Rickettsia parkeri and Candidatus Rickettsia andeanae in Tick of the Amblyomma maculatum Group, Mexico.
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ABSTRACT:
SUBMITTER: Delgado-de la Mora J
PROVIDER: S-EPMC6433039 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:We determined prevalence of Rickettsia spp. in 172 ticks of the Amblyomma maculatum group collected from 16 urban sites in Oklahoma City, Oklahoma, USA, during 2017 and 2018. Most ticks (59.3%) were collected from 1 site; 4 (2.3%) were infected with Rickettsia parkeri and 118 (68.6%) with Candidatus Rickettsia andeanae.
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Project description:Amblyomma maculatum Koch (Acari: Ixodidae), the primary vector for Rickettsia parkeri, may also be infected with a rickettsia of unknown pathogenicity, "Candidatus Rickettsia andeanae." Infection rates with these rickettsiae vary geographically, and coinfected ticks have been reported. In this study, infection rates of R. parkeri and "Ca. R. andeanae" were evaluated, and rickettsial DNA levels quantified, in 335 questing adult A. maculatum collected in 2013 (n = 95), 2014 (n = 139), and 2015 (n = 101) from Oktibbeha County, MS. Overall infection rates of R. parkeri and "Ca. R. andeanae" were 28.7% and 9.3%, respectively, with three additional A. maculatum (0.9%) coinfected. While R. parkeri-infected ticks were detected all three years (34.7% in 2013; 13.7% in 2014; 43.6% in 2015), "Ca. R. andeanae" was not detected in 2013, and was detected at rates of 10.8% in 2014, and 15.8% in 2015. Interestingly, rickettsial DNA levels in singly-infected ticks were significantly lower in "Ca. R. andeanae"-infected ticks compared to R. parkeri-infected ticks (P < 0.0001). Thus, both infection rates and rickettsial DNA levels were higher for R. parkeri than "Ca. R. andeanae." Infection rates of R. parkeri were also higher, and "Ca. R. andeanae" lower, here compared to A. maculatum reported previously in Kansas and Oklahoma. As we continue to monitor infection rates and levels, we anticipate that understanding temporal changes will improve our awareness of human risk for spotted fever rickettsioses. Further, these data may lead to additional studies to evaluate potential interactions among sympatric Rickettsia species in A. maculatum at the population level.
| S-EPMC5850715 | biostudies-literature
Project description:The Gulf Coast tick, Amblyomma maculatum, is a vector of Rickettsia parkeri, a recently identified human pathogen that causes a disease with clinical symptoms that resemble a mild form of Rocky Mountain spotted fever. Because the prevalence of R. parkeri infection in geographically distinct populations of A. maculatum is not fully understood, A. maculatum specimens collected as part of a tick and pathogen surveillance system in Fairfax County, Virginia, were screened to determine pathogen infection rates. Overall, R. parkeri was found in 41.4% of the A. maculatum that were screened. Additionally, the novel spotted fever group Rickettsia sp., tentatively named "Candidatus Rickettsia andeanae," was observed for the first time in Virginia.
| S-EPMC3231788 | biostudies-literature
Project description:Amblyomma maculatum (the Gulf Coast tick), an aggressive, human-biting, Nearctic and Neotropical tick, is the principal vector of Rickettsia parkeri in the United States. This pathogenic spotted fever group Rickettsia species has been identified in 8-52% of questing adult Gulf Coast ticks in the southeastern United States. To our knowledge, R. parkeri has not been reported previously from adult specimens of A. maculatum collected in Kansas or Oklahoma. A total of 216 adult A. maculatum ticks were collected from 18 counties in Kansas and Oklahoma during 2011-2014 and evaluated by molecular methods for evidence of infection with R. parkeri. No infections with this agent were identified; however, 47% of 94 ticks collected from Kansas and 73% of 122 ticks from Oklahoma were infected with "Candidatus Rickettsia andeanae" a spotted fever group Rickettsia species of undetermined pathogenicity. These preliminary data suggest that "Ca. R. andeanae" is well-adapted to survival in populations of A. maculatum in Kansas and Oklahoma, and that its ubiquity in Gulf Coast ticks in these states may effectively exclude R. parkeri from their shared arthropod host, which could diminish markedly or preclude entirely the occurrence of R. parkeri rickettsiosis in this region of the United States.
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Project description: Not available
| S-EPMC3471625 | biostudies-literature
Project description:Geographic distribution of Rickettsia parkeri in its US tick vector, Amblyomma maculatum, was evaluated by PCR. R. parkeri was detected in ticks from Florida, Georgia, Kentucky, Mississippi, Oklahoma, and South Carolina, which suggests that A. maculatum may be responsible for additional cases of R. parkeri rickettsiosis throughout much of its US range.
