Rickettsial agents from parasitic dermanyssoidea (Acari: Mesostigmata)

Mites are often overlooked as vectors of pathogens, but have been shown to harbor and transmit rickettsial agents such as Rickettsia akari and Orientia tsutsugamushi. We screened DNA extracts from 27 mites representing 25 species of dermanyssoids for rickettsial agents such as Anaplasma, Bartonella, Rickettsia, and Wolbachia by PCR amplification and sequencing. DNA from Anaplasma spp., a novel Bartonella sp., Spiroplasma sp., Wolbachia sp., and an unclassified Rickettsiales were detected in mites. These could represent mite-borne bacterial agents, bacterial DNA from blood meals, or novel endosymbionts of mites.

[Rickettsia helvetica: an emerging tick-borne pathogen in Hungary and Europe]

Rickettsia helvetica belonging to spotted fever group rickettsiae was recently detected by polymerase chain reaction followed by sequencing in European sheep ticks (Ixodes ricinus) from Hungary. Current knowledge on these rickettsiae and the clinical and diagnostic aspects of R. helvetica infection is summarized. In acute cases, R. helvetica is generally responsible for flu-like symptoms. Nevertheless, recent data indicate that in chronic cases, these rickettsiae can be responsible for perimyocarditis resulting sudden cardiac death and might play a role in the pathogenesis of aortic valve disease. The diagnosis can be based on serological, molecular and histological methods. A summary of the information available from Hungary and neighbouring countries on the prevalence of tick-borne encephalitis virus, Anaplasma, Borrelia, Francisella, Rickettsia and Babesia infections in I. ricinus is also presented.

Rickettsia parkeri as a Paradigm for Multiple Causes of Tick-Borne Spotted Fever in the Western Hemisphere

Among the many contributions made to rickettsiology by entomologist and rickettsiologist Ralph R. Parker was his discovery in 1937 of a novel rickettsia isolated from the Gulf Coast tick, Amblyomma maculatum. This bacterium was subsequently characterized as a unique rickettsial species in 1965 and named Rickettsia parkeri in honor of its discoverer. During the next several decades R. parkeri was generally considered as one of several "nonpathogenic" spotted fever group (SFG) rickettsiae that resided in ticks of the United States. The identification of novel rickettsioses on other continents during the last two decades of the twentieth century provided important evidence of the frequent coexistence of multiple and unique tick-borne SFG rickettsiae sharing common geographic regions. Surprisingly, this paradigm, which was repeatedly demonstrated in Europe, Africa, and Australia during the last 10 years, had no confirmed correlate in the United States until 2002, when R. parkeri was isolated from a patient from the state of Virginia. Several pieces of epidemiologic, laboratory, and clinical evidence are compelling enough to suggest that this infection has occurred in other U.S. patients who reside within the range of the Gulf Coast tick. Just as important are new data indicating relatively high infection rates of A. maculatum ticks with R. parkeri, documenting the occurrence of R. parkeri in Amblyomma triste ticks from Uruguay, and providing evidence that other Amblyomma species might serve as efficient vectors of R. parkeri. The recognition of R. parkeri as a cause of disease in humans will hopefully encourage a closer examination for specific etiologies of tick-borne spotted fever rickettsioses in the United States and other countries of the Western Hemisphere.

Phylogenetic Analysis of a Novel Molecular Isolate of Spotted Fever Group Rickettsiae from Northern Peru: Candidatus Rickettsia andeanae

