Seroprevalence of Rickettsia rickettsii and Rickettsia parkeri in dogs during a Brazilian Spotted Fever outbreak in the State of Rio de Janeiro

ABSTRACT The present paper is the first to perform this evaluation in dogs from the cities of Natividade, Porciuncula and Varre-Sai. The aim of this study is to search for Spotted Fever Group Rickettsia in canine sera using indirect immunofluorescence assay and to identify the probable causative agent of sera reactions in animals. Of the 253 sampled canines, 67.59% (171/253) were seroreactive for Rickettsia rickettsii and 11.07% (28/253) for Rickettsia parkeri, both in dilution 1:64. Titration of tested sera against R. rickettsii antigens reached 1:131.072 and, for R. parkeri, 1:4.096. We conclude that dogs are important sentinels for R. rickettsii infection, and can be infected regardless of sex, age, the habit of visiting woodlands or being in direct contact with equines and capybaras. Serological diagnosis has highlighted many dogs infected by R. rickettsii, and ambient conditions, such as the presence of flowing water bodies, was important for the occurrence of Brazilian Spotted Fever in the northwestern of Rio de Janeiro State.

摘要 本研究为首次针对纳蒂维达迪（Natividade）、波尔西翁库拉（Porciuncula）以及瓦雷赛（Varre-Sai）三地的犬只开展此项评估。本研究旨在通过间接免疫荧光试验（indirect immunofluorescence assay）检测犬血清中的斑点热群立克次体（Spotted Fever Group Rickettsia），并明确引发受试动物血清学反应的潜在病原体。在253只采样犬只中，分别有67.59%（171/253）和11.07%（28/253）的血清在1:64稀释度下对立氏立克次体（Rickettsia rickettsii）和帕克氏立克次体（Rickettsia parkeri）呈血清学反应阳性。受试血清对立氏立克次体抗原的滴定效价可达1:131.072，针对帕克氏立克次体抗原的效价则为1:4.096。本研究结论表明，犬只可作为立氏立克次体感染的重要哨兵动物，且其感染风险与性别、年龄、进入林地的习性，以及是否直接接触马类和水豚均无关联。血清学诊断结果证实存在大量感染立氏立克次体的犬只；而流动水体存在等环境条件，是里约热内卢州西北部地区发生巴西斑点热（Brazilian Spotted Fever）的重要影响因素。