detection of the rocky mountain spotted fever agent, rickettsia rickettsii, in dead ticks, dermacentor andersoni.rickettsia rickettsii remained viable and retained chromophilic properties for not more than 24 h after dermacentor andersoni were killed by freezing. antigenic reactivity was detected for at least 71 days by direct immunofluorescence. however, rickettsiae in ticks suffocated with mineral oil remained pathogenic for at least 14 days. accordingly, ticks removed from a host by mineral oil or dying from desiccation in transit are still suitable for rickettsial examination.197897233
detection of rickettsia rickettsii in saliva, hemolymph and triturated tissues of infected dermacentor andersoni ticks by polymerase chain reaction.the technique of polymerase chain reaction (pcr) is potentially superior to existing methods for detecting rickettsial infections in ticks. for this reason, we developed assays for identifying rickettsial infections in ticks by pcr. our assays amplified a 500 bp fragment from the gene encoding the romp b protein of rickettsia rickettsii. the selected primers amplified fragments of the predicted size from all spotted fever group rickettsiae (r. rickettsii, r. parkeri, r. conorii, r. sibirica) tes ...19921528203
rocky mountain spotted fever.rocky mountain spotted fever is an endemic tickborne disease found throughout the united states and other regions of the world. exposure may result in a spectrum of disease from subclinical infection to severe or fatal multiorgan collapse. the disease is maintained in nature in ixodid tick vectors and their hosts. the most important ticks in the united states are dermacentor variabilis and dermacentor andersoni. small mammals are the natural reservoirs in the wild. dogs become infected when a ti ...19912014623
the population dynamics of two vertically transmitted infections.the transmission of keystone virus in the mosquito aedes atlanticus and of rickettsia rickettsii in the tick dermacentor andersoni is modeled and analyzed. both of these infections can be transmitted vertically from an infective parent to newborn offspring as well as horizontally via direct or indirect contacts with infected individuals. the vertical transmission mechanism plays a major role in the maintenance of these infections and its effects are analyzed in detail. this same mechanism can ac ...19883148206
natural history of tick-borne spotted fever in the usa. susceptibility of small mammals to virulent rickettsia the ecology of spotted fever rickettsiae, one of the as yet unsolved problems concerns the significance of small animals in the distribution of rickettsia rickettsii in nature. in the bitter root valley of western montana, a great variety of rodents, rabbits and hares are known to serve as the preferred hosts for the immature stages of the vector tick, dermacentor andersoni.the authors analyse the susceptibility of various species of small mammals to virulent r. rickettsii and evaluate their ...19665296999
biochemical and immunochemical analysis of rickettsia rickettsii strains of various degrees of virulence.six strains of rickettsia rickettsii from montana and north carolina were examined in an effort to identify rickettsial constituents associated with virulence. fever responses, scrotal reactions, and mortalities of male guinea pigs inoculated intraperitoneally with 1,000 pfu of rickettsial strains revealed that the two montana patient strains ( sheila smith and norgaard ) and one montana strain ( sawtooth female 2) from the wood tick, dermacentor andersoni, could be placed in the group of highes ...19846427110
serotypes of spotted fever group rickettsiae isolated from dermacentor andersoni (stiles) ticks in western dermacentor andersoni ticks were collected by flagging vegetation in 18 canyons bordering the bitterroot valley, montana, an area where nearly 400 cases of rocky mountain spotted fever (rmsf) have occurred since 1900. three hundred and nine (8.3%) of the 3,705 ticks collected contained hemocyte-associated rickettsia-like organisms of three morphologic types, coccobacillary, fine bacillary, and coarse bacillary (long forms). only the coccobacillary and fine bacillary organisms stained with ...19816782899
reactivation of rickettsia rickettsii in dermacentor andersoni ticks: an ultrastructural analysis.virulent rickettsia in dermacentor andersoni lose their pathogenicity and virulence for guinea pigs when subjected to physiological stresses, such as starvation (overwintering), of its tick vector. however, incubation of infected ticks at an elevated temperature (37 degrees c) for 24 to 48 h or feeding for a time (usually greater than 10 h) induces r. rickettsii to revert to a virulent state, a phenomenon defined as "reactivation." electron microscopy reveals that the microcapsular and slime lay ...19826811439
the role of cottontail rabbits (sylvilagus spp.) in the ecology of rickettsia rickettsii in the united states.rocky mountain (sylvilagus nuttallii) and eastern (s. floridanus) cottontails were examined for their susceptibility to virulent and avirulent strains of the spotted fever agent, rickettsia rickettsii. both species of rabbits responded to inoculation of yolk sac suspensions containing 500 egg ld50 of either virulent or avirulent rickettsiae, with rickettsemias detectable as early as 3 days after inoculation and lasting up to 7 days. when fed upon by infected ticks, only one of three rocky mounta ...19807406116
dna typing of rickettsiae in naturally infected ticks using a polymerase chain reaction/restriction fragment length polymorphism system.we used the polymerase chain reaction/restriction fragment length polymorphism (pcr/rflp) rickettsial typing system of regnery and others to rapidly identify rickettsiae in naturally infected ticks. unlike previously described methods, our pcr assays type rickettsiae directly from tick tissues without first isolating the organisms. we collected 226 adult dermacentor andersoni ticks in the bitterroot mountains of western montana and analyzed them for possible rickettsial infection by hemolymph te ...19947906924
