First molecular detection of the human pathogen Rickettsia raoultii and other spotted fever group rickettsiae in Ixodid ticks from wild and domestic mammals

Valentina Chisu, Cipriano Foxi, Giovanna Masala

Tick-borne rickettsioses are recognized as emerging vector-borne infections capable of infecting both human and animal hosts worldwide. This study focuses on the detection and molecular identification of species belonging to the genus Rickettsia in ticks sampled from human, vegetation, and domestic and wild vertebrates in Sardinia. Ticks were tested by PCR targeting gltA, ompA, and ompB genes, followed by sequencing analysis. The results provide evidences of a great variety of Rickettsia species of the Spotted fever group in Ixodid ticks and allow establishing for the first time the presence of R. raoultii in Rhipicephalus sanguineus s.l. and Dermacentor marginatus ticks in Sardinia island. Rickettsia massiliae was detected on R. sanguineus s.l. and R. aeschlimannii in Hyalomma marginatum and Hy. lusitanicum ticks. In addition, eight D. marginatus ticks were positive for R. slovaca. This study provides further evidence that different Rickettsia species are widespread in Sardinian ticks and that detailed investigations are required to understand the role these tick species play on spotted fever group rickettsiae circulation. More studies will provide new background on molecular epidemiology of zoonotic rickettsiae, the geographical distribution of tick-transmitted rickettsial pathogens, and the involvement of vertebrate hosts in propagation and maintenance of these bacteria in nature.