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[change in the frequency of blocking in xenopsylla cheopis (aphaniptera) fleas infected with the causative agent of plague under the action of indandione blood anticoagulants]. 1979583178
suncus murinus. observations on ecology, distribution, status to plague in bombay.the common house shrew suncus murinus has been shown to play an important role in maintenance and perpetuation of plague infection by earlier plague workers. with the control of human plague there is no knowledge about foci of plague in small mammals associated with man. present study was carried out to fill in this lacuna. studies carried out in the present paper reveal that s. murinus does not harbour any plague infection in bombay. this species is widely distributed in bombay and is found to ...19892723422
use of dna hybridizations probes for detection of the plague bacillus (yersinia pestis) in fleas (siphonaptera: pulicidae and ceratophyllidae).the detection of active plaque in nature relies primarily on demonstration of the etiologic agent of the disease. yersinia pestis, in the flea vectors and susceptible mammalian hosts. a live animal assay is currently used for identification of a y. pestis virulence antigen that is not expressed in the flea. we have found that dna hybridization probes specific for y. pestis, used in very simple sample preparation schemes, allow detection of y. pestis in three species of fleas as well as tissues o ...19892769715
[pathogenic action of the plague microbe on the flea xenopsylla cheopis and the ultrastructure of the causative agent at various times of its stay in the vector].pathology of gastro-intestinal tract of xenopsylla cheopis fleas infected with plague microbe was determined by means of electron microscopy. ultrastructure of plague microbe during different periods of its stay in the vector was studied.19863703571
[characteristics of the multiplication of a virulent strain of the plague microbe in xenopsylla cheopis fleas infected parenterally].xenopsylla cheopis fleas infected parenterally with the virulent strain of plague microbe of gerbil variant preserved the agent to the end of their lives. in the body cavity the microbes retained their ability for reproduction which was, however, limited. during the first seven days after the infection the number of microbes slightly increased and later became stabilized. its mean indices (mean g) varied within the limits of 500 to 2000 microbe cells per 1 individual, maximum index rarely exceed ...19854047718
effect of differences in ambient temperature upon the fate of pasteurella pestis in xenopsylla cheopis. 19695789111
evidence for the extinction of plague in hawaii.plague (infection by yersinia pestis) was present in hawaii for the period 1899-1957 and caused at least 370 fatalities. the first infections came from immigrant commensal rats, probably rattus rattus and rattus norvegicus, on ships from the orient. both species were already established in hawaii and became the widespread local carriers of plague, supplemented by rattus exulans which had colonized the islands in ancient polynesian times. the flea xenopsylla vexabilis arrived with r. exulans, and ...19846364800
[characteristics of microbial multiplication in parenterally infected xenopsylla cheopis (siphonaptera) fleas].being inoculated parenterally various microbes cause the fleas x. cheopis a stable infection which, as a rule, is preserved in experimental insects to the end of life. reproducing intensively listeria monocytogenes and salmonella typhimurium caused the death of all ectoparasites in 3 to 5 days. the increase in abundance of escherichia coli, yersinia pseudotuberculosis, y. enterocolitica and vaccine strains of y. pestis "ev" and francisella tularensis went on gradually and infected fleas lived up ...19806780964
plague in central java, indonesia.plague in man occurred from 1968 to 1970 in mountain villages of the boyolali regency in central java. infected fleas, infected rats, and seropositive rats were collected in villages with human plague cases. subsequent isolations of yersinia pestis and seropositive rodents, detected during investigations of rodent plague undertaken by the government of indonesia and the who, attested to the persistence of plague in the region from 1972 to 1974.since 1968, the incidence of both rodent and human p ...19806968252
[histological study of xenopsylla cheopis fleas infected with the ulegeic subspecies of the plague microbe, yersinia pestis ulegeica].the plague microbe of the ulegei subspecies is able to cause the stable infection of fleas of x. cheopis, which is accompanied by the formation of "block" in most individuals. the preservation of the plague agent in these ectoparasites is characterized by its variation in the number that undergoes cyclic changes depending on the feeding rate and digestion. the bloodsucking is accompanied by the excretion of some microbes and by the reproduction of the remaining ones in the midgut and proventricu ...19807402697