rickettsia peacockii sp. nov., a new species infecting wood ticks, dermacentor andersoni, in western montana.rickettsia peacockii, a new species of spotted fever group rickettsiae, was identified from rocky mountain wood ticks (dermacentor andersoni) collected in the sapphire mountain range on the eastern side of bitterroot valley, montana. dna from r. peacockii skalkahot (t = type strain) in naturally infected tick tissue was amplified by a pcr assay with primer sets derived from eubacterial 16s ribosomal dna (rdna), rickettsial citrate synthase, and 190-kda surface antigen (rompa) genes. partial 16s ...19979103635
lethal effect of rickettsia rickettsii on its tick vector (dermacentor andersoni).rickettsia rickettsii, the causative agent of rocky mountain spotted fever, was lethal for the majority of experimentally and transovarially infected rocky mountain wood ticks (dermacentor andersoni). overall, 94.1% of nymphs infected as larvae by feeding on rickettsemic guinea pigs died during the molt into adults and 88. 3% of adult female ticks infected as nymphs died prior to feeding. in contrast, only 2.8% of uninfected larvae failed to develop into adults over two generations. infected fem ...19999925615
identification of rickettsia rickettsii in the wood tick, dermacentor andersoni, by means of fluorescent antibody. 196013688983
sequence and expression analysis of the ompa gene of rickettsia peacockii, an endosymbiont of the rocky mountain wood tick, dermacentor andersoni.the transmission dynamics of rocky mountain spotted fever in montana appears to be regulated by rickettsia peacockii, a tick symbiotic rickettsia that interferes with transmission of virulent rickettsia rickettsii. to elucidate the molecular relationships between the two rickettsiae and glean information on how to possibly exploit this interference phenomenon, we studied a major rickettsial outer membrane protein gene, ompa, presumed to be involved in infection and pathogenesis of spotted fever ...200415528527
molecular typing of novel rickettsia rickettsii isolates from isolates of rickettsia rickettsii were obtained from a skin biopsy, two whole-blood specimens, and from rhipicephalus sanguineus ticks from eastern arizona. molecular typing of seven isolates of r. rickettsii and dna samples from two other rh. sanguineus ticks infected with r. rickettsii was conducted by pcr and dna sequencing of rompa and 12 variable-number tandem repeat regions (vntrs). all dna specimens from arizona were identical to each other and to reference human and dermacentor and ...200617114781
prevalence of rickettsia species in canadian populations of dermacentor andersoni and d. variabilis.we determined the prevalence of rickettsiae in dermacentor adults at 15 localities in canada. rickettsia rickettsii was not detected in any tick, whereas rickettsia peacockii was present in 76% of dermacentor andersoni adults and rickettsia montanensis in 8% of dermacentor variabilis adults. this host specificity was maintained in localities where both tick species occurred in sympatry.200919151178
the characterization and manipulation of the bacterial microbiome of the rocky mountain wood tick, dermacentor north america, ticks are the most economically impactful vectors of human and animal pathogens. the rocky mountain wood tick, dermacentor andersoni (acari: ixodidae), transmits rickettsia rickettsii and anaplasma marginale to humans and cattle, respectively. in recent years, studies have shown that symbiotic organisms are involved in a number of biochemical and physiological functions. characterizing the bacterial microbiome of d. andersoni is a pivotal step towards understanding symbiont-hos ...201526653035
detection and identification of spotted fever group rickettsiae in dermacentor species from southern california.dermacentor occidentalis marx and dermacentor variabilis (say) commonly bite humans in california. these dermacentor species may play a role in transmitting spotted fever group (sfg) rickettsiae to humans in many parts of the state where dermacentor andersoni stiles, a known vector for the etiologic agent of rocky mountain spotted fever, rickettsia rickettsii, is absent. however, the specific rickettsial agents present in these ticks and their current prevalence are poorly understood. in total, ...200818533446
detection of colorado tick fever virus by using reverse transcriptase pcr and application of the technique in laboratory diagnosis.colorado tick fever (ctf) virus elicits an acute illness in humans, producing nonspecific flu-like symptoms and a biphasic fever in approximately 50% of patients. the disease is transmitted by the adult rocky mountain wood tick (dermacentor andersoni), and therefore incidence is limited by the habitat and life cycle of that vector. the early symptoms of infection are difficult to distinguish from those of several other agents, especially rickettsia rickettsii. serologic testing is usually unable ...19979114408
effect of rickettsia rickettsii (rickettsiales: rickettsiaceae) infection on the biological parameters and survival of its tick vector-dermacentor variabilis (acari: ixodidae).rocky mountain spotted fever, caused by rickettsia rickettsii, is a potentially fatal tick-borne disease spread from north america to argentina. the major vectors of r. rickettsii in the united states are dermacentor andersoni stiles and dermacentor variabilis (say). it is generally believed that vector ticks serve as major reservoirs of r. rickettsii in nature; however, the ability of ticks to support the indefinite perpetuation of r. rickettsii has been challenged by reports of deleterious eff ...201626494822
genome sequence of the endosymbiont rickettsia peacockii and comparison with virulent rickettsia rickettsii: identification of virulence factors.rickettsia peacockii, also known as the east side agent, is a non-pathogenic obligate intracellular bacterium found as an endosymbiont in dermacentor andersoni ticks in the western usa and canada. its presence in ticks is correlated with reduced prevalence of rickettsia rickettsii, the agent of rocky mountain spotted fever. it has been proposed that a virulent sfg rickettsia underwent changes to become the east side agent. we determined the genome sequence of r. peacockii and provide a compariso ...200920027221
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