Genetic Identification of Rickettsial Isolates from Fatal Cases of Brazilian Spotted Fever and Comparison with Rickettsia rickettsii Isolates from the American Continents

Abstract

dFifteen bacterial isolates from spotted fever group rickettsiosis in Brazil were genetically identified as Rickettsia rickettsii. In a phylogenetic analysis with other R. rickettsii isolates from GenBank, the Central/South American isolates showed low polymorphism and formed a clade distinct from two North American clades, with the North American clades having greater in-branch polymorphism.

Rickettsia infection in Amblyomma tonelliae, a tick species from the Amblyomma cajennense complex

“…Therefore, the negative results presented in this work are not unexpected, because only 68 ticks were evaluated for Rickettsia infection. Labruna et al (2014) have confirmed that a Central/South American clade of R. rickettsii is found in A. patinoi of Colombia and A. sculptum of Brazil but it is unknown if this vector-pathogen association occurs in the remaining four species of A. cajennense complex. In Argentina, fatal cases of spotted fever caused by R. rickettsii were reported in northwestern areas where specimens of A. cajennense s.l were found to be infected with this Rickettsia species .…”

A fatal case of Brazilian spotted fever in a non-endemic area in Brazil: the importance of having health professionals who understand the disease and its areas of transmission

“…Fatal cases of Rickettsia rickettsii infection have thus far been reported inonly four Brazilian states, all of which are located in the Southeastern region of the country: São Paulo (6) , Minas Gerais (7) , Rio de Janeiro (8) , and Espírito Santo (9) . The case-fatality rate has been found to range from 30% to 50% (5) .…”

Vectorial competence of Amblyomma tonelliae to transmit Rickettsia rickettsii

“…Although Labruna et al . () did not find genetic differences in some genes and intergenic regions of the two rickettsial strains, further studies are needed to test these hypotheses.…”

“…Rickettsia rickettsii is an obligate intracellular organism. Its primary vectors to humans are the hard ticks Dermacentor variabilis (Ixodida: Ixodidae), Dermacentor andersoni , Rhipicephalus sanguineus sensu lato (Ixodida: Ixodidae), Amblyomma aureolatum , and three species of the Amblyomma cajennense species complex, namely Amblyomma sculptum , Amblyomma mixtum and Amblyomma patinoi (Parola et al ., ; Szabó et al ., ; Labruna et al ., ; Faccini‐Martínez et al ., ).…”