[epidemiology of the plague. changes in the concept in research of infection chains since the discovery of the plague pathogen in 1894].three major plague epidemics have been recorded worldwide up to this day: the justinian plague in the 6th century, the black death in the 14th century and the recent 20th century pandemic. the latter occurred at a time of advanced microbiological knowledge which permitted the etiology and the modes of transmission and spread of this bacterial infectious disease to be clarified. the present thesis is an attempt to describe the changes in plague research that occurred during that period of time. w ...19938142341
effect of yersinia pestis infection on temperature preference and movement of the oriental rat flea (xenopsylla cheopis) (siphonaptera: pulicidae).previous laboratory studies have shown that inoculation of bacterial endotoxin into the hemocoel of some arthropods, or natural infection by a number of pathogens, causes them to seek out a higher ambient temperature. this phenomenon has been called behavioral fever. yersinia pestis is an endotoxin-producing bacterium that relies on infection of fleas for transmission. behavioral fever in fleas might enhance the transmission of plague if infected fleas were induced to seek out a warm-bodied host ...19938433328
entomological and rodent surveillance in plague-suspected areas during september 1994 and thereafter.studies carried out in the states of maharashtra, gujarat, uttar pradesh and union territory of delhi after the bubonic plague outbreak during 1994 revealed the presence of seven species of rodents, viz. rattus rattus, r. norvegicus, mus. musculus, tatera indica, suncus murinus, bandicoota bengalensis and b. indica. the flea species encountered were xenopsylla cheopis and x. astia. the x. cheopis and x. astia index recorded in different areas of beed district of maharashtra; surat, vadodra and b ...19979556751
entomological and rodent surveillance of suspected plague foci in agro-environmental and feral biotopes of a few districts in maharashtra and gujarat states of india.studies carried out on entomological and rodent surveillance in agroclimatic and feral biotopes of five districts of maharashtra and two districts of gujarat revealed that the terrain features of the seven districts surveyed were conducive to wild rodent species, tatera indica, a natural reservoir of plague and vector flea species, xenopsylla cheopis. a total of 214 tatera indica and three bandicoota bengalensis were collected from burrows by the digging method and 89 rat fleas were retrieved. t ...19979789784
[differences in the blocking of the proventriculus in male and female xenopsylla cheopis (siphonaptera: pulicidae)].frequency of block formation was studied in xenopsylla cheopis infected with the triptophan-dependent and the typical strains of yersinia pestis from the mountain-altai natural plague focus. it was shown that the rate of blocked males in comparison with that of females was statistically higher. in experiments with the triptophan-dependent strain the frequency of blocking in males was 40.9% and exceeded that in females at four times. the highest rate of blocked males was marked at 7-10th and that ...200010750156
a combination of different polymerase chain reaction (pcr) assays for the presumptive identification of yersinia pestis.a combination of four polymerase chain reaction (pcr) assays targeting the yersinia pestis-specific plasmoidal genes of the fraction 1 capsular antigen and plasminogen activator/coagulase, the gene of the v antigen of the yersinia virulence plasmid, and the chromosomal 16s rrna gene was evaluated for the identification of y. pestis isolates. all four assays were subjected to the same sample preparation technique, reagents and cycling conditions. eighteen y. pestis, 66 y. pseudotuberculosis, 40 y ...200011075545
quantitative competitive pcr as a technique for exploring flea-yersina pestis dynamics.we used a quantitative competitive polymerase chain reaction assay to quantify yersinia pestis loads in fleas and bacteremia levels in mice that were used as sources of infectious blood meals for feeding the fleas. xenopsylla cheopis, the oriental rat flea, achieved higher infection rates, developed greater bacterial loads, and became infectious more rapidly than oropsylla montana, a ground squirrel flea. both flea species required about 10(6) y. pestis cells per flea to be able to transmit to m ...200011289663
