Isolation of Rickettsia rhipicephali and Rickettsia bellii from Haemaphysalis juxtakochi Ticks in the State of São Paulo, Brazil

Abstract

In the present study, attempts to isolate Rickettsia in cell culture were performed individually in seven specimens of Haemaphysalis juxtakochi ticks collected in the state of São Paulo (southeastern Brazil). Rickettsia was successfully isolated by the shell vial technique and established in Vero cell culture from six ticks (six isolates). DNA extracted from infected cells of these isolates was tested by PCR and DNA sequencing, using genus-specific Rickettsia primers targeting the genes gltA, htrA, ompA, and ompB. After the generated sequences were compared with available sequences in GenBank, five out of the six isolates were identified as Rickettsia bellii (isolates HJ#1, HJ#2, HJ#3, HJ#4, and HJ#7). The sixth isolate (HJ#5) was closest to Rickettsia sp. strain R300, previously detected in H. juxtakochi in northern Brazil, and to Rickettsia rhipicephali, isolated from ticks in the United States. Following recent gene sequence-based criteria proposed for the identification of Rickettsia isolates, both isolate HJ#5 and strain R300 were identified as South American strains of R. rhipicephali, which was confirmed in this continent for the first time. Isolation of R. bellii from H. juxtakochi ticks, added to eight other tick species that have been reported to be infected with this bacterium in Brazil, indicates that R. bellii is indeed the most frequent Rickettsia species infecting ticks in Brazil. Currently, the role of both R. rhipicephali and R. bellii as human pathogens is regarded as unknown.

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

“…R. bellii has been the most frequent rickettsia species infecting ticks in Brazil, being reported in at least nine tick species (Labruna et al 2007c). In contrast to the present study, there has been substantial serological evidence that R. bellii produces infection in capybaras, which are often parasitized by A. dubitatum ).…”

“…Technically, these diagnostic procedures have not allowed a precise identification of the rickettsial agent; at best, defining SFG rickettsiosis, since the three employed techniques could be efficient for any spotted fever group Rickettsia species. During the last six years, four SFG species other than R. rickettsii were reported in Brazil, two of them recognized as agents of spotted fever rickettsiosis in humans (R. parkeri and R. felis) (Raoult et al 2001, b, Horta et al 2005, Labruna et al 2007c, Silveira et al 2007). Thus, it is possible that some of the BSF cases diagnosed in the state of São Paulo could be caused by other SFG rickettsia, such as R. parkeri or R. felis.…”

Survey of rickettsiae in humans, dogs, horses, and ticks in Northern Paraná, Brazil

“…bellii has been the most common rickettsia found infecting ticks in Brazil, including those tick species more frequently associated with canine and humans infestation, such as A. aureolatum, Amblyomma ovale, Amblyomma oblonguttatum, and Amblyomma scapturatum (LABRUNA et al, 2005, PINTER;. However, this Rickettsia species are not currently recognized as human or animal pathogen 2007a, 2007b.…”

Infección por rickettsia en capibaras (Hydrochoerus hydrochaeris) de São Paulo, Brasil: evidencia serológica de infección por Rickettsia bellii y Rickettsia parkeri

“…These include the SFG species R. amblyommii in the state of Rondônia (10) and R. rhipicephali in Rondônia and São Paulo (11,12). R. bellii, a species classified neither in the TG or SFG, has also been reported in Rondônia and São Paulo (7,10,12). While serological evidence of canine infection due to R. amblyommii and R. rhipicephali has been reported in the state of Rondônia (13) there has been no evidence for R. bellii natural infection in vertebrate hosts.…”