Detection of tick-borne rickettsial pathogens in naturally infected dogs and dog-associated ticks in Medellin, Colombia

Abstract Tick-borne rickettsial pathogens (TBRP) are important causes of infections in both dogs and humans. Dogs play an important role as a biological host for several tick species and can serve as sentinels for rickettsial infections. Our aim was to determine the presence of TBRP in dogs and in dog-associated ticks and their potential risk to human diseases in Medellin, Colombia. DNA for E. canis (16S rRNA and dsb) and A. platys (groEl) was detected in 17.6% (53/300) and 2.6% (8/300) of dogs, respectively. Antibodies against Ehrlichia spp. 82 (27.3%) and Anaplasma spp. 8 (2.6%) were detected in dogs. Antibody reactivity against both agents were found in 16 dogs (5.3%). Eight dogs showed antibody for Rickettsia spp. with titers that suggest 3 of them had a probable exposure to R. parkeri. Rhipicephalus sanguineus s.l. (178/193) was the main tick in dogs, followed by R. microplus (15/193). The minimum infection rates (MIR) in R. sanguineus were 11.8% for E. canis and 3.4% for A. platys. E. canis and A. platys are the main TBRP infecting dogs and ticks and R. sanguineus s.l. is likely involved in the transmission of both agents. Interestingly, we found serological evidence of exposure in dogs for spotted fever group rickettsiae.

摘要 蜱传立克次体病原体（Tick-borne rickettsial pathogens, TBRP）是引发犬类与人类感染的重要致病因子。犬类作为多种蜱类的生物宿主发挥关键作用，同时可作为立克次体感染的哨兵动物。本研究旨在探明哥伦比亚麦德林地区犬只及犬相关蜱类中TBRP的存在情况，及其对人类健康的潜在感染风险。本研究通过检测发现，300份犬只样本中，犬埃立克体（E. canis，靶标基因为16S rRNA与dsb）与血小板无形体（A. platys，靶标基因为groEL）的DNA检出率分别为17.6%（53/300）与2.6%（8/300）。犬只血清中，埃立克体属（Ehrlichia spp.）抗体阳性率为27.3%（82例），无形体属（Anaplasma spp.）抗体阳性率为2.6%（8例）；另有16只犬（5.3%）同时对两种病原体呈现血清学阳性反应。8只犬的立克次体属（Rickettsia spp.）抗体检测呈阳性，其抗体滴度提示其中3只可能曾暴露于帕克里克立克次体（R. parkeri）。犬只体表采集的193份蜱类样本中，血红扇头蜱复合群（Rhipicephalus sanguineus s.l.，178/193）为优势蜱种，其次为微小牛蜱（R. microplus，15/193）。血红扇头蜱复合群的最低感染率（minimum infection rates, MIR）：犬埃立克体为11.8%，血小板无形体为3.4%。研究表明，犬埃立克体与血小板无形体是感染犬只及蜱类的主要TBRP，血红扇头蜱复合群可能参与这两种病原体的传播循环。值得关注的是，本研究发现犬只存在斑点热群立克次体感染的血清学暴露证据。