Last data update: Oct 07, 2024. (Total: 47845 publications since 2009)
Records 1-11 (of 11 Records) |
Query Trace: Allerdice MEJ[original query] |
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Applying MALDI-TOF MS to resolve morphologic and genetic similarities between two Dermacentor tick species of public health importance
Galletti Mfbm , Hecht JA , McQuiston JR , Gartin J , Cochran J , Blocher BH , Ayres BN , Allerdice MEJ , Beati L , Nicholson WL , Snellgrove AN , Paddock CD . Sci Rep 2024 14 (1) 19834 Hard ticks (Acari: Ixodidae) have been historically identified by morphological methods which require highly specialized expertise and more recently by DNA-based molecular assays that involve high costs. Although both approaches provide complementary data for tick identification, each method has limitations which restrict their use on large-scale settings such as regional or national tick surveillance programs. To overcome those obstacles, the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been introduced as a cost-efficient method for the identification of various organisms, as it balances performance, speed, and high data output. Here we describe the use of this technology to validate the distinction of two closely related Dermacentor tick species based on the development of the first nationwide MALDI-TOF MS reference database described to date. The dataset obtained from this protein-based approach confirms that tick specimens collected from United States regions west of the Rocky Mountains and identified previously as Dermacentor variabilis are the recently described species, Dermacentor similis. Therefore, we propose that this integrative taxonomic tool can facilitate vector and vector-borne pathogen surveillance programs in the United States and elsewhere. |
Phylogenetic Differentiation of Rickettsia parkeri Reveals Broad Dispersal and Distinct Clustering within North American Strains.
Allerdice MEJ , Paddock CD , Hecht JA , Goddard J , Karpathy SE . Microbiol Spectr 2021 9 (2) e0141721 The tick-borne pathogen Rickettsia parkeri causes a mild rickettsiosis, with cases reported from several countries to its known distribution in the Americas. Molecular analyses have identified a clear distinction between strains of R. parkeri sensu stricto (s. s.) and R. parkeri sensu lato (s. l.) as well as separation between North American and South American R. parkeri s. s. strains. To expand on this previous work, we developed a multilocus sequence typing analysis with two aims: first, to investigate the genetic diversity within strains of North American R. parkeri s. s., and second, to further the understanding of the genetic relationships between R. parkeri s. s. and R. parkeri s. l. Sixty-four R. parkeri isolates and 12 R. parkeri-positive tick lysates were analyzed using a novel typing scheme consisting of four coding regions and two intergenic regions. A concatenated Bayesian phylogeny that identified eight clades was constructed: three represent the R. parkeri s. l. strains, and five represent the R. parkeri s. s. strains. The clades appear to be generally phylogeographically organized and associated with specific tick vectors. However, while one of the four R. parkeri s. s. North American clades appears to be limited to the southwestern United States, the other North American clades exhibit broad dispersal, most notably seen in the largest group, which includes representative samples extending from northern Mexico to Delaware. This work highlights the increasingly recognized geographic range of R. parkeri in the Americas and suggests a potential public health risk for these areas. IMPORTANCE Since 1937, when Rickettsia parkeri was originally identified in Amblyomma maculatum group ticks, the recognized range and associated vectors for this pathogen have expanded significantly. In recent years, R. parkeri has been identified in 12 tick species from seven countries in the Americas. Herein, we provide evidence that the greatest genetic diversity within R. parkeri exists in North America, where one R. parkeri sensu lato and four R. parkeri sensu stricto genotypes are present. While one distinct R. parkeri sensu stricto genotype exists only in the southwestern United States, three genotypes are broadly distributed in the eastern United States, with the largest of these found across the known range of R. parkeri in North America. In contrast, the South American R. parkeri sensu stricto samples represent a single genotype and are completely clonal at the loci analyzed, irrespective of their country of origin. |
Reproductive incompatibility between Amblyomma maculatum (Acari: Ixodidae) group ticks from two disjunct geographical regions within the USA.
