Publications

comparative vertical transmission of rickettsia by dermacentor variabilis and amblyomma maculatum.	the geographical overlap of multiple rickettsia and tick species coincides with the molecular detection of a variety of rickettsial agents in what may be novel tick hosts. however, little is known concerning transmissibility of rickettsial species by various tick hosts. to examine the vertical transmission potential between select tick and rickettsial species, two sympatric species of ticks, dermacentor variabilis and amblyomma maculatum, were exposed to five different rickettsial species, inclu ...	2017	28433729
prevalence of rickettsia species in dermacentor variabilis ticks from ontario, canada.	relatively little is known about the prevalence of rickettsial species in dermacentor ticks in eastern canada. in this study, dermacentor ticks from the province of ontario, canada, were tested for the presence of spotted fever group rickettsial (sfgr) species, coxiella burnetii and francisella tularensis. rickettsia rickettsii was not detected in any ticks tested, but r. montanensis was detected at a prevalence of 2.2% in d. variabilis (17/778). two other sfgr species, r. parkeri and candidatus ...	2016	27318438
first report of rickettsia identical to r. slovaca in colony-originated d. variabilis in the united states: detection, laboratory animal model, and vector competence of ticks.	ticks of the genus dermacentor are known vectors of rickettsial pathogens in both the old world and new world. in north america, dermacentor variabilis and d. andersoni are vectors of rickettsia rickettsii, while in europe, d. marginatus and d. reticulatus transmit r. slovaca and r. raoultii, respectively. neither the presence of r. slovaca in the americas nor the ability of american tick species to maintain this pathogen have been reported. here we describe detection of rickettsia genetically i ...	2016	26808054
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 ...	2016	26494822
molecular detection of rickettsia species within ticks (acari: ixodidae) collected from arkansas united states.	rocky mountain spotted fever (rmsf), caused by the etiological agent rickettsia rickettsii, is the most severe and frequently reported rickettsial illness in the united states, and is commonly diagnosed throughout the southeast. with the discoveries of rickettsia parkeri and other spotted fever group rickettsiae (sfgr) in ticks, it remains inconclusive if the cases reported as rmsf are truly caused by r. rickettsii or other sfgr. arkansas reports one of the highest incidence rates of rmsf in the ...	2015	26334827
"rickettsia amblyommii" and r. montanensis infection in dogs following natural exposure to ticks.	to determine the risk of canine infection with spotted fever group (sfg) rickettsia spp. following natural tick exposure, 10 dogs determined to be free of evidence of exposure to or infection with tick-borne disease agents were exposed to ticks via weekly walks in a wooded area in north-central oklahoma. after each walk, dogs were examined and the number and species of ticks present were recorded. the dogs were then returned to outdoor kennels to allow the infestations and subsequent transmissio ...	2014	24359419
prevalence of antibodies to spotted fever group rickettsia spp. and ehrlichia spp. in coyotes (canis latrans) in oklahoma and texas, usa.	coyotes (canis latrans) are commonly infested with ticks, including amblyomma americanum, the predominant vector of ehrlichia chaffeensis and ehrlichia ewingii; dermacentor variabilis, an important vector of rickettsia rickettsii; and amblyomma maculatum, a major vector of rickettsia parkeri, a spotted fever group (sfg) rickettsia. to determine the degree to which coyotes are infected with or exposed to tick-borne bacterial disease agents, serum samples collected from coyotes in oklahoma and tex ...	2013	23778619
modelling spatial concordance between rocky mountain spotted fever disease incidence and habitat probability of its vector dermacentor variabilis (american dog tick).	the spatial distribution of dermacentor variabilis, the most commonly identified vector of the bacterium rickettsia rickettsii which causes rocky mountain spotted fever (rmsf) in humans, and the spatial distribution of rmsf, have not been previously studied in the south central united states of america, particularly in texas. from an epidemiological perspective, one would tend to hypothesise that there would be a high degree of spatial concordance between the habitat suitability for the tick and ...	2012	23242684