studies on pasteurella pestis in fleas. iv. experimental blocking of xenopsylla vexabilis hawaiiensis and xenopsylla cheopis with an avirulent strain. 195613365622
poor vector competence of fleas and the evolution of hypervirulence in yersinia pestis.population genetics and comparative genomics analyses of the pathogenic yersinia species have indicated that arthropodborne transmission is an evolutionarily recent adaptation in yersinia pestis, the agent of plague. we show that the infectivity of y. pestis to its most proficient vector, the rat flea xenopsylla cheopis, and subsequent transmission efficiency are both low. the poor vector competence of fleas likely imposed selective pressure that favored the emergence and continued maintenance o ...200515871125
plague from eating raw camel liver.we investigated a cluster of 5 plague cases; the patients included 4 with severe pharyngitis and submandibular lymphadenitis. these 4 case-patients had eaten raw camel liver. yersinia pestis was isolated from bone marrow of the camel and from jirds (meriones libycus) and fleas (xenopsylla cheopis) captured at the camel corral.200516229781
serotype differences and lack of biofilm formation characterize yersinia pseudotuberculosis infection of the xenopsylla cheopis flea vector of yersinia pestis.yersinia pestis, the agent of plague, is usually transmitted by fleas. to produce a transmissible infection, y. pestis colonizes the flea midgut and forms a biofilm in the proventricular valve, which blocks normal blood feeding. the enteropathogen yersinia pseudotuberculosis, from which y. pestis recently evolved, is not transmitted by fleas. however, both y. pestis and y. pseudotuberculosis form biofilms that adhere to the external mouthparts and block feeding of caenorhabditis elegans nematode ...200616428415
surveillance of egyptian fleas for agents of public health significance: anaplasma, bartonella, coxiella, ehrlichia, rickettsia, and yersinia pestis.serologic surveys in egypt have documented human and animal exposure to vector-borne bacterial pathogens, but the presence and distribution of these agents in arthropods has not been determined. between july 2002 and july 2003, fleas were collected from 221 mammals trapped in 17 cities throughout egypt. a total of 987 fleas were collected, representing four species (ctenocephalides felis, echidnophaga gallinacea, leptopsylla segnis, and xenopsylla cheopis); 899 of these fleas were x. cheopis fro ...200616837707
zoonotic focus of plague, algeria.after an outbreak of human plague, 95 xenopsylla cheopis fleas from algeria were tested for yersinia pestis with pcr methods. nine fleas were definitively confirmed to be infected with y. pestis biovar orientalis. our results demonstrate the persistence of a zoonotic focus of y. pestis in algeria.200617326957
source of host blood affects prevalence of infection and bacterial loads of yersinia pestis in fleas.yersinia pestis, the etiological agent of plague, is transmitted by multiple flea species. previous studies have reported wide variability in transmission efficiency among competent vectors. however, it is unclear to what extent such variation is explained by methodological differences among studies. to optimize an artificial feeding system where fleas are infected with controlled numbers of y. pestis under standardized laboratory conditions that could be used to systematically compare vector ef ...200818826038
[study on the epidemiological significance related to community-structural difference of the rat plague host and vectors in western yunnan, china].to study the epidemiological significance of community-structural difference regarding both small mammal and flea communities on rattus flavipectus in dehong and baoshan areas, yunnan province, during 1982 to 1996.200818843991
bacterial communities associated with flea vectors of plague.the microbial flora associated with fleas may affect their ability to transmit specific pathogens, including yersinia pestis, and also could be used to develop paratransgenesis-based approaches to interfere with transmission. to begin addressing this hypothesis, the microbial flora associated with the relatively efficient y. pestis vectors xenopsylla cheopis (rothschild) (siphonaptera: pulicidae) and oropsyllamontana (baker) (siphonaptera: ceratophyllidae), and the inefficient vector ctenocephal ...200919960708
effects of temperature on early-phase transmission of yersina pestis by the flea, xenopsylla cheopis.sharp declines in human and animal cases of plague, caused by the bacterium yersinia pestis (yersin), have been observed when outbreaks coincide with hot weather. failure of biofilm production, or blockage, to occur in the flea, as temperatures reach 30 degrees c has been suggested as an explanation for these declines. recent work demonstrating efficient flea transmission during the first few days after fleas have taken an infectious blood meal, in the absence of blockage (e.g., early-phase tran ...201121485382