Phylogenetic analysis of five rickettsial genes (17-kDa gene, gltA, ompB, ompA, and sca4) from two molecular isolates of Candidatus Rickettsia andeanae from two ticks (Amblyomma maculatum and Ixodes boliviensis) collected from two domestic horses living in two separate locations in northern Peru (Coletas and Naranjo) was conducted to more clearly characterize this recently reported novel spotted fever group (SFG) rickettsia. Following nested polymerase chain reaction (PCR) amplification of the 17-kDa gene, gltA, ompB, ompA, and sca4, amplicons were purified, sequenced, and compared to those downloaded from GenBank. Phylogenetic analyses of the Candidatus Rickettsia andeanae sequences generated from 17-kDa gene (483 bp), gltA (1185 bp), ompA (1598 bp), ompB (4839 bp), and sca4 (2634 bp) demonstrated that they aligned strongly with those of SFG rickettsiae. Moreover, the sequences of these five genes most closely aligned with the following rickettsiae: ompA: Rickettsia sp RpA4 (98.03%), R. sp DnS28 (97.90%), and R. rhipicephali and R. massiliae (97.11%); ompB: R. aeschlimannii (97.22%), R. rhipicephali (97.20%), and R. sp Bar 29 (97.10%); and sca4: R. massiliae (97.8%), R. rhipicephali, and R. slovaca (97.7%). These results from the additional phylogenetic analyses of Candidatus Rickettsia andeanae confirm its inclusion within, and distance and uniqueness from, other known SFG rickettsiae.

Bartonella and Rickettsia in fleas and lice from mammals in South Carolina, U.S.A

Species in the genera Bartonella and Rickettsia are vector-borne pathogens of humans and domestic animals. The natural reservoirs and enzootic transmission cycles of these bacteria are poorly known in South Carolina. Thirteen species of lice and fleas were collected from urban animals and screened for the presence of Bartonella and Rickettsia by PCR amplification using genus-specific primers. Bartonella henselae was present in cat fleas (Ctenocephalides felis) from Virginia opossums (Didelphis virginiana) and a novel genotype of Bartonella was detected in Orchopeas howardi from an eastern gray squirrel (Sciurus carolinensis). We detected R. typhi and three novel genotypes Rickettsia in other species of fleas and lice. Rickettsia typhi, the causative agent of murine typhus, was detected in two pools of lice (Enderleinellus marmotae) from the woodchuck (Marmota monax). Cat fleas harbored one of two novel genotypes of Rickettsia. A third novel Rickettsia was detected in Orchopeas howardi from an eastern gray squirrel.

Tick species and tick-borne infections identified in population from a rural area of Spain

To determine the tick species that bite humans in the province of Soria (Spain) and ascertain the tick-borne pathogens that threaten people's health in that province, 185 tick specimens were collected from 179 patients who sought medical advice at health-care centres. The ticks were identified, and their DNA examined by PCR for pathogens. Most ticks were collected in autumn and spring (59 and 57 respectively). Nine species of ticks were identified, the most frequent being Dermacentor marginatus (55.7%), Ixodes ricinus (12.4%) and Rhipicephalus bursa (11.9%). Ninety-seven females, 66 males, 21 nymphs and one larva were identified. Twenty-six ticks carried DNA from Rickettsia spp. (11 Rickettsia slovaca, 6 Rickettsia spp. RpA4/DnS14, 1 Rickettsia massiliae/Bar29, and 8 unidentified); two ticks carried DNA from Borrelia burgdorferi sensu lato and seven ticks harboured DNA from Anaplasma phagocytophilum.

Purification and antigenic characteristics of a rickettsia-like organism from the oyster Crassostrea ariakensis

A rickettsia-like organism (RLO) has been suggested to be the etiological agent responsible for heavy losses of the oyster Crassostrea ariakensis Gould in China. Because of the lack of molluscan cell lines for in vitro culture of intracellular prokaryotes, antigenic analysis of RLOs has been limited by the inherent difficulties of their purification. In this report, we describe the use of differential speed centrifugation and renografin density gradient centrifugation to purify the RLO directly from infected oyster tissues. The purity and integrity of purified prokaryotes were validated by transmission electron microscopy. Thirteen major constituent proteins, with molecular weights ranging between 17 and 99 kDa, were electrophoretically identified by silver staining, and 8 major proteins were identified with Coomassie blue R staining. Specific mouse polyclonal antiserum was prepared for serological characterization of the RLO and was used in an immunoblot assay, and 3 major antigen groups were identified. The present results advance our knowledge of RLO protein antigens, and several proteins have been identified that could potentially be useful for diagnostic assays or for production of experimental immunostimulants.