| S-EPMC2738460 | biostudies-literature
Project description:BACKGROUND:The Gulf Coast tick (Amblyomma maculatum) is an arthropod vector of Rickettsia parkeri, the causative agent of American boutonneuse fever and an infectious agent of public health significance. In this study, we evaluated the biological significance of the superoxide dismutases (SODs) of A. maculatum in hematophagy and R. parkeri colonization within the tick host. METHODS:An RNA interference approach was used to measure the functional roles of tick SODs (Cu/Zn-SOD and Mn-SOD) in R. parkeri colonization of the tick vector. Total microbial load, R. parkeri infection rate, and compensatory mechanisms by tick genes were examined using quantitative polymerase chain reaction (PCR) and quantitative reverse-transcriptase PCR assays. SOD enzymatic activity assays and malondialdehyde (MDA) lipid peroxidation were employed to determine the redox states in the tick tissues. RESULTS:Knockdown of the Cu/Zn-SOD gene caused the upregulation of Mn-SOD in transcript levels. Single and dual knockdowns of the SOD genes caused an increase in MDA lipid peroxidation while SOD enzymatic activities did not show a significant change. Mn-SOD knockdown resulted in a substantial increase in the microbial load; however, Cu/Zn-SOD transcript depletion prompted an upsurge in the midgut bacterial load, and significantly decreased the bacterial load in salivary gland tissues. Additionally, Cu/Zn-SOD transcript silencing led to significantly fewer R. parkeri DNA copy numbers in both tick tissues (midguts and salivary glands). CONCLUSIONS:SOD enzymes play an important function in the regulation of bacterial communities associated with tick vectors and also in the defense mechanisms against the damage caused by reactive oxygen species within the tick. Knockdown experiments increased the levels of total oxidative stress in ticks, revealing the interplay between SOD isozymes that results in the transcriptional regulation of tick antioxidants. Moreover, the tick's Cu/Zn-SOD aids in the colonization of R. parkeri in tick tissues providing evidence of A. maculatum's vectorial success for a spotted fever group rickettsial pathogen.
| S-EPMC4873992 | biostudies-literature
Project description:Adult ticks of the species Amblyomma parvum were collected from the vegetation in the Pantanal biome (state of Mato Grosso do Sul) and from horses in the Cerrado biome (state of Piauí) in Brazil. The ticks were individually tested for rickettsial infection via polymerase chain reaction (PCR) targeting three rickettsial genes, gltA, ompA and ompB. Overall, 63.5% (40/63) and 66.7% (2/3) of A. parvum ticks from Pantanal and Cerrado, respectively, contained rickettsial DNA, which were all confirmed by DNA sequencing to be 100% identical to the corresponding fragments of the gltA, ompA and ompB genes of Candidatus Rickettsia andeanae. This report is the first to describe Ca. R. andeanae in Brazil.
| S-EPMC4015251 | biostudies-literature
Project description:The Gulf Coast tick (Amblyomma maculatum) has evolved as a competent vector of the spotted-fever group rickettsia, Rickettsia parkeri. In this study, the functional role of catalase, an enzyme responsible for the degradation of toxic hydrogen peroxide, in the colonization of the tick vector by R. parkeri and transovarial transmission of this pathogen to the next tick generation, was investigated. Catalase gene (CAT) expression in midgut, salivary glands and ovarian tissues exhibited a 2-11-fold increase in transcription level upon R. parkeri infection. Depletion of CAT transcripts using an RNA-interference approach significantly reduced R. parkeri infection levels in midgut and salivary gland tissues by 53-63%. The role of CAT in transovarial transmission of R. parkeri was confirmed by simultaneously blocking the transcript and the enzyme by injecting double-stranded RNA for CAT and a catalase inhibitor (3-amino-1,2,4-triazole) into gravid females. Simultaneous inhibition of the CAT transcript and the enzyme significantly reduced the egg conversion ratio with a 44% reduction of R. parkeri transovarial transmission. These data suggest that catalase is required for rickettsial colonization of the tick vector and transovarial transmission to the next generation.
| S-EPMC5496812 | biostudies-literature
Project description:The Gram-negative obligate intracellular bacterium Rickettsia parkeri is an emerging tick-borne human pathogen. Recently, R. parkeri Sca2 and RickA have been implicated in adherence and actin-based motility in vertebrate host cell infection models; however, the rickettsia-derived factors essential to tick infection are unknown. Using R. parkeri mutants lacking functional Sca2 or RickA to compare actin polymerization, replication, and cell-to-cell spread in vitro, similar phenotypes in tick and mammalian cells were observed. Specifically, actin polymerization in cultured tick cells is controlled by the two separate proteins in a time-dependent manner. To assess the role of Sca2 and RickA in dissemination in the tick host, Rickettsia-free Amblyomma maculatum, the natural vector of R. parkeri, was exposed to wild-type, R. parkeri rickA::tn, or R. parkeri sca2::tn bacteria, and individual tick tissues, including salivary glands, midguts, ovaries, and hemolymph, were analyzed at 12 h and after continued bloodmeal acquisition for 3 or 7 days postexposure. Initially, ticks exposed to wild-type R. parkeri had the highest rickettsial load across all organs; however, rickettsial loads decreased and wild-type rickettsiae were cleared from the ovaries at 7 days postexposure. In contrast, ticks exposed to R. parkeri rickA::tn or R. parkeri sca2::tn had comparatively lower rickettsial loads, but bacteria persisted in all organs for 7 days. These data suggest that while RickA and Sca2 function in actin polymerization in tick cells, the absence of these proteins did not change dissemination patterns within the tick vector.
| S-EPMC5964526 | biostudies-literature