evaluation of the murine immune response to xenopsylla cheopis flea saliva and its effect on transmission of yersinia pestis.arthropod-borne pathogens are transmitted into a unique intradermal microenvironment that includes the saliva of their vectors. immunomodulatory factors in the saliva can enhance infectivity; however, in some cases the immune response that develops to saliva from prior uninfected bites can inhibit infectivity. most rodent reservoirs of yersinia pestis experience fleabites regularly, but the effect this has on the dynamics of flea-borne transmission of plague has never been investigated. we exami ...201425255317
detection of rickettsia felis, rickettsia typhi, bartonella species and yersinia pestis in fleas (siphonaptera) from africa.little is known about the presence/absence and prevalence of rickettsia spp, bartonella spp. and yersinia pestis in domestic and urban flea populations in tropical and subtropical african countries.201425299702
new method for plague surveillance using polymerase chain reaction to detect yersinia pestis in fleas.yersinia pestis, the plague bacillus, infects a variety of mammals throughout the world and is transmitted by fleas. we developed a polymerase chain reaction (pcr) test using primers designed from the y. pestis plasminogen activator gene to directly detect plague-infected fleas. as few as 10 y. pestis cells were detected, even in the presence of flea tissue, by pcr and then agarose gel electrophoresis and ethidium bromide staining. the feasibility of the assay was demonstrated by using naturally ...19938314993
comparative ability of oropsylla montana and xenopsylla cheopis fleas to transmit yersinia pestis by two different mechanisms.transmission of yersinia pestis by flea bite can occur by two mechanisms. after taking a blood meal from a bacteremic mammal, fleas have the potential to transmit the very next time they feed. this early-phase transmission resembles mechanical transmission in some respects, but the mechanism is unknown. thereafter, transmission occurs after yersinia pestis forms a biofilm in the proventricular valve in the flea foregut. the biofilm can impede and sometimes completely block the ingestion of blood ...201728081130
effectiveness of fipronil as a systemic control agent against xenopsylla cheopis (siphonaptera: pulicidae) in madagascar.fipronil was evaluated as a systemic control agent for the rat flea xenopsylla cheopis (rothschild), the main vector of yersinia pestis (yersin), the causative agent of plague, in madagascar. the effectiveness of fipronil as a systemic control agent against x. cheopis was assessed by determining the toxicity values of the "lethal dose 50" (ld50). two techniques were used to evaluate the systemic action of the insecticide on the vector: 1) an artificial feeding device filled with blood-fipronil m ...201728122816
preliminary survey of ectoparasites and associated pathogens from norway rats in new york city.the norway rat (rattus norvegicus) is a reservoir of many zoonotic pathogens and lives in close proximity to humans in urban environments. human infection with rodent-borne disease occurs either directly through contact with a rat or its excreta, or indirectly via arthropod vectors such as fleas and ticks. here, we report on the diversity and abundance of ectoparasitic arthropod species and associated pathogenic bacteria from 133 norway rats trapped over a 10-mo period in manhattan, new york, ny ...201526336309
evaluation of the role of the opggh operon in yersinia pseudotuberculosis and its deletion during the emergence of yersinia pestis.the opggh operon encodes glucosyltransferases that synthesize osmoregulated periplasmic glucans (opgs) from udp-glucose, using acyl carrier protein (acp) as a cofactor. opgs are required for motility, biofilm formation, and virulence in various bacteria. opgh also sequesters ftsz in order to regulate cell size according to nutrient availability. yersinia pestis (the agent of flea-borne plague) lost the opggh operon during its emergence from the enteropathogen yersinia pseudotuberculosis. when ex ...201526150539
