Diversity of spotted fever group rickettsiae and their association with host ticks in Japan

Abstract

Spotted fever group (SFG) rickettsiae are obligate intracellular Gram-negative bacteria mainly associated with ticks. In Japan, several hundred cases of Japanese spotted fever, caused by Rickettsia japonica, are reported annually. Other Rickettsia species are also known to exist in ixodid ticks; however, their phylogenetic position and pathogenic potential are poorly understood. We conducted a nationwide cross-sectional survey on questing ticks to understand the overall diversity of SFG rickettsiae in Japan. Out of 2,189 individuals (19 tick species in 4 genera), 373 (17.0%) samples were positive for Rickettsia spp. as ascertained by real-time PCR amplification of the citrate synthase gene (gltA). Conventional PCR and sequencing analyses of gltA indicated the presence of 15 different genotypes of SFG rickettsiae. Based on the analysis of five additional genes, we characterised five Rickettsia species; R. asiatica, R. helvetica, R. monacensis (formerly reported as Rickettsia sp. In56 in Japan), R. tamurae, and Candidatus R. tarasevichiae and several unclassified SFG rickettsiae. We also found a strong association between rickettsial genotypes and their host tick species, while there was little association between rickettsial genotypes and their geographical origins. These observations suggested that most of the SFG rickettsiae have a limited host range and are maintained in certain tick species in the natural environment.

Rickettsia africae an Agent of African Tick Bite Fever in Ticks Collected from Domestic Animals in Eastern Cape, South Africa

“…Unlike most SFGR, infections with R. tamurae are not associated with high fever, generalized rash, lymphadenopathy as it is often seen in other spotted fever rickettsioses. R.tamurae was first isolated from A. testudinarium ticks in Japan and has the wild boar and domestic pigs as it primary host although it can also infest deer, cattle, other ungulates and domestic livestock as well as humans [47][48][49]. R. tamurae has been isolated from the skin biopsy specimen from wild boars and also in ticks [47].…”

“…R. tamurae infection according to Imaokaa et al [ 47 ] is associated with symptoms such as mild local inflammatory signs like swellings, erythema, redness heat and pain. Symptoms of R. tamurae infection mimics cellulitis with increased serum titers of antibody against the organism [ 48 ]. Unlike most SFGR, infections with R. tamurae are not associated with high fever, generalized rash, lymphadenopathy as it is often seen in other spotted fever rickettsioses.…”

Complete Genome Sequence of Rickettsia asiatica Strain Maytaro1284, a Member of Spotted Fever Group Rickettsiae Isolated from an Ixodes ovatus Tick in Japan

“…tamurae, R. monacensis, and R. asiatica , and several other uncharacterized rickettsial species/genotypes have been detected (4, 5). R. asiatica is the only named species of these whose genome sequence is not available.…”

“…R. asiatica , initially described as a Rickettsia strain IO-1 T , was first isolated from Ixodes ovatus ticks collected in Fukushima Prefecture, Japan, in 1993 (6, 7). A recent study revealed that R. asiatica had a strong host specificity, where it was detected only in I. ovatus (5).…”

Prevalence of spotted fever group rickettsiae in Poland

“…R. conorii, są kleszcze należące do jednego gatunku, podczas gdy innych (np. R. rickettsii) są kleszcze należące do kilku rodzajów [9].…”