Rickettsial skin disease: uncommon presentations

Rickettsioses occurring worldwide show a significant morbidity and mortality when not properly treated. Early diagnosis is mandatory for better outcome. Clinical symptoms and patient's history are essential, but uncommon presentation of these arthropod-borne diseases may be a challenge.

Tick-borne rickettsioses around the world: emerging diseases challenging old concepts

During most of the 20th century, the epidemiology of tick-borne rickettsioses could be summarized as the occurrence of a single pathogenic rickettsia on each continent. An element of this paradigm suggested that the many other characterized and noncharacterized rickettsiae isolated from ticks were not pathogenic to humans. In this context, it was considered that relatively few tick-borne rickettsiae caused human disease. This concept was modified extensively from 1984 through 2005 by the identification of at least 11 additional rickettsial species or subspecies that cause tick-borne rickettsioses around the world. Of these agents, seven were initially isolated from ticks, often years or decades before a definitive association with human disease was established. We present here the tick-borne rickettsioses described through 2005 and focus on the epidemiological circumstances that have played a role in the emergence of the newly recognized diseases.

Continous alert for rickettsiosis in Sicily: molecular characterization of Rickettsia sp. obtained from ticks and human beings (1986-2001)

Several strains of Rickettsia sp. were isolated from patients in western Sicily with MSF (Mediterranean Spotted Fever) as well as ticks. Strains isolated were examined by PCR and identified as belonging to R. conorii sp. Importantly a strain of Israeli Spotted Fever Rickettsiae, obtained from a tick, was also identified. Our data prove that strains other than the classical R. conorii also circulate in Sicily.

Characterization of a tandem repeat polymorphism in Rickettsia strains

Mediterranean spotted fever (MSF) is a tick-borne rickettsiosis caused by 'Rickettsia conorii complex' strains. In Portugal, R. conorii and Israeli tick typhus (ITT) are the aetiological agents of this disease. A novel 65 bp tandem repeat was identified by the analysis of the R. conorii Malish 7 whole genome sequence with an appropriate algorithm for searching for repeated sequences. The variable number tandem repeat (VNTR) was named VNTR Rc-65 and this locus was amplified by PCR and sequenced in order to characterize the repeat diversity within different rickettsial strains including Portuguese strains isolated from clinical and vector samples. The VNTR Rc-65 has seven alleles within the rickettsial strains studied and a diversity index value of 0.71, meaning that this locus has a great discriminatory capacity and therefore can be used for identification of closely related strains. PCR amplification of the Rc-65 locus can be used to differentiate between the Portuguese R. conorii Malish-like and Israeli tick typhus strains, enabling a more accurate and rapid identification of these rickettsial isolates.

Transmission of Rickettsia massiliae in the tick, Rhipicephalus turanicus

Rickettsia massiliae, strain Bar29, was detected in engorged female ticks of the Rhiphicephalus sanguineus group collected in Corsica, a French Mediterranean island. Ticks were identified by molecular analysis as Rhipicephalus turanicus (Pomerantsev) (Acari: Ixodidae). Twenty larvae of the second generation obtained from a R. massiliae-infected, engorged female were tested by polymerase chain reaction (PCR) and all were positive for R. massiliae. Larvae of the same cohort were fed on rabbits and specimens of subsequent stages of the second and third generation of ticks were tested by PCR. Both transovarial and transstadial transmission were demonstrated; the transovarial transmission rate was estimated at 100%. A high filial infection rate was demonstrated; 132 out of 134 larvae obtained from five infected females of the fourth generation were infected. When saliva samples from half-engorged Rh. turanicus of the second generation were tested by PCR, four out of five were positive. Rickettsia massiliae was detected in faeces of infected ticks by PCR and immunofluorescence assay, although no rickettsiae could be maintained in culture. Co-feeding/transsexual transmission of R. massiliae Bar29 was demonstrated by feeding male Rh. turanicus on a rabbit with Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) females (the latter were the only uninfected ticks available). Infection was subsequently detected in nine out of the thirteen females (69.2%). These results suggest that Rh. turanicus ticks are potential vectors and reservoirs for R. massiliae Bar29.

