Borrelia,Ehrlichia, andRickettsiaspp. in Ticks Removed from Persons, Texas, USA

Williamson, Phillip; Billingsley, Peggy M.; Teltow, Glenna J.; Seals, Janel P.; Turnbough, Meredith; Atkinson, Samuel F.

doi:10.3201/eid1603.091333

Cited by 80 publications

(84 citation statements)

References 33 publications

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“…For example, in 2001, when B. lonestari, an RF group Borrelia species found in A. americanum, was tentatively linked to a case of southern tick-associated rash illness (STARI) (5), HTTKP testing was modified to include testing for B. lonestari (21)(22)(23)(24). However, epidemiological studies of STARI patients did not support the hypothesized link between STARI and B. lonestari (6,7,25), so targeting of this Borrelia species in the HTTKP ended in 2009.…”

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Borrelia burgdorferi Not Confirmed in Human-Biting Amblyomma americanum Ticks from the Southeastern United States

et al. 2015

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The predominant human-biting tick throughout the southeastern United States is Amblyomma americanum. Its ability to transmit pathogens causing Lyme disease-like illnesses is a subject of ongoing controversy. Results of previous testing by the Department of Defense Human Tick Test Kit Program and other laboratories indicated that it is highly unlikely that A. americanum transmits any pathogen that causes Lyme disease. In contrast, a recent publication by Clark and colleagues (K. L. Clark, B. Leydet, and S. Hartman, Int. J. Med. Sci. 10:915-931, 2013) reported detection of Lyme group Borrelia in A. americanum using a nested-flagellin-gene PCR. We evaluated this assay by using it and other assays to test 1,097 A. americanum ticks collected from humans. Using the Clark assay, in most samples we observed nonspecific amplification and nonrepeatability of results on subsequent testing of samples. Lack of reaction specificity and repeatability is consistent with mispriming, likely due to high primer concentrations and low annealing temperatures in this protocol. In six suspect-positive samples, Borrelia lonestari was identified by sequencing of an independent gene region; this is not a Lyme group spirochete and is not considered zoonotic. B. burgdorferi was weakly amplified from one pool using some assays, but not others, and attempts to sequence the amplicon of this pool failed, as did attempts to amplify and sequence B. burgdorferi from the five individual samples comprising this pool. Therefore, B. burgdorferi was not confirmed in any sample. Our results do not support the hypothesis that A. americanum ticks are a vector for Lyme group Borrelia infections. T he vectors and etiologic agents of Lyme-like diseases in the southeastern United States are a subject of ongoing controversy (1, 2). In the United States, most Lyme disease is caused by infection with Borrelia burgdorferi sensu stricto, a bacterium that is phylogenetically within the B. burgdorferi sensu lato "Lyme group" of spirochetes vectored by hard ticks. The Lyme group also includes genospecies implicated as the etiologic agents of Lyme disease in other geographic regions, including B. garinii, B. afzelii, B. spielmanii, and B. valaisiana in Europe. Additional Lyme group genospecies continue to be described. In the United States, these include B. americana, B. andersonii, and B. carolinensis, all of unknown pathogenicity, and B. bissettii, which has been implicated in cases of human illness (1). In contrast to the Lyme group, the relapsing fever (RF) group spirochetes, many of which are vectored by soft ticks, are a separate phylogenetic cluster that includes agents associated with RF disease in humans. In the United States, genospecies within the RF group include B. hermsii, B. turicatae, and B. parkeri, vectored by soft ticks, and B. miyamotoi, B. davisii, and B. lonestari, vectored by hard ticks. B. hermsii is the main cause of tick-borne relapsing fever in the United States; B. turicatae and B. parkeri have also been associated with human disease (3). B...