evaluation of the effect of host immune status on short-term yersinia pestis infection in fleas with implications for the enzootic host model for maintenance of y. pestis during interepizootic periods.plague, a primarily flea-borne disease caused by yersinia pestis, is characterized by rapidly spreading epizootics separated by periods of quiescence. little is known about how and where y. pestis persists between epizootics. it is commonly proposed, however, that y pestis is maintained during interepizootic periods in enzootic cycles involving flea vectors and relatively resistant host populations. according to this model, while susceptible individuals serve as infectious sources for feeding fl ...201425276941
effects of temperature on the transmission of yersinia pestis by the flea, xenopsylla cheopis, in the late phase period.traditionally, efficient flea-borne transmission of yersinia pestis, the causative agent of plague, was thought to be dependent on a process referred to as blockage in which biofilm-mediated growth of the bacteria physically blocks the flea gut, leading to the regurgitation of contaminated blood into the host. this process was previously shown to be temperature-regulated, with blockage failing at temperatures approaching 30°c; however, the abilities of fleas to transmit infections at different t ...201121958555
biofilm formation is not required for early-phase transmission of yersinia pestis.early-phase transmission (ept) is a recently described model of plague transmission that explains the rapid spread of disease from flea to mammal host during an epizootic. unlike the traditional blockage-dependent model of plague transmission, ept can occur when a flea takes its first blood meal after initially becoming infected by feeding on a bacteraemic host. blockage of the flea gut results from biofilm formation in the proventriculus, mediated by the gene products found in the haemin storag ...201020395271
analysis of hmsh and its role in plague biofilm formation.the yersinia pestis hms(+) phenotype is a manifestation of biofilm formation that causes adsorption of congo red and haemin at 26 degrees c but not at 37 degrees c. this phenotype is required for blockage of the proventricular valve of the oriental rat flea and plays a role in transmission of bubonic plague from fleas to mammals. genes responsible for this phenotype are located in three separate operons, hmshfrs, hmst and hmsp. hmsh and hmsf are outer membrane (om) proteins, while the other four ...201020093287
evaluation of a yersinia pestis mutant impaired in a thermoregulated type vi-like secretion system in flea, macrophage and murine models.type vi secretion systems (t6sss) have been identified recently in several gram-negative organisms and have been shown to be associated with virulence in some bacterial pathogens. a t6ss of yersinia pestis co92 (locus ypo0499-ypo0516) was deleted followed by investigation of the phenotype of this mutation. we observed that this t6ss locus of y. pestis was preferentially expressed at 26 degrees c in comparison to 37 degrees c suggesting a possible role in the flea cycle. however, we found that th ...200919716410
studies of vector competency and efficiency of north american fleas for yersinia pestis: state of the field and future research needs.the etiological agent of plague, yersinia pestis, is most commonly transmitted by the bite of infectious fleas. to date, at least 28 flea species occurring in north america have been experimentally confirmed as vectors of y. pestis. transmission efficiency differs among species and also between different studies of a single species. these differences may, however, in large part reflect nonstandardized experimental conditions used during the first half of the 20th century when such studies were c ...200919645275
potential roles of pigs, small ruminants, rodents, and their flea vectors in plague epidemiology in sinda district, eastern zambia.a cross-sectional study was conducted in the eastern part of zambia that previously reported a plague outbreak. the aim of the study was to evaluate the potential role of pigs, goats, and sheep as sero-surveillance hosts for monitoring plague, and to investigate the flea vectors and potential reservoir hosts to establish the current status of plague endemicity in the district. serum samples were collected from 96 rodents, 10 shrews, 245 domestic pigs, 232 goats, and 31 sheep, whereas 106 organs ...201728399281
early-phase transmission of yersinia pestis by cat fleas (ctenocephalides felis) and their potential role as vectors in a plague-endemic region of uganda.in recent decades, the majority of human plague cases (caused by yersinia pestis) have been reported from africa. in northwest uganda, which has had recent plague outbreaks, cat fleas (ctenocephalides felis) have been reported as the most common fleas in the home environment, which is suspected to be a major exposure site for human plague in this country. in the past, c. felis has been viewed as only a nuisance-biting insect because limited laboratory studies suggested it is incapable of transmi ...200818541775
