Distribution of Rickettsia rickettsii in ovary cells of Rhipicephalus sanguineus (Latreille1806) (Acari: Ixodidae)

The results showed a general distribution of R. rickettsii in the ovary cells, being found in oocytes in all stages of development (I, II, III, IV and V) most commonly in the periphery of the oocyte and also in the cytoplasm of pedicel cells.The histological analysis of the ovaries of R. sanguineus infected females confirmed the presence of the bacterium, indicating that the infection can interfere negatively in the process of reproduction of the ticks, once alterations were detected both in the shape and cell structure of the oocytes which contained bacteria.Rickettsia rickettsii, the etiological agent of Brazilian Spotted Fever (BSF) in Brazil and Rocky Mountain Spotted Fever in the United States [1] is an obligatory intracellular gram-negative bacterium which survives for a short time out of the host [2], being transmitted to humans and other animals by different species of ticks. These organisms are usually 0.8 to 2 μm long, with a diameter of 0.3 to 0.5 μm [3] and having a cellular wall formed by peptidoglycan and lipopolysaccharides [4]. The infection caused by rikettsiae is systemic in ticks as they multiply in the cytoplasm of the intestine, ovaries, salivary glands, Malpighian tubules cells and are also found in the hemolymph of the ectoparasite [5]. Following infection of the ovaries, transstadial and transovarial transmission of the pathogen can happen [6].Rickettsia rickettsii is considered the most pathogenic species of rickettsia, being reported in Canada, United State, Mexico, Costa Rica, Panama, Brazil, Colombia and Argentina [7]. Many ticks are known as vectors of R. rickettsia in the world. In Brazil the known vectors are Amblyomma cajennense, tick vector in most of the endemic areas in the country and A. aureolatum, responsible for the transmission in some metropolitan areas of S？o Paulo [8,9]. Recent studies point to R. sanguineus as a possible vector of R. rickettsii for humans in some regions of Brazil. Moraes-Filho et al. [10] reported the pre