Allerdice MEJ , Snellgrove AN , Hecht JA , Hartzer K , Jones ES , Biggerstaff BJ , Ford SL , Karpathy SE , Delgado-de la Mora J , Delgado-de la Mora D , Licona-Enriquez JD , Goddard J , Levin ML , Paddock CD . Exp Appl Acarol 2020 82 (4) 543-557 The Amblyomma maculatum Koch group of ixodid ticks consists of three species: A. maculatum, A. triste, and A. tigrinum. However, since Koch described this group in 1844, the systematics of its members has been the subject of ongoing debate. This is especially true of A. maculatum and A. triste; recent molecular analyses reveal insufficient genetic divergence to separate these as distinct species. Further confounding this issue is the discovery in 2014 of A. maculatum group ticks in southern Arizona (AZ), USA, that share morphological characteristics with both A. triste and A. maculatum. To biologically evaluate the identity of A. maculatum group ticks from southern Arizona, we analyzed the reproductive compatibility between specimens of A. maculatum group ticks collected from Georgia (GA), USA, and southern Arizona. Female ticks from both Arizona and Georgia were mated with males from both the Georgia and Arizona Amblyomma populations, creating two homologous and two heterologous F1 cohorts of ticks: GA ♀/GA ♂, AZ ♀/AZ ♂, GA ♀/AZ ♂, and AZ ♀/GA ♂. Each cohort was maintained separately into the F2 generation with F1 females mating only with F1 males from their same cohort. Survival and fecundity parameters were measured for all developmental stages. The observed survival parameters for heterologous cohorts were comparable to those of the homologous cohorts through the F1 generation. However, the F1 heterologous females produced F2 egg clutches that did not hatch, thus indicating that the Arizona and Georgia populations of A. maculatum group ticks tested here represent different biological species. |
Integrating population genetic structure, microbiome, and pathogens presence data in Dermacentor variabilis .
Lado P , Luan B , Allerdice MEJ , Paddock CD , Karpathy SE , Klompen H . PeerJ 2020 8 e9367 Tick-borne diseases (TBDs) continue to emerge and re-emerge in several regions of the world, highlighting the need for novel and effective control strategies. The development of effective strategies requires a better understanding of TBDs ecology, and given the complexity of these systems, interdisciplinary approaches are required. In recent years, the microbiome of vectors has received much attention, mainly because associations between native microbes and pathogens may provide a new promising path towards the disruption of pathogen transmission. However, we still do not fully understand how host genetics and environmental factors interact to shape the microbiome of organisms, or how pathogenic microorganisms affect the microbiome and vice versa. The integration of different lines of evidence may be the key to improve our understanding of TBDs ecology. In that context, we generated microbiome and pathogen presence data for Dermacentor variabilis, and integrated those data sets with population genetic data, and metadata for the same individual tick specimens. Clustering and multivariate statistical methods were used to combine, analyze, and visualize data sets. Interpretation of the results is challenging, likely due to the low levels of genetic diversity and the high abundance of a few taxa in the microbiome. Francisella was dominant in almost all ticks, regardless of geography or sex. Nevertheless, our results showed that, overall, ticks from different geographic regions differ in their microbiome composition. Additionally, DNA of Rickettsia rhipicephali, R. montanensis, R. bellii, and Anaplasma spp., was detected in D. variabilis specimens. This is the first study that successfully generated microbiome, population genetics, and pathogen presence data from the same individual ticks, and that attempted to combine the different lines of evidence. The approaches and pre-processing steps used can be applied to a variety of taxa, and help better understand ecological processes in biological systems. |
Distribution and Occurrence of Amblyomma maculatum sensu lato (Acari: Ixodidae) and Rickettsia parkeri (Rickettsiales: Rickettsiaceae), Arizona and New Mexico, 2017-2019.