infrequency of rickettsia rickettsii in dermacentor variabilis removed from humans, with comments on the role of other human-biting ticks associated with spotted fever group rickettsiae in the united states.	abstract from 1997 to 2009, the tick-borne disease laboratory of the u.s. army public health command (usaphc) (formerly the u.s. army center for health promotion and preventive medicine) screened 5286 dermacentor variabilis ticks removed from department of defense (dod) personnel, their dependents, and dod civilian personnel for spotted fever group rickettsiae using polymerase chain reaction and restriction fragment length polymorphism analysis. rickettsia montanensis (171/5286 = 3.2%) and ricke ...	2010	21142953
molecular detection of rickettsia bellii, rickettsia montanensis, and rickettsia rickettsii in a dermacentor variabilis tick from nature.	rickettsial diseases, such as rocky mountain spotted fever, pose a public health threat because of humans' interrelationship with common arthropod species, such as ticks, mites, fleas, and lice. individuals may come in contact with these vectors of disease on a fairly regular basis either directly or indirectly through pets or wildlife species, at home or in recreational areas. therefore, it is of vital importance to know and understand the geographical distribution and prevalence of disease and ...	2010	19485770
closing the gaps between genotype and phenotype in rickettsia rickettsii.	rocky mountain spotted fever (rmsf) caused by rickettsia rickettsii is a severe rickettsiosis that occurs in nearly every state of the continental usa. rmsf is endemic in central and southern america, with recent well-documented cases in mexico, costa rica, panama, colombia, brazil, and argentina. rmsf is the most malignant among known rickettsioses causing severe multiorgan dysfunction and high case fatality rates, which can reach 73% in untreated cases. variations in pathogenic biotypes of r. ...	2009	19538260
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.	2009	19151178
tick-borne diseases in north carolina: is "rickettsia amblyommii" a possible cause of rickettsiosis reported as rocky mountain spotted fever?	cases of rocky mountain spotted fever (rmsf) in north carolina have escalated markedly since 2000. in 2005, we identified a county in the piedmont region with high case numbers of rmsf. we collected ticks and examined them for bacterial pathogens using molecular methods to determine if a novel tick vector or spotted fever group rickettsiae (sfgr) might be emerging. amblyomma americanum, the lone star tick, comprised 99.6% of 6,502 specimens collected in suburban landscapes. in contrast, dermacen ...	2008	18447622
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, ...	2008	18533446
a rickettsial mixed infection in a dermacentor variabilis tick from ohio.	we present the first report of superinfection in a dermacentor variabilis tick from nature. the single tick, collected in ohio, was found infected with rickettsia belli, r. nontanensis, and r. rickettsii.	2006	17114734
rodent ectoparasites from two locations in northwestern florida.	from feb.-apr. 1999, 19 species of ectoparasitic arthropods (2 sucking lice, 4 fleas, 4 ticks, 2 mesostigmatid mites, 5 chiggers, 2 fur mites) were recovered from 106 rodents belonging to 5 species (cotton mouse, peromyscus gossypinus, n = 64; cotton rat, sigmodon hispidus, n = 23; eastern woodrat, neotoma floridana, n = 9; golden mouse, ochrotomys nuttalli, n = 9; eastern gray squirrel, sciurus carolinensis, n = 1) at tall timbers research station, leon county, florida. during the same period, ...	2000	11217221
hemocytic rickettsia-like organisms in ticks: serologic reactivity with antisera to ehrlichiae and detection of dna of agent of human granulocytic ehrlichiosis by pcr.	ixodid ticks were collected from connecticut, massachusetts, missouri, pennsylvania, rhode island, and british columbia (canada) during 1991 to 1994 to determine the prevalence of infection with hemocytic (blood cell), rickettsia-like organisms. hemolymph obtained from these ticks was analyzed by direct and indirect fluorescent antibody (fa) staining methods with dog, horse, or human sera containing antibodies to ehrlichia canis, ehrlichia equi, or rickettsia rickettsii. of the 693 nymphal and a ...	1995	8567911
granulocytic ehrlichiosis and meningitis in a dog.	a 4-year-old male mixed-breed dog from the sierra nevada mountains in california was referred because of epistaxis and signs of cervical pain. dermacentor variabilis ticks were found on the dog at the time of physical examination. clinicopathologic abnormalities included nonregenerative anemia, thrombocytopenia, and rare intracytoplasmic morulae within circulating neutrophils. abnormalities of the csf included pleocytosis and intracytoplasmic morulae in approximately 9% of neutrophils. serum ant ...	1994	7730122
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 ...	1991	2014623
