First detection of Rickettsia felis in Ctenocephalides felis fleas parasitizing rats in Cyprus

Rickettsia felis was identified by polymerase chain reaction amplification and DNA sequencing analysis in Ctenocephalides felis fleas parasitizing rats in Cyprus. Murine typhus caused by R. typhi was believed to be the only flea-transmitted rickettsiosis on the island. This is the first report of this pathogen in southeastern Europe.     

Rickettsia felis and Bartonella henselae in fleas from Lebanon

A total of 155 fleas collected in 2009 in Lebanon from 16 cats (104 Ctenocephalides felis specimens, 1 C. canis specimen) and 2 dogs (50 C. canis specimens) were tested for the presence of Rickettsia spp. and Bartonella spp. using molecular methods, including real-time quantitative polymerase chain reaction (PCR), regular PCR, and sequencing of amplified PCR products. Rickettsia felis, the agent of the emerging flea-borne spotted fever in humans, was identified in 17 (16%) C. felis cat fleas. Bartonella henselae, an agent of cat scratch disease, was identified in three (2.9%) C. felis. Our results emphasize the potential risk of these emerging flea-borne infections in Lebanon.     

Identification of Rickettsia felis in the salivary glands of cat fleas

Rickettsia felis, a flea-associated rickettsial pathogen, has been identified in many tissues, including the digestive and reproductive tissues, within the cat flea, Ctenocephalides felis. We utilized transmission electron microscopy and polymerase chain reaction to identify R. felis in the salivary glands of fed fleas and further define the distribution of R. felis within the arthropod host. We identified Rickettsia-like organisms in salivary glands using electron microscopy. Sequence analysis of portions of the Rickettsia genus-specific 17-kDa antigen gene and R. felis plasmid confirmed the morphological identification of R. felis in cat flea salivary glands. This is the first report of R. felis in tissues critical for horizontal transmission of rickettsiae.     

First molecular detection of Rickettsia felis in fleas from Algeria

Fleas collected in Algeria in the district of Oran between July and September 2003 were tested by polymerase chain reaction for the presence of Rickettsia spp. DNA using primers amplifying gltA and OmpA genes. Two gltA sequences identical to those of an emerging pathogen, Rickettsia felis, were detected including i) R. felis California 2 in Ctenocephalides canis from rodents and ii) R. felis RF2125 in Archeopsylla erinacei from hedgehogs.     

Polygenic detection of Rickettsia felis in cat fleas (Ctenocephalides felis) from Israel

The presence of Rickettsia felis, an emerging bacterial pathogen, was investigated in 79 cat flea (Cteno-cephalides felis) pools from Israel (5 to 20 fleas each) by polymerase chain reaction (PCR) and sequencing of 5 different genes. Amplified targets included both metabolic (gltA and fusA) and surface antigen (ompA, ompB, and the 17-kDa antigen) genes. R. felis DNA was detected in 7.6% of the flea pools. Two genotypes similar in their housekeeping gene sequences but markedly different in their surface antigenic genetic milieus were characterized. This is the first detection of this flea-transmitted rickettsia within its vector in Israel and the Middle East. Although no clinical case has been reported in human beings in Israel to date, these findings suggest that this infection is prevalent in Israel.     

Rickettsia felis and Bartonella spp. in fleas from cats in Albania

Fleas can serve as vectors for bacterial pathogens like Bartonella and Rickettsia species, which have been isolated worldwide. However, the knowledge of the epidemiology of vector-borne diseases in general and thus on flea-borne diseases in Albania is limited. Therefore, from 78 free-roaming cats in Tirana, Albania, fleas (371 Ctenocephalides felis and 5 Ctenocephalides canis) were collected to examine them for the presence of Rickettsia and Bartonella species. Ten of the 371 C. felis (2.7%) were positive for Rickettsia felis, and 24 (6.5%) for Bartonella spp. (B. henselae and B. clarridgeiae). In total, fleas from 15 cats (19.2%) were positive for either one or the other of the pathogens. The results of this study provided evidence for the presence of R. felis (causing flea-borne spotted fever) and Bartonella spp. (causing cat scratch disease) in Albania. Thus, these infectious diseases should be considered as differential diagnoses when febrile symptoms are presented, especially after contact with cats or their fleas.     