Hecht JA , Allerdice MEJ , Karpathy SE , Yaglom HD , Casal M , Lash RR , Delgado-de la Mora J , Licona-Enriquez JD , Delgado-de la Mora D , Groschupf K , Mertins JW , Moors A , Swann DE , Paddock CD . J Med Entomol 2020 57 (6) 2030-2034 Amblyomma maculatum Koch sensu lato (s.l.) ticks are the vector of Rickettsia parkeri in Arizona, where nine cases of R. parkeri rickettsiosis have been identified since the initial case in 2014. The current study sought to better define the geographic ranges of the vector and pathogen and to assess the potential public health risk posed by R. parkeri in this region of the southwestern United States. A total of 275 A. maculatum s.l. ticks were collected from 34 locations in four counties in Arizona and one county in New Mexico and screened for DNA of Rickettsia species. Rickettsia parkeri was detected in 20.4% of the ticks, including one specimen collected from New Mexico, the first report of R. parkeri in A. maculatum s.l. from this state. This work demonstrates a broader distribution of A. maculatum s.l. ticks and R. parkeri in the southwestern United States than appreciated previously to suggest that R. parkeri rickettsiosis is underrecognized in this region. |
Rickettsia parkeri and "Candidatus Rickettsia andeanae" in Amblyomma maculatum (Acari: Ixodidae) collected from the Atlanta metropolitan area, Georgia, United States
Allerdice MEJ , Hecht JA , Lash RR , Karpathy SE , Paddock CD . Ticks Tick Borne Dis 2019 10 (5) 1066-1069 Rickettsia parkeri is a recently recognized human pathogen transmitted in the southeastern United States by Amblyomma maculatum, the Gulf Coast tick. Since R. parkeri was conclusively identified as a human pathogen in 2004, over 40 cases of R. parkeri rickettsiosis have been identified in the United States, most of which occur in the southeastern states. During 2012-2014, five of these cases were identified by a single urgent care practice in Coweta County, a Georgia county within the Atlanta metropolitan area. To investigate the occurrence of R. parkeri-infected A. maculatum in the Atlanta metropolitan area, ticks were collected from 6 counties around the city of Atlanta and evaluated for infection with a Rickettsia species. A total of 263 questing adult A. maculatum were collected during 2015 and 2016. Of these, 93 (35%) were PCR-positive for DNA of R. parkeri and an additional 46 (17%) were PCR-positive for DNA of "Candidatus Rickettsia andeanae," a spotted fever group Rickettsia species of unknown pathogenicity. No co-infections of these two rickettsiae were detected; however four of the six counties sampled showed presence of both rickettsial organisms. The high frequency of R. parkeri in these tick populations indicates a potential risk for those living, working, or recreating in A. maculatum-infested habitats within these six counties in the Atlanta metropolitan area. |
Multistate Survey of American Dog Ticks (Dermacentor variabilis) for Rickettsia Species.
Hecht JA , Allerdice MEJ , Dykstra EA , Mastel L , Eisen RJ , Johnson TL , Gaff HD , Varela-Stokes AS , Goddard J , Pagac BB , Paddock CD , Karpathy SE . Vector Borne Zoonotic Dis 2019 19 (9) 652-657 Dermacentor variabilis, a common human-biting tick found throughout the eastern half and along the west coast of the United States, is a vector of multiple bacterial pathogens. Historically, D. variabilis has been considered a primary vector of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever. A total of 883 adult D. variabilis, collected between 2012 and 2017 from various locations in 12 states across the United States, were screened for rickettsial DNA. Tick extracts were evaluated using three real-time PCR assays; an R. rickettsii-specific assay, a Rickettsia bellii-specific assay, and a Rickettsia genus-specific assay. Sequencing of ompA gene amplicons generated using a seminested PCR assay was used to determine the rickettsial species present in positive samples not already identified by species-specific real-time assays. A total of 87 (9.9%) tick extracts contained R. bellii DNA and 203 (23%) contained DNA of other rickettsial species, including 47 (5.3%) with Rickettsia montanensis, 11 (1.2%) with Rickettsia amblyommatis, 2 (0.2%) with Rickettsia rhipicephali, and 3 (0.3%) with Rickettsia parkeri. Only 1 (0.1%) tick extract contained DNA of R. rickettsii. These data support multiple other contemporary studies that indicate infrequent detection of R. rickettsii in D. variabilis in North America. |
The Amblyomma maculatum Koch, 1844 (Acari: Ixodidae) group of ticks: phenotypic plasticity or incipient speciation?