Presence of human past infections due to the Bar29 rickettsial strain in Southern Spain

The prevalence of past infections due to Bar29 rickettsial strain in a population from Southern Europe, as well as the possible risk factors associated to exposure to this rickettsia, were analysed. Among the 504 subjects included, global prevalence of past infections was 3.4%. Past infections were significantly more frequent in rural areas compared to urban (10.8 vs. 3.2%, OR 3.6 [1.1-12.3], P = .05), and suburban areas (10.8 vs. 1.9%, OR 6.2 [1.3-28.9], P = .02). In multivariate analysis the factors that were independently associated to past infection due to Bar29 strain were higher age (P = .037; factor of 1.033 [1.002-1.066]), and a risk profession (P = .005; OR = 5.7 [1.6-19.6]). These data point towards the presence of past Bar29 strain infections in a population from Southern Spain.

Simultaneous detection of "Rickettsia mongolotimonae" in a patient and in a tick in Greece

Rickettsia conorii, a spotted fever group rickettsia which is transmitted by Rhipicephalus sp. complex ticks, was considered until now the only pathogenic rickettsia prevalent in Greece. Here, we report the presence of "Rickettsia mongolotimonae" (proposed name) detected simultaneously in a patient and in a Hyalomma anatolicum excavatum tick, sampled on the patient.

Not only ‘Flinders Island’ spotted fever

AIM

To demonstrate that Flinders Island spotted fever (FISF), a spotted fever group rickettsial infection caused by Rickettsia honei, is found not only on Flinders Island (Bass Strait), Tasmania, but elsewhere in south-east Australia.

METHODS

Cases of FISF were identified by rickettsial serology, culture and the detection of rickettsial DNA via PCR. Isolates and PCR products were sequenced to identify the aetiological agent as R. honei.

RESULTS

Three new cases of FISF were detected outside of Flinders Island. One on Schouten Island, south of the Freycinet Peninsula, Tasmania, and two in south-eastern South Australia (McLaren Vale and Goolwa).

CONCLUSIONS

These cases show that FISF extends beyond Flinders Island and most likely has the same distribution across south-east Australia as its vector, the reptile tick Aponomma hydrosauri. FISF should be considered as a differential diagnosis in patients from south-eastern Australia presenting with fever, headache and rash following a tick bite.

Detection of Rickettsia, Borrelia, and Bartonella in Carios kelleyi (Acari: Argasidae)

Carios kelleyi (Colley & Kohls 1941), a tick associated with bats and bat habitats, has been reported to feed on humans, but there is little published data regarding the presence of vector-borne pathogens in these ticks. C. kelleyi nymphs and adults were collected from residential and community buildings in Jackson County, Iowa, and tested by polymerase chain reaction for Rickettsia, Borrelia, Bartonella, Coxiella, and Anaplasma. Rickettsia DNA was detected in 28 of 31 live ticks. Sequences of the 17-kDa and rOmpA genes suggest that this agent is a novel spotted fever group Rickettsia. Transstadial and transovarial transmission of this Rickettsia were demonstrated. The flagellin gene of a Borrelia, closely related to B. turicatae, was detected in one of 31 live ticks. The 16S-23S intergenic spacer region of Bartonella henselae also was detected in one of 31 live ticks. Coxiella or A. phagocytophilum DNA were not detected in these ticks.