Bartonella clarridgeiae, B. henselae and Rickettsia felis in fleas from Morocco

A total of 554 fleas were collected in the Moroccan Casablanca and Tiznit regions from domesticated animals and ruminants between August 2007 and October 2008 and were tested for the presence of Rickettsia spp. and Bartonella spp. using molecular methods. For the first time in Morocco, we found Rickettsia felis, the agent of flea-borne spotted fever in Ctenocephalides felis; B. henselae, an agent of cat scratch disease; and Bartonella clarridgeiae, a cat pathogen and potentially a human pathogen.     

Rickettsia felis in Ctenocephalides felis from Argentina

This article reports on the detection of Rickettsia felis in Argentina in Ctenocephalides felis fleas collected from a dog and analyzed by polymerase chain reaction (PCR) amplification and DNA sequencing.     

Detection of Rickettsia felis and Rickettsia typhi and seasonal prevalence of fleas collected from small mammals at Gyeonggi Province in the Republic of Korea

Fleas were collected from live-captured small mammals to identify flea-borne pathogens, host associations, and seasonal prevalence of flea species, as part of the 65th Medical Brigade rodent-borne disease surveillance program at 20 military installations and training sites, Gyeonggi Province, Republic of Korea, 2005-2007. A total of 1251 fleas were recovered from 2833 small mammals. Apodemus agrarius, the striped field mouse, accounted for 93.1% (2,637/2,833) of all small mammals captured, followed by Crocidura lasiura (3.1%), Mus musculus (1.3%), Microtus fortis (0.7%), Myodes regulus (0.7%), Micromys minutus (0.5%), Rattus norvegicus (0.4%), Tscherskia triton (0.1%), Apodemus peninsulae (< 0.1%), Rattus rattus (< 0.1%), and Mogera robusta (< 0.1%). A total of 6/11 species of mammals captured were infested with fleas with infestation rates ranging from a high of 26.3% (A. agrarius and M. regulus) to a low of 5.3% (M. fortis). Flea indices among infested mammals were highest for R. norvegicus (2.50), followed by C. lasiura (2.20), A. agrarius (1.71), M. regulus (1.20), M. musculus (1.0), and M. fortis (1.0). The predominant flea species collected were Stenoponia sidimi (56.5%), followed by Ctenophthalmus congeneroides (38.3%) and Rhadinopsylla insolita (3.9%). The minimum field infection rates [number of positive pools/total number of fleas (600)] for Rickettsia typhi and for Rickettsia felis were 1.7% and 1.0%, respectively.     

Rickettsia felis in Ctenocephalides felis from Guatemala and Costa Rica

Rickettsia felis is an emerging human pathogen associated primarily with the cat flea Ctenocephalides felis. In this study, we investigated the presence of Rickettsia felis in C. felis from Guatemala and Costa Rica. Ctenocephalides felis were collected directly from dogs and cats, and analyzed by polymerase chain reaction for Rickettsia-specific fragments of 17-kDa protein, OmpA, and citrate synthase genes. Rickettsia DNA was detected in 64% (55 of 86) and 58% (47 of 81) of flea pools in Guatemala and Costa Rica, respectively. Sequencing of gltA fragments identified R. felis genotype URRWXCal(2) in samples from both countries, and genotype Rf2125 in Costa Rica. This is the first report of R. felis in Guatemala and of genotype Rf2125 in Costa Rica. The extensive presence of this pathogen in countries of Central America stresses the need for increased awareness and diagnosis.     