Lado P , Nava S , Mendoza-Uribe L , Caceres AG , Delgado-de la Mora J , Licona-Enriquez JD , Delgado-de la Mora D , Labruna MB , Durden LA , Allerdice MEJ , Paddock CD , Szabo MPJ , Venzal JM , Guglielmone AA , Beati L . Parasit Vectors 2018 11 (1) 610 BACKGROUND: The goal of this study was to reassess the taxonomic status of A. maculatum, A. triste and A. tigrinum by phylogenetic analysis of five molecular markers [four mitochondrial: 12S rDNA, 16S rDNA, the control region (DL) and cytochrome c oxidase 1 (cox1), and one nuclear: ribosomal intergenic transcribed spacer 2 (ITS2)]. In addition, the phenotypic diversity of adult ticks identified as A. maculatum and A. triste from geographically distinct populations was thoroughly re-examined. RESULTS: Microscopic examination identified four putative morphotypes distinguishable by disjunct geographical ranges, but very scant fixed characters. Analysis of the separated mitochondrial datasets mostly resulted in conflicting tree topologies. Nuclear gene sequences were almost identical throughout the geographical ranges of the two species, suggesting a very recent, almost explosive radiation of the terminal operational taxonomic units. Analysis of concatenated molecular datasets was more informative and indicated that, although genetically very close to the A. maculatum - A. triste lineage, A. tigrinum was a monophyletic separate entity. Within the A. maculatum - A. triste cluster, three main clades were supported. The two morphotypes, corresponding to the western North American and eastern North American populations, consistently grouped in a single monophyletic clade with many shared mitochondrial sequences among ticks of the two areas. Ticks from the two remaining morphotypes, south-eastern South America and Peruvian, corresponded to two distinct clades. CONCLUSIONS: Given the paucity of morphological characters, the minimal genetic distance separating morphotypes, and more importantly the fact that two morphotypes are genetically indistinguishable, our data suggest that A. maculatum and A. triste should be synonymized and that morphological differences merely reflect very recent local adaptation to distinct environments in taxa that might be undergoing the first steps of speciation but have yet to complete lineage sorting. Nonetheless, future investigations using more sensitive nuclear markers and/or crossbreeding experiments might reveal the occurrence of very rapid speciation events in this group of taxa. Tentative node dating revealed that the A. tigrinum and A. maculatum - A. triste clades split about 2 Mya, while the A. maculatum - A.triste cluster radiated no earlier than 700,000 years ago. |
Rickettsia parkeri (Rickettsiales: Rickettsiaceae) detected in ticks of the Amblyomma maculatum (Acari: Ixodidae) group collected from multiple locations in southern Arizona
Allerdice MEJ , Beati L , Yaglom H , Lash RR , Delgado-de la Mora J , Licona-Enriquez JD , Delgado-de la Mora D , Paddock CD . J Med Entomol 2017 54 (6) 1743-1749 Rickettsia parkeri is an emerging human pathogen transmitted by Amblyomma ticks in predominately tropical and subtropical regions of the western hemisphere. In 2014 and 2015, one confirmed case and one probable case of R. parkeri rickettsiosis were reported from the Pajarita Wilderness Area, a semi-arid mountainous region in southern Arizona. To examine more closely the potential public health risk of R. parkeri in this region, a study was initiated to investigate the pervasiveness of Amblyomma maculatum Koch group ticks in mountainous areas of southern Arizona and to ascertain the infection frequencies of R. parkeri in these ticks. During July 2016, a total of 182 adult ticks were collected and evaluated from the Pajarita Wilderness Area in Santa Cruz County and two additional sites in Cochise and Santa Cruz counties in southern Arizona. DNA of R. parkeri was detected in a total of 44 (24%) of these ticks. DNA of "Candidatus Rickettsia andeanae" and Rickettsia rhipicephali was detected in three (2%) and one (0.5%) of the samples, respectively. These observations corroborate previous collection records and indicate that established populations of A. maculatum group ticks exist in multiple foci in southern Arizona. The high frequency of R. parkeri in these tick populations suggests a public health risk as well as the need to increase education of R. parkeri rickettsiosis for those residing, working in, or visiting this area. |
