and reservoir potential in dogs were evaluated by both experimental inoculation and epidemiologic survey. In the experimental inoculation study, dogs 1 and 2 were pretreated with an immunosuppressive dose of cyclosporine 14 days before inoculation and became ill after exposure to R. japonica. Dogs exhibited clinical signs, including fever, anorexia, depression, and decreased water consumption, between 36 and 96 h after inoculation, but these signs disappeared spontaneously by 5 days after inoculation. Dogs 3 and 4 were not pretreated with cyclosporine, and no clinical signs were detected in them throughout the 14-day observation period. The control dog was clinically normal and had a normal rectal temperature throughout the study period. We attempted to detect rickettsial DNA from peripheral blood and aspiration samples from kidney and spleen by nested PCR, but all samples examined were negative. The control dog lacked detectable titers to R. japonica antigen on day 14, while positive antibodies to R. japonica were detected in all four experimentally infected dogs, with titers of 1:160 to 1:80. In the epidemiologic survey, 24 (1.8%) of the 1,363 dogs examined throughout Japan had antibodies against R. japonica, with titers of 1:40 or more. However, we observed neither clinical signs at the time of sample collection nor nested PCR results indicative of rickettsial infection in these dogs. In conclusion, dogs in Japan can be exposed to R. japonica, and infected dogs with immunosuppressive conditions can temporarily develop clinical symptoms, including fever, anorexia, depression, and decreased water consumption.
通过实验接种和流行病学调查对日本立克次体在犬类中的致病机制和储存宿主潜力进行了评估。在实验接种研究中，犬1和犬2在接种前14天用免疫抑制剂量的环孢素进行预处理，在接触日本立克次体后发病。犬在接种后36至96小时出现临床症状，包括发热、厌食、抑郁和饮水量减少，但这些症状在接种后5天自行消失。犬3和犬4未用环孢素预处理，在整个14天的观察期内未检测到临床症状。对照犬在整个研究期间临床正常，直肠温度正常。我们试图通过巢式PCR从外周血以及肾脏和脾脏的穿刺样本中检测立克次体DNA，但所有检测样本均为阴性。对照犬在第14天未检测到针对日本立克次体抗原的滴度，而在所有四只实验感染的犬中均检测到针对日本立克次体的阳性抗体，滴度为1:160至1:80。在流行病学调查中，在日本各地检查的1363只犬中有24只（1.8%）具有针对日本立克次体的抗体，滴度为1:40或更高。然而，在这些犬中，我们在样本采集时既未观察到临床症状，也未观察到表明立克次体感染的巢式PCR结果。总之，日本的犬类可能接触到日本立克次体，免疫抑制状态下感染的犬可能会暂时出现包括发热、厌食、抑郁和饮水量减少在内的临床症状。