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Borrelia burgdorferi Not Confirmed in Human-Biting Amblyomma americanum Ticks from the Southeastern United States

et al. 2015

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“…Testing of TDSHS samples by UTNHSC is an ongoing endeavour and the study reported here not only includes the 903 ticks collected between 2004 and 2008 in our original study (Williamson et al, 2010), but also includes 555 additional tick submissions collected between 2008 and 2010. The occurrence data were aggregated by TDSHS to the zip-code level.…”

Section: Habitat Probability Mappingmentioning

confidence: 99%

“…The occurrence data were aggregated by TDSHS to the zip-code level. Molecular screening for tick-borne pathogens, including R. rickettisii, was performed at UNTHSC using the method of Williamson et al (2010). These data were spatially tagged with the zip code of where the tick was encountered.…”

Section: Habitat Probability Mappingmentioning

confidence: 99%

“…We have recently reported (Williamson et al, 2010) the results of a study where a total of 903 ticks, representing 11 tick species, which had been submitted to the University of North Texas Health Science Center's (UNTHSC) Tick-Borne Disease Research Laboratory for analysis of both tick identification and rates of Rickettsia infection. These ticks had been attached to, and removed from humans, and were subjected to molecular analysis for detection of Rickettsia spp.…”

Section: Introductionmentioning

confidence: 99%

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Modelling spatial concordance between Rocky Mountain spotted fever disease incidence and habitat probability of its vector Dermacentor variabilis (American dog tick)

et al. 2012

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Abstract. 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 the incidence of the disease. Both maximum-entropy modelling of the tick's habitat suitability and spatially adaptive filters modelling of the human incidence of RMSF disease provide reliable portrayals of the spatial distributions of these phenomenons. Even though rates of human cases of RMSF in Texas and rates of Dermacentor ticks infected with Rickettsia bacteria are both relatively low in Texas, the best data currently available allows a preliminary indication that the assumption of high levels of spatial concordance would not be correct in Texas (Kappa coefficient of agreement = 0.17). It will take substantially more data to provide conclusive findings, and to understand the results reported here, but this study provides an approach to begin understanding the discrepancy.

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“…17,20,[34][35][36][37][38][39][40][41][42][43][44] Because of these large differences in prevalence, exposure to R. rickettsii may be rare relative to exposure to "Ca. Rickettsia amblyommii".…”

Section: Discussionmentioning

confidence: 99%

Expanding Range of Amblyomma americanum and Simultaneous Changes in the Epidemiology of Spotted Fever Group Rickettsiosis in the United States

Dahlgren¹,

Paddock²,

Springer³

et al. 2016

The American Society of Tropical Medicine and Hygiene

109

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Abstract. Spotted fever group (SFG) Rickettsia species are etiologic agents of a wide range of human infections from asymptomatic or mild infections to severe, life-threatening disease. In the United States, recent passive surveillance for SFG rickettsiosis shows an increased incidence and decreased severity of reported cases. The reasons for this are not well understood; however, we hypothesize that less pathogenic rickettsiae are causing more human infections, while the incidence of disease caused by more pathogenic rickettsiae, particularly Rickettsia rickettsii, is relatively stable. During the same period, the range of Amblyomma americanum has expanded. Amblyomma americanum is frequently infected with "Candidatus Rickettsia amblyommii", a SFG Rickettsia of unknown pathogenicity. We tested our hypothesis by modeling incidence rates from 1993 to 2013, hospitalization rates from 1981 to 2013, and case fatality rates from 1981 to 2013 regressed against the presence of A. americanum, the decade of onset of symptoms, and the county of residence. Our results support the hypothesis, and we show that the expanding range of A. americanum is associated with changes in epidemiology reported through passive surveillance. We believe epidemiological and acarological data collected on individual cases from enhanced surveillance may further elucidate the reasons for the changing epidemiology of SFG rickettsiosis.

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Borrelia,Ehrlichia, andRickettsiaspp. in Ticks Removed from Persons, Texas, USA

Abstract: Some tick-borne agents may pose yet-unknown public health risks.

Cited by 80 publications

References 33 publications

Borrelia burgdorferi Not Confirmed in Human-Biting Amblyomma americanum Ticks from the Southeastern United States

Borrelia burgdorferi Not Confirmed in Human-Biting Amblyomma americanum Ticks from the Southeastern United States

Modelling spatial concordance between Rocky Mountain spotted fever disease incidence and habitat probability of its vector Dermacentor variabilis (American dog tick)

Expanding Range of Amblyomma americanum and Simultaneous Changes in the Epidemiology of Spotted Fever Group Rickettsiosis in the United States

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