examining the vector-host-pathogen interface with quantitative molecular tools.we developed pcr assays to detect and quantitate yersinia pestis, the bacterial agent of plague, in flea vector and mammalian host tissues. bacterial numbers in fleas, fleabite sites, and infected lymph nodes were determined using real-time pcr with primers and probes for a gene target on a multi-copy plasmid specific to y. pestis. tissue-matched standard curves used to determine absolute bacterial numbers in unknown samples were linear over at least five orders of magnitude. the methods were ap ...200818287752
early-phase transmission of yersinia pestis by unblocked xenopsylla cheopis (siphonaptera: pulicidae) is as efficient as transmission by blocked fleas.for almost a century, the oriental rat flea, xenopsylla cheopis (rothschild) (siphonaptera: pulicidae), was thought to be the most efficient vector of the plague bacterium yersinia pestis (yersin). approximately 2 wk after consuming an infectious bloodmeal, a blockage often forms in the flea's proventriculus, which forces the flea to increase its biting frequency and consequently increases the likelihood of transmission. however, if fleas remain blocked and continue to feed, they usually die wit ...200717695025
[the history of the flea in art and literature].the flea has been, indirectly, one of the protagonists in the history of man. as one of the two vectors of yersinia pestis, the etiological agents of the black death, the flea (xenopsylla cheopis) has contributed, over the centuries, to the death of millions of people in many countries. galileo galilei was the first to observe the flea with a microscope (1624), but the credit of depicting it with a stunning drawing goes to the britisher robert hooke in 1665. a number of zoologists, including ant ...200415305680
studies on pasteurella pestis in fleas, comparative plague-vector efficiency of xenopsylla vexabilis hawaiiensis and xenopsylla cheopis.the authors report on a study carried out to determine the experimental plague-vector efficiency of x. v. hawaiiensis compared with x. cheopis after both species had been infected with a virulent hawaiian plague strain (s113). in deriving the numerical values for vector efficiency the concepts of wheeler and douglas were followed with some modifications. an additional component, the blocking-survival potential, was used to obtain a vector index.the experiments showed that the mean extrinsic incu ...195613356144
transmission of yersinia pestis cultures with different plasmid content from xenopsylla cheopis to calomys callosus.most brazilian yersinia pestis isolates display a typical plasmid profile composed of the three classical plasmids: pyv, ppst and pfra. however, some cultures lack at least one of these plasmids, while a few of them harbour atypical dna bands of molecular weight ranging from 147 to 11.5 kb. to investigate whether y. pestis displaying atypical plasmid content could be propagated among rodents in nature through flea bites, we carried out studies with fleas ( xenopsylla cheopis) and rodents ( calom ...200312541056
role of yersinia murine toxin in survival of yersinia pestis in the midgut of the flea vector.transmission by flea bite is a relatively recent adaptation that distinguishes yersinia pestis, the plague bacillus, from closely related enteric bacteria. here, a plasmid-encoded phospholipase d (pld), previously characterized as yersinia murine toxin (ymt), was shown to be required for survival of y. pestis in the midgut of its principal vector, the rat flea xenopsylla cheopis. intracellular pld activity appeared to protect y. pestis from a cytotoxic digestion product of blood plasma in the fl ...200211976454
[resurgence of the plague in the ikongo district of madagascar in 1998. 2. reservoirs and vectors implicated].our survey of mammals and fleas arose as a result of an outbreak of bubonic plague at an usually low altitude in the ikongo district (madagascar), while a previous study had found anti-f1 antibodies in an endemic hedgehog. animals were sampled with live traps in two hamlets (antanambao-vohidrotra, 540 m alt. and ambalagoavy, 265 m alt.) and with pitfall traps in a neighbouring forest (750 m alt.). rat fleas were collected by brushing the fur and free-living fleas by use of light traps. the intro ...200111475029
[diversity of flea vectors as a function of plague foci].the indian model of plague transmission by xenopsylla cheopis, discovered by p.l. simond, has been largely adopted even though it is flawed. x. cheopis cannot be the primitive vector, for neither its nor the rats' cradle is the same as for plague. furthermore, the insect's vital cycle is impaired by proventriculus blocking. the combination of three factors--the synathropic rat, x. cheopis and yersinia pestis--coupled with man's seafaring was what led to the multiplication of plague foci. this in ...199911000954