hispid cotton rats (sigmodon hispidus) as a source for infecting immature dermacentor variabilis (acari: ixodidae) with rickettsia rickettsii.	hispid cotton rats (sigmodon hispidus say and ord) were susceptible to infection with rickettsia rickettsii wolbach under laboratory conditions and were capable of serving as sources for infecting ticks with rickettsiae. cotton rats developed rickettsemias that could be detected for as long as 6 h following intraperitoneal inoculation of 10(5) plaque-forming units (pfus) of r. rickettsii (morgan strain). an estimate of the median infectious dose (id50) was made by inoculating six groups (eight a ...	1990	2117665
computer simulation of rocky mountain spotted fever transmission by the american dog tick (acari: ixodidae).	a computer model was developed for simulation of the transmission of rickettsia rickettsii, the causative agent of rocky mountain spotted fever (rmsf), by the american dog tick, dermacentor variabilis (say). the model of rmsf was combined with a model for population dynamics of the american dog tick and included simulation of infection and transmission of rickettsiae between ticks and host mammals and transmission of rmsf to humans. the model simulated the effects of biotic and environmental var ...	1990	2388242
a focus of rocky mountain spotted fever within new york city.	in the spring and summer of 1987, four persons acquired rocky mountain spotted fever within new york city, an area in which the disease had not previously been known to be endemic. three of the four patients were residents of the soundview area of the bronx. all diagnoses were confirmed by indirect fluorescent-antibody tests. environmental investigation revealed that the tick vector for rickettsia rickettsii, dermacentor variabilis, was present in a local park. of the 66 specimens of d. variabil ...	1988	3130574
rickettsia rickettsii and rickettsia montana from ixodid ticks in connecticut.	dermacentor variabilis, infected with spotted fever group rickettsiae, parasitized 8 of 70 raccoons captured in newtown, connecticut. the spotted fever agent, rickettsia rickettsii, was isolated and identified from 4 adult d. variabilis and from 1 nymphal ixodes texanus removed from raccoons. this verifies the presence of this etiologic agent in ticks in an area where 6 people had clinical signs and symptoms of rocky mountain spotted fever (rmsf) and antibodies to r. rickettsii. these are the fi ...	1986	3946737
rickettsia-like organisms in ticks and antibodies to spotted fever-group rickettsiae in mammals from northern mississippi.	studies were conducted from april through august during 1974 and 1975 on 30 randomly selected trapping sites in wall doxey state park, holly springs national forest, and 1.6 km south of the park in marshall county, mississippi to provide information on the occurrence of ticks involved in the maintenance and transmission of spotted fever-group rickettsiae in nature. of 365 animals (14 species) collected, 186 (51%) were parasitized by 4,169 ticks. species of ticks collected included: dermacentor v ...	1985	3923212
spotted fever group rickettsiae in immature and adult ticks (acari: ixodidae) from a focus of rocky mountain spotted fever in connecticut.	immature and adult ixodid ticks were collected during 1983 and 1984 in newtown, connecticut, an area endemic for rocky mountain spotted fever (rmsf), to determine prevalence of infection by spotted fever group (sfg) rickettsiae. direct fluorescent-antibody (fa) staining revealed sfg organisms in 6 (1.8%) of 332 dermacentor variabilis larvae, 5 (7.8%) of 64 d. variabilis nymphs, and in 2 (40%) of 5 ixodes cookei nymphs removed from small- and medium-sized mammals. hemolymph tests detected rickett ...	1985	3938341
epidemiology of rocky mountain spotted fever in ohio, 1981: serologic evaluation of canines and rickettsial isolation from ticks associated with human case exposure sites.	a survey for the prevalence of rocky mountain spotted fever (rmsf) antibodies in dogs associated with confirmed human cases in ohio was conducted during 1981. twelve of 14 confirmed cases (85%) had a history of dog association prior to onset of rmsf. a total of 29 dogs were included in the study, with 16 dogs providing serum samples for antibody testing and the remainder providing tick samples. serum samples tested by indirect microimmunofluorescence techniques revealed 12/16 dogs (75%) to be se ...	1984	6435461