Detection of Rickettsia, Borrelia, and Bartonella in Carios kelleyi (Acari: Argasidae)

Carios kelleyi (Colley & Kohls 1941), a tick associated with bats and bat habitats, has been reported to feed on humans, but there is little published data regarding the presence of vector-borne pathogens in these ticks. C. kelleyi nymphs and adults were collected from residential and community buildings in Jackson County, Iowa, and tested by polymerase chain reaction for Rickettsia, Borrelia, Bartonella, Coxiella, and Anaplasma. Rickettsia DNA was detected in 28 of 31 live ticks. Sequences of the 17-kDa and rOmpA genes suggest that this agent is a novel spotted fever group Rickettsia. Transstadial and transovarial transmission of this Rickettsia were demonstrated. The flagellin gene of a Borrelia, closely related to B. turicatae, was detected in one of 31 live ticks. The 16S-23S intergenic spacer region of Bartonella henselae also was detected in one of 31 live ticks. Coxiella or A. phagocytophilum DNA were not detected in these ticks.

Spotted fever group and typhus group rickettsioses in humans, South Korea

Multiplex-nested PCR and sequencing analysis indicated rickettsialike agents in serum specimens from febrile patients.

The presence of the nucleic acid of the spotted fever group (SPG) and typhus group (TG) rickettsiae was investigated in 200 serum specimens seropositive for SFG rickettsiae by multiplex-nested polymerase chain reaction with primers derived from the rickettsial outer membrane protein B gene. The DNA of SFG, TG, or both rickettsiae was amplified in the 24 serum specimens, and sequence analysis showed Rickettsia conorii, R. japonica, and R. felis in the specimens. R. conorii and R. typhi were found in 7 serum specimens, which indicated the possibility of dual infection in these patients. These findings suggest that several kinds of rickettsial diseases, including boutonneuse fever, rickettsialpox, R. felis infection, and Japanese spotted fever, as well as scrub typhus and murine typhus, are occurring in Korea.

Lymphangitis-associated rickettsiosis, a new rickettsiosis caused by Rickettsia sibirica mongolotimonae: seven new cases and review of the literature

BACKGROUND

Rickettsia sibirica mongolotimonae has been found in Hyalomma ticks in Inner Mongolia (in China) and Niger and in humans in France and South Africa. To date, only 3 cases of human infection have been reported.

METHODS

Patients received a diagnosis of R. sibirica mongolotimonae infection on the basis of culture and/or PCR results plus serological test results.

RESULTS

From January 2000 to June 2004, R. sibirica mongolotimonae infection was diagnosed in 7 patients. In 3 patients, the bacterium was cultivated from the inoculation eschar. The other 4 patients had cases that were diagnosed with use of PCR of samples obtained from the eschar (2 patients) or blood (2 patients), plus specific Western blot before (2 patients) and after (2 patients) cross-adsorption. The clinical presentation included fever (temperature, >38.5 degrees C), a maculopapular rash, and > or =1 inoculation eschar in 6 patients, enlarged regional lymph nodes in 4 patients, and lymphangitis in 3 patients. On the basis of the study of 9 cases, R. sibirica mongolotimonae infection differed from other tick-borne rickettsioses in the Mediterranean area in the following ways: it involved a specific incidence in the spring, the presence of 2 eschars in 2 (22%) of the patients, the presence of a draining lymph node in 5 (55%) of the patients, and lymphangitis expanding from the inoculation eschar to the draining node in 4 (44%) of the patients. The most recent patient in our series received a clinical diagnosis on the basis of such findings. All patients recovered without any sequelae.

CONCLUSIONS

We propose that this new rickettsiosis be named "lymphangitis-associated rickettsiosis." Lymphangitis-associated rickettsiosis should be considered in the differential diagnosis of tick-borne rickettsioses in Europe, Africa, and Asia.