Characterization of Rickettsia tsutsugamushi strains in two species of naturally infected, laboratory-reared chiggers

The strains of Rickettsia tsutsugamushi found in naturally infected, laboratory-reared Leptotrombidium (Leptotrombidium) arenicola and L. (L.) fletcheri chiggers were characterized by direct immunofluorescence (FA) and by mouse and monkey virulence tests. The strains existing in the L. (L.) arenicola chiggers consisted of different combinations of TA716, TA763, TA686, Karp, and Kato. In addition to these five strains, Gilliam was found in the L. (L.) fletcheri chiggers. Results indicate that individual chiggers can be simultaneously infected with several antigenic strains of R. tsutsugamushi. Although these antigens appear to remain stable within familial lines when several generations were viewed, the antigenic patterns observed in two succeeding generations did not always correlate. This variable expression of antigens was considered to be due to a quantitative fluctuation from one generation to the next in the strains of rickettsiae combined with a lack of sensitivity of the direct FA test in detecting small numbers of antigenically different rickettsiae. Phenotypic variation was considered to be a less probable explanation. Morbidity and mortality were minimal in ICR mice fed upon by individual chiggers of either species, but infection rates were 85-99%. Tissue suspensions prepared from mice infected by L. (L.) arenicola produced higher mortality and longer duration of illness in mice than those prepared from L. (L.) fletcheri-infected mice. Silvered leaf and cynomolgus monkeys were fed upon by the two species of chiggers or inoculated with the mouse tissue suspensions. In both cases, minimal clinical responses were observed.     

Urban focus of Rickettsia typhi and Rickettsia felis in Los Angeles, California

Classic murine typhus, caused by Rickettsia typhi, is endemic in the continental United States in areas of Texas and southern California. We conducted an environmental investigation in an urban area of Los Angeles identified as the probable exposure site for a case of murine typhus. Four Rattus norvegicus heavily infested with Xenopsylla cheopis (average 32.5 fleas per animal, range 20-42) were trapped, and fleas, blood, and tissues were collected. DNAs from all specimens were tested for R. typhi and Rickettsia felis using a TaqMan assay targeting the rickettsial citrate synthase gene. Although rickettsiemia was not detected, DNA of R. felis was detected in at least one tissue from each rat. Tissues from 3 rats were also positive for R. typhi DNA. R. typhi and R. felis DNAs were detected in fleas collected from each animal with average minimal infection rates of 10% and 32.3%, respectively. Although R. typhi still circulates in urban Los Angeles in the classic Oriental flea-rat cycle, R. felis is more prevalent, even in this association.     

Molecular detection of Rickettsia felis, Bartonella henselae, and B. clarridgeiae in fleas from domestic dogs and cats in Malaysia

The presence of Rickettsia felis, Bartonella henselae and B. clarridgeiae in 209 fleas (Ctenocephalides felis) obtained from domestic cats and dogs in several locations in Malaysia was investigated in this study. Using a polymerase chain reaction specific for the citrate synthase (gltA) and 17-kD antigenic protein (17kD) genes of rickettsiae, we detected R. felis DNA in 6 (2.9%) fleas. For detection of bartonellae, amplification of the heme-binding protein (pap31) and riboflavin synthase (ribC) genes identified B. henselae and B. clarridgeiae DNA in 24 (11.5%) and 40 (19.1%) fleas, respectively. The DNA of B. henselae and B. clarridgeiae was detected in 10 (4.8%) fleas. Two B. henselae genogroups (Marseille and Houston-1) were detected in this study; genogroup Marseille (genotype Fizz) was found more often in the fleas. The findings in this study suggest fleas as potential vectors of rickettsioses and cat-scratch disease in this country.     

First report of the isolation and molecular characterization of Rickettsia amblyommii and Rickettsia felis in Central America

During 2010, 15 adult ticks, identified as Amblyomma cajennense, were collected from horses in Cahuita and Turrialba districts, whereas 7 fleas, identified as Ctenocephalides felis, were collected from a dog in San Jose city, Costa Rica. In the laboratory, three A. cajennense specimens, two from Cahuita and one from Turrialba, were individually processed for rickettsial isolation in cell culture, as was a pool of seven fleas. Rickettsiae were successfully isolated and established in Vero cell culture from the three ticks and from a pool of seven fleas in C6/36 cell culture. The three tick isolates were genotypically identified as Rickettsia amblyommii, and the flea isolate was identified as Rickettsia felis through DNA sequencing of portions of the rickettsial genes gltA, ompA, and ompB of each isolate. In addition, other seven ticks were shown to contain rickettsial DNA. Polymerase chain reaction products of at least two of these ticks were sequenced and also showed to correspond to R. amblyommii. Overall, 66.7% (10/15) of the A. cajennense adult ticks were found to be infected with rickettsiae. This is the first report of a successful isolation in cell culture of R. amblyommii and R. felis from Central America.     