antibodies to spotted fever-group rickettsiae in dogs and prevalence of infected ticks in southern connecticut.	blood samples and ticks were obtained from dogs to assess canine exposure to spotted fever-group (sfg) rickettsiae during 1978-1980 in southern connecticut. of the 1,576 dog sera screened by microimmunofluorescence. 174 (11.0%) contained specific antibodies at titers greater than or equal to 1:64 against rickettsia montana (n = 34), r rickettsii (n = 31), r rhipicephali (n = 19), or the unclassified 369-c rickettsia (n = 90). end points greater than or equal to 1:8,192 to r rickettsii and to r r ...	1982	6803626
endemicity of spotted fever group rickettsiae in connecticut.	to compare rickettsial infectivity and seropositivity rates against spotted fever group (sfg) rickettsiae, ticks and wild mammals were collected from three areas where rickettsia rickettsii was thought to be enzootic in connecticut during 1978-1979, and from four additional sites (with no reported human cases) between 1976 and 1979. of the 1,001 dermacentor variabilis examined by the hemolymph test, 59 (5.9%) contained rickettsia-like organisms; direct immunofluorescence tests verified the prese ...	1981	6789690
rocky mountain spotted fever in clermont county, ohio. ii. distribution of population and infected ticks in an endemic area.	the epidemiology of rocky mountain spotted fever (rmsf) in relation to the distribution of the human population and infected ticks has not been defined. a study was undertaken in clermont county, ohio, to describe the distribution of population in a highly endemic focus of rmsf and to determine the prevalence of ticks infected with rickettsiae of the spotted fever group. this area was compared to another area of similar size in the same county where the incidence of rmsf was much lower. the popu ...	1980	7352458
spotted fever group rickettsiae in dermacentor variabilis from cape cod, massachusetts.	spotted fever group (sfg) rickettsiae were identified by indirect immunofluorescent antibody tests in 1.1% of 6,956 specimens of dermacentor variabilis collected on cape cod, massachusetts. forty-one of 45 rickettsial isolates were serotyped as rickettsia montana, one as rickettsia rickettsii, and three were unidentified. studies of canines and humans with clinical evidence of spotted fever, and of healthy dogs with antibody to sfg rickettsiae, indicated that exposure of the canine population to ...	1980	6773430
rocky mountain spotted fever in connecticut: human cases, spotted-fever group rickettsiae in ticks, and antibodies in mammals.	three parameters were used in 1976 and 1977 to assess the status of rocky mountain spotted fever (rmsf) in connecticut--compilation and review of clinical data on suspected human cases for the 13-year period 1965--1977, examination of tick tissues for spotted fever-group rickettsiae by the hemolymph test and direct immunofluorescence, and analyses of mammalian sera for antibodies against rickettsia rickettsii. there were six presumptive rmsf cases which probably originated in connecticut. four o ...	1979	111543
distribution and prevalence of spotted fever group rickettsiae in ticks from south carolina, with an epidemiological survey of persons bitten by infected ticks.	live ticks removed from human hosts were tested for the presence of spotted fever group rickettsiae from 1974 through 1976. spotted fever group rickettsiae were detected in dermacentor variabilis, amblyomma americanum, amblyomma maculatum, and ixodes scapularis. persons from whom positive ticks were removed in 1974 and 1975 were questioned about ensuing illness. eleven of 51 persons from whom rickettsia-positive d. variabilis were removed reported some unexplained combination of symptoms compati ...	1978	103448
rocky mountain spotted fever in mississippi: survey for spotted fever antibodies in dogs and for spotted fever group reckettsiae in dog ticks.	during epidemiologic studies of rocky mountain spotted fever in mississippi in 1973, dogs were surveyed for antibodies tp spotted fever group antigens and for tick parasites infected with rickettsiae of the spotted fever group. fifty-three (46%) of 116 serum samples had complement-fixing antibody titers greater than or equal to 1:8 as compared to only one (5%) of 21 samples from a group of dogs obtained from metropolitan chicage. fifty-two per cent of the dogs tested from mississippi had microag ...	1976	814809
rocky mountain spotted fever (tick-borne typhus) in south carolina: an educational program and tick/rickettsial survey in 1973 and 1974.	because the incidence of spotted fever is increasing in south carolina, campaigns were carried out in 1973 and 1974 to provide the public and medical practitioners, through pamphlets and news media, with information about spotted fever and the ticks which transmit the causative agent, rickettsia rickettsii. people were also invited to save and submit live ticks removed from vegetation, animals and humans, for examination by the hemolymph test. a total of 1,186 ticks consisting of 987 dermacentor ...	1975	811127