Serosurvey of Rickettsia spp. in cats from a Brazilian spotted fever-endemic area

Abstract Rickettsia spp. bacteria are responsible for tick-borne diseases worldwide, mostly maintained by rickettsial amplifiers capybaras in Brazilian endemic areas. The campus of the University of São Paulo, in southeastern Brazil, is an area endemic for Brazilian spotted fever (BSF), with high density of capybaras and Amblyomma spp., along with confirmed human cases. Besides capybaras, the university has also an in-campus high population of sheltered and free-roaming cats. Accordingly, the aim of this study was to determine the prevalence and characteristics associated with Rickettsia rickettsii, Rickettsia parkeri and Rickettsia felis exposure among cats in a BSF-endemic area. Out of 51 cats sampled, 23/35 shelter (65.7%) and 5/16 free-roaming (31.2%) were positive (titers ≥ 64) for at least one Rickettsia species. Ticks species were present in 3/16 free-roaming cats (18.8%), consisting of Amblyomma spp., nymphs of Amblyomma sculptum and adult Rhipicephalus sanguineus sensu lato. Despite sharing the capybaras environment, the seropositivity among the free-roaming and shelter cats was lower than owned cats in other endemic areas. Whether equally or less exposed to rickettsial infection, compared with owned cats in endemic areas, free-roaming and shelter cats may be used as environmental sentinels for human exposure to rickettsiae in such areas.摘要 立克次体属（Rickettsia spp.）细菌是全球范围内蜱传疾病的致病菌，在巴西流行区主要由作为立克次体扩增宿主的水豚维持其自然循环。位于巴西东南部的圣保罗大学（University of São Paulo）校园是巴西斑疹热（Brazilian spotted fever, BSF）的流行区域，校内水豚与钝缘蜱属（Amblyomma spp.）种群密度较高，且已确诊存在人间感染病例。除水豚外，该校园内还存在大量收容猫与自由放养猫。本研究旨在明确该巴西斑疹热流行区内，猫群对立氏立克次体（Rickettsia rickettsii）、帕氏立克次体（Rickettsia parkeri）及菲氏立克次体（Rickettsia felis）的暴露率及其相关关联特征。本次共采集51只受试猫样本，其中35只收容猫中有23只（65.7%）、16只自由放养猫中有5只（31.2%）至少对1种立克次体属细菌呈血清学阳性（抗体滴度≥64）。16只自由放养猫中有3只（18.8%）携带蜱虫，经鉴定为钝缘蜱属蜱虫、钝形钝缘蜱（Amblyomma sculptum）若虫以及血红扇头蜱复合群（Rhipicephalus sanguineus sensu lato）成虫。尽管与水豚共享栖息环境，但本研究中自由放养猫与收容猫的血清阳性率低于其他流行区的家养猫。与流行区的家养猫相比，无论立克次体感染暴露水平是否更低，自由放养猫与收容猫均可作为该类区域内人类立克次体暴露风险的环境哨兵。