evaluation of the role of the yersinia pestis plasminogen activator and other plasmid-encoded factors in temperature-dependent blockage of the flea.yersinia pestis, the plague bacillus, has a plasminogen activator (pla) gene on the 9.5-kb plasmid ppla that is hypothesized to play a role in producing the foregut blockage in the flea vector that precedes transmission. in this study, however, y. pestis that lacked ppla, the 70-kb virulence plasmid, or both plasmids, proved able to block xenopsylla cheopis fleas normally. blockage rates decreased with increasing environmental temperature for fleas infected with either wild type or ppla- y. pest ...19989780262
5' nuclease pcr assay to detect yersinia pestis.the 5' nuclease pcr assay uses a fluorescently labeled oligonucleotide probe (taqman) to rapidly detect and quantitate dna templates in clinical samples. we developed a 5' nuclease pcr assay targeting the plasminogen activator gene (pla) of yersinia pestis. the assay is species specific, with a detection threshold of 2.1 x 10(5) copies of the pla target or 1.6 pg of total cell dna. the assay detected y. pestis in experimentally infected xenopsylla cheopis fleas and in experimentally infected mon ...19989666006
xenopsylla brasiliensis fleas in plague focus areas, madagascar. 201627513742
the yersinia pestis hmscde regulatory system is essential for blockage of the oriental rat flea (xenopsylla cheopis), a classic plague vector.the second messenger molecule cyclic diguanylate is essential for yersinia pestis biofilm formation that is important for blockage-dependent plague transmission from fleas to mammals. two diguanylate cyclases (dgcs) hmst and y3730 (hmsd) are responsible for biofilm formation in vitro and biofilm-dependent blockage in the oriental rat flea xenopsylla cheopis respectively. here, we have identified a tripartite signalling system encoded by the y3729-y3731 operon that is responsible for regulation o ...201525586342
lps modification promotes maintenance of yersinia pestis in fleas.yersinia pestis, the causative agent of plague, can be transmitted by fleas by two different mechanisms: by early-phase transmission (ept), which occurs shortly after flea infection, or by blocked fleas following long-term infection. efficient flea-borne transmission is predicated upon the ability of y. pestis to be maintained within the flea. signature-tagged mutagenesis (stm) was used to identify genes required for y. pestis maintenance in a genuine plague vector, xenopsylla cheopis. the stm s ...201525533446
delineation and analysis of chromosomal regions specifying yersinia pestis.yersinia pestis, the causative agent of plague, has recently diverged from the less virulent enteropathogen yersinia pseudotuberculosis. its emergence has been characterized by massive genetic loss and inactivation and limited gene acquisition. the acquired genes include two plasmids, a filamentous phage, and a few chromosomal loci. the aim of this study was to characterize the chromosomal regions acquired by y. pestis. following in silico comparative analysis and pcr screening of 98 strains of ...201020605981
acute oral toxicity of yersinia pseudotuberculosis to fleas: implications for the evolution of vector-borne transmission of plague.yersinia pestis diverged from yersinia pseudotuberculosis</= 20 000 years ago, during which time it evolved to be transmitted by fleas. in comparing the ability of these closely related species to infect the rat flea xenopsylla cheopis, we found that y. pseudotuberculosis, unlike y. pestis, is orally toxic to fleas. fleas showed signs of acute toxicity, including diarrhoea, immediately after feeding on blood containing y. pseudotuberculosis in response to protein toxin(s) produced by the bacteri ...200717587333
identification of critical amino acid residues in the plague biofilm hms proteins.yersinia pestis biofilm formation causes massive adsorption of haemin or congo red in vitro as well as colonization and eventual blockage of the flea proventriculus in vivo. this blockage allows effective transmission of plague from some fleas, like the oriental rat flea, to mammals. four hms proteins, hmsh, hmsf, hmsr and hmss, are essential for biofilm formation, with hmst and hmsp acting as positive and negative regulators, respectively. hmsh has a beta-barrel structure with a large periplasm ...200617074909