Proposal to reclassify Ehrlichia muris as Ehrlichia muris subsp. muris subsp. nov. and description of Ehrlichia muris subsp. eauclairensis subsp. nov., a newly recognized tick-borne pathogen of humans
Pritt BS , Allerdice MEJ , Sloan LM , Paddock CD , Munderloh UG , Rikihisa Y , Tajima T , Paskewitz SM , Neitzel DF , Hoang Johnson DK , Schiffman E , Davis JP , Goldsmith CS , Nelson CM , Karpathy SE . Int J Syst Evol Microbiol 2017 67 (7) 2121-2126 We have previously described a novel taxon of the genus Ehrlichia (type strain WisconsinT), closely related to Ehrlichia muris, that causes human ehrlichiosis among patients with exposures to ticks in the upper midwestern USA. DNA from this bacterium was also detected in Ixodes scapularis and Peromyscus leucopus collected in Minnesota and Wisconsin. To determine the relationship between the E. muris-like agent (EMLA) and other species of the genus Ehrlichia phenotypic, genotypic and epidemiologic comparisons were undertaken, including sequence analysis of eight gene loci (3906 nucleotides) for 39 EMLA DNA samples and the type strain of E. muris AS145T. Three loci were also sequenced from DNA of nine strains of E. muris from mouse spleens from Japan. All sequences from E. muris were distinct from homologous EMLA sequences, but differences between them were less than those observed among other species of the genus Ehrlichia. Phenotypic comparison of EMLA and E. muris revealed similar culture and electron microscopic characteristics, but important differences were noted in their geographic distribution, ecological associations and behavior in mouse models of infection. Based on these comparisons, we propose that type strain WisconsinT represents a novel subspecies, Ehrlichia murissubsp. eauclairensis,subsp. nov. This strain is available through the Centers for Disease Control and Prevention Rickettsial Isolate Reference Collection (CRIRC EMU002T) and through the Collection de Souches de l'Unite des Rickettsies (CSURP2883 T). The subspecies Ehrlichia murissubsp. muris subsp. nov. is automatically created and the type strain AS145T is also available through the same collections (CRIRC EMU001T, CSUR E2T). Included is an emended description of E. muris. |
Spotted fever group rickettsiae in immature Amblyomma maculatum (Acari: Ixodidae) from Mississippi
Goddard J , Allerdice MEJ , Paddock CD , Portugal JS . J Entomol Sci 2016 51 (4) 329-331 Very little is known about the vector potential posed by larval and nymphal Amblyomma maculatum Koch (Gulf Coast ticks) to humans or other vertebrate species. Rickettsia parkeri Lackman, the causative agent of American boutonneuse fever in humans, which is transmitted by the Gulf Coast tick (Parker et al. 1939, Public Health Rep. 54: 1482–1484; Goddard 2004, Infect. Med. 21: 207–210; Paddock et al. 2004, Clin. Infect. Dis. 38: 805–811) has been detected in Mississippi on several occasions (Paddock et al. 2008, Clin. Infect. Dis. 47: 1188–1196; Ferrari et al. 2012, Emerg. Infect. Dis. 18: 1705–1707; Ekenna et al. 2014, J. Miss. State Med. Assoc. 55: 216–219), as well as other states in the United States and several countries in South America. The role played by immatures in the ecology of R. parkeri has only recently been considered. Another spotted fever group rickettsia (SFGR), “Candidatus Rickettsia andeanae,” occurs in Gulf Coast ticks from North and South America (Blair et al. 2004, J. Clin. Microbiol. 42: 4961–4967; Paddock et al. 2010, Appl. Environ. Microbiol. 76: 2689–2696; Ferrari et al. 2012). It is unknown if “Ca. R. andeanae” is a pathogen of humans; however, it is possible that this SFGR may play a role in the natural history of R. parkeri by rickettsial interference (Paddock et al. 2015, Ticks Tick Borne Dis. 6: 297–302). | Rickettsia parkeri is transmitted transovarially under laboratory conditions (Wright et al. 2015, Ticks Tick Borne Dis. 6: 568–573), and immature stages of A. maculatum have been shown to attach to humans (Goddard 2002, J. Agromed. 8: 25–32; Portugal and Goddard 2015, J. Med. Entomol. doi: 10.1093/jme/tjv185). To our knowledge, neither R. parkeri nor “Ca. R. andeanae” have ever been detected in questing immature specimens of A. maculatum (Fornadel et al. 2011, Vector Borne Zoonotic Dis. 12: 1535–1538; Florin et al. 2013, Syst. Appl. Acarol. 18: 27–29; Nadolny et al. 2014, Ticks Tick Borne Dis. 5: 53–57). This study was initiated to document rickettsial infection in questing (unfed) immature Gulf Coast ticks to better assess the relative risk posed by these stages in the transmission of R. parkeri to humans. |
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