Rickettsia typhi and Rickettsia felis in Xenopsylla cheopis and Leptopsylla segnis parasitizing rats in Cyprus

Fleas collected from rats during a three-year period (2000-2003) in 51 areas of all provinces of Cyprus were tested by molecular analysis to characterize the prevalence and identity of fleaborne rickettsiae. Rickettsia typhi, the causative agent of murine typhus, was detected in Xenopsylla cheopis (4%) and in Leptopsylla segnis (6.6%). Rickettsia felis was detected in X. cheopis (1%). This is the first report of R. typhi in X. cheopis and L. segnis from rats, in Cyprus, and the first report of R. felis in X. cheopis in Europe. The role of fleas (mainly X. cheopis) was confirmed in the epidemiologic cycle of murine typhus in Cyprus by interrelation of current results with those of previous studies. The geographic distribution of fleas coincided with the geographic distribution of the pathogen they can harbor, which emphasizes the potential risk of flea-transmitted infections in Cyprus.     

Rickettsia mooseri infection in the fleas Leptopsylla segnis and Xenopsylla cheopis

Detailed observations on the acquisition and propagation of experimental Rickettsia mooseri infection in two species of fleas are presented. Rickettsia mooseri infection became detectable by means of the direct fluorescent antibody test about 2 days earlier in Leptopsylla segnis than in the putative vector, Xenopsylla cheopis. By the 6th day after the infective feeding, the entire lining and the lumen of the midgut in L. segnis contained masses of rickettsiae and the agent was being passed in the feces of the flea, whereas in X. cheopis these events did not occur until the 8th day. Basic behavioral differences in the two species of flea may explain these discrepancies and also influence their ability to serve as vectors of murine typhus. As a semisessile flea and sustained feeder, L. segnis only rarely attaches to a second individual and thus has an opportunity to acquire a heavy dose of rickettsiae, if feeding on a rickettsemic host. X. cheopis, in contrast, feeds rapidly and intermittently, even on man, and generally leaves its host soon thereafter, later returning to the same or another host to feed again. While L. segnis may not be as efficient a vector as X. cheopis regarding the intramurine cycle or transmission to man of murine typhus, the dense accumulation of infective feces on certain sites on the fur of the host raises the possibility of air-borne infection to man or rodent. Infection with R. mooseri had no effect on the survival of X. cheopis and L. segnis. Furthermore, no visible cytopathological effect was found in the paraffin-embedded sections of infected fleas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phylogenetic analysis of the rompB genes of Rickettsia felis and Rickettsia prowazekii European-human and North American flying-squirrel strains

The rickettsial outer membrane protein B (rompB) gene encodes the major surface antigens of Rickettsia species. We undertook sequencing and molecular analysis of the rompB gene of Rickettsia felis and a comparison with its homologs in spotted fever group (SFG) and typhus group (TG) rickettsiae, including the complete sequences of two North American flying squirrel strains and two European human strains of Rickettsia prowazekii. We sequenced 5,226 base pairs (bp) of the R. felis rompB, encoding a protein of 1,654 amino acids. We also sequenced 5,015 bp of rompB of the flying squirrel strains, encoding a protein of 1,643 amino acids. Analysis of the R. felis rompB gene sequence showed 10-13% divergence from SFG rickettsiae and 18% divergence from the TG rickettsiae. The rompB of all sequenced strains of R. prowazekii showed an overall similarity of 99.7-99.9%.