yersinia murine toxin is not required for early-phase transmission of yersinia pestis by oropsylla montana (siphonaptera: ceratophyllidae) or xenopsylla cheopis (siphonaptera: pulicidae).plague, caused by yersinia pestis, is characterized by quiescent periods punctuated by rapidly spreading epizootics. the classical 'blocked flea' paradigm, by which a blockage forms in the flea's proventriculus on average 1-2 weeks post-infection (p.i.), forces starving fleas to take multiple blood meals, thus increasing opportunities for transmission. recently, the importance of early-phase transmission (ept), which occurs prior to blockage formation, has been emphasized during epizootics. whil ...201425187626
[interaction of plague microbe strains varying in plasmid composition with the fleas xenopsylla cheopis (roths. 1903)].the interaction of two yersinia pestis strains varying in plasmid composition with the fleas xenopsylla cheopis was studied. the reference virulent strain i-2638 having four plasmids (pcad, ppst, pfra, and ptp 33) and its selected avirulent strain i-3480 that had lost the plasmids pcad and ppst formed a proventricular block in the fleas with equal frequency. there were no differences in the block-forming capacity of these strains among the infected females; however, the stock strain was more act ...201121797060
effect of temperature and relative humidity on the development times and survival of synopsyllus fonquerniei and xenopsylla cheopis, the flea vectors of plague in madagascar.plague, a zoonosis caused by yersinia pestis, is found in asia, the americas but mainly in africa, with the island of madagascar reporting almost one third of human cases worldwide. in the highlands of madagascar, plague is transmitted predominantly by two flea species which coexist on the island, but differ in their distribution. the endemic flea, synopsyllus fonquerniei, dominates flea communities on rats caught outdoors, while the cosmopolitan flea, xenopsylla cheopis, is found mostly on rats ...201626864070
feeding behavior modulates biofilm-mediated transmission of yersinia pestis by the cat flea, ctenocephalides felis.the cat flea, ctenocephalides felis, is prevalent worldwide, will parasitize animal reservoirs of plague, and is associated with human habitations in known plague foci. despite its pervasiveness, limited information is available about the cat flea's competence as a vector for yersinia pestis. it is generally considered to be a poor vector, based on studies examining early-phase transmission during the first week after infection, but transmission potential by the biofilm-dependent proventricular- ...201626829486
[risk assessments and control strategies of plague in five key surveillance counties, zhejiang province].to analyze the epidemiology data on plague in five counties in zhejiang province and to evaluate the risk of plague in theses areas.201526813723
[relationships of the plague pathogen and vector from different parasitic systems].the specific features of interaction of the strains of the plague microbe of the main subspecies, which circulate in the area of natural foci of mongolia and china, with citellophilus tesquorum sungaris fleas, the major vector of the plague pathogen in a transbaikalian natural focus, as well as with xenopsylla cheopis ones, the classical vector, were revealed. experiments used virulent yersinia pestis strains, such as i-3230 isolated from c.tesquorum in mongolia in 1998 and 2155 isolated from hu ...201323805481
gene expression analysis of xenopsylla cheopis (siphonaptera: pulicidae) suggests a role for reactive oxygen species in response to yersinia pestis infection.fleas are vectors for a number of pathogens including yersinia pestis, yet factors that govern interactions between fleas and y. pestis are not well understood. examining gene expression changes in infected fleas could reveal pathways that affect y. pestis survival in fleas and subsequent transmission. we used suppression subtractive hybridization to identify genes that are induced in xenopsylla cheopis (rothschild) (siphonaptera: pulicidae) in response to oral or hemocoel infection with y. pest ...201222493856
evaluation and modification of off-host flea collection techniques used in northwest uganda: laboratory and field studies.quantifying the abundance of host-seeking fleas is critical for assessing risk of human exposure to flea-borne disease agents, including yersinia pestis, the etiological agent of plague. yet, reliable measures of the efficacy of existing host-seeking flea collection methods are lacking. in this study, we compare the efficacy of passive and active methods for the collection of host-seeking fleas in both the laboratory and human habitations in a plague-endemic region of northwest uganda. in the la ...201222308790
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