Rickettsia infection in five areas of the state of São Paulo, Brazil

Abstract

This study investigated rickettsial infection in animals, humans, ticks, and fleas collected in five areas of the state of São Paulo. Eight flea species (Adoratopsylla antiquorum antiquorum, Ctenocephalides felis felis, Polygenis atopus, Polygenis rimatus, Polygenis roberti roberti, Polygenis tripus, Rhopalopsyllus lugubris, and Rhopalopsyllus lutzi lutzi), and five tick species (Amblyomma aureolatum, Amblyomma cajennense, Amblyomma dubitatum, Ixodes loricatus, and Rhipicephalus sanguineus) were collected from dogs, cats, and opossums. Rickettsia felis was the only rickettsia found infecting fleas, whereas Rickettsia bellii was the only agent infecting ticks, but no animal or human blood was shown to contain rickettsial DNA. Testing animal and human sera by indirect immunofluorescence assay against four rickettsia antigens (R. rickettsii, R. parkeri, R. felis, and R. bellii), some opossum, dog, horse, and human sera reacted to R. rickettsii with titers at least four-fold higher than to the other three rickettsial antigens. These sera were considered to have a predominant antibody response to R. rickettsii. Using the same criteria, opossum, dog, and horse sera showed predominant antibody response to R. parkeri or a very closely related genotype. Our serological results suggest that both R. rickettsii and R. parkeri infected animals and/or humans in the studied areas.Key words: Rickettsia -spotted fever -fleas -ticks -opossum -domestic animals Rickettsiae are obligate intracellular bacteria that have been classically divided into two groups: the typhus group (TG), composed of Rickettsia prowazekii and Rickettsia typhi, which are associated with lice and fleas, respectively; and the spotted fever group (SFG), which includes more than 20 valid species, mostly associated with ticks (e.g., Rickettsia rickettsii, Rickettsia parkeri), and at least one species associated with fleas (Rickettsia felis). Other species, such as Rickettsia bellii and Rickettsia canadensis, both associated with ticks, have been considered a distinct group sharing antigenic, genetic and ecological characters with both TG and SFG rickettsiae (Parola et al. 2005b). Since all SFG Rickettsia share common outer membrane antigens, conventional serological assays employing a single Rickettsia antigen (e.g., R. rickettsii) allow detecting a SFG infection, but they do not identify the Rickettsia species responsible for the infection, even in the presence of high titers (La Scola & Raoult 1997). For a more specific serological diagnosis, it is recommended techniques such as testing serum against all known Rickettsia species present in a given area, or serum cross-absorption tests (La Scola & Raoult 1997, Parola et al. 2005b).For many years, SFG rickettsiosis in the Americas was thought to be caused only by R. rickettsii, transmitted by ticks (Weiss & Moulder 1984). This rickettsia has been reported in several countries from North, Central, and South America causing an acute, highly lethal febrile disease receiving different names according to the country...

Inquérito Epidemiológico De Suposto Foco De Febre Maculosa

“…Semelhante ao ocorrido neste estudo, um equino do município de Piracicaba, área endêmica para FM em São Paulo, reagiu de forma cruzada para R. rickettsii, R. parkeri, R. felis e R. belii, mas indicou a homologia da reação para R. parkeri com título 1:4096 (38) . Já quanto a R. bellii, atualmente a riquétsia mais prevalente em carrapatos no Brasil (15,16) , não há evidência que comprove a patogenicidade dessa bactéria para humanos ou animais (18) .…”

“…Essas cepas foram isoladas de carrapatos do Brasil, conforme trabalhos de Horta et al (14) , Labruna et al (15) e Pinter e Labruna (16) . Para obtenção dos antígenos, foram utilizados cultivos de células Vero infectadas com Rickettsia spp.…”

Serological evidence of Rickettsia parkeri as the etiological agent of rickettsiosis in Uruguay

“…Erythromycin was prescribed and no clinical abnormalities were observed in the following week. Patient's blood serum collected two weeks after onset of fever was tested for rickettsiosis through IFA for R. parkeri, R. rickettsii, R. felis, R. amblyommii, R. rhipicephali, and R. bellii antigens, as previously described 7,8 . Serum end-point titers to these six antigens were 2,048, 1,024, 64, 256, 512, and < 64, respectively.…”

Serological evidence of exposure to tick-borne agents in opossums (Didelphis spp.) in the state of São Paulo, Brazil

“…These animals are abundant in all areas endemic for BSF, where they present high antibody titers to R. rickettsii (HORTA et al, 2007) and are usually infested with ticks of the A. cajennense complex, the most important vector in South America (LABRUNA, 2009).…”